BAIL 2006 Book of Abstracts - Institut für Numerische und ...
BAIL 2006 Book of Abstracts - Institut für Numerische und ...
BAIL 2006 Book of Abstracts - Institut für Numerische und ...
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<strong>BAIL</strong> <strong>2006</strong><br />
International Conference on<br />
Bo<strong>und</strong>ary and Interior Layers<br />
Göttingen,<br />
24th - 28th July, <strong>2006</strong><br />
L. Prandtl<br />
<strong>Book</strong> <strong>of</strong> <strong>Abstracts</strong><br />
Organized by:<br />
Georg-August Universität Göttingen<br />
Deutsches Zentrum <strong>für</strong> Luft- <strong>und</strong> Raumfahrt (DLR)<br />
Sponsored by:<br />
Land Niedersachsen,<br />
Graduiertenkolleg 1023<br />
Gesellschaft <strong>für</strong> Angewandte Mathematik <strong>und</strong> Mechanik (GAMM)<br />
German Academic Exchange Service (DAAD)<br />
Georg-August Universität Göttingen<br />
Deutsches Zentrum <strong>für</strong> Luft- <strong>und</strong> Raumfahrt (DLR)
Greeting<br />
It gives me great pleasure to welcome all participants to the <strong>BAIL</strong> <strong>2006</strong> conference in<br />
Goettingen, Germany. This conference is the latest in a long line <strong>of</strong> international conferences<br />
on Bo<strong>und</strong>ary and Interior Layers, that have been held in many parts <strong>of</strong> the world.<br />
The first three conferences were held in Dublin, Ireland in 1980, 1982 and 1984. These<br />
were followed by conferences in Novosibirsk, USSR (1986), Shanghai, China (1988),<br />
Copper Mountain, USA (1992) and Beijing, China (1994).<br />
After a gap <strong>of</strong> some years, an international steering committee was formed to advise on<br />
the creation <strong>of</strong> a new series <strong>of</strong> <strong>BAIL</strong> conferences. This committee made a positive recommendation,<br />
which has resulted in three further <strong>BAIL</strong> conferences being held, specifically:<br />
<strong>BAIL</strong> 2002 in Perth, Australia, <strong>BAIL</strong> 2004 in Toulouse, France and this year’s <strong>BAIL</strong> <strong>2006</strong><br />
in Goettingen, Germany.<br />
It is heartening to see how well <strong>BAIL</strong> <strong>2006</strong> is supported. Indeed, the number <strong>of</strong> participants<br />
appears to be growing with each successive conference in the new series. I am<br />
delighted to thank the members <strong>of</strong> the International Steering Committee for their good<br />
advice over the years. It is a particular pleasure also to thank the local organizers and<br />
their teams for the hard work involved in the organization <strong>of</strong> each <strong>of</strong> these conferences.<br />
Only someone who has organized such a conference is aware <strong>of</strong> just how much work is<br />
involved! I believe that the success <strong>of</strong> the <strong>BAIL</strong> <strong>2006</strong> organizers, especially in making<br />
this event attractive to a large number <strong>of</strong> participants, is an important milestone in the<br />
development <strong>of</strong> this series <strong>of</strong> conferences. On behalf <strong>of</strong> all participants I thank the organizers<br />
and, in addition, I wish everyone a productive and enjoyable meeting.<br />
John J H Miller<br />
Dublin, Ireland<br />
July <strong>2006</strong><br />
<strong>BAIL</strong> conferences<br />
• <strong>BAIL</strong> 2004, Toulouse, France<br />
• <strong>BAIL</strong> 2002 , Perth, Australia<br />
• <strong>BAIL</strong> VII, Beijing, China (1994)<br />
• <strong>BAIL</strong> VI, Colorado, USA (1992)<br />
• <strong>BAIL</strong> V, Shanghai, China (1988)<br />
• <strong>BAIL</strong> IV, Novosibirsk, USSR (1986)<br />
• <strong>BAIL</strong> III, Dublin, Ireland (1984)<br />
• <strong>BAIL</strong> II, Dublin, Ireland (1982)<br />
• <strong>BAIL</strong> I, Dublin, Ireland (1980)<br />
3 <strong>BAIL</strong> <strong>2006</strong>
Plenary Session 1 Session 2 Session 3 Session 4 Evening<br />
Talks<br />
9:15-10:15 10:45-12:25 14:00 - 14:50 15:10 - 16:25 16:45-18:00<br />
S<strong>und</strong>ay<br />
Welcome<br />
July 23<br />
Reception<br />
(17:00-20:00,<br />
House 6)<br />
Monday Room SL P. Huerre Applied Applied Minisymposium Minisymposium Get Together<br />
Aerodynamics Aerodynamics Stynes, O’Riordan Stynes,O’Riordan Party<br />
July 24 Room MPI (Room Asymptotic Asymptotic Special<br />
(Old Town-hall,<br />
MPI) Methods Methods Flows<br />
19:00-20:30)<br />
Public Talk<br />
Pr<strong>of</strong>. Gersten<br />
Minisymposium<br />
Hartmann, Hou-<br />
Minisymposium<br />
Hartmann, Hou-<br />
Flows in Special<br />
Geometries<br />
Tuesday Room SL M. Stynes Heat<br />
Transfer<br />
Room SL<br />
(20:00-21:30)<br />
ston<br />
Numerical<br />
Methods 1<br />
ston<br />
Numeric. Methods<br />
for Fluid Flows<br />
Minisymposium<br />
Maubach, Tselishcheva<br />
Minisymposium<br />
Maubach,<br />
Tselishcheva<br />
July 25 Room MPI (Room<br />
MPI)<br />
Excursion<br />
Conference Dinner<br />
Open<br />
Discussion 1<br />
Wall<br />
functions 2<br />
Wednesday Room SL W. Wall Numerical<br />
Methods 2<br />
July 26 Room MPI (Room Wall<br />
MPI) functions 1<br />
Minisymposium<br />
Shishkin, Hemker<br />
Open<br />
Discussion 2<br />
Minisymposium<br />
Shishkin, Hemker<br />
Anisotropic<br />
Meshes 2<br />
Thursday Room SL P. Houston Anisotropic<br />
Meshes 1 Ro<strong>und</strong> Tour<br />
July 27 Room MPI (Room Turbulence (DLR,<br />
MPI) Modelling Math. Inst.)<br />
End <strong>of</strong> Conference<br />
Friday Room SL Minisymposium: Das,Sengupta<br />
(9:15-10:30, 11:00-12:15)<br />
5 <strong>BAIL</strong> <strong>2006</strong><br />
July 28 Room MPI
Room School-Lab (SL) Room MPI<br />
S<strong>und</strong>ay, 23 July<br />
17:00 - 20:00 Welcome Reception<br />
Monday, 24 July<br />
8:00 - 9:00 Registration<br />
9:00 - 9:15 Opening<br />
9:15 - 10:15 Plenary Talk:<br />
P. Huerre: Dynamics <strong>of</strong> hot jets: a numerical and theo-<br />
6 <strong>BAIL</strong> <strong>2006</strong><br />
retical study.<br />
10:15 - 10:45 C<strong>of</strong>fee Break<br />
Session: Applied Aerodynamics<br />
Session: Asymptotic methods<br />
P. Svacek: Numerical Approximation <strong>of</strong> Flow Induced<br />
M. Hamouda, R. Temam: Bo<strong>und</strong>ary layers for the<br />
Airfoil Vibrations (10:45-11:10)<br />
Navier-Stokes equations: asymptotic analysis (10:45-<br />
A. Firooz, M. Gadami: Turbulence Flow for NACA<br />
11:10)<br />
4412 in Unbo<strong>und</strong>ed Flow and Grow Effect with Diffe-<br />
N.V. Tarasova: Full asymptotic analysis <strong>of</strong> the Navier-<br />
rent Turbulence Models and Two Gro<strong>und</strong> Conditions:<br />
10:45 - 12:25<br />
Stokes equations in the problems <strong>of</strong> gas flows over bodies<br />
Fixed and Moving Gro<strong>und</strong> Conditions (11:10-11:35)<br />
with large Reynolds number (11:10-11:35)<br />
B. Eisfeld: Computation <strong>of</strong> complex compressible<br />
N. Neuss: Numerical approximation <strong>of</strong> bo<strong>und</strong>ary layers<br />
aerodynamic flows with Reynolds stress turbulence<br />
for rough bo<strong>und</strong>aries (11:35-12:00)<br />
model (11:35-12:00)
Room School-Lab (SL) Room MPI<br />
Session: Asymptotic methods<br />
Session: Applied Aerodynamics<br />
A.-M. Il’in, B.I. Suleimanov: The coefficients <strong>of</strong> in-<br />
A. Nastase: Qualitative Analysis <strong>of</strong> the Navier-Stokes<br />
10:45 - 12:25<br />
ner asymptotic expansions for solutions <strong>of</strong> some singular<br />
Solutions on Vicinty <strong>of</strong> their Critical Lines (12:00-12:25)<br />
bo<strong>und</strong>ary value problems (12:00-12:25)<br />
12:30 - 14:00 Lunch Break<br />
Session: Applied Aerodynamics<br />
Session: Asymptotic methods<br />
Z.-H. Yang, Y.-Z. Li, Y. Zhu: Application <strong>of</strong> Bi-<br />
C.H. Tai, C.-Y. Chao, J.-C. Leong, Q.S. Hong:<br />
furcation Method to Computing Numerical Solutions <strong>of</strong><br />
Effects <strong>of</strong> golf ball dimple configuration on aerodyna-<br />
Lane-Emden Equation (14:00-14:25)<br />
mics, trajectory, and acoustics (14:00-14:25)<br />
14:00 - 14:50<br />
7 <strong>BAIL</strong> <strong>2006</strong><br />
H. Tian: Uniformly Convergent Numerical Methods<br />
W.S. Islam, V.R. Raghavan: Numerical Simulation<br />
for Singularly Perturbed Delay Differential Equations<br />
<strong>of</strong> High Sub-critical Reynolds Number Flow Past a Cir-<br />
(14:25-14:50)<br />
cular Cylinder (14:25-14:50)<br />
14:50 - 15:10 C<strong>of</strong>fee Break<br />
Session: Special Flows<br />
Minisyposium: M. Stynes, E. O’Riordan<br />
B. Rasuo: On Bo<strong>und</strong>ary Layer Control in Two-<br />
H. Wang: A Component-Based Eulerian-Lagrangian<br />
Dimensional Transonic Wind Tunnels (15:10-15:35)<br />
Formulation for Compositional Flow in Porous Media<br />
M. Vasiliev: About unsteady Bo<strong>und</strong>ary Layer on a di-<br />
G.I. Shishkin: A posteriori adapted meshes in the<br />
approximation <strong>of</strong> singularly perturbed quasilinear<br />
15:10 - 16:25<br />
hedral angle (15:35-16:00)<br />
K. Mansour: Bo<strong>und</strong>ary Layer Solution for Laminar<br />
parabolic convection-diffusion equations<br />
Flow through a Loosely Curved Pipe by using Stokes<br />
W. Layton, I. Stanculescu: Numerical Analysis <strong>of</strong><br />
Expansion (16:00-16:25)<br />
Approximate Deconvolution Models <strong>of</strong> Turbulence
Room School-Lab (SL) Room MPI<br />
16:25 - 16:45 C<strong>of</strong>fee break<br />
Minisymposium: M. Stynes, E. O’Riordan<br />
R.K. Dunne, E. O’Riordan, M.M. Turner:<br />
A singular perturbation problem arising in the model-<br />
16:45 - 18:00<br />
ling <strong>of</strong> plasma sheats<br />
19:00 - 21:00 Get Together Party<br />
Old Town Hall<br />
8 <strong>BAIL</strong> <strong>2006</strong>
Room School-Lab (SL) Room MPI<br />
Tuesday, 25 July<br />
Plenary Talk:<br />
M. Stynes: Convection-diffusion problems, SD-<br />
9:15 - 10:15<br />
FEM/SUPG and a priori meshes.<br />
10:15 - 10:45 C<strong>of</strong>fee break<br />
Minisymposium: J.Maubach, I.V.Tselishcheva:<br />
M. Anthonissen, I. Sedykh, J. Maubach: A con-<br />
vergence pro<strong>of</strong> <strong>of</strong> local defect correction for convection-<br />
Session: Heat Transfer<br />
M. Hölling, H. Herwig: Computation <strong>of</strong> turbulent<br />
9 <strong>BAIL</strong> <strong>2006</strong><br />
diffusion problems<br />
J. Maubach: On the difference between left and right<br />
natural convection at vertical walls using new wall<br />
preconditioning for convection dominated convection-<br />
functions (10:45-11:10)<br />
diffusion problems<br />
O. Shishkina, C. Wagner: Bo<strong>und</strong>ary and Interior<br />
10:45 - 12:25<br />
A. Hegarty, St. Sikwila, G.I. Shishkin: An adap-<br />
Layers in Turbulent Thermal Convection (11:10-11:35)<br />
tive method for the numerical solution <strong>of</strong> an elliptic<br />
K. Morinishi: Rarefied Gas Bo<strong>und</strong>ary Layer Predicted<br />
convection diffusion problem<br />
with Continuum and Kinetic Approaches (11:35-12:00)<br />
P. Zegeling: An Adaptive Grid Method for the Solar<br />
Coronal Loop Model<br />
12:30 - 14:00 Lunch Break
Room School-Lab (SL) Room MPI<br />
Minisymposium: J.Maubach, I.V.Tselishcheva:<br />
A.I. Zadorin: Numerical method for the Blasius equa-<br />
Session: Flows in Special Geometries<br />
tion on an infinite interval<br />
D. Kachuma, I. Sobey: Fast waves during transient<br />
S. Li , L.P. Shishkina, G.I. Shishkin, Parameter-<br />
flow in an asymmetric channel (14:00-14:25)<br />
14:00 - 14:50<br />
uniform method for a singularly perturbed parabolic<br />
J. Mauss, J. Cousteix: Global Interactive Bo<strong>und</strong>ary<br />
equation modelling the Black-Scholes equation in the<br />
Layer (GIBL) for a Channel (14:25-14:50)<br />
presence <strong>of</strong> interior and bo<strong>und</strong>ary layers<br />
14:50 - 15:10 C<strong>of</strong>fee Break<br />
Session: Numer. Methods for Fluid Flows<br />
10 <strong>BAIL</strong> <strong>2006</strong><br />
P. Knobloch: On methods dimishing spurious oscilla-<br />
tions in finite element solutions <strong>of</strong> convection-diffusion<br />
Minisymposium: R. Hartmann, P. Houston<br />
equations (15:10-15:35)<br />
J. Mackenzie, A. Nicola: A Discontinuous Galerkin<br />
G. Matthies, L. Tobiska: Mass conservation <strong>of</strong> finite<br />
Moving Mesh Method for Hamilton-Jacobi Equations<br />
element methods for coupled flow-transport problems<br />
R. Schneider, P. Jimack: Anisotropic mesh adaption<br />
15:10 - 16:25<br />
(15:35-16:00)<br />
based on a posteriori estimates and optimisation <strong>of</strong> node<br />
M. Olshanskii: An Augmented Lagrangian Based<br />
positions<br />
Solver for the low-viscosity incompressible flows (16:00-<br />
S. Perotto: Layer Capturing via Anisotropic Adaption<br />
16:25)<br />
16:25 - 16:45 C<strong>of</strong>fee break
Room School-Lab (SL) Room MPI<br />
Session: Numerical Methods 1<br />
M. Bause: Apects <strong>of</strong> SUPG/PSPG and GRAD-DIV<br />
Stabilized Finite Element Approximation <strong>of</strong> Compres-<br />
Minisymposium: R. Hartmann, P. Houston<br />
sible Viscous Flow (16:45-17:10)<br />
V. Heuveline: On a new refinement strategy for adap-<br />
F. Nataf, G. Rapin: Application <strong>of</strong> the Smith Fac-<br />
tive hp finite element<br />
torisation to Domain Decomposition Methods for the<br />
16:45 - 18:00<br />
R. Hartmann: Discontinuous Galerkin methods for<br />
Stokes Equations (17:10-17:35)<br />
compressible flows: higher order accuracy, error estima-<br />
A. Cangiani, E.H. Georgoulis, M. Jensen:<br />
tion and adaptivity<br />
Continuous-Discontinuous Finite Element Methods for<br />
Convection-Diffusion Problems (17:35-18:00):<br />
11 <strong>BAIL</strong> <strong>2006</strong><br />
Public Talk:<br />
Gersten: Vom Kochtopf bis zum Fußballspiel: Epi-<br />
soden zu der weltweiten Wirkung der Göttinger<br />
20:00 - 21:30<br />
Strömungsforscher (in german)
Room School-Lab (SL) Room MPI<br />
Wednesday, 26 July<br />
Plenary Talk:<br />
W. Wall: Variational Multiscale Methods for incom-<br />
9:15 - 10:15<br />
pressible flows.<br />
10:15 - 10:45 C<strong>of</strong>fee Break<br />
Session: Numerical Methods 3<br />
Session: Wall Functions 1<br />
F. Alizard, J.-Ch. Robinet: Two-dimensional tem-<br />
T. Knopp: Model-consistent universal wall-function for<br />
poral modes in nonparallel flows (10:45-11:10)<br />
RANS turbulence modelling (10:45-11:10)<br />
Q. Ye: Numerical simulation <strong>of</strong> turbulent bo<strong>und</strong>ary<br />
12 <strong>BAIL</strong> <strong>2006</strong><br />
Th. Alrutz, T. Knopp: Near wall grid adaption for<br />
for stagnation-flow in the spray-painting process (11:10-<br />
wall functions (11:10-11:35)<br />
11:35)<br />
Z. Hammouch: Similiarity solutions <strong>of</strong> a power-law<br />
10:45 - 12:25<br />
A.I. Tolstykh, M.V. Lipavskii, E.N. Chigerev:<br />
non-Newtonian laminar bo<strong>und</strong>ary layer flows (11:35-<br />
Highly accurate 9th-order schemes and their applicati-<br />
12:00)<br />
ons to DNS <strong>of</strong> thin shear layer instability (11:35-12:00)<br />
B. Scheichl, A. Kluwick: On Turbulent Marginal Se-<br />
N. Parumasur, J. Banasiak, J.M. Kozakiewicz:<br />
paration: How the Logarithmic Law <strong>of</strong> the Wall is Su-<br />
Numerical and Asymptotic Analysis <strong>of</strong> Singularly Per-<br />
perseded by the Half-Power Law (12:00-12:25)<br />
turbed PDEs <strong>of</strong> Kinetic Theory (12:00-12:25)<br />
12:30 - 14:00 Lunch Break
Room School-Lab (SL) Room MPI<br />
Session: Wall Functions 2<br />
Open Discussion I<br />
V.D. Liseykin, Y.V. Likhanova, D.V. Patrakhin,<br />
I.A. Vaseva: Application <strong>of</strong> bo<strong>und</strong>ary layer-type func-<br />
How to prevent spurious oscillations in bo<strong>und</strong>ary and<br />
14:00 - 15:00<br />
tions to comprehensive grid generation codes (14:00-<br />
interior layers?<br />
14:25)<br />
16:00 - 22:00 Excursion + Conference Dinner<br />
13 <strong>BAIL</strong> <strong>2006</strong>
Room School-Lab (SL) Room MPI<br />
Thursday, 27 July<br />
Plenary Talk:<br />
P. Houston: Discontinuous Galerkin Finite Element<br />
9:15 - 10:15<br />
Methods for CFD: A Posteriori Error Estimation and<br />
Adaptivity.<br />
10:15 - 10:45 C<strong>of</strong>fee Break<br />
Session: Anisotropic Meshes 1<br />
Session: Turbul. Modelling<br />
H.-G. Roos: A Comparison <strong>of</strong> Stabilization Methods<br />
Boguslawski: Sheare Stress Distribution on Sphere<br />
for Convection-Diffusion-Reaction Problems on Layer-<br />
14 <strong>BAIL</strong> <strong>2006</strong><br />
Surface at Different Inflow Turbulence (10:45-11:10)<br />
Adapted Meshes (10:45-11:10)<br />
H. Lüdecke: Detached Eddy Simulation <strong>of</strong> Supersonic<br />
H.-G. Roos, H. Zarin: Discontinuous Galerkin stabi-<br />
Shear Layer Wake Flows (11:10-11:35)<br />
lization for convection-diffusion problems (11:10-11:35)<br />
O. Mierka, D. Kuzmin: On the implementation <strong>of</strong><br />
10:45 - 12:25<br />
L. Tobiska: Using rectangular Qp elements in the SD-<br />
turbulence models in incompressible flow solvers based<br />
FEM for a convection-diffusion problem with a bo<strong>und</strong>a-<br />
on a finite element discretization (11:35-12:00)<br />
ry layer (11:35-12:00)<br />
S.A. Gaponov, G.V. Petrov, B.V. Smorodsky:<br />
C. Clavero, J.L. Gracia, F. Lisbona: A second order<br />
Bo<strong>und</strong>ary layer interaction with external disturbances<br />
uniform convergent method for a singularly perturbed<br />
(12:00-12:25)<br />
parabolic system <strong>of</strong> reaction-diffusion type (12:00-12:25)<br />
12:30 - 14:00 Lunch Break<br />
14:00 - 14:50 Ro<strong>und</strong> Tours (DLR or Mathematical <strong>Institut</strong>e)<br />
14:50 - 15:10 C<strong>of</strong>fee Break
Room School-Lab (SL) Room MPI<br />
Minisymposium: G.I. Shishkin, P. Hemker<br />
Session: Anisotropic Meshes 2<br />
G.I. Shishkin: Grid approximation <strong>of</strong> parabolic equa-<br />
A.E.P. Veldmann: High-order symmetry-preserving<br />
tions with nonsmooth initial condition in the presence<br />
discretization on strongly stretched grids (15:10-15:35)<br />
<strong>of</strong> bo<strong>und</strong>ary layers <strong>of</strong> different types<br />
Th. Apel, G. Matthies: A family <strong>of</strong> non-conforming<br />
L.P. Shishkina, G.I. Shishkin: A difference scheme<br />
finite elements <strong>of</strong> arbitrary order for the Stokes problem<br />
<strong>of</strong> improved accuracy for a quasilinear singularly per-<br />
15:10 - 16:25<br />
on anisotropic quadrilateral meshes (15:35-16:00)<br />
turbed elliptic convection-diffusion equation in the case<br />
G. Lube: A stabilized finite element method with aniso-<br />
<strong>of</strong> the third-kind bo<strong>und</strong>ary condition<br />
tropic mesh refinement for the Oseen equations (16:00-<br />
D. Branley, A. Hegarty, H. MacMullen and<br />
16:25)<br />
G.I. Shishkin: A Schwarz method for a convection-<br />
diffusion problem with a corner singularity<br />
16:25 - 16:45 C<strong>of</strong>fee Break<br />
Minisymposium: G.I. Shishkin, P. Hemker<br />
I.V. Tselishcheva, G.I. Shishkin: Domain decom-<br />
position method for a semilinear singularly perturbed<br />
elliptic convection-diffusion equation with concentrated<br />
sources<br />
Th. Linss, M. Madden: Layer-adapted meshes for<br />
15 <strong>BAIL</strong> <strong>2006</strong><br />
Open Discussion 2<br />
Anisotropic mesh generation for advection-dominated<br />
16:45 - 18:00<br />
problems and for incompressible flow problems<br />
time-dependent reaction diffusion<br />
S. Hemavathi, S.Valarmathi: A parameter-uniform<br />
numerical method for a system <strong>of</strong> singularly perturbed<br />
ordinary differential equations
Room School-Lab (SL) Room MPI<br />
Friday, 28 July<br />
Minisymposium: D. Das, T.K. Sengupta<br />
M.H. Buschmann M. Gad-El-Hak: Turbulent<br />
Bo<strong>und</strong>ary Layers: Reality and Myth<br />
L. Savic, H. Steinrück: Asymptotic Analysis <strong>of</strong> the<br />
9:15 - 10:30<br />
mixed convection flow past a horizontal plate near the<br />
trailing edge<br />
10:30 - 11:00 C<strong>of</strong>fee Break<br />
16 <strong>BAIL</strong> <strong>2006</strong><br />
Minisymposium: D. Das, T.K. Sengupta<br />
T.K. Sengupta, A. Kameswara Rao: Spatio-<br />
temporal growing waves in bo<strong>und</strong>ary-layers by Bron-<br />
wich contour integral method<br />
A. Nayak, D. Das: Three-dimensional Temporal<br />
11:00 - 12:25<br />
Instability <strong>of</strong> Unsteady Pipe Flow<br />
J. Hussong, N. Bleier, V.I.V. Ram: The structure<br />
<strong>of</strong> the critical layer <strong>of</strong> a swirling annular flow in transi-<br />
tion<br />
12:25 - 12:40 Closing Session<br />
12:40 - 14:00 Lunch
Contents<br />
Greetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3<br />
Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5<br />
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17<br />
Plenary Presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1<br />
KL. GERSTEN:<br />
Vom Kochtopf bis zum Fußballspiel (Public Talk) . . . . . . . . . 3<br />
P. HOUSTON:<br />
Discontinuous Galerkin Finite Element Methods for CFD: A Posteriori<br />
Error Estimation and Adaptivity . . . . . . . . . . . . . . 4<br />
L. LESSHAFFT, P. HUERRE, P. SAGAUT, M. TERRACOL:<br />
Dynamics <strong>of</strong> Hot Jets: A Numerical and Theoretical Study . . . . 5<br />
M. STYNES:<br />
Convection-diffusion problems, SDFEM/SUPG and a priori meshes 6<br />
V. GRAVEMEIER, S. LENZ, W.A. WALL:<br />
Variational Multiscale Methods for incompressible flows . . . . . 8<br />
Minisymposia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13<br />
MS: N. Kopteva, M. Stynes, E. O’Riordan . . . . . . . . . . . . . . . . . . . . 13<br />
R.K. DUNNE, E. O’RIORDAN, M.M. TURNER:<br />
A singular perturbation problem arising in the modelling <strong>of</strong> plasma<br />
sheaths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14<br />
G.I. SHISHKIN:<br />
A posteriori adapted meshes in the approximation <strong>of</strong> singularly<br />
perturbed quasilinear parabolic convection-diffusion equations . . 16<br />
W. LAYTON, I. STANCULESCU:<br />
Numerical Analysis <strong>of</strong> Approximate Deconvolution Models <strong>of</strong><br />
Turbulence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18<br />
H. WANG:<br />
A Component-Based Eulerian-Lagrangian Formulation for Compositional<br />
Flow in Porous Media . . . . . . . . . . . . . . . . . . 19<br />
MS: P. Houston, R. Hartmann . . . . . . . . . . . . . . . . . . . . . . . . . . . 21<br />
R. HARTMANN:<br />
Discontinuous Galerkin methods for compressible flows: higher<br />
order accuracy, error estimation and adaptivity . . . . . . . . . . 22<br />
17 <strong>BAIL</strong> <strong>2006</strong>
CONTENTS<br />
V. HEUVELINE:<br />
On a new refinement strategy for adaptive hp finite element method 24<br />
J.A. MACKENZIE, A. NICOLA:<br />
A Discontinuous Galerkin Moving Mesh Method for Hamilton-<br />
Jacobi Equations . . . . . . . . . . . . . . . . . . . . . . . . . . 25<br />
S. PEROTTO:<br />
Layer Capturing via Anisotropic Mesh Adaption . . . . . . . . . 27<br />
R. SCHNEIDER, P. JIMACK:<br />
Anisotropic mesh adaption based on a posteriori estimates and<br />
optimisation <strong>of</strong> node positions . . . . . . . . . . . . . . . . . . . 28<br />
MS: Debopam Das, Tapan Sengupta . . . . . . . . . . . . . . . . . . . . . . . 31<br />
M.H. BUSCHMANN, M. GAD-EL-HAK:<br />
Turbulent Bo<strong>und</strong>ary Layers: Reality and Myth . . . . . . . . . . 32<br />
A. NAYAK, D. DAS:<br />
Three-dimesnional Temporal Instability <strong>of</strong> Unsteady Pipe Flow . 35<br />
J. HUSSONG, N. BLEIER, V.V. RAM:<br />
The structure <strong>of</strong> the critical layer <strong>of</strong> a swirling annular flow in<br />
transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37<br />
T.K. SENGUPTA, A. KAMESWARA RAO:<br />
Spatio-temporal growing waves in bo<strong>und</strong>ary-layers by Bromwich<br />
contour integral method . . . . . . . . . . . . . . . . . . . . . . 39<br />
L. SAVIĆ, H. STEINRÜCK:<br />
Asymptotic Analysis <strong>of</strong> the mixed convection flow past a horizontal<br />
plate near the trailing edge . . . . . . . . . . . . . . . . . 41<br />
MS: G.I. Shiskin, P. Hemker . . . . . . . . . . . . . . . . . . . . . . . . . . . 43<br />
D. BRANLEY, A.F. HEGARTY, H. PURTILL, G.I. SHISHKIN:<br />
A Schwarz method for a convection-diffusion problem with a corner<br />
singularity . . . . . . . . . . . . . . . . . . . . . . . . . . . 44<br />
T. LINSS, N. MADDEN:<br />
Layer-adapted meshes for time-dependent reaction-diffusion . . . 47<br />
G.I. SHISHKIN:<br />
Grid Approximation <strong>of</strong> Parabolic Equations with Nonsmooth Initial<br />
Condition in the Presence <strong>of</strong> Bo<strong>und</strong>ary Layers <strong>of</strong> Different<br />
Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48<br />
L.P. SHISHKINA, G.I. SHISHKIN:<br />
A Difference Scheme <strong>of</strong> Improved Accuracy for a Quasilinear<br />
Singularly Perturbed Elliptic Convection-Diffusion Equation in<br />
the Case <strong>of</strong> the Third-Kind Bo<strong>und</strong>ary Condition . . . . . . . . . . 49<br />
I.V. TSELISHCHEVA, G.I. SHISHKIN:<br />
Domain Decomposition Method for a Semilinear Singularly Perturbed<br />
Elliptic Convection-Diffusion Equation with Concentrated<br />
Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51<br />
18 <strong>BAIL</strong> <strong>2006</strong>
CONTENTS<br />
S. HEMAVATHI, S. VALARMATHI:<br />
A parameter-uniform numerical method for a system <strong>of</strong> singularly<br />
perturbed ordinary differential equations . . . . . . . . . . . . . . 53<br />
MS: J. Maubach, I, Tselishcheva . . . . . . . . . . . . . . . . . . . . . . . . . 55<br />
A.F. HEGARTY, S. SIKWILA, G.I. SHISKIN:<br />
An adaptive method for the numerical solution <strong>of</strong> an elliptic convection<br />
diffusion problem . . . . . . . . . . . . . . . . . . . . . 56<br />
M. ANTHONISSEN, I. SEDYKH, J. MAUBACH:<br />
A Convergence Pro<strong>of</strong> <strong>of</strong> Local Defect Correction for Convection-<br />
Diffusion Problems . . . . . . . . . . . . . . . . . . . . . . . . . 57<br />
J. MAUBACH:<br />
On the Difference between Left and Right Preconditioning for<br />
Convection Dominated Convection-Diffusion Problems . . . . . . 58<br />
S. LI, L.P. SHISHKINA, G.I. SHISHKIN:<br />
Parameter-Uniform Method for a Singularly Perturbed Parabolic<br />
Equation Modelling the Black-Scholes equation in the Presence<br />
<strong>of</strong> Interior and Bo<strong>und</strong>ary Layers . . . . . . . . . . . . . . . . . . 59<br />
A.I. ZADORIN:<br />
Numerical Method for the Blasius Equation on an Infinite Interval 61<br />
P. ZEGELING:<br />
An Adaptive Grid Method for the Solar Coronal Loop Model . . . 63<br />
Contributed Presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . 67<br />
F. ALIZARD, J.-CH. ROBINET:<br />
Two-dimensional temporal modes in nonparallel flows . . . . . . 67<br />
TH. ALRUTZ, T. KNOPP:<br />
Near-wall grid adaptation for wall functions . . . . . . . . . . . . 69<br />
TH. APEL, G. MATTHIES:<br />
A family <strong>of</strong> non-conforming finite elements <strong>of</strong> arbitrary order for<br />
the Stokes problem on anisotropic quadrilateral meshes . . . . . . 71<br />
M. BAUSE:<br />
Aspects <strong>of</strong> SUPG/PSPG and GRAD-DIV Stabilized Finite Element<br />
Approximation <strong>of</strong> Compressible Viscous Flow . . . . . . . 72<br />
L. BOGUSLAWSKI:<br />
Sheare Stress Distribution on Sphere Surface at Different Inflow<br />
Turbulence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73<br />
A.CANGIANI, E.H.GEORGOULIS, M. JENSEN:<br />
Continuous-Discontinuous Finite Element Methods for Convection-<br />
Diffusion Problems . . . . . . . . . . . . . . . . . . . . . . . . . 75<br />
C. CLAVERO, J.L. GRACIA, F. LISBONA:<br />
A second order uniform convergent method for a singularly perturbed<br />
parabolic system <strong>of</strong> reaction-diffusion type . . . . . . . . . 77<br />
19 <strong>BAIL</strong> <strong>2006</strong>
CONTENTS<br />
B. EISFELD:<br />
Computation <strong>of</strong> complex compressible aerodynamic flows with a<br />
Reynolds stress turbulence model . . . . . . . . . . . . . . . . . 79<br />
A. FIROOZ, M. GADAMI:<br />
Turbulence Flow for NACA 4412 in Unbo<strong>und</strong>ed Flow and Gro<strong>und</strong><br />
Effect with Different Turbulence Models and Two Gro<strong>und</strong> Conditions:<br />
Fixed and Moving Gro<strong>und</strong> Conditions . . . . . . . . . . 81<br />
S.A. GAPONOV, G.V. PETROV, B.V. SMORODSKY:<br />
Bo<strong>und</strong>ary layer intercation with external disturbances . . . . . . . 85<br />
Z.HAMMOUCH:<br />
Similarity solutions <strong>of</strong> a power-law non-Newtonian laminar bo<strong>und</strong>ary<br />
layer flows . . . . . . . . . . . . . . . . . . . . . . . . . . . 87<br />
M. HAMOUDA, R. TEMAM:<br />
Bo<strong>und</strong>ary layers for the Navier-Stokes equations : asymptotic<br />
analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88<br />
M. HÖLLING, H. HERWIG:<br />
Computation <strong>of</strong> turbulent natural convection at vertical walls using<br />
new wall functions . . . . . . . . . . . . . . . . . . . . . . . 91<br />
A.-M. IL’IN, B.I. SULEIMANOV:<br />
The coefficients <strong>of</strong> inner asymptotic expansions for solutions <strong>of</strong><br />
some singular bo<strong>und</strong>ary value problems . . . . . . . . . . . . . . 93<br />
W.S. ISLAM, V.R. RAGHAVAN:<br />
Numerical Simulation <strong>of</strong> High Sub-critical Reynolds Number Flow<br />
Past a Circular Cylinder . . . . . . . . . . . . . . . . . . . . . . 96<br />
D. KACHUMA, I. SOBEY:<br />
Fast waves during transient flow in an asymmetric channel . . . . 98<br />
A. KAUSHIK, K.K. SHARMA:<br />
A Robust Numerical Approach for Singularly Perturbed Time Delayed<br />
Parabolic Partial Differential Equations . . . . . . . . . . . 100<br />
P. KNOBLOCH:<br />
On methods diminishing spurious oscillations in finite element<br />
solutions <strong>of</strong> convection-diffusion equations . . . . . . . . . . . . 102<br />
T. KNOPP:<br />
Model-consistent universal wall-functions for RANS turbulence<br />
modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104<br />
J.-S. LEU, J.-Y. JANG, Y.-C. CHOU:<br />
Evaporating cooling <strong>of</strong> liquid film along an inclined plate coverd<br />
with a porous layer . . . . . . . . . . . . . . . . . . . . . . . . . 106<br />
V.D. LISEYKIN, Y.V. LIKHANOVA, D.V. PATRAKHIN, I.A. VASEVA:<br />
Application <strong>of</strong> bo<strong>und</strong>ary layer-type functions to comprehensive<br />
grid generation codes . . . . . . . . . . . . . . . . . . . . . . . . 108<br />
20 <strong>BAIL</strong> <strong>2006</strong>
CONTENTS<br />
G. LUBE:<br />
A stabilized finite element method with anisotropic mesh refinement<br />
for the Oseen equations . . . . . . . . . . . . . . . . . . . . 109<br />
H. LÜDEKE:<br />
Detached Eddy Simulation <strong>of</strong> Supersonic Shear Layer Wake Flows 111<br />
K. MANSOUR:<br />
Bo<strong>und</strong>ary Layer Solution For laminar flow through a Loosely<br />
curved Pipe by Using Stokes Expansion . . . . . . . . . . . . . . 113<br />
G. MATTHIES, L. TOBISKA:<br />
Mass conservation <strong>of</strong> finite element methods for coupled flowtransport<br />
problems . . . . . . . . . . . . . . . . . . . . . . . . . 115<br />
J. MAUSS, J. COUSTEIX:<br />
Global Interactive Bo<strong>und</strong>ary Layer (GIBL) for a Channel . . . . . 116<br />
O. MIERKA, D. KUZMIN:<br />
On the implementation <strong>of</strong> turbulence models in incompressible<br />
flow solvers based on a finite element discretization . . . . . . . . 118<br />
K. MORINISHI:<br />
Rarefied Gas Bo<strong>und</strong>ary Layer Predicted with Continuum and Kinetic<br />
Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . 120<br />
A. NASTASE:<br />
Qualitative Analysis <strong>of</strong> the Navier-Stokes Solutions in Vicinity <strong>of</strong><br />
their Critical Lines . . . . . . . . . . . . . . . . . . . . . . . . . 122<br />
F. NATAF, G. RAPIN:<br />
Application <strong>of</strong> the Smith Factorization to Domain Decomposition<br />
Methods for the Stokes equations . . . . . . . . . . . . . . . . . 124<br />
N. NEUSS:<br />
Numerical approximation <strong>of</strong> bo<strong>und</strong>ary layers for rough bo<strong>und</strong>aries 126<br />
M.A. OLSHANSKII:<br />
An Augmented Lagrangian based solver for the low-viscosity incompressible<br />
flows . . . . . . . . . . . . . . . . . . . . . . . . . 128<br />
N. PARUMASUR, J. BANASIAK, J.M. KOZAKIEWICZ:<br />
Numerical and Asymptotic Analysis <strong>of</strong> Singularly Perturbed PDEs<br />
<strong>of</strong> Kinetic Theory . . . . . . . . . . . . . . . . . . . . . . . . . . 130<br />
B. RASUO:<br />
On Bo<strong>und</strong>ary Layer Control in Two-Dimensional Transonic Wind<br />
Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132<br />
H.-G. ROOS:<br />
A Comparison <strong>of</strong> Stabilization Methods for Convection-Diffusion-<br />
Reaction Problems on Layer-Adapted Meshes . . . . . . . . . . . 134<br />
H.-G. ROOS, H. ZARIN:<br />
Discontinuous Galerkin stabilization for convection-diffusion problems<br />
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135<br />
21 <strong>BAIL</strong> <strong>2006</strong>
B. SCHEICHL, A. KLUWICK:<br />
On Turbulent Marginal Separation: How the Logarithmic Law <strong>of</strong><br />
the Wall is Superseded by the Half-Power Law . . . . . . . . . . 136<br />
O. SHISHKINA, C. WAGNER:<br />
Bo<strong>und</strong>ary and Interior Layers in Turbulent Thermal Convection . 138<br />
M. STYNES, L. TOBISKA:<br />
Using rectangular Qp elements in the SDFEM for a convectiondiusion<br />
problem with a bo<strong>und</strong>ary layer . . . . . . . . . . . . . . 140<br />
P. SVÁ ˘CEK:<br />
Numerical Approximation <strong>of</strong> Flow Induced Airfoil Vibrations . . 141<br />
N.V. TARASOVA:<br />
Full asymptotic analysis <strong>of</strong> the Navier-Stokes equations in the<br />
problems <strong>of</strong> gas flows over bodies with large Reynolds number . . 143<br />
C.H. TAI, C.-Y. CHAO, J.-C. LEONG, Q.-S. HONG:<br />
Effects <strong>of</strong> golf ball dimple configuration on aerodynamics, trajectory,<br />
and acoustics . . . . . . . . . . . . . . . . . . . . . . . . . 145<br />
H. TIAN:<br />
Uniformly Convergent Numerical Methods for Singularly Perturbed<br />
Delay Differential Equations . . . . . . . . . . . . . . . . 147<br />
A.I. TOLSTYKH, M.V. LIPAVSKII, E.N. CHIGEREV:<br />
Highly accurate 9th-order schemes and their applications to DNS<br />
<strong>of</strong> thin shear layer instability . . . . . . . . . . . . . . . . . . . . 149<br />
M. VASILIEV:<br />
About unsteady Bo<strong>und</strong>ary Layer on a dihedral angle . . . . . . . 150<br />
A.E.P. VELDMANN:<br />
High-order symmetry-preserving discretization on strongly stretched<br />
grids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152<br />
Z.-H. YANG, Y.-Z. LI, Y. ZHU:<br />
Application <strong>of</strong> Bifurcation Method to Computing Numerical Solutions<br />
<strong>of</strong> Lane-Emden Equation . . . . . . . . . . . . . . . . . . 154<br />
Q. YE:<br />
Numerical simulation <strong>of</strong> turbulent bo<strong>und</strong>ary for stagnation-flow<br />
in the spray-painting process . . . . . . . . . . . . . . . . . . . . 156<br />
Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159<br />
Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164<br />
22 <strong>BAIL</strong> <strong>2006</strong>
Plenary Presentations
KL. GERSTEN: Vom Kochtopf bis zum Fußballspiel (Public Talk)<br />
✬<br />
✫<br />
Öffentlicher Vortrag<br />
am 25. Juli <strong>2006</strong> – 20:00 Uhr<br />
im DLR_School_Lab - Bunsenstraße 10 – 37073 Göttingen<br />
im Rahmen der International Conference Bo<strong>und</strong>ary and Interior Layers <strong>2006</strong> (<strong>BAIL</strong> <strong>2006</strong>)<br />
Vom Kochtopf bis zum Fußballspiel<br />
Episoden zu den weltweiten Wirkungen der Göttinger Strömungsforschung<br />
Pr<strong>of</strong>essor Dipl. Math. Dr.-Ing. Dr.-Ing. E.h. Klaus Gersten<br />
Ruhr-Universität Bochum<br />
Im Vortrag werden unter anderem folgende Fragen erörtert:<br />
� Als Modell <strong>für</strong> ein Herz mit defekten Herzklappen entwickelte der Arzt Dr. Liebau in den fünfziger<br />
Jahren eine ventillose Pumpe. Weshalb funktionierte die Pumpe?<br />
� Wie lässt sich die Bananenflanke beim Fußballspiel physikalisch erklären?<br />
� Kann die Kraftfahrzeug-Aerodynamik von der Flugzeug-Aerodynamik lernen?<br />
� Wie kann der Besitzer eines Automobils mit Schrägheck leicht feststellen, ob sein<br />
Fahrzeug gute aerodynamische Eigenschaften besitzt?<br />
� Warum sind bestimmte bei der Umströmung von Körpern auftretende Strömungsstrukturen je nach<br />
Anwendung erwünscht (Überschallflugzeug) oder unerwünscht (Automobil)?<br />
� Welches <strong>für</strong> die Göttinger Strömungsforschung charakteristische Konzept liegt allen bisher<br />
genannten Fragen zugr<strong>und</strong>e?<br />
Zur Person:<br />
Pr<strong>of</strong>essor Gersten, Jahrgang 1929, studierte Mathematik <strong>und</strong> Physik an der TH<br />
Braunschweig. Als Assistent arbeitete er am <strong>Institut</strong> <strong>für</strong> Strömungsmechanik der TH<br />
Braunschweig unter der Leitung von Pr<strong>of</strong>essor Hermann Schlichting. Nach seiner Promotion<br />
zum Dr.-Ing. leitete er die Abteilung Theoretische Aerodynamik <strong>und</strong> wurde anschließend<br />
Stellvertretender Direktor des <strong>Institut</strong>es <strong>für</strong> Aerodynamik der Deutschen Forschungsanstalt<br />
<strong>für</strong> Luftfahrt (DFL) Braunschweig. Nach seiner Habilitation <strong>für</strong> das Fach Strömungsmechanik<br />
lehrte er dreißig Jahre als Ordentlicher Pr<strong>of</strong>essor an der Ruhr-Universität Bochum. Während<br />
dieser Zeit war er als Visiting Pr<strong>of</strong>essor an der University <strong>of</strong> Rio de Janeiro, Brazil, der Nagoya<br />
University, Japan <strong>und</strong> an der University <strong>of</strong> Arizona, Tucson, USA tätig. 1992 wurde er zum<br />
Dr.-Ing. E.h. der Universität Essen ernannt. Er ist Mitglied der Österreichischen Akademie der<br />
Wissenschaften in Wien. 2003 wurde Pr<strong>of</strong>essor Gersten der Ludwig-Prandtl-Ring, die<br />
höchste Auszeichnung im Bereich der Flugwissenschaften, von der Deutschen Gesellschaft<br />
<strong>für</strong> Luft- <strong>und</strong> Raumfahrt Lilienthal-Oberth e.V. (DGLR) verliehen.<br />
Kontakt:<br />
DLR, Dr. H. J. Heinemann<br />
0551- 709 2108, hajo.heinemann@dlr.de<br />
Universität Göttingen, Pr<strong>of</strong>. Dr. G. Lube<br />
0551- 39 4503, lube@math.uni-goettingen.de<br />
Speaker: GERSTEN, KL. 3 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
P. HOUSTON: Discontinuous Galerkin Finite Element Methods for CFD: A Posteriori<br />
Error Estimation and Adaptivity<br />
✬<br />
✫<br />
Discontinuous Galerkin Finite Element Methods for CFD: A Posteriori Error Estimation and<br />
Adaptivity<br />
Paul Houston<br />
School <strong>of</strong> Mathematical Sciences, University <strong>of</strong> Nottingham, UK.<br />
In recent years there has been considerable interest in the mathematical design and<br />
practical application <strong>of</strong> nonconforming finite element methods that are based on discontinuous<br />
piecewise polynomial approximation spaces; such approaches are referred to as<br />
discontinuous Galerkin (DG) methods. The main advantages <strong>of</strong> these methods lie in their<br />
conservation properties, their ability to treat a wide range <strong>of</strong> problems within the same<br />
unified framework, and their great flexibility in the mesh-design. Indeed, DG methods can<br />
easily handle non-matching grids and non-uniform, even anisotropic, polynomial approximation<br />
degrees, which makes them ideally suited for application within adaptive finite<br />
element s<strong>of</strong>tware.<br />
In this talk we present an overview <strong>of</strong> some recent developments concerning the a posteriori<br />
error analysis and adaptive mesh design <strong>of</strong> h– and hp–version DG finite element<br />
methods for the numerical approximation <strong>of</strong> second–order elliptic bo<strong>und</strong>ary value problems.<br />
In particular, we consider the derivation <strong>of</strong> computable upper and lower bo<strong>und</strong>s<br />
on the error measured in terms <strong>of</strong> an appropriate (mesh–dependent) energy norm. The<br />
pro<strong>of</strong>s <strong>of</strong> the upper bo<strong>und</strong>s are based on rewriting the method in a non-consistent manner<br />
using polynomial lifting operators and employing an appropriate decomposition result<br />
for the <strong>und</strong>erlying discontinuous spaces. Applications to the numerical approximation<br />
<strong>of</strong> second–order linear elliptic problems, including Poisson’s equation, Stokes equations,<br />
nearly–incompressible elasticity, and the time harmonic eddy current problem, as well<br />
as second–order quasilinear bo<strong>und</strong>ary value problems, which typically arise in the modelling<br />
<strong>of</strong> non-Newtonian flows, will be considered. Numerical experiments confirming the<br />
reliability and efficiency <strong>of</strong> the proposed a posteriori error bo<strong>und</strong>s within an automatic<br />
mesh refinement algorithm employing both local mesh subdivision and local polynomial<br />
enrichment will be presented.<br />
This research has been carried out in collaboration with Dominik Schötzau (University<br />
<strong>of</strong> British Columbia), Thomas Wihler (University <strong>of</strong> Minnesota), and Ilaria Perugia<br />
(University <strong>of</strong> Pavia).<br />
References<br />
[1] P. Houston, I. Perugia, and D. Schötzau. An posteriori error indicator for discontinuous<br />
Galerkin discretizations <strong>of</strong> H(curl)–elliptic partial differential equations.<br />
Submitted to IMA J. Numer. Anal.<br />
[2] P. Houston, D. Schötzau, and T. Wihler. Energy norm a posteriori error estimation<br />
for mixed discontinuous Galerkin approximations <strong>of</strong> the Stokes problem. J. Sci.<br />
Comp., 22(1):357–380, 2005.<br />
[3] P. Houston, D. Schötzau, and T. Wihler. An hp-adaptive mixed discontinuous<br />
Galerkin FEM for nearly incompressible linear elasticity. Comput. Methods Appl.<br />
Mech. Engrg., (to appear).<br />
[4] P. Houston, D. Schötzau, and T. P. Wihler. Energy norm a posteriori error estimation<br />
<strong>of</strong> hp-adaptive discontinuous Galerkin methods for elliptic problems. Math.<br />
Models Methods Appl. Sci., (to appear).<br />
1<br />
Speaker: HOUSTON, P. 4 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
L. LESSHAFFT, P. HUERRE, P. SAGAUT, M. TERRACOL: Dynamics <strong>of</strong> Hot Jets: A<br />
Numerical and Theoretical Study<br />
✬<br />
✫<br />
<strong>BAIL</strong> <strong>2006</strong><br />
DYNAMICS OF HOT JETS: A NUMERICAL AND THEORETICAL STUDY<br />
Lutz Lesshafft 1.2 , Patrick Huerre 1 , Pierre Sagaut 3 and Marie Terracol 2<br />
1Laboratoire d'Hydrodynamique (LadHyX), CNRS – École Polytechnique, F-91128 Palaiseau, France<br />
2ONERA, Department <strong>of</strong> CFD and Aeroacoustics, 29 avenue de la Division Leclerc, F-92322<br />
Châtillon, France<br />
3Laboratoire de Modélisation en Mécanique, Université Pierre et Marie Curie, Boîte 162, 4 place<br />
Jussieu, F-75252 Paris cedex 05, France<br />
Since the experiments <strong>of</strong> Monkewitz, Bechert, Barsikow & Lehmann (1990), sufficiently hot circular<br />
jets have been known to give rise to self-sustained synchronized oscillations induced by a locally<br />
absolutely unstable region. Numerical simulations (Lesshafft, Huerre, Sagaut & Terracol 2005, <strong>2006</strong>)<br />
have been carried out in order to determine if such synchronized states correspond to a nonlinear<br />
global mode <strong>of</strong> the <strong>und</strong>erlying basic flow, as predicted in the context <strong>of</strong> Ginzburg-Landau amplitude<br />
evolution equations by Couairon & Chomaz (1997, 1999), Pier, Huerre, Chomaz & Couairon (1998)<br />
and Pier, Huerre & Chomaz (2001). In the presence <strong>of</strong> a pocket <strong>of</strong> absolute instability embedded<br />
within a convectively unstable jet, global oscillations are generated by a steep nonlinear front located<br />
at the upstream station <strong>of</strong> marginal absolute instability. The global frequency is given, within 10%<br />
accuracy, by the absolute frequency at the front location. For jet flows displaying absolutely unstable<br />
inlet conditions, global instability is observed to arise if the streamwise extent <strong>of</strong> the absolutely<br />
unstable region is sufficiently large: While local absolute instability sets in for ambient-to-jet<br />
temperature ratios S < 0.453, global modes only appear for S < 0.325. In agreement with theoretical<br />
predictions, the selected frequency near the onset <strong>of</strong> global instability coincides with the absolute<br />
frequency at the inlet, provided that the ratio <strong>of</strong> jet radius R to shear layer momentum thickness θ is<br />
sufficiently small (R/ θ ∼ 10, thick shear layers). For thinner shear layers (R/ θ ∼ 25), the numerically<br />
determined global frequency gradually departs from the inlet absolute frequency.<br />
References<br />
Couairon, A. & Chomaz, J.-M. 1997 Absolute and convective instabilities, front velocities and global<br />
modes in nonlinear systems. Physica D 108, 236-276<br />
Couairon, A. & Chomaz, J.-M. 1999 Fully nonlinear global modes in slowly varying flows. Phys.<br />
Fluids 11, 3688-3703.<br />
Lesshafft, L., Huerre, P., Sagaut, P. & Terracol, M. 2005 Global modes in hot jets, absolute /<br />
convective instabilities and acoustic feedback. 10 pages 11th AIAA / CEAS Aeroacoustics Conference,<br />
Monterey, USA, May 23-25, 2005.<br />
Lesshaft, L., Huerre, P., Sagaut, P. & Terracol, M. <strong>2006</strong> Nonlinear global modes in hot jets. J. Fluid<br />
Mech., in press.<br />
Monkewitz, P. A., Bechert, D. W., Barsikow, B & Lehmann, B. 1990 Self-excited oscillations and<br />
mixing in a heated ro<strong>und</strong> jet. J. Fluid Mech. 213, 611-639.<br />
Speaker: HUERRE, P. 5 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
M. STYNES: Convection-diffusion problems, SDFEM/SUPG and a priori meshes<br />
✬<br />
✫<br />
Convection-diffusion problems, SDFEM/SUPG<br />
and a priori meshes<br />
Martin Stynes ∗<br />
Abstract<br />
Linear convection-diffusion problems will be briefly described (cf. [15]). The nature and<br />
structure <strong>of</strong> their solutions will be examined, including the main features <strong>of</strong> exponential<br />
and characteristic/parabolic layers. Next, Shishkin meshes will be described and discussed<br />
[4, 11, 15]; these piecewise-uniform meshes are suited to the numerical solution <strong>of</strong> convectiondiffusion<br />
problems with bo<strong>und</strong>ary layers — yet they do not fully resolve these layers.<br />
Then the Streamline Diffusion Finite Element Method (SDFEM), which is also known<br />
as the Streamline-Upwinded Petrov-Galerkin method (SUPG), will be introduced. Since<br />
its inception [6] in 1979, this method has been the subject <strong>of</strong> a huge number <strong>of</strong> theoretical<br />
analyses and numerical investigations that continue to this day; see the references in [12, 13,<br />
15]. The main body <strong>of</strong> the talk is a comprehensive survey <strong>of</strong> the application <strong>of</strong> the method<br />
to convection-diffusion problems, including discussions <strong>of</strong> its strengths and weaknesses, and<br />
presenting recent theoretical results. In particular the following topics will be addressed:<br />
References<br />
• stability and the choice <strong>of</strong> SDFEM parameter [1, 5, 12]<br />
• quasioptimality [3, 14]<br />
• accuracy on general meshes [9, 18]<br />
• accuracy on Shishkin meshes [5, 10, 16, 17]<br />
• variants <strong>of</strong> SDFEM:<br />
(i) nonconforming spaces [7]<br />
(ii) nonlinear shock-capturing modifications <strong>of</strong> SDFEM [2, 8]<br />
— the references given here are only a subset <strong>of</strong> those available.<br />
[1] J. E. Akin and T. E. Tezduyar. Calculation <strong>of</strong> the advective limit <strong>of</strong> the SUPG stabilization<br />
parameter for linear and higher-order elements. Comput. Methods Appl. Mech. Engrg.,<br />
193:1909–1922, 2004.<br />
[2] E. Burman and A. Ern. Stabilized Galerkin approximation <strong>of</strong> convection-diffusion-reaction<br />
equations: discrete maximum principle and convergence. Math. Comp., 74:1637–1652 (electronic),<br />
2005.<br />
[3] L. Chen and J. Xu. An optimal streamline diffusion finite element method for a singularly<br />
perturbed problem. In Z.C Shi, Z. Chen, T. Tang, and D. Yu, editors, Recent Advances in<br />
Adaptive Computation, volume 383 <strong>of</strong> Contemporary Mathematics, pages 236–246. American<br />
Mathematical Society, 2005.<br />
∗ Mathematics Department, National University <strong>of</strong> Ireland, Cork, Ireland<br />
1<br />
Speaker: STYNES, M. 6 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
M. STYNES: Convection-diffusion problems, SDFEM/SUPG and a priori meshes<br />
✬<br />
✫<br />
[4] P.A. Farrell, A.F. Hegarty, J.J. Miller, E. O’Riordan, and G.I. Shishkin. Robust Computational<br />
Techniques for Bo<strong>und</strong>ary Layers. Chapman & Hall/CRC, Boca Raton, 2000.<br />
[5] S. Franz and T. Linß. Superconvergence analysis <strong>of</strong> Galerkin FEM and SDFEM for elliptic<br />
problems with characteristic layers. Technical Report MATH-NM-03-<strong>2006</strong>, <strong>Institut</strong> <strong>für</strong><br />
<strong>Numerische</strong> Mathematik, Technische Universität Dresden, <strong>2006</strong>.<br />
[6] T.J.R. Hughes and A.N. Brooks. A multidimensional upwind scheme with no crosswind<br />
diffusion. In T.J.R. Hughes, editor, Finite Element Methods for Convection Dominated<br />
Flows, volume 34 <strong>of</strong> AMD. ASME, New York, 1979.<br />
[7] P. Knobloch and L. Tobiska. The P mod<br />
1<br />
element: a new nonconforming finite element for<br />
convection-diffusion problems. SIAM J. Numer. Anal., 41:436–456 (electronic), 2003.<br />
[8] T. Knopp, G. Lube, and G. Rapin. Stabilized finite element methods with shock capturing<br />
for advection-diffusion problems. Comput. Methods Appl. Mech. Engrg., 191:2997–3013,<br />
2002.<br />
[9] N. Kopteva. How accurate is the streamline-diffusion FEM inside characteristic (bo<strong>und</strong>ary<br />
and interior) layers? Comput. Methods Appl. Mech. Engrg., 193:4875–4889, 2004.<br />
[10] T. Linß and M. Stynes. Numerical methods on Shishkin meshes for linear convectiondiffusion<br />
problems. Comput. Methods Appl. Mech. Engrg., 190:3527–3542, 2001.<br />
[11] J.J.H. Miller, E. O’Riordan, and G.I. Shishkin. Solution <strong>of</strong> singularly perturbed problems<br />
with ε-uniform numerical methods–introduction to the theory <strong>of</strong> linear problems in one and<br />
two dimensions. World Scientific, Singapore, 1996.<br />
[12] H.-G. Roos, M. Stynes, and L. Tobiska. Numerical methods for singularly perturbed differential<br />
equations, volume 24 <strong>of</strong> Springer Series in Computational Mathematics. Springer-<br />
Verlag, Berlin, 1996.<br />
[13] H.-G. Roos, M. Stynes, and L. Tobiska. Numerical methods for singularly perturbed differential<br />
equations. Springer Series in Computational Mathematics. Springer-Verlag, Berlin,<br />
Second edition, (to appear).<br />
[14] G. Sangalli. Quasi optimality <strong>of</strong> the SUPG method for the one-dimensional advectiondiffusion<br />
problem. SIAM J. Numer. Anal., 41:1528–1542 (electronic), 2003.<br />
[15] M. Stynes. Steady-state convection-diffusion problems. Acta Numer., 14:445–508, 2005.<br />
[16] M. Stynes and L. Tobiska. The SDFEM for a convection-diffusion problem with a bo<strong>und</strong>ary<br />
layer: optimal error analysis and enhancement <strong>of</strong> accuracy. SIAM J. Numer. Anal., 41:1620–<br />
1642, 2003.<br />
[17] M. Stynes and L. Tobiska. Using rectangular Qp elements in the SDFEM for a convectiondiffusion<br />
problem with a bo<strong>und</strong>ary layer. Technical Report 08-<strong>2006</strong>, Faculty <strong>of</strong> Mathematics,<br />
Otto-von-Guericke-Universität, Magdeburg, <strong>2006</strong>.<br />
[18] G. Zhou. How accurate is the streamline diffusion finite element method? Math. Comp.,<br />
66:31–44, 1997.<br />
Speaker: STYNES, M. 7 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
V. GRAVEMEIER, S. LENZ, W.A. WALL: Variational Multiscale Methods for incompressible<br />
flows<br />
✬<br />
✫<br />
1. Introduction<br />
Variational Multiscale Methods for incompressible flows<br />
V. Gravemeier, S. Lenz & W.A. Wall<br />
Chair for Computational Mechanics<br />
Technische Universität München<br />
Boltzmannstr. 15, D-85747 Garching b. München<br />
http://www.lnm.mw.tum.de<br />
(vgravem,lenz,wall)@lnm.mw.tum.de<br />
The numerical simulation <strong>of</strong> incompressible flows governed by the Navier-Stokes equations requires<br />
to deal with subgrid phenomena. Particularly in turbulent flows, the scale spectra are<br />
notably widened and need to be handled adequately to get a reasonable numerical solution.<br />
Separating the complete scale range into subranges enables a different treatment <strong>of</strong> any <strong>of</strong> these<br />
subranges. In this talk, we will present the general framework <strong>of</strong> a two- and a three-scale separation<br />
<strong>of</strong> the incompressible Navier-Stokes equations based on the variational multiscale method<br />
as proposed in [Hughes et al. (2000)] and [Collis (2001)]. In a two-scale separation, resolved<br />
and unresolved scales are distinguished, and in a three-scale separation, large resolved scales,<br />
small resolved scales, and unresolved scales are differentiated. After having presented the general<br />
framework, three different approaches to numerical realizations will be addressed (i.e., a<br />
global, a local, and a new residual-based approach). A comprehensive overview may be fo<strong>und</strong><br />
in [Gravemeier (<strong>2006</strong>b)].<br />
2. The variational multiscale framework<br />
A variational form <strong>of</strong> the incompressible Navier-Stokes equations reads<br />
BNS (v,q;u,p) = (v,f) Ω ∀(v,q) ∈ Vup (1)<br />
where Vup denotes the combined form <strong>of</strong> the weighting function spaces for velocity and pressure<br />
in the sense that Vup := Vu × Vp.<br />
In a three-scale separation, which will be focused on in the present abstract, the solution<br />
functions are separated as<br />
u = u + u ′ + û, p = p + p ′ + ˆp, (2)<br />
where (·), (·) ′ , and ˆ (·) denote the large resolved, small resolved, and unresolved scales, respectively.<br />
The weighting functions are separated accordingly. Due to the linearity <strong>of</strong> the weighting<br />
functions, the variational equation (1) may now be decomposed into a system <strong>of</strong> three variational<br />
equations reading<br />
� � ′ ′<br />
BNS v,q;u + u + û,p + p + ˆp = (v,f)Ω ∀(v,q) ∈ Vup (3)<br />
� � � �<br />
′ ′ ′ ′ ′<br />
BNS v ,q ;u + u + û,p + p + ˆp = v ,f ∀ Ω � v ′ ,q ′� ∈ V ′ up (4)<br />
� �<br />
′ ′ ˆv, ˆq;u + u + û,p + p + ˆp = (ˆv,f)Ω ∀(ˆv, ˆq) ∈ ˆ Vup (5)<br />
BNS<br />
Furthermore, it is assumed that the direct influence <strong>of</strong> the unresolved scales on the large resolved<br />
scales is close to zero, relying on a clear separation <strong>of</strong> the large-scale space and the space <strong>of</strong><br />
unresolved scales. This leads to a simplified equation system.<br />
1<br />
Speaker: WALL, W.A. 8 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
V. GRAVEMEIER, S. LENZ, W.A. WALL: Variational Multiscale Methods for incompressible<br />
flows<br />
✬<br />
✫<br />
It is not intended to resolve anything called unresolved a priori. Taking into account the<br />
effect <strong>of</strong> the unresolved scales onto the small scales is the only desire. Some alternatives lend<br />
themselves for this purpose, but the focus in this talk will be on the subgrid viscosity approach<br />
as a usual and well-established way <strong>of</strong> taking into account the effect <strong>of</strong> unresolved scales in<br />
the traditional LES. In the variational multiscale approach to LES, the subgrid viscosity term<br />
directly acts only on the small resolved scales. Indirect influence on the large resolved scales,<br />
however, is ensured due to the coupling <strong>of</strong> the large- and the small-scale equations.<br />
3. Practical methods<br />
At this stage, it should be pointed out that the variational multiscale method is a theoretical<br />
framework for the separation <strong>of</strong> scales. Thus, it is essential to develop corresponding practical<br />
implementations by incorporating the variational multiscale framework into a specific numerical<br />
method. For such practical methods, it is crucial that the aforementioned separation <strong>of</strong> the<br />
different scale groups is actually achieved. Implementations <strong>of</strong> the three-scale separation have<br />
already been done within continuous Galerkin finite element methods, discontinuous Galerkin<br />
finite element methods, finite volume methods, finite difference methods, and spectral methods.<br />
According to the numerical treatment <strong>of</strong> the smaller <strong>of</strong> the resolved scales, a global (see,<br />
e.g., [Gravemeier (<strong>2006</strong>a)]) and a local (see, e.g., [Gravemeier et al. (2005)]) approach may be<br />
distinguished.<br />
Recently [Calo (2005)], a new residual-based approach has been developed where only resolved<br />
and unresolved scales are distinguished (i.e., a two-scale separation). This new concept<br />
approxmiates the unresolved scales by analytical expressions. It may be considered an<br />
advanced stabilized method which takes into account the nonlinear nature <strong>of</strong> the Navier-Stokesequations.<br />
Our results obtained with the residual-based approach are about to be published in<br />
[Lenz & Wall (<strong>2006</strong>)].<br />
All three approaches (i.e., the global, the local, and the residual-based approach) will be<br />
presented together with numerical results in this talk.<br />
References<br />
[Calo (2005)] Calo, V.M. 2005 Residual-based Multiscale Turbulence Modeling: Finite Volume<br />
Simulations <strong>of</strong> Bypass Transition. PhD thesis, Department <strong>of</strong> Civil and Environmental<br />
Engineering, Stanford University.<br />
[Collis (2001)] Collis, S.S. 2001 Monitoring unresolved scales in multiscale turbulence modeling.<br />
Phys. Fluids 13, 1800-1806.<br />
[Gravemeier (<strong>2006</strong>a)] Gravemeier, V. <strong>2006</strong> Scale-separating operators for variational multiscale<br />
large eddy simulation <strong>of</strong> turbulent flows. J. Comp. Phys. 212, 400-435.<br />
[Gravemeier (<strong>2006</strong>b)] Gravemeier, V. <strong>2006</strong> The variational multiscale method for laminar and<br />
turbulent flow. Arch. Comp. Meth. Engrg. , in press.<br />
[Gravemeier et al. (2005)] Gravemeier, V., Wall, W.A. and Ramm, E. 2005 Large eddy<br />
simulation <strong>of</strong> turbulent incompressible flows by a three-level finite element method Int. J.<br />
Numer. Meth. Fluids 48, 1067-1099.<br />
[Hughes et al. (2000)] Hughes, T. J. R., Mazzei, L. & Jansen, K. E. 2000 Large eddy<br />
simulation and the variational multiscale method. Comput. Visual. Sci. 3, 47-59.<br />
[Lenz & Wall (<strong>2006</strong>)] Lenz, S. and Wall, W.A. <strong>2006</strong> A residual-based variational multiscale<br />
method and its application to turbulent channel flow. To be submitted to Theoret. Comput.<br />
Fluid Dyn.<br />
Speaker: WALL, W.A. 9 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
Minisymposia
Speaker:<br />
N. Kopteva, M. Stynes, E. O’Riordan<br />
Robust methods for nonlinear singularly perturbed differential equations<br />
This minisymposium is concerned with nonlinear singularly perturbed<br />
differential equations such as semilinear reaction-diffusion problems,<br />
quasilinear parabolic convection-diffusion equations, flows in porous<br />
media, and the modelling <strong>of</strong> catalytic chemical reactions and <strong>of</strong> turbulence.<br />
The talks deal with methods that are ”robust” for such problems,<br />
i.e., that yield accurate approximations <strong>of</strong> the solution for a broad range<br />
<strong>of</strong> values <strong>of</strong> the singular perturbation parameter. This includes numerical<br />
methods for which numerical experiments demonstrate robustness<br />
for a wide range <strong>of</strong> values <strong>of</strong> the parameter, even though no theoretical<br />
pro<strong>of</strong> <strong>of</strong> convergence exists.<br />
• Eugene O’Riordan: A singular perturbation problem arising in the modelling <strong>of</strong><br />
plasma sheaths<br />
• Grigory I. Shishkin: A posteriori adapted meshes in the approximation <strong>of</strong> singularly<br />
perturbed quasilinear parabolic convection-diffusion equations<br />
• Iuliana Stanculescu: Numerical Analysis <strong>of</strong> Approximate Deconvolution Models<br />
<strong>of</strong> Turbulence<br />
• Hong Wang: An Eulerian-Langrangian Formulation for Compositional Flow in<br />
Porous Media
R.K. DUNNE, E. O’RIORDAN, M.M. TURNER: A singular perturbation problem<br />
arising in the modelling <strong>of</strong> plasma sheaths<br />
✬<br />
✫<br />
A singular perturbation problem arising in the<br />
modelling <strong>of</strong> plasma sheaths ∗<br />
R. K. Dunne † , E. O’Riordan ‡ and M. M. Turner §<br />
Abstract<br />
Consider the interaction <strong>of</strong> a flowing plasma with a planar Langmuir probe [2]. Assume<br />
that the plasma flows in the plane <strong>of</strong> the probe surface and that the plasma consists<br />
solely <strong>of</strong> positive ions with density n+ and electrons with density ne. Downstream <strong>of</strong><br />
the probe, the ions are moving with a velocity <strong>of</strong> u = (ui, uv + uF ) and (u0, uF ) is<br />
the flow velocity <strong>of</strong> the ions upstream <strong>of</strong> the probe. We wish to consider the influence<br />
<strong>of</strong> the probe on the flow <strong>of</strong> the ions. Let X be the horizontal distance to the right <strong>of</strong><br />
the probe and Y the distance along the probe (from the tip <strong>of</strong> the probe). Assuming<br />
a collision-less plasma and that the ions are cold, the continuity equations for the ion<br />
density and momentum are [2]<br />
∂n+<br />
∂t + ∇ · (n+u) = 0<br />
�∂u<br />
m+n+<br />
∂t + (u · ∇)u� = en+E<br />
where E = (Ex, Ey) = −∇ ˜ φ is the electric field and m+ is the mass <strong>of</strong> the ions. Our<br />
interest is in the steady state case and if uF >> uv, we disregard terms involving uv.<br />
Hence this system is approximated with the system<br />
∂<br />
∂X (n+ui)<br />
∂n+<br />
+ uF = 0<br />
∂Y<br />
∂ui ∂ui e<br />
ui + uF = EX<br />
∂X ∂Y m+<br />
where (if EX >> EY ) then the electric field is determined from solving Poisson’s equation<br />
− ∂EX<br />
∂X = ∂2 ˜ φ<br />
∂X 2 = e(n+ − ne)<br />
.<br />
Since me
R.K. DUNNE, E. O’RIORDAN, M.M. TURNER: A singular perturbation problem<br />
arising in the modelling <strong>of</strong> plasma sheaths<br />
✬<br />
✫<br />
where Te is the electron temperature, k is Boltzmann’s constant, ɛ0 is the permittivity<br />
<strong>of</strong> free space and e is the electron charge.<br />
In a similar fashion to the scaling <strong>of</strong> the variables used in [3], we introduce the nondimensional<br />
independent variables x, y and the non-dimensional dependent variables<br />
n, u and φ, which are defined as follows:<br />
n = n+<br />
n0<br />
u = ui<br />
cs<br />
φ = e ˜ φ<br />
, x =<br />
kTe<br />
X<br />
L<br />
y = Y cs<br />
uF L<br />
where the ion so<strong>und</strong> speed cs and the electron Debyre length λD are defined by<br />
c 2 s = kTe<br />
, λ<br />
m+<br />
2 D = ɛ0kTe<br />
.<br />
n0e2 The length L is a distance sufficiently far from the probe so that the effect <strong>of</strong> the probe<br />
on the plasma at this distance is negligible. Introduce the small parameter<br />
ε = λD<br />
L .<br />
After reformulating the problem with the above transformations and formulating<br />
suitable bo<strong>und</strong>ary and initial conditions we propose to examine the related mathematical<br />
problem :<br />
Find (u(x, y), n(x, y), φ(x, y)) which satisfy the following system <strong>of</strong> differential equations<br />
in the domain (x, y) ∈ (0, 1) × (0, T ]<br />
∂n ∂(nu)<br />
+ = 0,<br />
∂y ∂x<br />
(x, y) ∈ [0, 1) × (0, T ]<br />
∂u<br />
+ u∂u = −∂φ ,<br />
∂y ∂x ∂x<br />
(x, y) ∈ [0, 1) × (0, T ]<br />
ε 2 ∂2 φ<br />
∂x 2 = eφ − n, (x, y) ∈ (0, 1) × (0, T ]<br />
subject to the following set <strong>of</strong> bo<strong>und</strong>ary and initial conditions<br />
φ(0, y) = −A, φ(1, y) = 0, y ≥ 0 φ(x, 0) = φ0(x), 0 ≤ x ≤ 1<br />
n(x, 0) = 1, 0 ≤ x ≤ 1; ny(1, y) = −(nux)(1, y), y ≥ 0<br />
u(x, 0) = ũ0, 0 ≤ x ≤ 1; uy(1, y) = −φx(1, y), y ≥ 0.<br />
The parameters ũ0 and A are assumed to be known and the initial condition φ0(x) is<br />
chosen so that ε 2 φ ′′<br />
0(x) = e φ0(x) − 1, φ0(0) = −A, φ0(1) = 0.<br />
Due to the presence <strong>of</strong> the singular perturbation parameter ε, layers or sheaths<br />
appear in the solutions. The system is discretized using simple upwinding and a special<br />
piecewise-uniform Shishkin-type mesh [1]. Numerical results are presented to display<br />
the robustness <strong>of</strong> the numerical algorithm with respect to ε.<br />
References<br />
[1] P. A. Farrell, A.F. Hegarty, J. J. H. Miller, E. O’Riordan and G. I. Shishkin, Robust<br />
Computational Techniques for Bo<strong>und</strong>ary Layers, Chapman and Hall/CRC Press,<br />
Boca Raton, U.S.A., (2000).<br />
[2] M. A. Lieberman and A. J. Lichtenberg, Principles <strong>of</strong> plasma discharges and materials<br />
processing, Wiley and sons, (1994).<br />
[3] H. Liu and M. Slemrod, KDV Dynamics in the plasma-sheath transition, Appl.<br />
Math. Lett., 17 (2004) 401-419.<br />
2<br />
Speaker: O’RIORDAN, E. 15 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
G.I. SHISHKIN: A posteriori adapted meshes in the approximation <strong>of</strong> singularly<br />
perturbed quasilinear parabolic convection-diffusion equations<br />
✬<br />
✫<br />
A posteriori adapted meshes in the approximation<br />
<strong>of</strong> singularly perturbed quasilinear parabolic<br />
convection-diffusion equations ∗<br />
Grigory I. Shishkin<br />
A Dirichlet problem on a segment for a quasilinear parabolic<br />
convection-diffusion equation with a small (perturbation) parameter<br />
ε multiplying the highest derivative is considered. For this<br />
problem, a solution <strong>of</strong> the classical finite difference scheme on a<br />
uniform mesh converges only <strong>und</strong>er the condition h ≪ ε, where<br />
h is the step-size <strong>of</strong> the space mesh; moreover, the order <strong>of</strong> convergence<br />
in x is O � ε N −1� , where N + 1 is the number <strong>of</strong> nodes<br />
in the uniform mesh with respect to x.<br />
To improve the accuracy <strong>of</strong> the approximate solution, we apply<br />
a posteriori sequential procedure <strong>of</strong> grid refinement in the<br />
subdomains that are defined by the gradient <strong>of</strong> solutions <strong>of</strong> intermediate<br />
discrete problems. The correction <strong>of</strong> the grid solutions<br />
is performed only on these subdomains, where uniform meshes<br />
are used. We construct a difference scheme that converges ”almost<br />
ε-uniformly”, i.e., with an error weakly depending on the<br />
parameter ε.<br />
�<br />
The convergence rate <strong>of</strong> the constructed scheme is O<br />
where N1 + 1 and N0 + 1 are the numbers <strong>of</strong> mesh points with<br />
respect to x and t, respectively, ν is an arbitrary number from<br />
(0, 1]. Thus, the scheme on a posteriori adapted meshes converges<br />
<strong>und</strong>er the condition N −1 ≪ εν , which is essentially weaker<br />
in comparison with the scheme on uniform meshes.<br />
ε −ν N −1<br />
1<br />
+ N −1/2<br />
1<br />
∗ This research was supported in part by the Russian Fo<strong>und</strong>ation for Basic Research<br />
(grant No 04-01-00578, 04–01–89007–NWO a), by the Dutch Research Organisation NWO<br />
<strong>und</strong>er grant No 047.016.008 and by the Boole Centre for Research in Informatics, National<br />
University <strong>of</strong> Ireland, Cork.<br />
2<br />
+ N −1<br />
�<br />
0 ,<br />
Speaker: SHISHKIN, G.I. 16 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
G.I. SHISHKIN: A posteriori adapted meshes in the approximation <strong>of</strong> singularly<br />
perturbed quasilinear parabolic convection-diffusion equations<br />
✬<br />
✫<br />
A scheme on a posteriori adapted meshes in the case <strong>of</strong> a<br />
linear problem is considered in [1].<br />
References<br />
[1] G.I. Shishkin, A posteriori adapted (to the solution gradient)<br />
grids in the approximation <strong>of</strong> singularly perturbed<br />
convection-diffusion equations, Vychisl. Tekhnol. (Computational<br />
Technologies), 6 (1), 72-87 (2001) (in Russian).<br />
Speaker: SHISHKIN, G.I. 17 <strong>BAIL</strong> <strong>2006</strong><br />
3<br />
✩<br />
✪
W. LAYTON, I. STANCULESCU: Numerical Analysis <strong>of</strong> Approximate Deconvolution<br />
Models <strong>of</strong> Turbulence<br />
✬<br />
✫<br />
Numerical Analysis <strong>of</strong> Approximate Deconvolution Models <strong>of</strong><br />
Turbulence<br />
William Layton ∗ and Iuliana Stanculescu †<br />
Abstract<br />
If the NSE are averaged with a local, spacial, convolution type filter the resulting<br />
system is not closed due to the term g ∗ (uu). A deconvolution operator GN is one<br />
which satisfies:<br />
u = GN(g ∗ u) + O(δ 2N+2 ) (0.1)<br />
where δ is the filter width. This yields the closure method:<br />
g ∗ (uu) = g ∗ (GN(g ∗ u)GN(g ∗ u)) + O(δ 2N+2 ) (0.2)<br />
We will review several solutions to the ill-possed deconvolution problem, present<br />
an ”optimal” deconvolution procedure and present numerical analysis and numerical<br />
experiments with it.<br />
∗<br />
Department <strong>of</strong> Mathematics, University <strong>of</strong> Pittsburgh, Pittsburgh, PA,15260, U.S.A.; email:<br />
wjl@pitt.edu, www.math.pitt.edu/˜wjl<br />
†<br />
Department <strong>of</strong> Mathematics, University <strong>of</strong> Pittsburgh, Pittsburgh, PA,15260, U.S.A.; email:<br />
ius1@pitt.edu, www.math.pitt.edu/˜ius1<br />
Speaker: STANCULESCU, I. 18 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
H. WANG: A Component-Based Eulerian-Lagrangian Formulation for Compositional<br />
Flow in Porous Media<br />
✬<br />
✫<br />
A Component-Based Eulerian-Lagrangian Formulation<br />
for Compositional Flow in Porous Media<br />
Hong Wang ∗<br />
Introduction Compositional models describe the simultaneous transport <strong>of</strong> multiple components<br />
flowing in coexisting phases in porous media [1, 4]. Because each component can transfer<br />
between different phases, the mass <strong>of</strong> each phase or a component within a particular phase is<br />
no longer conserved. Instead, the total mass <strong>of</strong> each component among all the phases must be<br />
conserved, leading to strongly coupled systems <strong>of</strong> transient nonlinear advection-diffusion equations.<br />
These equations are closely coupled to a set <strong>of</strong> constraining equations, which are strongly<br />
nonlinear, implicit functions <strong>of</strong> phase pressure, temperature, and composition. These equations<br />
need to be solved in all spatial cells at each iterative step <strong>of</strong> each time step via thermodynamic<br />
flash calculation. In industrial applications, upwind methods have commonly been used to stabilize<br />
the numerical approximations [1, 4]. However, these methods <strong>of</strong>ten generate excessive<br />
numerical dispersion and serious spurious effects due to grid orientation.<br />
Eulerian-Lagrangian methods symmetrize the transport equations and generate accurate<br />
numerical solutions even if large time steps and coarse spatial grids are used. They have demonstrated<br />
excellent performance in the numerical simulations <strong>of</strong> single-phase flow [3, 5] and immiscible<br />
two phase flow [2]. However, there exist serious mathematical and numerical difficulties in<br />
the development <strong>of</strong> Eulerian-Lagrangian methods for multiphase multicomponent compositional<br />
flow. We present a component-based Eulerian-Lagrangian formulation for compositional flow,<br />
which can be used by many Eulerian-Lagrangian methods.<br />
Numerical experiments We simulate the transport <strong>of</strong> Methane, Propane, and n-Hexane,<br />
flowing in coexisting liquid and vapor phases in a horizontal porous medium reservoir Ω =<br />
(0, 1000) × (0, 1000) ft 2 with a thickness <strong>of</strong> 1 ft over a time period <strong>of</strong> 20 years. An injection well<br />
is located at the upper-right corner <strong>of</strong> Ω with a volumetric injection rate <strong>of</strong> Q =15ft 3 /day. A<br />
production well is located at the lower-left corner with a production rate <strong>of</strong> Q = −15 ft 3 /day.<br />
The porosity φ = 0.1. The permeability is 60 md. The effect <strong>of</strong> capillary pressure is neglected.<br />
The relative permeability k r,l =(s l ) 2 and k r,v =(1−s l ) 2 . The initial reservoir pressure is 2100<br />
psia and the reservoir temperature is 350 o K. The composition <strong>of</strong> the resident fluid is cMethane<br />
= 0.5, cP ropane =0.2, and cn−Hexane =0.3, which is in liquid phase at the given temperature<br />
and pressure. The composition <strong>of</strong> the injected fluid is ¯cMethane = 0.8, ¯cP ropane =0.15, and<br />
¯cn−Hexane =0.05, which is in vapor phase.<br />
We use a uniform coarse spatial grid <strong>of</strong> ∆x =∆y= 25 ft. We use a time step <strong>of</strong> ∆tel =1<br />
year for the Eulerian-Lagrangian method, and <strong>of</strong> ∆tup = 2 days for the upwind method that is<br />
the largest possible. In Figure 1(a) we present the plots <strong>of</strong> the overall mole fraction cMethane<br />
generated by the Eulerian-Lagrangian method at t = 5 and 20 years. In Figure 1(b) we present<br />
the plots <strong>of</strong> the normalized molar amount n v Methane = ρv s v c v Methane /(ρ cMethane), where ρ v and<br />
sv are density and saturation <strong>of</strong> the vapor phase and ρ is bulk molar density <strong>of</strong> the fluid mixture.<br />
Note that nv i represents the fraction <strong>of</strong> ci in the vapor phase. Thus, nv i = 1 or 0 indicates that<br />
component i stays in the vapor phase or liquid phase completely. 0
H. WANG: A Component-Based Eulerian-Lagrangian Formulation for Compositional<br />
Flow in Porous Media<br />
✬<br />
✫<br />
Figure 1: The ELLAM ((a)-(b)) and upwind ((c)-(d)) simulation at 5 and 20 years.<br />
(a) The overall mole fraction <strong>of</strong> Methane (b) The molar amount <strong>of</strong> Methane in vapor<br />
(c) The overall mole fraction <strong>of</strong> Methane (d) The molar amount <strong>of</strong> Methane in vapor<br />
Discussion The numerical results show that the Eulerian-Lagrangian formulation generates<br />
stable and accurate solutions (overall mole fractions) that have preserved physically reasonable<br />
moving steep fronts, even if a large time step <strong>of</strong> ∆tel = 1 year is used. With the (largest<br />
possible) fine time step ∆tup = 2 days, the upwind method generates qualitatively similar (but<br />
much more diffusive) overall mole fraction. We observe a similar comparison in terms <strong>of</strong> the<br />
normalized molar amounts in the vapor and liquid phases.<br />
It is instructive to look at the computational efficiency. Although the Eulerian-Lagrangian<br />
method uses more CPU time than the upwind method in solving the mass balance equations,<br />
both simulators have to perform the same computations on the pressure system and the thermodynamic<br />
flash calculations which consume a larger portion <strong>of</strong> the CPU time per iterative step<br />
at each time step. These results indicate that the Eulerian-Lagrangian simulator uses less than<br />
twice the CPU time an upwind simulator uses per time step. Therefore, the Eulerian-Lagrangian<br />
method generates accurate and stable solutions with steeper fronts using much less CPU time.<br />
References<br />
[1] H. Aziz and A. Settari, Petroleum Reservoir Simulation, Applied Science Publishers, 1979.<br />
[2] M.S. Espedal and R.E. Ewing, Characteristic Petrov-Galerkin sub-domain methods for twophase<br />
immiscible flow, Comput. Meth. Appl. Mech. Engrg., 64, (1987) 113–135.<br />
[3] R.E. Ewing, T.F. Russell, and M.F. Wheeler, Simulation <strong>of</strong> miscible displacement using<br />
mixed methods and a modified method <strong>of</strong> characteristics, SPE 12241, (1983), 71–81.<br />
[4] R. Helmig, Multiphase Flow and Transport Processes in the Subsurface, Springer Verlag,<br />
Berlin, 1997.<br />
[5] H. Wang, D. Liang, R.E. Ewing, S.L. Lyons, and G. Qin, An ELLAM-MFEM solution<br />
technique for compressible fluid flows in porous media with point sources and sinks, J. Comput.<br />
Phys., 159, (2000) 344–376.<br />
Speaker: WANG, H. 20 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
Speaker:<br />
P. Houston, R. Hartmann<br />
Self-adaptive Methods for PDEs<br />
Many processes in science and engineering are formulated in terms <strong>of</strong><br />
partial differential equations. Typically, for problems <strong>of</strong> practical interest,<br />
the <strong>und</strong>erlying analytical solution exhibits localised phenomena<br />
such as bo<strong>und</strong>ary and interior layers and corner and edge singularities,<br />
for example, and their numerical approximation presents a challenging<br />
computational task. Indeed, in order to resolve such localised features,<br />
in an accurate and efficient manner, it is essential to exploit so-called<br />
self-adaptive methods.<br />
Such approaches are typically based on a posteriori error estimates for<br />
the <strong>und</strong>erlying discretization method in terms <strong>of</strong> local quantities, such<br />
as local residuals, computed from the discrete solution. Over the last<br />
few years, there have been significant developments within this field in<br />
terms <strong>of</strong> both rigorous a posteriori error analysis, as well as the subsequent<br />
design <strong>of</strong> optimal meshes. In this minisymposium, a number <strong>of</strong><br />
recent developments, such as the design <strong>of</strong> high-order and hp-adaptive<br />
finite element methods will be considered, as well as anisotropic mesh<br />
adaptation and mesh movement.<br />
• Ralf Hartmann: Discontinuous Galerkin methods for compressible flows: higher<br />
order accuracy, error estimation and adaptivity<br />
• Vincent Heuveline: On a new refinement strategy for adaptive hp finite element<br />
method<br />
• John Mackenzie: A Discontinuous Galerkin Moving Mesh Method for Hamilton-<br />
Jacobi Equations<br />
• Simona Perotto: Layer Capturing via Anisotropic Mesh Adaption<br />
• Rene Schneider: Anisotropic mesh adaption based on a posteriori estimates and<br />
optimisation <strong>of</strong> node positions
R. HARTMANN: Discontinuous Galerkin methods for compressible flows: higher order<br />
accuracy, error estimation and adaptivity<br />
✬<br />
✫<br />
Discontinuous Galerkin methods for compressible flows:<br />
higher order accuracy, error estimation and adaptivity<br />
Ralf Hartmann<br />
<strong>Institut</strong>e <strong>of</strong> Aerodynamics and Flow Technology, German Aerospace Center (DLR),<br />
Lilienthalplatz 7, 38108 Braunschweig, Germany<br />
The Discontinuous Galerkin (DG) method for the compressible Euler equations is extended<br />
to the symmetric interior penalty (SIP)DG method for the compressible Navier-Stokes equations,<br />
see Hartmann & Houston [2]. Shock-capturing is used to avoid overshoots near shocks, see Hartmann<br />
[1]. The nonlinear equations are solved using a fully implicit solver. We demonstrate the<br />
accuracy <strong>of</strong> higher order DG discretizations with respect to the approximation <strong>of</strong> aerodynamical<br />
force coefficients and to the approximation <strong>of</strong> viscous bo<strong>und</strong>ary layers, see Figure 1 and<br />
Hartmann & Houston [2].<br />
Finally, we demonstrate the use <strong>of</strong> a posteriori error estimation and goal-oriented (also<br />
called weighted-residual-based or adjoint-based) adaptive mesh refinement for subsonic flows,<br />
Hartmann & Houston [3], and for supersonic compressible flows, see Figure 2 and Hartmann [1].<br />
References<br />
[1] R. Hartmann. Adaptive discontinuous Galerkin methods with shock-capturing for the compressible<br />
Navier-Stokes equations. Int. J. Numer. Meth. Fluids, <strong>2006</strong>. To appear.<br />
[2] R. Hartmann and P. Houston. Symmetric interior penalty DG methods for the compressible<br />
Navier–Stokes equations I: Method formulation. Int. J. Num. Anal. Model., 3(1):1–20, <strong>2006</strong>.<br />
[3] R. Hartmann and P. Houston. Symmetric interior penalty DG methods for the compressible<br />
Navier–Stokes equations II: Goal–oriented a posteriori error estimation. Int. J. Num. Anal.<br />
Model., 3(2):141–162, <strong>2006</strong>.<br />
Speaker: HARTMANN, R. 22 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
R. HARTMANN: Discontinuous Galerkin methods for compressible flows: higher order<br />
accuracy, error estimation and adaptivity<br />
✬<br />
✫<br />
c dp<br />
0.024<br />
0.022<br />
0.02<br />
0.018<br />
0.016<br />
0.014<br />
0.012<br />
0.01<br />
0.008<br />
0.006<br />
reference cdp<br />
DG(3), global refinement<br />
DG(2), global refinement<br />
DG(1), global refinement<br />
10000 100000<br />
number <strong>of</strong> elements<br />
|c dp − 0.0222875|<br />
0.01<br />
0.001<br />
0.0001<br />
(a) (b)<br />
DG(1), global refinement<br />
DG(2), global refinement<br />
DG(3), global refinement<br />
10000 100000<br />
number <strong>of</strong> elements<br />
Figure 1: Subsonic laminar flow aro<strong>und</strong> the NACA0012 airfoil at M = 0.5, α = 0 and Re = 5000:<br />
Convergence <strong>of</strong> the pressure induced drag cdp <strong>und</strong>er global refinement for DG(p), p = 1,2,3: (a)<br />
cdp versus number <strong>of</strong> elements; (b) Error in cdp (reference cdp − cdp) versus number <strong>of</strong> elements.<br />
For more detail cf. Hartmann & Houston [2].<br />
8<br />
4<br />
0<br />
-4<br />
-8<br />
-4 0 4 8<br />
8<br />
4<br />
0<br />
-4<br />
-8<br />
-4 0 4 8<br />
(a) (b)<br />
Figure 2: Supersonic laminar flow aro<strong>und</strong> the NACA0012 airfoil at M = 1.2, α = 0 and<br />
Re = 1000: (a) Residual-based refined mesh <strong>of</strong> 17670 elements with 282720 degrees <strong>of</strong> freedom<br />
and |Jcdp (u) − Jcdp (uh)| = 1.9 · 10 −3 ; (b) Adjoint-based refined mesh for cdp: mesh <strong>of</strong> 10038<br />
elements with 160608 degrees <strong>of</strong> freedom and |Jcdp (u) − Jcdp (uh)| = 1.6 · 10 −4 . For more detail<br />
cf. Hartmann [1].<br />
Speaker: HARTMANN, R. 23 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
V. HEUVELINE: On a new refinement strategy for adaptive hp finite element method<br />
✬<br />
✫<br />
On a new refinement strategy for adaptive hp finite<br />
element method<br />
V. Heuveline<br />
University Karlsruhe (TH)<br />
<strong>Institut</strong>e for Applied Mathematics II<br />
vincent.heuveline@math.uni-karlsruhe.de<br />
Abstract<br />
We consider finite element methods with varying meshsize h as well as varying<br />
polynomial degree p. Such methods have been proven to show exponentially fast<br />
convergence in some classes <strong>of</strong> partial differential equations if an adequate distribution<br />
<strong>of</strong> h− and p−refinement is chosen. In order to find hp−refinement strategies<br />
that show up automaticaly with optimal complexity, it is a first step to establish<br />
convergent adaptive algorithms. We develop a strategy that automatically construct<br />
a solution adapted approximation space by combining local h− and p− refinement<br />
and that can be proven for the 1d case to be convergent with a linear rate. This<br />
construction is based on an a posteriori error estimate with respect to the error<br />
in the energy norm. We then extend the proposed approach to the 2d and 3d<br />
case. Numerical experiments as well as implementation issues are considered in<br />
that framework.<br />
Speaker: HEUVELINE, V. 24 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
J.A. MACKENZIE, A. NICOLA: A Discontinuous Galerkin Moving Mesh Method for<br />
Hamilton-Jacobi Equations<br />
✬<br />
✫<br />
A Discontinuous Galerkin Moving Mesh Method for<br />
Hamilton-Jacobi Equations<br />
1 Introduction<br />
J.A. Mackenzie and A. Nicola<br />
Department <strong>of</strong> Mathematics<br />
University <strong>of</strong> Strathclyde<br />
26 Richmond St, Glasgow<br />
G1 1XH, U.K.<br />
jam@maths.strath.ac.uk<br />
Abstract<br />
In this talk we consider the adaptive numerical solution <strong>of</strong> Hamilton-Jacobi (HJ) equations<br />
φt + H(φx1, . . .,φxd ) = 0, φ(x, 0) = φ0(x), (1)<br />
where x = (x1, . . . , xd) ∈ IR d , t > 0. HJ equations arise in many practical areas such<br />
as differential games, mathematical finance, image enhancement and front propagation. It<br />
is well known that solutions <strong>of</strong> (1) are Lipschitz continuous but derivatives can become<br />
discontinuous even if the initial data is smooth. Since generalised solutions are not unique, a<br />
selection principle is required to pick out the physically relevant solution. For HJ equations<br />
the most commonly used condition is the vanishing viscosity condition which requires that the<br />
correct solution should be the vanishing viscosity limit <strong>of</strong> smooth solutions <strong>of</strong> corresponding<br />
viscous problems. The notion <strong>of</strong> viscosity solutions was introduced by Crandall and Lions<br />
[5], where the questions <strong>of</strong> existence, uniqueness and stability <strong>of</strong> solutions were addressed.<br />
Crandall and Lions were also the first to study numerical approximations <strong>of</strong> (1) and<br />
introduced the important class <strong>of</strong> monotone methods which were shown to converge to the<br />
viscosity solution [4]. However, monotonic schemes are well known to be at most first-order<br />
accurate.<br />
There is a close relation between HJ equations and hyperbolic conservation laws. With<br />
this in mind, it not surprising to find that many <strong>of</strong> the numerical methods used to solve HJ<br />
equations are motivated by conservative finite difference or finite volume methods for conservation<br />
laws. Methods that have been proposed include high-order essentially nonoscillatory<br />
(ENO) schemes, weighted ENO schemes and high resolution central schemes.<br />
An increasingly popular approach to solve hyperbolic conservation laws is the discontinuous<br />
Galerkin (DG) finite element method [2], [3]. Recently, Hu and Shu [7] proposed a DG<br />
method to solve HJ equations by first rewriting (1) as a system <strong>of</strong> conservation laws<br />
(wi)t + (H(w))xi = 0, i = 1, . . .,d, w(x, 0) = ∇φ0(x), (2)<br />
where w = ∇φ. The usual DG formulation would be obtained if w belonged to a space<br />
<strong>of</strong> piecewise polynomials. However, we note that wi, i = 1, . . .,d are not independent due<br />
to the restriction that w = ∇φ. In [7] a least squares procedure was used to enforce this<br />
condition. More recently it was shown that it is possible to enforce the gradient condition<br />
using a smaller solution space [12]. Theoretical analysis <strong>of</strong> the accuracy and stability <strong>of</strong> the<br />
method was performed in [11].<br />
One <strong>of</strong> the <strong>of</strong>ten cited advantages <strong>of</strong> DG methods is that since the numerical solution is<br />
not continuous across inter-element bo<strong>und</strong>aries then, in theory, this makes solution adaptive<br />
strategies much easier to implement. This has lead to the development <strong>of</strong> a number <strong>of</strong><br />
adaptive methods based on hp-refinement strategies for hyperbolic conservation laws [1] [6].<br />
1<br />
Speaker: MACKENZIE, J.A. 25 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
J.A. MACKENZIE, A. NICOLA: A Discontinuous Galerkin Moving Mesh Method for<br />
Hamilton-Jacobi Equations<br />
✬<br />
✫<br />
An alternative adaptive strategy that has worked well for time dependent problems is<br />
to use moving meshes. A useful way to construct an adaptive moving mesh is to regard it<br />
as the image <strong>of</strong> a uniform mesh covering a computational domain <strong>und</strong>er a time-dependent<br />
transformation that clusters mesh elements towards areas where improved spatial resolution<br />
is required. The transformation is <strong>of</strong>ten fo<strong>und</strong> through a variational formulation where the<br />
mapping is the minimiser <strong>of</strong> a functional involving properties <strong>of</strong> the mesh and the solution<br />
(see e.g. [10]). To improve the stability and smooth the evolution <strong>of</strong> the moving mesh<br />
Russell, Huang and coworkers [9] [8] fo<strong>und</strong> it useful to obtain the mapping as the solution <strong>of</strong><br />
parabolic moving mesh PDEs which are modified gradient flow equations for the minimisation<br />
<strong>of</strong> a suitable mesh functional.<br />
For problems where solution discontinuities exist the correct choice <strong>of</strong> an adaptivity<br />
criterion, or monitor function, is problematic. It is not unusual to find in the literature that<br />
many grid adaptation criteria are singular at solution discontinuities. To prevent singularities<br />
producing degenerate meshes either some form <strong>of</strong> smoothing procedure is employed or a<br />
regularised functional is used in the variational formulation.<br />
The aim <strong>of</strong> this talk is to consider the use <strong>of</strong> the DG method <strong>of</strong> Hu and Shu [7] to solve<br />
HJ equation using a moving mesh method based on the solution <strong>of</strong> MMPDEs. The governing<br />
equation are transformed to include the effect <strong>of</strong> the movement <strong>of</strong> the mesh and this is done<br />
in such a way that the conservation properties <strong>of</strong> the original equation are not lost. The<br />
adaptive mesh is driven by a monitor function which is shown to be non-singular in the<br />
presence <strong>of</strong> solution discontinuities. To produce an acceptable mesh we smooth the monitor<br />
function before it is used to drive the adaptive procedure. Numerical examples in one and<br />
two dimensions are presented to demonstrate the effectiveness <strong>of</strong> the adaptive procedure..<br />
References<br />
[1] K.S. Bey and J.T. Oden. hp-version discontinuous Galerkin methods for hyperbolic<br />
conservation laws. Comput. Methods Appl. Mech. Engrg., 133:259–286, 1996.<br />
[2] B. Cockburn, G.E. Karniadakis, and C.W. Shu. Discontinuous Galerkin methods: Theory,<br />
Computation and Applications. Springer, 2000.<br />
[3] B. Cockburn and C.W. Shu. The Runge-Kutta discontinuous Galerkin finite element<br />
method for conservation laws V: Multidimensional systems. Journal <strong>of</strong> Computational<br />
Physics, 141:199–224, 1998.<br />
[4] M.G. Crandall and P.L. Lions. Two Approximations <strong>of</strong> Solutions <strong>of</strong> Hamilton-Jacobi<br />
Equations. Mathematics <strong>of</strong> Computation, 43(167):1–19, 1984.<br />
[5] M.J. Crandall and P.L. Lions. Viscosity Solutions <strong>of</strong> Hamilton-Jacobi Equations. Transactions<br />
<strong>of</strong> the American Mathematical Society, 277(1):1–42, 1983.<br />
[6] P. Houston, B. Senior, and E. Suli. hp-discontinuous Galerkin finite element methods<br />
for hyperbolic problems: analysis and adaptivity. Int. J. Numer. Methods in Fluids,<br />
40:153–169, 2002.<br />
[7] C. Hu and C.W. Shu. A Discontinuous Galerkin Finite Element Method for Hamilton-<br />
Jacobi Equations. SIAM Journal on Scientific Computing, 21(2):666–690, 1999.<br />
[8] W. Huang. Practical aspects <strong>of</strong> formulation and solution <strong>of</strong> moving mesh partial differential<br />
equations. Journal <strong>of</strong> Computational Physics, 171:753–775, 2001.<br />
[9] W. Huang and R. D. Russell. Moving mesh strategy based upon a gradient flow equation<br />
for two-dimensional problems. SIAM Journal on Scientific Computing, 20:998–1015,<br />
1999.<br />
[10] P. Knupp and S. Steinberg. Fo<strong>und</strong>ations <strong>of</strong> Grid Generation. CRC Press, Boca Raton,<br />
1994.<br />
[11] O. Lepsky, C. Hu, and C. W. Shu. Analysis <strong>of</strong> the discontinuous Galerkin method for<br />
Hamilton-Jacobi equations. Appl. Numer. Math., 33:423–434, 2000.<br />
[12] F. Li and C.W. Shu. Reinterpretation and simplified implementation <strong>of</strong> a discontinuous<br />
Galerkin method for Hamilton-Jacobi equations. Applied Mathematics Letters, 18:1204–<br />
1209, 2005.<br />
Speaker: MACKENZIE, J.A. 26 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
S. PEROTTO: Layer Capturing via Anisotropic Mesh Adaption<br />
✬<br />
✫<br />
Layer Capturing via Anisotropic Mesh Adaption<br />
Simona Perotto<br />
MOX - Dipartimento di Matematica “F. Brioschi”<br />
Politecnico di Milano, Via Bonardi 9<br />
I-20133 Milano, Italy<br />
simona.perotto@mate.polimi.it<br />
The numerical approximation <strong>of</strong> many problems in Computational Fluid Dynamics (CFD) leads<br />
<strong>of</strong>ten to deal with solutions exhibiting directional features, namely great variations along certain<br />
directions and less significant changes along the other ones. This is the case <strong>of</strong> bo<strong>und</strong>ary and<br />
internal layers typical, for instance, <strong>of</strong> the advection-diffusion and Navier-Stokes equations as<br />
well as <strong>of</strong> shocks in the case <strong>of</strong> Euler equations. In view <strong>of</strong> an efficient numerical approach to<br />
this kind <strong>of</strong> problems, it turns out advisable to resort to a suitably oriented and deformed (i.e.,<br />
anisotropic) computational mesh, matching the local directional features <strong>of</strong> the solution. For<br />
a fixed solution accuracy, a considerable reduction <strong>of</strong> the number <strong>of</strong> the degrees <strong>of</strong> freedom is<br />
shown in the presence <strong>of</strong> an anisotropic grid, besides a sharper capture <strong>of</strong> the solution features.<br />
In this regard, we have introduced a theoretically so<strong>und</strong> anisotropic framework moving from<br />
the spectral properties <strong>of</strong> the standard affine map between the reference and the general mesh<br />
element [2]. As first step, we have derived suitable anisotropic interpolation error estimates for<br />
piecewise linear finite elements. Then, in view <strong>of</strong> an anisotropic mesh adaption driven by an a<br />
posteriori error estimator, these anisotropic estimates have been merged with the standard dualbased<br />
approach proposed by R. Becker and R. Rannacher in [1]. Thus the final outcome <strong>of</strong> our<br />
analysis consists <strong>of</strong> an automatic tool able to properly orient and stretch the mesh elements so<br />
that a goal-functional <strong>of</strong> the exact solution, representing a quantity <strong>of</strong> interest, is approximated<br />
within a user-defined tolerance [3, 4].<br />
In this communication the leading ideas <strong>of</strong> our anisotropic framework are presented together<br />
with some numerical results associated with the goal-oriented a posteriori analysis.<br />
References<br />
[1] R. Becker and R. Rannacher, “A feed-back approach to error control in finite element<br />
methods: basic analysis and examples”, East-West J. Numer. Math., 4(4), 237–264 (1996).<br />
[2] L. Formaggia and S. Perotto, “New anisotropic a priori error estimates”, Numer. Math.,<br />
89, 641–667 (2001).<br />
[3] L. Formaggia and S. Perotto, “Anisotropic error estimates for elliptic problems”, Numer.<br />
Math., 94, 67–92 (2003).<br />
[4] L. Formaggia, S. Micheletti and S. Perotto, “Anisotropic mesh adaptation in Computational<br />
Fluid Dynamics: application to the advection-diffusion-reaction and the Stokes problems.”,<br />
Appl. Numer. Math., 51 (4), 511–533 (2004).<br />
1<br />
Speaker: PEROTTA, S. 27 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
R. SCHNEIDER, P. JIMACK: Anisotropic mesh adaption based on a posteriori estimates<br />
and optimisation <strong>of</strong> node positions<br />
✬<br />
✫<br />
Anisotropic mesh adaption based on a posteriori estimates and<br />
optimisation <strong>of</strong> node positions<br />
Abstract<br />
Introduction<br />
René Schneider ∗ & Peter Jimack †<br />
Efficient numerical approximation <strong>of</strong> solution features like bo<strong>und</strong>ary or interior layers by means<br />
<strong>of</strong> the finite element method requires the use <strong>of</strong> layer adapted meshes. Anisotropic meshes, like<br />
for example Shishkin meshes, allow the most efficient approximation <strong>of</strong> these highly anisotropic<br />
solution features. However, application <strong>of</strong> this approach relies on a priori analysis on the thickness,<br />
position and stretching direction <strong>of</strong> the layers. If it is impossible to obtain this information<br />
a priori, as it is <strong>of</strong>ten the case for problems with interior layers <strong>of</strong> unknown position for example,<br />
automatic mesh adaption based on a posteriori error estimates or error indicators is essential in<br />
order to obtain efficient numerical approximations.<br />
Historically the majority <strong>of</strong> work on automatic mesh adaption used locally uniform refinement,<br />
splitting each element into smaller elements <strong>of</strong> similar shape. This procedure is clearly not<br />
suitable to produce anisotropically refined meshes. The resulting meshes are over-refined in at<br />
least one spatial direction, rendering the approach far less efficient than that <strong>of</strong> the anisotropic<br />
meshes based on a priori analysis.<br />
Automatic anisotropic mesh adaption is an area <strong>of</strong> active research, e.g. [2, 1]. Here we present<br />
a new approach to this problem, based upon using not only an a posteriori error estimate to<br />
guide the mesh refinement, but its sensitivities with respect to the positions <strong>of</strong> the nodes in the<br />
mesh as well.<br />
Outline <strong>of</strong> the approach<br />
The <strong>und</strong>erlying idea is to use techniques from mathematical optimisation to minimise the estimated<br />
error by moving the positions <strong>of</strong> the nodes in the mesh appropriately. This basic idea is<br />
<strong>of</strong> course not new, but the approach taken to realise it is.<br />
A key ingredient is the utilisation <strong>of</strong> the discrete adjoint technique to evaluate the sensitivities<br />
<strong>of</strong> an error estimate J = J(uh(s),s) with respect to the node positions s, where uh = uh(s)<br />
denotes the solution <strong>of</strong> the discretised PDE, R(uh,s) = 0, which depends upon the node positions<br />
s. The sensitivities<br />
� ∂R<br />
∂uh<br />
DJ ∂J ∂uh ∂J<br />
= +<br />
Ds ∂uh ∂s ∂s<br />
� T<br />
∗ Chemnitz University <strong>of</strong> Technology, Germany<br />
† School <strong>of</strong> Computing, University <strong>of</strong> Leeds, UK<br />
= ∂J<br />
∂s<br />
∂R<br />
− ΨT , (1)<br />
∂s<br />
Ψ = ∂J<br />
, (2)<br />
∂uh<br />
Speaker: SCHNEIDER, R. 28 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
R. SCHNEIDER, P. JIMACK: Anisotropic mesh adaption based on a posteriori estimates<br />
and optimisation <strong>of</strong> node positions<br />
✬<br />
✫<br />
y<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
−0.2<br />
−0.4<br />
−0.6<br />
−0.8<br />
−1<br />
initial mesh<br />
−1 −0.5 0<br />
x<br />
0.5 1<br />
y<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
−0.2<br />
−0.4<br />
−0.6<br />
−0.8<br />
−1<br />
final mesh for eps=1.0e−03<br />
−1 −0.5 0<br />
x<br />
0.5 1<br />
(a) (b)<br />
Figure 1: Initial (a) and adapted (b) meshes for model problem (3) with a bo<strong>und</strong>ary layer aro<strong>und</strong><br />
the square hole<br />
are thereby evaluated according to (1), utilising the adjoint solution Ψ which is defined by (2).<br />
This way, DJ/Ds can be evaluated without computing ∂uh/∂s first, reducing the number <strong>of</strong><br />
equation systems to be solved from O(dim(s)) to just two, independent <strong>of</strong> dim(s). As the<br />
number <strong>of</strong> nodes can easily be larger than one h<strong>und</strong>red even in extremely coarse meshes (if the<br />
domain geometry is complicated), this approach is <strong>of</strong> f<strong>und</strong>amental importance to make gradient<br />
based optimisation methods feasible for this type <strong>of</strong> problem. Fast optimisation algorithms like<br />
BFGS-type methods can be applied to obtain significant reductions in the error estimate J after<br />
a few optimisation steps. The aim <strong>of</strong> this procedure is to provide a mesh with problem adapted<br />
anisotropic elements, which may then be used as a good basis for further locally uniform adaptive<br />
mesh refinement.<br />
Numerical results<br />
To demonstrate feasibility <strong>of</strong> the approach it is applied to a number <strong>of</strong> model problems. For the<br />
purpose <strong>of</strong> this abstract we consider a reaction diffusion equation,<br />
−∆u + 1<br />
ε2u = 1<br />
ε2 in Ω := (−1,1) 2 \ (−1 1<br />
5 , 5 )2<br />
subject to u = 0 on ΓD := � −1 ⎫<br />
⎪⎬<br />
�<br />
1 2 � �<br />
1 1 2<br />
5 , 5 \ −5 , (3)<br />
5<br />
⎪⎭<br />
∂u<br />
∂n = 0 on ΓN := [−1,1] 2 \ (−1,1) 2 .<br />
Figure 1 shows an initial mesh for this problem and an adapted one for ε = 10 −3 . Concentration<br />
<strong>of</strong> the elements in the bo<strong>und</strong>ary layer which forms aro<strong>und</strong> the hole at the centre <strong>of</strong> the domain is<br />
clearly visible, and significantly increased aspect ratios in the bo<strong>und</strong>ary layer may be observed.<br />
For more detail on the approach and the example we refer to [3].<br />
References<br />
[1] L. Formaggia, S. Micheletti, and S. Perotto. Anisotropic mesh adaptation in computational fluid dynamics:<br />
Application to the advection-diffusion-reaction and the Stokes problems. Applied Numerical<br />
Mathematics, 51(4):511–533, December 2004.<br />
[2] G. Kunert. Toward anisotropic mesh construction and error estimation in the finite element method.<br />
Numerical Methods for Partial Differential Equations, 18(5):625–648, 2002.<br />
[3] R. Schneider and P.K. Jimack. Toward anisotropic mesh adaption based upon sensitivity <strong>of</strong> a posteriori<br />
estimates. School <strong>of</strong> Computing Research Report Series 2005.03, University <strong>of</strong> Leeds, http://www.<br />
comp.leeds.ac.uk/research/pubs/reports/2005/2005_03.pdf, 2005.<br />
Speaker: SCHNEIDER, R. 29 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
Speaker:<br />
Debopam Das, Tapan Sengupta:<br />
Asymptotic Methods for Laminar and Turbulent bo<strong>und</strong>ary Layers<br />
The minisymposium will have contributions dealing with laminar/turbulent<br />
flows- their morphology and structures. Specifically, results<br />
would be presented that discuss the very concept <strong>of</strong> turbulent<br />
bo<strong>und</strong>ary layers. Also, detailed flow structures arising in mixed convection<br />
problem involving velocity and thermal bo<strong>und</strong>ary/ interior layers<br />
will be a focus <strong>of</strong> another contribution. This session will also have<br />
contributions dealing specifically with temporal and/or spatio-temporal<br />
growth <strong>of</strong> waves in bo<strong>und</strong>ary/ interior layers. For example, existence<br />
<strong>of</strong> spatio-temporal growth <strong>of</strong> waves in bo<strong>und</strong>ary layer is established for<br />
the first time that is related non-orthogonal modes proposed earlier for<br />
Couette and channel flows. The focus will be on receptivity and stability<br />
<strong>of</strong> equilibrium steady flows as well as unsteady bi-directional pipe<br />
flows that identifies non-axisymmetric modes.<br />
• Matthias H. Buschman: Turbulent Bo<strong>und</strong>ary Layers: Reality and Myth (Key-Note<br />
Lecture)<br />
• Debopam Das: Three-dimensional Temporal Instability <strong>of</strong> Unsteady Pipe Flow.<br />
• Venkatesa I. Vasanta Ram: The structure <strong>of</strong> the critical layer <strong>of</strong> a swirling annular<br />
flow in transition.<br />
• T.K. Sengupta: Spatio-temporal growing waves in bo<strong>und</strong>ary-layers by Bromwich<br />
contour integral method<br />
• Herbert Steinrueck: Asymptotic Analysis <strong>of</strong> the mixed convection flow past a horizontal<br />
plate near the trailing edge.
M.H. BUSCHMANN, M. GAD-EL-HAK: Turbulent Bo<strong>und</strong>ary Layers: Reality and<br />
Myth<br />
✬<br />
International Conference on Bo<strong>und</strong>ary and Interior Layers—Computational & Asymptotic Methods<br />
(<strong>BAIL</strong> <strong>2006</strong>)<br />
Abstract <strong>of</strong> keynote lecture for the<br />
Minisymposium on Asymptotic Methods for Laminar and Turbulent Bo<strong>und</strong>ary Layers<br />
Turbulent Bo<strong>und</strong>ary Layers: Reality and Myth<br />
Matthias H. Buschmann<br />
Privatdozent, <strong>Institut</strong> <strong>für</strong> Strömungsmechanik, Technische Universität Dresden, Dresden, Germany<br />
Mohamed Gad-el-Hak<br />
Caudill Pr<strong>of</strong>essor and Chair <strong>of</strong> Mechanical Engineering,<br />
Virginia Commonwealth University, Richmond, VA 23284-3015, USA<br />
H<strong>und</strong>red years after Ludwig Prandtl’s f<strong>und</strong>amental lecture on bo<strong>und</strong>ary layer theory, 1 the meanvelocity<br />
pr<strong>of</strong>ile and the shear-stress distribution <strong>of</strong> the seemingly simplest case <strong>of</strong> wall-bo<strong>und</strong>ed<br />
flow, the zero-pressure-gradient turbulent bo<strong>und</strong>ary layer (ZPG TBL), still appears to be terra<br />
incognita. Even less is known about confined and semi-confined flows <strong>und</strong>ergoing pressure<br />
gradients, such as pipe and channel flows and wall-bo<strong>und</strong>ed flows approaching pressure-driven<br />
separation. The problem is <strong>of</strong> course related to the lack <strong>of</strong> analytical solutions to the<br />
instantaneous, nonlinear Navier–Stokes equations that govern the stochastic dependent variables<br />
<strong>of</strong> almost all turbulent flows. What little we know about turbulence comes from experiments and<br />
heuristic modeling, not first-principles solutions. (Direct numerical simulations provide firstprinciples<br />
integration <strong>of</strong> the instantaneous Navier–Stokes equations, but are at present limited to<br />
modest Reynolds numbers and simple geometries.)<br />
Consider a two-dimensional, isothermal, incompressible, steady flow over a body <strong>of</strong> length L.<br />
The fluid may have constant density ρ and constant dynamic viscosity µ. Assuming that the<br />
characteristic velocity is U, we write the Reynolds number as<br />
Re= !UL µ (1)<br />
It was Prandtl’s genius that discovered that, at sufficiently high Reynolds number, a thin shear<br />
layer exists close to the body. The thickness <strong>of</strong> this layer δ is much smaller than L. Due to the<br />
strong streamwise velocity gradient normal to the wall, even a small viscosity such as that for air<br />
or water can cause considerable viscous shear stress, ! = µ "u "y . Originally Prandtl called this<br />
layer therefore Reibungsschicht, which literally translates to friction layer.<br />
Introducing the transformation<br />
! ! ! ! ! $<br />
( x,y<br />
,u ,v , p ) ! & L x,Re<br />
%<br />
" 1<br />
2 L y,U u,Re " 1<br />
'<br />
2 2<br />
U v,#U p)<br />
(<br />
1 Prandtl, L., “Über Flüssigkeitsbewegung bei sehr kleiner Reibung,” Proc. Third Int. Math. Cong., pp. 484–491,<br />
Heidelberg, Germany, 1904.<br />
✫<br />
M. H. Buschmann & M. Gad-el-Hak, Abstract for <strong>BAIL</strong> <strong>2006</strong><br />
Speaker: BUSCHMANN, M.H. 32 <strong>BAIL</strong> <strong>2006</strong><br />
(2)<br />
✩<br />
✪
M.H. BUSCHMANN, M. GAD-EL-HAK: Turbulent Bo<strong>und</strong>ary Layers: Reality and<br />
Myth<br />
✬<br />
✫<br />
into the Navier-Stokes equations and taking the limit Re → ∞, leads to Prandtl’s bo<strong>und</strong>ary layer<br />
equations<br />
The bo<strong>und</strong>ary conditions are<br />
uu x + vu y = ! p x + u yy ;<br />
y = 0 :<br />
u = v = 0 and<br />
0 = p y ;<br />
y ! " :<br />
The task is now to find physically appropriate solution for eqn. (3).<br />
ux + v = 0 (3)<br />
y<br />
u ! U e x ( ) (4)<br />
What goals do we have when solving eqn. (3)? One <strong>of</strong> the main objectives is to find self-similar<br />
solutions. Bo<strong>und</strong>ary layers are self-similar when normalization can be fo<strong>und</strong> so that data <strong>of</strong><br />
different physical realizations (e.g., experiments in different wind tunnels, pr<strong>of</strong>iles at different<br />
downstream positions within one experiment) can be collapsed within one single curve.<br />
Examples are the mean velocity pr<strong>of</strong>iles <strong>of</strong> the Blasius’ laminar zero-pressure-gradient bo<strong>und</strong>ary<br />
layer and the fully-developed turbulent flow in pipes.<br />
y<br />
u( x, y )<br />
u( x, y )<br />
x 1<br />
3 x<br />
x 2<br />
Which physical problems do we face when solving eqn. (3)? We neither know if for a certain<br />
type <strong>of</strong> wall-bo<strong>und</strong>ed flow a transformation as searched for in the first question exists in general,<br />
nor do we know what the transformation parameters are. The physically appropriate<br />
transformation is a non-dimensionalization that is much more than simply changing the<br />
coordinates. The crucial issue is top choose the scaling based on the physics <strong>of</strong> the problem. At a<br />
minimum, the scale basis has to satisfy two criteria. It should consist <strong>of</strong> characteristic<br />
parameters and represent problem-intrinsic scales. The fo<strong>und</strong>ation <strong>of</strong> dimensional analysis is the<br />
Π-theorem formulated by Buckingham. 2<br />
f ( x 1 ,x 2 ,...xn ) 0<br />
Here xi denote the n variables <strong>of</strong> the system having m dimensions and Δi are the non-dimensional<br />
similarity parameters <strong>of</strong> the problem.<br />
2 Buckingham, E., “On physically similar systems: illustrations <strong>of</strong> the use <strong>of</strong> dimensional equations,” Phys. Rev., 2.<br />
Ser., vol. 4, pp. 1119–1126, 1914.<br />
u( x, y )<br />
Π-theorem<br />
y<br />
!<br />
Find proper<br />
scaling parameters<br />
Δ and U<br />
= ( 1 2 n m)<br />
u( x, y)<br />
U<br />
F ! , ! ,... ! " = 0<br />
M. H. Buschmann & M. Gad-el-Hak, Abstract for <strong>BAIL</strong> <strong>2006</strong><br />
Speaker: BUSCHMANN, M.H. 33 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
M.H. BUSCHMANN, M. GAD-EL-HAK: Turbulent Bo<strong>und</strong>ary Layers: Reality and<br />
Myth<br />
✬<br />
Which mathematical techniques do we have to solve eqn. (3)? Basically we have analytical,<br />
numerical, and asymptotic methods and combination <strong>of</strong> those. 3 In this paper, we will focus on<br />
recent advances in analytical and asymptotic approaches.<br />
During the mid 1990s, a new debate on the aforementioned subject arose. Caused by new<br />
unconventional approaches questioning one <strong>of</strong> the cornerstones <strong>of</strong> modern fluid mechanics—the<br />
logarithmic law <strong>of</strong> turbulent bo<strong>und</strong>ary layers—several new scalings were developed. In<br />
conjunction with these theoretical investigations, high-quality experiments in zero-pressuregradient<br />
turbulent bo<strong>und</strong>ary layers and turbulent pipe and channel flows were <strong>und</strong>ertaken. In<br />
general, the physical picture <strong>of</strong> wall-bo<strong>und</strong>ed flow is now much more complex than was thought<br />
a decade ago. However, the physical picture seems to be also more controversial than ever<br />
before. Which <strong>of</strong> these new approaches will survive and contribute substantially to fluid<br />
mechanics in the future is still open.<br />
The present talk will discuss four main schools <strong>of</strong> thought, which can be summarized as follows:<br />
(1) Standard Logarithmic Overlap Layer<br />
Above a certain critical Reynolds number, a pure logarithmic region exists in the<br />
mean-velocity pr<strong>of</strong>ile <strong>of</strong> ZPG TBL and channel and pipe flows. The parameters <strong>of</strong><br />
this logarithmic law are completely Reynolds number invariant.<br />
(2) Power Law Based On Similarity Assumption<br />
An inner and an outer power law describe the overlap layer <strong>of</strong> ZPG TBL and<br />
channel and pipe flows. Both laws exhibit Reynolds number dependent<br />
parameters, and never achieve an asymptotic state.<br />
(3) Asymptotic Invariance Principle<br />
Full similarity solutions have to be searched separately for the inner and outer<br />
equations. Because in the limit the outer bo<strong>und</strong>ary layer equations are independent<br />
<strong>of</strong> Reynolds number, the properly scaled pr<strong>of</strong>iles for the outer region must also be<br />
independent <strong>of</strong> Reynolds number.<br />
(4) Higher-Order Asymptotic Matching<br />
Based on asymptotic matching, a higher-order approach with respect to Reynolds<br />
number and the wall-normal coordinate can be derived. In the limit <strong>of</strong> infinite<br />
Reynolds number, the classical logarithmic law is recovered. At finite Re,<br />
however, the similarity laws for both the mean and higher-order statistics are<br />
Reynolds-number dependent.<br />
The presentation will summarize, analyze and critique the recent theoretical and experimental<br />
investigations <strong>of</strong> a variety wall-bo<strong>und</strong>ed flows. Based on that analysis, open issues in the field<br />
will be highlighted.<br />
3 Gersten, K., and Herwig, H., Strömungsmechanik, F<strong>und</strong>amentals and Advances in the Engineering Science, Verlag<br />
Vieweg, 1992.<br />
✫<br />
Analytical<br />
methods<br />
Asymptotic<br />
methods<br />
Numerical<br />
methods<br />
M. H. Buschmann & M. Gad-el-Hak, Abstract for <strong>BAIL</strong> <strong>2006</strong><br />
Speaker: BUSCHMANN, M.H. 34 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
A. NAYAK, D. DAS: Three-dimesnional Temporal Instability <strong>of</strong> Unsteady Pipe Flow<br />
✬<br />
✫<br />
Three-dimensional Temporal Instability <strong>of</strong> Unsteady Pipe Flow<br />
By<br />
Avinash Nayak and Debopam Das<br />
Department <strong>of</strong> Aerospace Engineering<br />
Indian <strong>Institut</strong>e <strong>of</strong> Technology Kanpur, India<br />
Introduction:<br />
In this paper we present temporal three-dimensional linear stability analysis <strong>of</strong> unsteady<br />
bi-directional laminar flow in a duct. For a known but arbitrary volume flow rate, analytical<br />
solution <strong>of</strong> one-dimensional unsteady flow through a pipe has been obtained by Das & Arakeri<br />
(1998, 2000). Generalized form <strong>of</strong> this solution and the solution for unsteady flow through<br />
annular space between two concentric pipes has been obtained by Nayak (2005). Prior to this<br />
study, solutions that are available in the literature were for known pressure gradient (Womersley<br />
1955) and Uchida 1956). Das (1998) and Das & Arakeri (1998) have observed the transitional<br />
nature <strong>of</strong> this flow in a pipe and channel where the velocity pr<strong>of</strong>iles are inflectional and have<br />
reverse flow near wall. In their experiments, for flows with average volume flow rate varying like<br />
a trapezoidal function with time, shows that both axisymmetric and non-axisymmetric mode <strong>of</strong><br />
disturbance grows. In this paper through linear stability analysis <strong>of</strong> three dimensional disturbances<br />
some <strong>of</strong> the observed experimental facts are explained such as growth <strong>of</strong> helical modes for certain<br />
cases.<br />
Linear stability analysis:<br />
The disturbance stream-function is assumed as<br />
{ u , v,<br />
w,<br />
p}<br />
= { u(<br />
r)<br />
, v(<br />
r ) , w(<br />
r ) , p(<br />
r ) } exp[<br />
iα<br />
( z − ct)<br />
+ inθ<br />
] . (1)<br />
Here, u, v and w are radial, azimuthal and axial perturbation velocity components respectively and<br />
p is the fluctuating pressure. The disturbance quantities are substituted in perturbed Navier-Stokes<br />
equations in cylindrical coordinates and the governing equations after simplifications are,<br />
2<br />
1 ⎡1+<br />
n<br />
⎤ 2in<br />
1 ⎡ iv 2 3 3 3 ⎤<br />
u′<br />
′ + u′<br />
− ⎢ + α + iα<br />
Re( W − c)<br />
− −<br />
2<br />
⎥u<br />
v 2 2 ⎢u<br />
+ u′<br />
′<br />
− u′<br />
′ + u′<br />
− u<br />
2 3 4<br />
r<br />
⎥<br />
⎣ r<br />
⎦ r α ⎣ r r r r ⎦<br />
2<br />
in ⎡1<br />
2 3 3 ⎤ ⎡n<br />
2<br />
⎤⎧<br />
1 ⎡ 1 1 ⎤ in ⎡1<br />
1 ⎤⎫<br />
−<br />
Re( )<br />
2 ⎢ v′<br />
′<br />
− v′<br />
′ + v′<br />
− v<br />
2 3 4 ⎥ + ⎢ + α + iα<br />
W − c<br />
2<br />
⎥⎨<br />
+<br />
2 ⎢u′<br />
′ + u′<br />
− u 2 ⎥ 2 ⎢ v′<br />
− v 2 ⎥⎬<br />
α ⎣r<br />
r r r ⎦ ⎣ r<br />
⎦⎩α<br />
⎣ r r ⎦ α ⎣r<br />
r ⎦⎭<br />
2 ⎡ 2n<br />
⎤⎧<br />
1 ⎡ 1 ⎤ in ⎡1<br />
⎤⎫<br />
i i<br />
+ ⎢−<br />
+ iα<br />
ReW<br />
′<br />
− Re ′ ′ − Re ′<br />
= 0 − − − − − −(<br />
1)<br />
3<br />
⎥⎨<br />
+<br />
2 ⎢u′<br />
+ u⎥<br />
2 ⎢ v⎥⎬<br />
u W uW<br />
⎣ r<br />
⎦⎩α<br />
⎣ r ⎦ α ⎣r<br />
⎦⎭<br />
α α<br />
2<br />
1 ⎡1+<br />
n 2<br />
v′′<br />
+ v′<br />
−⎢<br />
+ α + iα<br />
Re<br />
2<br />
r ⎣ r<br />
2<br />
in⎡n<br />
2<br />
+ ⎢ + α + iαRe<br />
2<br />
r ⎣r<br />
( W −c)<br />
2<br />
⎤ 2in<br />
in ⎡1<br />
2 1 1 ⎤ n ⎡ 1 1 1 ⎤<br />
⎥v<br />
+ u − 2 2 ⎢ u ′′′ + u′′<br />
− u′<br />
+ u +<br />
2 3 4 ⎥ 2 ⎢ v′<br />
− v′<br />
+ v<br />
2 3 4 ⎥<br />
⎦ r α ⎣r<br />
r r r ⎦ α ⎣r<br />
r r ⎦<br />
⎤⎧<br />
1 ⎡ 1 ⎤ in ⎡1<br />
⎤⎫<br />
n ⎛1<br />
⎞<br />
⎥⎨<br />
⎜ ⎟<br />
2 ⎢<br />
+<br />
⎥ 2 ⎢ ⎥⎬<br />
⎦⎩α<br />
⎣ r ⎦ α ⎣r<br />
⎦⎭<br />
α ⎝r<br />
⎠<br />
( W −c)<br />
u′<br />
u + v + Re u W′<br />
= 0−<br />
−−<br />
−−<br />
−−(<br />
2)<br />
These equations are solved using the finite difference technique and it is written in the form<br />
<strong>of</strong> ⎧u<br />
⎫<br />
( [ ] [ ] )<br />
. The complex eigenvalues c , are obtained for a particular value <strong>of</strong> α and<br />
A − c B = 0<br />
⎨ ⎬<br />
⎩ v ⎭<br />
Re, using MATLAB. In these two sets <strong>of</strong> equations u has the highest 4 th derivative while has<br />
v<br />
rd<br />
the highest 3 derivative. Thus 7 bo<strong>und</strong>ary conditions are required to solve these two coupled<br />
equations. Following are the bo<strong>und</strong>ary conditions given for different values <strong>of</strong> n .<br />
n<br />
0<br />
R=0<br />
(center-line)<br />
R=1<br />
(at wall)<br />
u = 0<br />
u = 0<br />
v = 0<br />
v = 0<br />
u ′ = 0<br />
u ′ = 0<br />
1<br />
u + iv = 0 u ′ = 0 v ′ = 0<br />
−1<br />
lim ∝ n<br />
u r<br />
R=0<br />
(center-line)<br />
Speaker: DAS, D. 35 <strong>BAIL</strong> <strong>2006</strong><br />
r→0<br />
✩<br />
✪
A. NAYAK, D. DAS: Three-dimesnional Temporal Instability <strong>of</strong> Unsteady Pipe Flow<br />
✬<br />
✫<br />
2<br />
>2<br />
R=1<br />
(at wall)<br />
R=0<br />
(center-line)<br />
R=1<br />
(at wall)<br />
R=0<br />
(center-line)<br />
R=1<br />
(at wall)<br />
u = 0 v = 0 u ′ = 0<br />
u = 0 v = 0 u ′ + iv′<br />
= 0 3 u ′′ + 2iv<br />
′′ = 0<br />
u = 0 v = 0 u ′ = 0<br />
u = 0 v = 0 u ′ = 0 v ′ = 0<br />
u = 0 v = 0 u ′ = 0<br />
Table. 1 Bo<strong>und</strong>ary conditions for perturbation at wall and the centerline<br />
For n=0, the two equations decouple to give a fourth order equation in u and a second order<br />
n−1<br />
equation in v . For n=1, the seventh condition is u ∝ r when limr → 0 (Batchelor & Gill<br />
1962).<br />
4.4 Results and Discussions<br />
We have considered a case (case2 <strong>of</strong> Das & Arakeri 1998) in which a perceptible wave was<br />
observed through flow visualization at time t= t . During this period the piston has stopped after a<br />
p<br />
( 2<br />
trapezoidal motion and the pr<strong>of</strong>ile considered for analysis is at time<br />
1<br />
t t2<br />
t p t<br />
4<br />
− + = ) where, t2<br />
is<br />
the time when piston has stopped. The neutral stability curves are shown in figure 1. It is observed<br />
that critical Reynolds number for n=1 mode is minimum (=398). Figure 2 shows the<br />
corresponding flow visualization picture <strong>of</strong> Das & Arakeri (1998). The position <strong>of</strong> vortex wave at<br />
0<br />
90 phases between top and bottom portion <strong>of</strong> pipe is visible in figure 2. Hence the helical mode<br />
with n=1 is most unstable in this case. As the neutral curve for n=0 mode is close to n=1 mode for<br />
some cases n=0 mode might be most unstable mode. Symmetric modes has been observed as most<br />
unstable in other cases experimentally (Das & Arakeri 1998 case 3 ). The stability analysis will be<br />
shown in the final paper for these cases, but the neutral curves (figure1) itself indicate the<br />
possibility <strong>of</strong> growth <strong>of</strong> such axisymmetric modes. The calculated wave length is λ<br />
≈ 3.<br />
22<br />
δ<br />
matches with the wavelength observed in experiment, the value <strong>of</strong> which is approximately 3.0.<br />
alpha (α)<br />
8<br />
7<br />
6<br />
5<br />
4<br />
3<br />
2<br />
Neutral Stability Curve for n 0, 1 & 2<br />
n=0<br />
n=1<br />
n=2<br />
1<br />
200 300 400 500 600 700 800 900 1000 1100 1200<br />
Reynolds number (Re)<br />
Fig.1 Neutral Stability Curve for different n Fig. 2 Flow viz. picture <strong>of</strong> Das & Arakeri (case2)<br />
REFERENCES<br />
1. Batchelor, G. K. & Gill, A. E. 1962. J. Fluid Mech. 14, 529.<br />
2. Das, D. 1998 Ph.D Thesis, Department <strong>of</strong> Mechanical Engg, Indian <strong>Institut</strong>e <strong>of</strong> Science, Bangalore.<br />
3. Das, D. & Arakeri, J. H. 1998. J. Fluid Mech. 374, 251-283.<br />
4. Das, D. & Arakeri, J. H. 2000 Unsteady Jl. Applied Mech. 67, 274-281.<br />
5. Nayak, A. 2005 MTech report Dept <strong>of</strong> Aerospace Engg, Indian <strong>Institut</strong>e <strong>of</strong> Technology, Kanpur.<br />
6. Uchida, S. 1956 Z. Angrew. Math. Phys. 7, 403-422.<br />
7. Weinbaum, S. & Parker, K. 1975. J. Fluid Mech. 69, 729-752.<br />
Speaker: DAS, D. 36 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
J. HUSSONG, N. BLEIER, V.V. RAM: The structure <strong>of</strong> the critical layer <strong>of</strong> a swirling<br />
annular flow in transition<br />
✬<br />
✫<br />
The structure <strong>of</strong> the critical layer <strong>of</strong> a swirling annular<br />
flow in transition<br />
J. Hussong, N. Bleier and V. Vasanta Ram<br />
Ruhr-Universität Bochum, D-44780 Bochum, Germany<br />
Subject <strong>of</strong> our paper falls <strong>und</strong>er the heading <strong>of</strong> transition <strong>of</strong> the swirling flow<br />
in an annulus. Two transition mechanisms with some f<strong>und</strong>amental differences,<br />
which we call the Taylor and the Tollmien-Schlichting mechanisms, are generally<br />
in competition with each other in this flow. The salient difference referred to<br />
is the presence <strong>of</strong> a critical layer in the Tollmien-Schlichting mechanism. In<br />
contrast, such a critical layer is absent in the Taylor mechanism. The focus <strong>of</strong><br />
attention in our work is the modification swirl causes to the structure <strong>of</strong> this<br />
critical layer in annular flow.<br />
The characteristic feature <strong>of</strong> the critical layer is that the propagation velocity<br />
<strong>of</strong> the disturbance wave is the same as the local velocity in the basic flow.<br />
Mathematically, this results in the equations for the propagation <strong>of</strong> small amplitude<br />
disturbances exhibiting a turning point, i.e. the coefficient <strong>of</strong> a crucial<br />
term in the governing differential equations crossing a zero value (see eg. [5],<br />
[6], [2], [3], [7]). For this reason viscous effects gain importance in the critical<br />
layer which may be regarded as an internal layer in the flow. The viscous effects<br />
have to be taken properly into account in the critical layer in order to arrive at<br />
the stability characteristics <strong>of</strong> the flow <strong>of</strong> interest <strong>und</strong>ergoing transition.<br />
Our basic flow is the fully developed flow with swirl in the uniform annular<br />
gap between concentric circular cylinders. In the flow in this geometrical configuration,<br />
swirl comes into existence when the axial pressure gradient driving<br />
the flow acts in conjunction with a rotation <strong>of</strong> a cylinder about its own axis.<br />
We restrict our attention for the present to the case when the outer cylinder is<br />
set in rotation at an angular velocity Ωa and the inner cylinder is pulled axially<br />
at a translational velocity Vwi. Both <strong>of</strong> these flow bo<strong>und</strong>ary conditions tend to<br />
raise the critical Reynolds number <strong>of</strong> the flow. The geometrical and flow pa-<br />
rameters in our problem are, in a self-explanatory notation: the transverse curvature<br />
parameter ɛR = Ra−Ri<br />
Uref x (Ra−Ri)<br />
, the Reynolds number Re = Ra+Ri 2 ν with<br />
Uref x = (Ra−Ri)2 � �<br />
� dPG<br />
Uref �,<br />
ϕ<br />
8µ dx the swirl parameter Sa = Uref x with Uref ϕ = ΩaRa and<br />
the translational wall velocity parameter Twi = Vwi<br />
Uref x .<br />
We have approached the transition problem in this flow configuration by<br />
conducting a modal analysis <strong>of</strong> the dynamics <strong>of</strong> the propagation <strong>of</strong> disturbances<br />
in the basic flow in question, starting from small amplitude disturbances for<br />
which the governing equations may be linearised. The dispersion relationship<br />
for this linearized problem may formally be written as<br />
F(ɛR, Re, Sa, Twi, λx, nϕ, ω) = 0,<br />
Speaker: RAM, V.V. 37 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
J. HUSSONG, N. BLEIER, V.V. RAM: The structure <strong>of</strong> the critical layer <strong>of</strong> a swirling<br />
annular flow in transition<br />
✬<br />
✫<br />
where ω is the frequency, λx the disturbance wave number in the axial direction<br />
and nϕ the corresponding quantity in azimuthal direction which has to be an<br />
integer. nϕ = 0 represents an axisymmetric disturbance whereas nϕ �= 0 corresponds<br />
to helical disturbances. We have solved the linearised equations for<br />
the disturbance numerically by the spectral collocation method using Matlab<br />
over a range <strong>of</strong> parameters ɛR, Sa and Twi to determine the dependence <strong>of</strong> the<br />
critical Reynolds number on the parameters Sa and Twi from which the wave<br />
velocity and the location <strong>of</strong> the critical layer at this Reynolds number have been<br />
obtained. A sample <strong>of</strong> the computational results is presented in Fig. 1.<br />
c = omega / lambda x<br />
0.3<br />
0.29<br />
0.28<br />
0.27<br />
0.26<br />
0 0.1 0.2<br />
S<br />
a<br />
0.3 0.4<br />
c = omega / lambda x<br />
0.3<br />
0.28<br />
0.26<br />
0.24<br />
0.22<br />
0 0.1 0.2<br />
T<br />
wi<br />
0.3 0.4<br />
Figure 1: wave velocity for Twi = 0.1 (left) and Sa = 0.1 (right)<br />
An asymptotic analysis <strong>of</strong> the critical layer, conducted along the same lines<br />
as for the corresponding case in planar flow (see eg. [1], [4]), brings out the following<br />
points as the outstanding features <strong>of</strong> the critical layer <strong>und</strong>er the influence<br />
<strong>of</strong> swirl:<br />
• Swirl exerts no influence on the scale <strong>of</strong> thickness <strong>of</strong> the critical layer<br />
through its axisymmetric disturbance mode, nϕ = 0<br />
• For the nonaxisymmetric modes, nϕ �= 0, the thickness <strong>of</strong> the critical<br />
layer retains the same scale as in the case <strong>of</strong> classical planar flow , viz.<br />
1 − O(λxRe) 3 , as long as the product <strong>of</strong> the transverse curvature and swirl<br />
1 − parameters, ɛRSa, remains small to within O(Re 3 )<br />
Results obtained from this asymptotic analysis <strong>of</strong> the critical layer are set<br />
against the computational results outlined above.<br />
References<br />
[1] Drazin, Reid, Hydrodynamic stability, Cambridge Univ. Pr., 1982.<br />
[2] Hinch, E. J., Perturbation Methods, Cambridge Univ. Pr., 1992.<br />
[3] Holmes, M. H., Introduction to Perturbation Methods, 20 in the Series Texts in Applied<br />
mathematics, Springer, 1995.<br />
[4] Maslowe, S. A., Critical layers in shear flows. In Annual Review <strong>of</strong> Fluid Mechanics, 18,<br />
1986, 405-432.<br />
[5] Nayfeh, A. H., Perturbation Methods, John Wiley, 1973.<br />
[6] O Malley Jr., R. E., Introduction to Singular Perturbations, 14 in the Series Applied Mathematics<br />
and Mechanics, Academic Press, 1974.<br />
[7] Verhulst, F., Methods and Applications <strong>of</strong> Singular Perturbations, 50 in the Series Texts<br />
in Applied mathematics, Springer, 2000.<br />
2<br />
Speaker: RAM, V.V. 38 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
T.K. SENGUPTA, A. KAMESWARA RAO: Spatio-temporal growing waves in<br />
bo<strong>und</strong>ary-layers by Bromwich contour integral method<br />
✬<br />
✫<br />
��Ô�ÖØÑ�ÒØÓ���ÖÓ×Ô���Ò��Ò��Ö�Ò�ÁÁÌÃ�ÒÔÙÖÍÈ ËÔ�Ø�ÓØ�ÑÔÓÖ�Ð�ÖÓÛ�Ò�Û�Ú�×�Ò�ÓÙÒ��ÖÝÐ�Ý�Ö×�Ý�ÖÓÑÛ�� ÌÃË�Ò�ÙÔØ��Ò��Ã�Ñ�×Û�Ö�Ê�Ó ÓÒØÓÙÖ�ÒØ��Ö�ÐÑ�Ø�Ó�<br />
ÔÐ�Ý×Ô�Ø��Ð�ÖÓÛØ��Ú�ÒÛ��ÒØ��×�×ÔÓ×���×�×Ô��Ø�Ñ���Ô�Ò��ÒØÔÖÓ�Ð�Ñ ÁØ�×Û�ÐÐ�ÒÓÛÒØ��ØÙÒ×Ø��Ð�Þ�ÖÓÔÖ�××ÙÖ��Ö����ÒØ�ÓÙÒ��ÖÝÐ�Ý�Ö��× ÁÒ��� ��<br />
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×Ô�Ø��ÐÒÓÖÑ�ÐÑÓ��×��Ú����Ò�Ú�ÐÙ�Ø���Ý�Ö��×��Ö�Ø��Ò�ÕÙ��ÑÔÐÓÝ�Ò� Ñ�ÒØØ���Ò�××À�Ö���Ð�×�Ù×�ÓÙÒ��ÖÝÐ�Ý�Ö�×ÓÒ×���Ö��Û�Ó×��Ü�×Ø�Ò� Û��Ö�ÍÝ�×Ø��Ñ��ÒÓÛ�Ò�Ø��Ê�ÝÒÓÐ�×ÒÙÑ��Ö�×��×��ÓÒ��×ÔÐ�� Í ¬�«� «� Í���«Ê���Ú «� «��<br />
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��Õ�Ò�� �××ÓÐÚ���ÐÓÒ�Ø���ÖÓÑÛ��ÓÒØÓÙÖ×�� �¬Ö��¬��� ×Ù�Ø��Ø��Ù×�Ð�ØÝÔÖ�Ò�ÔÐ��×ÒÓØ �«Ö��«�� �Ö���ÐÓÛ<br />
Ö�ÓÒ×ØÖÙØØ����×ØÙÖ��Ò�¬�Ð��Ò�Õ ÑÓ��×�××Ø��Ð�Ø��ÓÒØÓÙÖ�ÒØ��Ö�ÐÖ�×ÙÐØ×�Ò¬�ÙÖ�×�ÓÛ��ÐÓ�Ð×ÓÐÙØ�ÓÒ� Ú�ÓÐ�Ø���Ò�Û�Ú�×ØÖ�Ú�Ð�ÒØ��ÓÖÖ�Ø��Ö�Ø�ÓÒÇ�Ø��Ò���×�Ö�Ù×��ØÓ �Ò¬�ÙÖ��ÓÖØ���×�Ó�¬���Ï��Ð�Ø��Ø��Ð�×�ÓÛ×�ÐÐØ�Ö��×Ô�Ø��Ð Ø�Ñ�Ø�����Ý�Ò�Û�Ú�ÓÖÖ�×ÔÓÒ�×ØÓÑÓ����Ò�Ø��Ô���ØÓÖÖ�×ÔÓÒ�×ØÓ ������Ý�Ò�Û�Ú��Ò�����Ø�ÑÔÓÖ�ÐÐÝ�ÖÓÛ�Ò�Û�Ú�Ô���Ø��Ø�Ö×ÙÆ��ÒØ �Ò�Ø��Ú�ÐÓ�Øݬ�Ð��Ö��×ÔÐÓØØ��<br />
Speaker: SENGUPTA, T.K. 39 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
T.K. SENGUPTA, A. KAMESWARA RAO: Spatio-temporal growing waves in<br />
bo<strong>und</strong>ary-layers by Bromwich contour integral method<br />
✬<br />
✫<br />
ÑÓ���Ó�Ø��Ð� �ØØ���Ø��ØÐ��ÖÐÝ���Ò�Ø���×Ø��ÑÓ��×��Ò���Ò�ÓØ��Ö×Ø��Ø�Ö�×� Ö�Ø�ÁÒ¬�ÙÖ��ÒÚ�Ö×�Ä�ÔÐ��ØÖ�Ò×�ÓÖÑÓ�Ø����Ø��××�ÓÛÒ�ÓÖØ��×��Ò�Ð Ó�Ø��×��Ò�Ð �Ù�ØÓ�ÒØ�Ö�Ø�ÓÒ×Ó�ÑÓ��×Ø��Ø×�ÓÛÙÔ�×Ø��×Ô�Ø�ÓØ�ÑÔÓÖ�ÐÔÖÓÔ���Ø�ÓÒ ÅÓ�� �×Ò�Ú�ÖÚ�×��Ð��Ù�ØÓ�Ø×�ÜØÖ�Ñ�ÐÝÐ�Ö�����Ý<br />
�Ò�Ø���Ö�ÒØ�Ö�Ø�ÓÒ×�ÑÔ��×�Þ�Ò�Ø��Ò���ØÓÔ�Ö�ÓÖÑ×Ô�Ø�ÓØ�ÑÔÓÖ�Ð�Ò�ÐÝ×�× �Ò×Ø���Ó�Ø�ÑÔÓÖ�ÐÓÖ×Ô�Ø��ÐØ��ÓÖ��× Ê���Ö�Ò�×� ÓÑÔ�Ö�×ÓÒ�ÓÖØ���×ÝÑÔØÓØ�Ô�ÖØÓ�Ø��×ÓÐÙØ�ÓÒÓÑÔÖ�×�Ò�Ó���«�Ö�ÒØÑÓ��× ÁÒØ��¬Ò�ÐÔ�Ô�ÖÛ�Û�ÐÐÔÖ�×�ÒØ�Ò�ÐÝ×�×�ÓÖØ��ÐÓ�Ð×ÓÐÙØ�ÓÒ�Ò���Ø��Ð��<br />
�℄ÄÆÌÖ���Ø��Ò�Ø�ÐË��Ò������� �℄ÌÃË�Ò�ÙÔØ��Ø�ÐÈ�Ý×�×�ÐÙ��×� Ä�ÔÐ��ÁÒØ��Ö�Ð��Ñ�Ö����ÍÒ�ÚÈÖ�××��� �℄�Î�Ò��ÖÈÓÐÀ�Ö�ÑÑ�ÖÇÔ�Ö�Ø�ÓÒ�Ð��ÐÙÐÙ×��×��ÓÒÌÛÓ×���� ���<br />
0.002<br />
u′<br />
0<br />
Table 1:<br />
β0 αr αi<br />
1) 0.0621 413 0.0696 594<br />
0.05<br />
2) 0.1607 670 0.0015 206<br />
3) 0.1894 256 0.3226 357<br />
0.15 4) 0.2728 701 0.1675 585<br />
5) 0.3940 036 0.0104 936<br />
t = 110.0<br />
-0.002<br />
0 100 200<br />
x<br />
300 400<br />
0.002<br />
0<br />
-0.002<br />
5 4<br />
0 100 200<br />
x<br />
300 400<br />
u′<br />
t = 411.6<br />
0.002<br />
0<br />
-0.002<br />
5 4<br />
0 100 200<br />
x<br />
300 400<br />
u′<br />
0.002<br />
t = 637.7<br />
0<br />
-0.002<br />
5 4<br />
0 100 200<br />
x<br />
300 400<br />
Figure 1: Streamwise disturbance velocity plotted as a function <strong>of</strong> x at different<br />
t for β0 = 0.15,Re = 1000 at y = 0.278δ ∗<br />
φ′<br />
0.6<br />
0.4<br />
0.2<br />
u′<br />
3 4 5<br />
t = 801.1<br />
0<br />
0 0.1 0.2<br />
α<br />
0.3 0.4 0.5<br />
Figure 2: FFT <strong>of</strong> streamwise disturbance velocity plotted as a function <strong>of</strong> α<br />
Speaker: SENGUPTA, T.K. 40 <strong>BAIL</strong> <strong>2006</strong><br />
t = 801.1<br />
✩<br />
✪
L. SAVIĆ, H. STEINRÜCK: Asymptotic Analysis <strong>of</strong> the mixed convection flow past a<br />
horizontal plate near the trailing edge<br />
✬<br />
✫<br />
Asymptotic Analysis <strong>of</strong> the mixed convection flow past a horizontal plate<br />
near the trailing edge<br />
1. Introduction<br />
Lj. Savić and H. Steinrück<br />
<strong>Institut</strong>e <strong>of</strong> Fluid Mechanics and Heat Transfer<br />
Vienna University <strong>of</strong> Technology<br />
Resselgasse 3, 1040 Vienna, Austria<br />
herbert.steinrueck@tuwien.ac.at<br />
The flow near the trailing edge <strong>of</strong> a horizontal heated plate which is aligned <strong>und</strong>er a small angle<br />
<strong>of</strong> attack φ to the oncoming parallel flow with velocity U∞ in the limit <strong>of</strong> large Reynolds Re<br />
and large Grash<strong>of</strong> Gr = gβ∆TL 3 /ν 2 number will be investigated (see figure 1). As usual β<br />
and ν denote the isobaric expansion coefficient and the kinematic viscosity, respectively. The<br />
difference between the plate temperature and the temperature <strong>of</strong> the oncoming fluid is ∆T and<br />
L is the length <strong>of</strong> the plate. A measure for the influence <strong>of</strong> the buoyancy onto the bo<strong>und</strong>ary<br />
layer flow along a horizontal plate is the buoyancy parameter K = GrRe−5/2 PSfrag replacements<br />
as defined in [4]).<br />
U∞ = 1, θ∞ = 0<br />
φ<br />
g<br />
−1 θp = 1<br />
0<br />
y<br />
Re −1/2<br />
K<br />
x<br />
Figure 1: Mixed convection flow past a horizontal plate.<br />
The starting point <strong>of</strong> the analysis are the Navier Stokes equations for an incompressible fluid<br />
using Bousinesq’s approximation to take buoyancy forces into account and the energy equation.<br />
Additionally to the above mentioned dimensionless parameters the Prandtl number Pr, which<br />
is assumed to be <strong>of</strong> order one, and the angle <strong>of</strong> attack φ enter the problem.<br />
To analyze the flow behavior near the trailing edge in the frame work <strong>of</strong> interacting bo<strong>und</strong>ary<br />
layers ([1, 2] it turns out that the buoyancy parameter K and the angle <strong>of</strong> attack φ have to be <strong>of</strong><br />
the order Re −1/4 . Thus we define the reduced buoyancy parameter κ = K Re 1/4 and the reduced<br />
inclination parameter λ = φK √ Re. We note that the magnitude <strong>of</strong> φ is not only dictated by<br />
the trailing edge analysis, but it is also a consequence <strong>of</strong> the analysis <strong>of</strong> the far field (see [5]). As<br />
we will see the inclination parameter λ will play no role in the trailing edge analysis. Only for<br />
positive values <strong>of</strong> λ an outer potential flow field exists [5]. We remark that in case <strong>of</strong> symmetric<br />
flow conditions (upper side <strong>of</strong> the plate heated, lower side cooled) the interaction mechanism<br />
would allow K to be larger, namely <strong>of</strong> order Re −1/8 . However, the scope <strong>of</strong> the present paper<br />
will be limited to the flow near the trailing edge.<br />
2. Asymptotic structure <strong>of</strong> the solution<br />
For the analysis <strong>of</strong> the flow field near the trailing edge the velocities, the pressure and the<br />
temperature are decomposed into a symmetric and anti-symmetric part. To leading order for<br />
the symmetric part the classical triple deck problem [1, 2] is obtained. For the anti-symmetric<br />
part (difference <strong>of</strong> the flow quantities above and below the plate) a new interaction mechanism<br />
is obtained. The difference <strong>of</strong> the displacement thicknesses between the upper and lower side<br />
Speaker: STEINRÜCK, H. 41 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
L. SAVIĆ, H. STEINRÜCK: Asymptotic Analysis <strong>of</strong> the mixed convection flow past a<br />
horizontal plate near the trailing edge<br />
✬<br />
✫<br />
<strong>of</strong> the plate ∆A interacts not only via the potential flow in the upper deck but also via the<br />
hydrostatic pressure in the main deck with the pressure ∆p in the lower deck. The interaction<br />
law for the pressure difference between the upper and lower side can be written in the form<br />
∆A ′ (x (3) ) + √ 3ash(x (3) �<br />
) x (3)� 1/3<br />
=<br />
� � 0 1 ∆ˆp(ξ) + 2as|ξ|<br />
−<br />
π −∞<br />
1/3<br />
x (3) dξ −<br />
− ξ<br />
1<br />
� ∞ As(ξ) − ash(ξ)|ξ|<br />
π −∞<br />
1/3<br />
x (3) �<br />
dξ<br />
− ξ<br />
Where As(x (3) ) is the displacement thickness obtained for the classical trailing edge problem<br />
[3, 1] and x (3) is the coordinate in the lower, main and upper deck parallel to the plate. Here as<br />
is a constant and h(.) the heayside function. It turns out that the difference pressure ∆p has a<br />
discontinuity at the trailing edge. Thus new sub-layers (in the main and lower deck) to resolve<br />
this discontinuity are introduced.<br />
In the following table we give an overview <strong>of</strong> the most important layers needed for the<br />
asymptotic analysis. We introduce the following notation according to the stretching factor as<br />
a power <strong>of</strong> the Reynolds number: x (α) = Re α/8 x and y (β) = Re β/8 y.<br />
α β flow region<br />
0 0 potential flow region<br />
0 4 bo<strong>und</strong>ary layer and wake<br />
3 3 upper deck<br />
3 4 main deck<br />
3 5 lower deck<br />
4 4 main deck - trailing edge<br />
5 5 lower deck - trailing edge<br />
Table 1: Scales <strong>of</strong> the different flow regions<br />
The new results <strong>of</strong> the analysis will be the local behavior <strong>of</strong> the difference pressure at the<br />
trailing edge. For both <strong>of</strong> the newly introduced sub-layers elliptic equations for the local pressure<br />
variation can be derived and will be solved numerically. Thus on triple deck scales there will be<br />
a flow aro<strong>und</strong> the trailing edge. Thus the perturbation <strong>of</strong> the classical triple deck problem by<br />
small buoyancy effects behaves quite differently than by small angles <strong>of</strong> attack [3].<br />
References<br />
[1] K. Stewartson, On the flow near the trailing edge <strong>of</strong> flat plate, Mathematika, 16, 106-121<br />
(1969).<br />
[2] A.F. Messiter, Bo<strong>und</strong>ary layer flow near the trailing edge <strong>of</strong> flat plate, SIAM J. Appl. Math.,<br />
18, 241-257, (1970).<br />
[3] R. Chow and R. E. Melnik, Numerical Solutions <strong>of</strong> Triple-Deck Equations for Laminar<br />
Trailing Edge Stall, Grumman Research Dept., Report RE-526J (1976).<br />
[4] W. Schneider and M. G. Wasel, Breakdown <strong>of</strong> the bo<strong>und</strong>ary-layer approximation for mixed<br />
convection flow above a horizontal plate, Int. J. Heat Transfer, 28, 2307-2313 (1985).<br />
[5] Lj. Savić and H. Steinrück, Mixed convection flow past a horizontal plate, Theoretical and<br />
Applied Mechanics, 32, 1-19 (2005).<br />
Speaker: STEINRÜCK, H. 42 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
G.I. Shiskin, P. Hemker<br />
Robust Methods for Problems with Layer Phenomena and Additional Singularities<br />
Speaker:<br />
The minisymposium will be concerned with singularly perturbed<br />
multiscale problems having additional singularities. A complicated<br />
geometry or unbo<strong>und</strong>edness <strong>of</strong> the domain and/or the lack <strong>of</strong> sufficient<br />
smoothness (or compatibility) <strong>of</strong> the problem data may result in<br />
singular solutions that have their own specific scales, besides bo<strong>und</strong>ary/interior<br />
layers. We intend to examine techniques for constructing<br />
numerical methods that converge parameter-uniformly (in the maximum<br />
norm).<br />
The following research aspects will be also considered: (i) As a rule,<br />
such parameter-uniformly convergent numerical methods have too low<br />
order <strong>of</strong> uniform convergence, which restricts their applicability in<br />
practice. With this respect, methods how to increase the accuracy <strong>of</strong><br />
parameter-uniformly convergent numerical methods will be considered.<br />
(ii) When standard numerical methods, for example, domain decomposition<br />
methods are used to find solutions <strong>of</strong> parameter-uniformly convergent<br />
discrete approximations, the decomposition errors <strong>of</strong> the discrete<br />
solutions and the number <strong>of</strong> iterations required to solve the discrete<br />
problem depend on the perturbation parameter and grow when it tends<br />
to zero. We will consider decomposition methods preserving the property<br />
<strong>of</strong> parameter-uniform convergence. Domain decomposition and<br />
local defect correction techniques allows us to reduce the construction<br />
<strong>of</strong> robust numerical methods for multiscale problems to locally robust<br />
methods for monoscale problems on the specific subdomains. Other aspects<br />
and applications will be also <strong>und</strong>er consideration. Problems for<br />
partial differential equations with different types <strong>of</strong> bo<strong>und</strong>ary and interior<br />
layers will be considered. To construct special numerical methods,<br />
fitted meshes, which are a priori and a posteriori condensing in the layer<br />
regions, are used.<br />
• Deirdre Branley: A Schwarz method for a convection-diffusion problem with a<br />
corner singularity<br />
• Thorsten Linss: Layer-adapted meshes for time-dependent reaction-diffusion<br />
• Grigory I. Shishkin: Grid Approximation <strong>of</strong> Parabolic Equations with Nonsmooth
Initial Condition in the Presence <strong>of</strong> Bo<strong>und</strong>ary Layers <strong>of</strong> Different Types<br />
• Lidia P. Shishkina: A Difference Scheme <strong>of</strong> Improved Accuracy for a Quasilinear<br />
Singularly Perturbed Elliptic Convection-Diffusion Equation in the Case <strong>of</strong> the<br />
Third-Kind Bo<strong>und</strong>ary Condition<br />
• Irina V. Tselishcheva: Domain Decomposition Method for a Semilinear Singularly<br />
Perturbed Elliptic Convection-Diffusion Equation with Concentrated Sources<br />
• S. Valarmathi: A parameter-uniform numerical method for a system <strong>of</strong> singularly<br />
perturbed ordinary differential equations
D. BRANLEY, A.F. HEGARTY, H. PURTILL, G.I. SHISHKIN: A Schwarz method<br />
for a convection-diffusion problem with a corner singularity<br />
✬<br />
✫<br />
A Schwarz method for a convection-diffusion problem with a corner<br />
singularity. ∗<br />
Deirdre Branley 1 , Alan F. Hegarty 1 , Helen Purtill 1 and Grigory I. Shishkin 2 .<br />
1 Department <strong>of</strong> Mathematics and Statistics, University <strong>of</strong> Limerick, Plassey, Limerick, Ireland.<br />
deirdre.branley@ul.ie, alan.hegarty@ul.ie, helen.purtill@ul.ie,<br />
2 <strong>Institut</strong>e <strong>of</strong> Mathematics and Mechanics, Ural Branch <strong>of</strong> Russian Academy <strong>of</strong> Sciences<br />
16 S. Kovalevskaya Street, Ekaterinburg 620219, Russia<br />
shishkin@imm.uran.ru<br />
We are concerned with two dimensional steady state convection-diffusion problems with<br />
singular outflow bo<strong>und</strong>ary conditions. It is well known that, where the bo<strong>und</strong>ary conditions<br />
are sufficiently smooth and compatible, such problems can be solved with uniform accuracy<br />
with respect to the small parameter ε using a standard finite difference operator on special<br />
piece-wise uniform meshes [1, 2]. Where the outflow bo<strong>und</strong>ary data are only weakly regular and<br />
compatible, parameter-uniform solutions may also be obtained by this method [2]. However,<br />
orders <strong>of</strong> convergence are relatively small and pointwise errors relatively large in this case.<br />
Numerical methods for singularly perturbed problems comprising domain decomposition and<br />
Schwarz iterative technique have been examined by a number <strong>of</strong> authors, for example in [1], [3],<br />
[4] and [5]. In particular, MacMullen et al. [5] constructed a parameter-uniform Schwarz method<br />
for singularly perturbed linear convection-diffusion problems in two dimensions with sufficiently<br />
smooth and compatible bo<strong>und</strong>ary data. We examine experimentally the performance <strong>of</strong> such<br />
methods extended to the class <strong>of</strong> singularly perturbed convection-diffusion problems with more<br />
general bo<strong>und</strong>ary conditions described below.<br />
We consider problems <strong>of</strong> the form<br />
Lu ≡ ε∆uε + a(x, y).∇u = f<br />
in a domain Ω, the unit square, with Dirichlet bo<strong>und</strong>ary conditions, where all components <strong>of</strong> a<br />
are strictly positive. Such problems exhibit regular layers along the outflow bo<strong>und</strong>aries, as well<br />
as a corner bo<strong>und</strong>ary layer at the outflow bo<strong>und</strong>ary corner. We deal with outflow bo<strong>und</strong>ary<br />
conditions, where the first derivatives are not compatible at the outflow bo<strong>und</strong>ary corner. We<br />
implement domain decomposition methods to isolate the neighbourhood <strong>of</strong> the singularity, along<br />
with a Schwarz iterative technique, with the aim <strong>of</strong> developing a Schwarz method to produce<br />
parameter-uniformly accurate solutions on the whole domain in the oresence <strong>of</strong> such a singularity.<br />
References<br />
[1] J.J.H. Miller, E.O’Riordan, G.I. Shishkin, Fitted Numerical Methods for Singular Perturbation<br />
Problems, World Scientific, Singapore, 1996.<br />
[2] P.A. Farrell, A.F. Hegarty, J.J.H. Miller, E. O’Riordan, G.I. Shishkin, Robust Computational<br />
Techniques for Bo<strong>und</strong>ary Layers, Chapman & Hall, CRC, Boca Raton, FL, 2000.<br />
[3] J.J.H. Miller, E. O’Riordan, G.I. Shishkin, S. Wang, A parameter-uniform Schwarz method<br />
for a singularly-perturbed reaction-diffusion problem with an interior layer, Appl. Num.<br />
Math., 35 (2000), 323-337.<br />
∗ This research was supported in part by the Irish Research Council for Science, Engineering and Technology<br />
and by the Russian Fo<strong>und</strong>ation for Basic Research <strong>und</strong>er grant No. 04-01-00578.<br />
1<br />
Speaker: BRANLEY, D. 45 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
D. BRANLEY, A.F. HEGARTY, H. PURTILL, G.I. SHISHKIN: A Schwarz method<br />
for a convection-diffusion problem with a corner singularity<br />
✬<br />
✫<br />
[4] H. MacMullen, J.J.H. Miller, E. O’Riordan, G.I. Shishkin, A second-order parameter uniform<br />
overlapping Schwarz method for reaction-diffusion problems with bo<strong>und</strong>ary layers, J.<br />
Comput. & Appl. Math., 130 (2001), 231-244.<br />
[5] H. MacMullen, E. O’Riordan, G.I. Shishkin, The convergence <strong>of</strong> classical Schwarz methods<br />
applied to convection-diffusion problems with regular bo<strong>und</strong>ary layers, Appl. Num. Math.,<br />
43 (2002), 297-313.<br />
Speaker: BRANLEY, D. 46 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
T. LINSS, N. MADDEN: Layer-adapted meshes for time-dependent reaction-diffusion<br />
✬<br />
✫<br />
Layer-adapted meshes for time-dependent reaction-diffusion<br />
Torsten Linß 1 , Niall Madden 2<br />
1 <strong>Institut</strong> <strong>für</strong> <strong>Numerische</strong> Mathematik, Technische Universität Dresden<br />
e-mail: torsten.linss@tu-dresden.de<br />
2 Department <strong>of</strong> Mathematics, National University <strong>of</strong> Ireland Galway<br />
e-mail: niall.madden@math.nuigalway.ie<br />
ABSTRACT<br />
We consider singularly perturbed reaction-diffusion problems <strong>of</strong> the type<br />
ut + Lεu = f in (0, 1) × (0, T],<br />
where Lεv := −ε 2 vxx + rv, subject to bo<strong>und</strong>ary conditions<br />
and initial condition<br />
u(0, t) = γ0(t), u(1, t) = γ1(t) in (0, T]<br />
u(·, 0) = u 0<br />
in (0, 1)<br />
where 0 < ε ≪ 1, r(x) > ρ 2 > 0 for x ∈ [0, 1]. The nature <strong>of</strong> the differential equation changes when<br />
ε → 0 giving rise to bo<strong>und</strong>ary layers that require special attention in the design <strong>of</strong> numerical methods,<br />
in particular local refinement <strong>of</strong> the meshes used.<br />
We study an inverse monotone difference scheme on arbitrary meshes. An maximum-norm error bo<strong>und</strong><br />
is derived that allows easy classification <strong>of</strong> various layer-adapted meshes proposed in the literature.<br />
For example, this general result implies<br />
�u − U� ∞ ≤ C<br />
�<br />
τ + N −2 ln 2 N for Shishkin meshes,<br />
τ + N −2 for Bakhvalov meshes,<br />
where τ is the maximal time-step size and N the number <strong>of</strong> mesh points used in the space discretization.<br />
Speaker: LINSS, T. 47 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
G.I. SHISHKIN: Grid Approximation <strong>of</strong> Parabolic Equations with Nonsmooth Initial<br />
Condition in the Presence <strong>of</strong> Bo<strong>und</strong>ary Layers <strong>of</strong> Different Types<br />
✬<br />
✫<br />
Grid Approximation <strong>of</strong> Parabolic Equations with Nonsmooth Initial<br />
Condition in the Presence <strong>of</strong> Bo<strong>und</strong>ary Layers <strong>of</strong> Different Types ∗<br />
Grigory I. Shishkin<br />
<strong>Institut</strong>e <strong>of</strong> Mathematics and Mechanics,<br />
Ural Branch <strong>of</strong> Russian Academy <strong>of</strong> Sciences,<br />
Yekaterinburg 620219, Russia<br />
shishkin@imm.uran.ru<br />
A Dirichlet problem for a singularly perturbed parabolic equation with the perturbation<br />
vector-parameter ε, ε = (ε1, ε2), is considered on a semiaxis. The highest derivative <strong>of</strong> the<br />
equation and also the first derivative with respect to x contain respectively the parameters<br />
ε1 and ε2, which take arbitrary values in the half-open interval (0, 1] and the segment [−1, 1].<br />
Depending on the parameter ε2, the type <strong>of</strong> the equation may be reaction-diffusion or convectiondiffusion.<br />
The first order derivative <strong>of</strong> the initial function has a discontinuity <strong>of</strong> the first kind at<br />
the point x0.<br />
For small values <strong>of</strong> the parameter ε1, a bo<strong>und</strong>ary layer appears in a neighbourhood <strong>of</strong> the<br />
lateral part <strong>of</strong> the domain bo<strong>und</strong>ary. Depending on the ratio between the parameters ε1 and<br />
ε2, these layers may be regular, parabolic or hyperbolic (characteristic scales <strong>of</strong> these bo<strong>und</strong>ary<br />
layers also depend on the ratio between ε1 and ε2).<br />
In a neighbourhood <strong>of</strong> the set S γ , that is, the characteristic <strong>of</strong> the reduced equation outgoing<br />
from the point (x0, 0), the parabolic transient layer arises.<br />
Using the method <strong>of</strong> piecewise uniform meshes condensing in a neighbourhood <strong>of</strong> the layer,<br />
we construct a special difference scheme that converges ε-uniformly.<br />
Numerical methods for problems with different types <strong>of</strong> bo<strong>und</strong>ary layers for elliptic convectiondiffusion<br />
equations in the case <strong>of</strong> sufficiently smooth bo<strong>und</strong>ary data are studied, e.g., in [1].<br />
References<br />
[1] G.I. Shishkin, “Grid approximation <strong>of</strong> a singularly perturbed elliptic equations with convective<br />
terms in the presence <strong>of</strong> various bo<strong>und</strong>ary layers”, Comput. Maths. Math. Phys.,<br />
45 (1), 104–119 (2005).<br />
∗ This research was supported in part by the Russian Fo<strong>und</strong>ation for Basic Research (grants No. 04-01-00578,<br />
04–01–89007–NWO a), by the Dutch Research Organisation NWO <strong>und</strong>er grant No. 047.016.008 and by the Boole<br />
Centre for Research in Informatics, National University <strong>of</strong> Ireland, Cork.<br />
Speaker: SHISHKIN G.I. 48 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
L.P. SHISHKINA, G.I. SHISHKIN: A Difference Scheme <strong>of</strong> Improved Accuracy for a<br />
Quasilinear Singularly Perturbed Elliptic Convection-Diffusion Equation in the Case <strong>of</strong><br />
the Third-Kind Bo<strong>und</strong>ary Condition<br />
✬<br />
✫<br />
A Difference Scheme <strong>of</strong> Improved Accuracy for a Quasilinear<br />
Singularly Perturbed Elliptic Convection-Diffusion Equation<br />
in the Case <strong>of</strong> the Third Kind Bo<strong>und</strong>ary Condition ∗<br />
Lidia P. Shishkina and Grigory I. Shishkin<br />
<strong>Institut</strong>e <strong>of</strong> Mathematics and Mechanics,<br />
Ural Branch <strong>of</strong> Russian Academy <strong>of</strong> Sciences,<br />
Yekaterinburg 620219, Russia<br />
Lida@convex.ru and shishkin@imm.uran.ru<br />
A bo<strong>und</strong>ary value problem for a quasilinear singularly perturbed elliptic convection-diffusion<br />
equation on a strip is considered. The third kind bo<strong>und</strong>ary condition admitting both Dirichlet<br />
and Neumann conditions is given on the domain bo<strong>und</strong>ary. For small values <strong>of</strong> the perturbation<br />
parameter ε, a bo<strong>und</strong>ary layer arises in a neighbourhood <strong>of</strong> the outflow part <strong>of</strong> the bo<strong>und</strong>ary. For<br />
such a problem, the base (nonlinear) difference scheme constructed by classical approximations<br />
<strong>of</strong> the problem on piecewise uniform meshes condensing in the layer converges ε-uniformly with<br />
an order <strong>of</strong> accuracy not higher than 1.<br />
Our aim is for this bo<strong>und</strong>ary value problem to construct grid approximations that converge<br />
ε-uniformly with an order <strong>of</strong> convergence close to two.<br />
Using the�Richardson technique, we construct a (nonlinear) scheme that converges ε-uniformly<br />
at the rate O N −2<br />
1 ln 2 N1+N −2<br />
�<br />
2 , where N1+1 is the number <strong>of</strong> nodes in the mesh with respect<br />
to x1 and N2+1 is the number <strong>of</strong> mesh points on a unit interval along the x2-axis. Based on the<br />
nonlinear Richardson scheme, a linearized iterative scheme is constructed where the nonlinear<br />
term is computed using the unknown function taken at the previous iteration. The solution <strong>of</strong><br />
this iterative scheme converges to the solution <strong>of</strong> the nonlinear Richardson scheme at the rate <strong>of</strong><br />
a geometry progression ε-uniformly with respect to the number <strong>of</strong> iterations. Thus, the number<br />
<strong>of</strong> iterations required for solving the problem (as well as the accuracy <strong>of</strong> the resulting solution)<br />
is independent <strong>of</strong> the parameter ε.<br />
The use <strong>of</strong> lower and upper solutions <strong>of</strong> the linearized iterative Richardson scheme as a<br />
stopping criterion allows us during the computational process to define a current iteration <strong>und</strong>er<br />
which the same ε-uniform accuracy <strong>of</strong> the solution is achieved as for the nonlinear Richardson<br />
scheme. To construct the improved scheme, the technique developed in [1]–[4] for a Dirichlet<br />
problem is applied.<br />
References<br />
[1] G.I. Shishkin, “The method <strong>of</strong> increasing the accuracy <strong>of</strong> solutions <strong>of</strong> difference schemes<br />
for parabolic equations with a small parameter at the highest derivative”, USSR Comput.<br />
Maths. Math. Phys., 24 (6), 150–157 (1984).<br />
[2] G.I. Shishkin, ”Finite-difference approximations <strong>of</strong> singularly perturbed elliptic equations”,<br />
Comp. Math. Math. Phys., 38 (12), 1909–1921 (1998).<br />
[3] G.I. Shishkin and L.P. Shishkina, “A high-order Richardson method for a quasilinear singularly<br />
perturbed elliptic reaction-diffusion equation”, Differential Equations, 41 (7), 1030–<br />
1039 (2005).<br />
∗ This research was supported in part by the Russian Fo<strong>und</strong>ation for Basic Research (grants No. 04-01-00578,<br />
04–01–89007–NWO a) and by the Dutch Research Organisation NWO <strong>und</strong>er grant No. 047.016.008.<br />
Speaker: SHISHKINA, L.P. 49 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
L.P. SHISHKINA, G.I. SHISHKIN: A Difference Scheme <strong>of</strong> Improved Accuracy for a<br />
Quasilinear Singularly Perturbed Elliptic Convection-Diffusion Equation in the Case <strong>of</strong><br />
the Third-Kind Bo<strong>und</strong>ary Condition<br />
✬<br />
✫<br />
[4] L. Shishkina and G. Shishkin, “The discrete Richardson method for semilinear parabolic singularly<br />
perturbed convection-diffusion equations”, in: Proceedings <strong>of</strong> the 10th International<br />
Conference “Mathematical Modelling and Analysis” 2005 and 2nd International Conference<br />
“Computational Methods in Applied Mathematics”, R. Čiegis ed., Vilnius, “Technika”,<br />
2005, pp. 259–264.<br />
2<br />
Speaker: SHISHKINA, L.P. 50 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
I.V. TSELISHCHEVA, G.I. SHISHKIN: Domain Decomposition Method for a Semilinear<br />
Singularly Perturbed Elliptic Convection-Diffusion Equation with Concentrated<br />
Sources<br />
✬<br />
✫<br />
Domain Decomposition Method for a Semilinear Singularly Perturbed<br />
Elliptic Convection-Diffusion Equation with Concentrated Sources ∗<br />
Irina V. Tselishcheva and Grigory I. Shishkin<br />
<strong>Institut</strong>e <strong>of</strong> Mathematics and Mechanics, Ural Branch <strong>of</strong> Russian Academy <strong>of</strong> Sciences<br />
16 S. Kovalevskaya Street, Ekaterinburg 620219, Russia<br />
tsi@imm.uran.ru, shishkin@imm.uran.ru<br />
For singularly perturbed bo<strong>und</strong>ary value problems in a composed domain (in particular,<br />
with concentrated sources) whose solution has several singularities such as bo<strong>und</strong>ary and interior<br />
layers, it is <strong>of</strong> keen interest to construct a parameter-uniform numerical method based on<br />
a domain decomposition technique so that each subdomain in the decomposition contains no<br />
more than a single singularity. Because <strong>of</strong> the thin layers, standard numerical methods applied<br />
to problems <strong>of</strong> this type yield unsatisfactorily large errors for small values <strong>of</strong> the singular perturbation<br />
parameter ε. The fact that the partial differential equation is nonlinear complicates<br />
the solution process.<br />
We develop monotone linearized schemes based on an overlapping Schwarz method for a<br />
semilinear singularly perturbed elliptic convection-diffusion equation on a compo<strong>und</strong> strip in the<br />
presence <strong>of</strong> concentrated sources acting inside the domain. We first study a special (base) scheme<br />
comprising a standard finite difference operator on a piecewise-uniform fitted mesh and an<br />
overlapping domain decomposition scheme constructed on the basis <strong>of</strong> the former that converge εuniformly<br />
at the rates O � N −1 � � −1<br />
and O N<br />
1 lnN1 + N −1<br />
2<br />
1 ln N1 + N −1<br />
2 + qt� , respectively. Here<br />
N1 +1 and N2 +1 are the number <strong>of</strong> mesh points in x1 and the minimal number <strong>of</strong> mesh points<br />
in x2 on a unit interval, q < 1 is the common ratio <strong>of</strong> a geometric progression, independent <strong>of</strong> ε,<br />
t is the iteration count. For these nonlinear schemes we construct monotone linearized schemes<br />
<strong>of</strong> the same ε-uniform accuracy, in which the nonlinear term is computed from the unknown<br />
function taken at the previous iteration.<br />
The linearized schemes are monotone, which admits to construct their upper and lower<br />
solutions. We apply the technique <strong>of</strong> upper and lower solutions to find aposteriori the (optimal)<br />
number <strong>of</strong> iterations T in the linearized scheme for which the accuracy <strong>of</strong> its solution is the same<br />
(up to a constant factor) as that for the base scheme, where T = O (ln(min[N1, N2])) (see also<br />
[1] for a reaction-diffusion problem). Thus, the number <strong>of</strong> required iterations is independent <strong>of</strong><br />
ε. With respect to total computational costs, the iterative method is close to a solution method<br />
for linear problems, since the number <strong>of</strong> iterations is only weakly depending on the number <strong>of</strong><br />
mesh points used. The linearized iterative schemes inherit the ε-uniform rate <strong>of</strong> convergence <strong>of</strong><br />
the nonlinear schemes.<br />
The decomposition schemes can be computed sequentially and in parallel (so that the suproblems<br />
on the overlapping subdomains are solved independently <strong>of</strong> each other).<br />
Note that schemes <strong>of</strong> the overlapping domain decomposition method were considered earlier<br />
by the authors in [2] for linear problems and in [3, 4] for nonlinear problems.<br />
References<br />
[1] G.I. Shishkin and L.P. Shishkina, “A high-order Richardson method for a quasilinear singularly<br />
perturbed elliptic reaction-diffusion equation”, Differential Equations, 41 (7), 1030–<br />
1039 (2005).<br />
∗ This research was supported in part by the Russian Fo<strong>und</strong>ation for Basic Research (grants No. 04-01-00578,<br />
04–01–89007–NWO a) and by the Dutch Research Organisation NWO grant No. 047.016.008.<br />
Speaker: TSELISHCHEVA, I.V. 51 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
I.V. TSELISHCHEVA, G.I. SHISHKIN: Domain Decomposition Method for a Semilinear<br />
Singularly Perturbed Elliptic Convection-Diffusion Equation with Concentrated<br />
Sources<br />
✬<br />
✫<br />
[2] G.I. Shishkin and I.V. Tselishcheva, “Parallel methods for solving singularly perturbed<br />
bo<strong>und</strong>ary value problems for elliptic equations”, (in Russian) Mat. Model., 8 (3), 111–127<br />
(1996).<br />
[3] I.V. Tselishcheva and G.I. Shishkin, “Monotone domain decomposition schemes for a singularly<br />
perturbed semilinear elliptic reaction-diffusion equation with Robin bo<strong>und</strong>ary conditions”,<br />
in: Proceedings <strong>of</strong> the 10th International Conference “Mathematical Modelling<br />
and Analysis” 2005 and 2nd International Conference “Computational Methods in Applied<br />
Mathematics”, R. Čiegis ed., Vilnius, “Technika”, 2005, pp. 251–258.<br />
[4] I.V. Tselishcheva and G.I. Shishkin, “Monotone domain decomposition schemes for a<br />
quasilinear singularly perturbed elliptic convection-diffusion equation with a concentrated<br />
source”, in: Grid Methods for Bo<strong>und</strong>ary Value Problems and Applications, Proceedings <strong>of</strong><br />
the VI-th All-Russian Workshop, Kazan, Kazan State University, 2005, pp. 251-255 (in<br />
Russian).<br />
Speaker: TSELISHCHEVA, I.V. 52 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
S. HEMAVATHI, S. VALARMATHI: A parameter-uniform numerical method for a<br />
system <strong>of</strong> singularly perturbed ordinary differential equations<br />
✬<br />
✫<br />
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Speaker: VALARMATHI, S. 53 <strong>BAIL</strong> <strong>2006</strong><br />
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S. HEMAVATHI, S. VALARMATHI: A parameter-uniform numerical method for a<br />
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Speaker: VALARMATHI, S. 54 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
J. Maubach, I, Tselishcheva<br />
Robust Numerical Methods for Problems with Layer Phenomena and Applications<br />
Speaker:<br />
Numerical modeling <strong>of</strong> many processes and physical phenomena leads<br />
to bo<strong>und</strong>ary value problems for PDEs having non-smooth solutions with<br />
singularities <strong>of</strong> thin layer type. Among them are convection-dominated<br />
convection-diffusion problems, Navier-Stokes equations and bo<strong>und</strong>arylayer<br />
equations at high Reynolds number, the drift-diffusion equations<br />
<strong>of</strong> semiconductor device simulation, flow problems with lift, drag, transition<br />
and interface phenomena, phenomena in plasma fluid dynamics,<br />
mathematical models for the spreading <strong>of</strong> pollutants, combustion, shock<br />
hydrodynamics or transport in porous media and other related problems.<br />
The solutions <strong>of</strong> these problems contain thin bo<strong>und</strong>ary and interior<br />
layers, shocks, discontinuities, shear layers, or current sheets, etc.<br />
The singular behaviour <strong>of</strong> the solution in such local structures generally<br />
gives rise to difficulties in the numerical solution <strong>of</strong> the problem in<br />
question by traditional methods on uniform meshes and requires the use<br />
<strong>of</strong> highly accurate discretization methods and adaptive grid refinement<br />
techniques. The problem <strong>of</strong> resolving layers, which is <strong>of</strong> great practical<br />
importance, is still not solved satisfactorily for a wide class <strong>of</strong> problems<br />
with layer phenomena and applications, which the minisymposium is<br />
concerned with.<br />
• Alan Hegarty: An adaptive method for the numerical solution <strong>of</strong> an elliptic convection<br />
diffusion problem<br />
• Joseph Maubach: A Convergence Pro<strong>of</strong> <strong>of</strong> Local Defect Correction for Convection-<br />
Diffusion Problems<br />
• Joseph Maubach: On the Difference between Left and Right Preconditioning for<br />
Convection Dominated Convection-Diffusion Problems<br />
• Lidia P. Shishkina: Parameter-Uniform Method for a Singularly Perturbed Parabolic<br />
Equation Modelling the Black-Scholes equation in the Presence <strong>of</strong> Interior and<br />
Bo<strong>und</strong>ary Layers<br />
• Alexander I. Zadorin: Numerical Method for the Blasius Equation on an Infinite<br />
Interval<br />
• Paul Zegeling: An Adaptive Grid Method for the Solar Coronal Loop Model
A.F. HEGARTY, S. SIKWILA, G.I. SHISKIN: An adaptive method for the numerical<br />
solution <strong>of</strong> an elliptic convection diffusion problem<br />
✬<br />
✫<br />
An adaptive method for the numerical solution <strong>of</strong> an elliptic convection<br />
diffusion problem ∗<br />
Alan F. Hegarty 1 , Stephen Sikwila 1 and Grigory I. Shishkin 2 .<br />
1 Department <strong>of</strong> Mathematics and Statistics, University <strong>of</strong> Limerick, Plassey, Limerick, Ireland.<br />
alan.hegarty@ul.ie, stephen.sikwila@ul.ie,<br />
2 <strong>Institut</strong>e <strong>of</strong> Mathematics and Mechanics, Ural Branch <strong>of</strong> Russian Academy <strong>of</strong> Sciences<br />
16 S. Kovalevskaya Street, Ekaterinburg 620219, Russia<br />
shishkin@imm.uran.ru<br />
A two dimensional elliptic linear convection diffusion problem:<br />
Pε :<br />
�<br />
ε∆uε + a.∇uε + d(x, y)uε = f(x, y),<br />
uε = g,<br />
(x, y) ∈ Ω;<br />
(x, y) ∈ Γ,<br />
is considered, where the diffusion parameter 0 < ε ≤ 1 is typically small. The use <strong>of</strong> special<br />
piecewise uniform meshes appropriately condensed in the bo<strong>und</strong>ary layer regions together<br />
with montone finite difference operators is well known to result in numerical methods which<br />
are uniformly convergent with respect to ε (see e.g., [1]). Such methods depend on a priori<br />
knowledge <strong>of</strong> the location <strong>of</strong> any bo<strong>und</strong>ary layers. Since such information may not be available<br />
for more complicated problems, it is <strong>of</strong> interest to examine whether robust numerical results can<br />
be obtained for the model problem (1), without using the a priori information.<br />
An adaptive technique is presented, based on piecewise uniform meshes, where the location<br />
<strong>of</strong> the transition point between the coarse and fine meshes is computed iteratively. This is an<br />
extension <strong>of</strong> the one dimensional method presented in [2] and [3].<br />
Numerical experiments are presented which indicate that the computational solutions obtained<br />
are uniformly in ε convergent and also that the number <strong>of</strong> iterations required does not<br />
increase significantly for small ε.<br />
References<br />
[1] P.A. Farrell, A.F. Hegarty, J.J.H. Miller, E. O’Riordan, G.I. Shishkin, Robust Computational<br />
Techniques for Bo<strong>und</strong>ary Layers, Chapman & Hall, CRC, Boca Raton, FL, 2000.<br />
[2] S. Sikwila, A.F. Hegarty and G.I. Shishkin, Novel robust adaptive techniques for the numerical<br />
solution <strong>of</strong> convection diffusion problem, Proceedings <strong>of</strong> <strong>BAIL</strong> 2004 Conference,<br />
Toulouse, July 2004, ONERA, 2004.<br />
[3] S. Sikwila, Novel robust layer resolving adaptive mesh methods for convection diffusion<br />
problems in one and two dimesnions, Ph.D. thesis, University <strong>of</strong> Limerick, 2005.<br />
∗ This work was supported by the Russian Fo<strong>und</strong>ation for Basic Research <strong>und</strong>er grant No. 04-01-00578.<br />
Speaker: HEGARTY, A.F. 56 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
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M. ANTHONISSEN, I. SEDYKH, J. MAUBACH: A Convergence Pro<strong>of</strong> <strong>of</strong> Local<br />
Defect Correction for Convection-Diffusion Problems<br />
✬<br />
✫<br />
A Convergence Pro<strong>of</strong> <strong>of</strong> Local Defect Correction<br />
for Convection–Diffusion Problems<br />
M. Anthonissen 1 , I. Sedykh 2 and J. Maubach 1<br />
1 Department <strong>of</strong> Mathematics and Computer Science, Eindhoven University <strong>of</strong> Technology,<br />
Eindhoven, The Netherlands<br />
m.j.h.anthonissen@tue.nl, j.m.l.maubach@tue.nl<br />
2 Department <strong>of</strong> Mechanics and Mathematics, Moscow State University, Moscow, Russia<br />
Examples <strong>of</strong> partial differential equations with solutions that are rapidly varying functions<br />
<strong>of</strong> the spatial or temporal coordinates appear e.g. in combustion, shock hydrodynamics or<br />
transport in porous media. For bo<strong>und</strong>ary value problems with solutions that have one or a few<br />
small regions with high activity, a fine grid is needed in regions with high activity, whereas a<br />
coarser grid would suffice in the rest <strong>of</strong> the domain. Rather than using a truly nonuniform grid,<br />
we study a method called Local Defect Correction (LDC) that is based on local uniform grid<br />
refinement.<br />
Several properties hold for the LDC fixed point iteration for convection-diffusion equations in<br />
two dimensions. We study the convergence behavior <strong>of</strong> the LDC method as an iterative process<br />
and derive an upper bo<strong>und</strong> for the norm <strong>of</strong> the iteration matrix for the linear two-dimensional<br />
convection-diffusion equation with constant coefficients on the unit square. The research results<br />
can be extended to the case <strong>of</strong> non-constant coefficients.<br />
Speaker: MAUBACH, J. 57 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
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J. MAUBACH: On the Difference between Left and Right Preconditioning for Convection<br />
Dominated Convection-Diffusion Problems<br />
✬<br />
✫<br />
On the Difference between Left and Right Preconditioning for Convection<br />
Dominated Convection–Diffusion Problems<br />
Joseph Maubach<br />
Department <strong>of</strong> Mathematics and Computer Science, Eindhoven University <strong>of</strong> Technology,<br />
Eindhoven, The Netherlands<br />
j.m.l.maubach@tue.nl<br />
For convection dominated convection-diffusion problems in several space dimensions discretized<br />
with finite differences on a locally fine tensor–grid, an approximate inverse operator<br />
Gn is calculated from the linear operator An. The spectral condition numbers κ2(GnAn)<br />
and κ2(AnGn) estimated numerically are different: κ2(GnAn) . = O(log h −1 ) and κ2(AnGn) . =<br />
O(h −1 ). This is corroborated by a pro<strong>of</strong> for the one-dimensional case for a modified approximate<br />
inverse operator Gn.<br />
Speaker: MAUBACH, J. 58 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
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S. LI, L.P. SHISHKINA, G.I. SHISHKIN: Parameter-Uniform Method for a Singularly<br />
Perturbed Parabolic Equation Modelling the Black-Scholes equation in the Presence<br />
<strong>of</strong> Interior and Bo<strong>und</strong>ary Layers<br />
✬<br />
✫<br />
Parameter–Uniform Method for a Singularly Perturbed Parabolic Equation<br />
Modelling the Black–Scholes equation in the Presence <strong>of</strong> Interior and<br />
Bo<strong>und</strong>ary Layers ∗<br />
Shuiying Li 1 , Lidia P. Shishkina 2 and Grigory I. Shishkin 2<br />
1 Department <strong>of</strong> Computational Science,<br />
National University <strong>of</strong> Singapore,<br />
Singapore 117543<br />
scip1075@nus.edu.sg<br />
2 <strong>Institut</strong>e <strong>of</strong> Mathematics and Mechanics,<br />
Ural Branch <strong>of</strong> Russian Academy <strong>of</strong> Sciences,<br />
Yekaterinburg 620219, Russia<br />
Lida@convex.ru and shishkin@imm.uran.ru<br />
Solutions <strong>of</strong> regular parabolic equations with nonsmooth initial data are <strong>of</strong> limited smoothness<br />
themselves (in a neighbourhood <strong>of</strong> the nonsmoothness <strong>of</strong> the data). When the equation<br />
is singularly perturbed, its solution has singularities such as initial, bo<strong>und</strong>ary and/or interior<br />
layers with own scales. These problems belong to the class <strong>of</strong> singularly perturbed multiscale<br />
problems. The multiscale behaviour <strong>of</strong> solutions complicates the construction and study <strong>of</strong><br />
efficient patameter-uniform numerical methods.<br />
A singularly perturbed parabolic convection-diffusion equation with the second derivative<br />
multiplied by a singular perturbation parameter ε, which ranges in (0, 1], arises when we model<br />
the Black-Scholes equation upon a European call option (see, e.g., [1]). There are a few singularities<br />
in the problem, i.e., a single discontinuity <strong>of</strong> the first derivative <strong>of</strong> the initial condition<br />
at a point x0, the unbo<strong>und</strong>ed growth <strong>of</strong> the initial condition at infinity and the unbo<strong>und</strong>ed<br />
domain in space. The solution <strong>of</strong> this initial value problem grows exponentially without bo<strong>und</strong><br />
as x → ∞. Thus, we deal with a singularly perturbed multiscale problem that has different<br />
types <strong>of</strong> singularities.<br />
In this presentation we consider a bo<strong>und</strong>ary value problem (in a bo<strong>und</strong>ed domain) for this<br />
singularly perturbed parabolic convection-diffusion equation with an additional singularity generated<br />
by the discontinuity <strong>of</strong> the first derivative <strong>of</strong> the initial function. For such a problem,<br />
singularities such as a bo<strong>und</strong>ary and an interior layer with own specific scales arise. For small<br />
values <strong>of</strong> the parameter ε, the interior layer due to nonsmooth initial data appears in a neighbourhood<br />
<strong>of</strong> the characteristic <strong>of</strong> the reduced equation passing through the point (x0, 0), and<br />
the regular bo<strong>und</strong>ary layer appears in a neighbourhood <strong>of</strong> the outflow bo<strong>und</strong>ary through which<br />
the convective flux leaves the domain.<br />
By using the singularity splitting method and piecewise uniform meshes condensing in the<br />
bo<strong>und</strong>ary layer, we construct a special difference scheme that allows us to approximate εuniformly<br />
the solution <strong>of</strong> the problem <strong>und</strong>er consideration, as well as the first derivative <strong>of</strong><br />
the solution. The corresponding theoretical and numerical results are provided in the paper.<br />
The description <strong>of</strong> the technique applied in this study can be fo<strong>und</strong> in [2]. Preliminary results<br />
for a similar problem with no bo<strong>und</strong>ary layer were given in [3].<br />
∗ This research was supported in part by the Russian Fo<strong>und</strong>ation for Basic Research (grant No 04-01-00578,<br />
04–01–89007–NWO a) and by the Dutch Research Organization NWO <strong>und</strong>er grant No 047.016.008.<br />
1<br />
Speaker: SHISHKINA, L.P. 59 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
S. LI, L.P. SHISHKINA, G.I. SHISHKIN: Parameter-Uniform Method for a Singularly<br />
Perturbed Parabolic Equation Modelling the Black-Scholes equation in the Presence<br />
<strong>of</strong> Interior and Bo<strong>und</strong>ary Layers<br />
✬<br />
✫<br />
References<br />
[1] J.J.H. Miller, G.I. Shishkin, “Robust numerical methods for the singularly perturbed Black-<br />
Scholes equation”, in: Proceedings <strong>of</strong> the Conference on Applied Mathematics and Scientific<br />
Computing, Springer, Dordrecht, 2005, pp. 95–105.<br />
[2] G.I. Shishkin, “Grid approximation <strong>of</strong> parabolic convection-diffusion equations with piecewise<br />
smooth initial conditions”, Doklady Akad. Nauk, 405 (1), 1–4 (2005); transl. in Doklady<br />
Mathematics, 72 (3) (2005).<br />
[3] Li Shuiying, D.B. Creamer, G.I. Shishkin, “Discrete approximations <strong>of</strong> a singularly perturbed<br />
Black-Scholes equation with nonsmooth initial data”, in: An International Conference<br />
on Bo<strong>und</strong>ary and Interior Layers — Computational and Asymptotic Methods <strong>BAIL</strong><br />
2004, ONERA, Toulouse, 5th-9th July, 2004, pp. 441-446.<br />
Speaker: SHISHKINA, L.P. 60 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
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A.I. ZADORIN: Numerical Method for the Blasius Equation on an Infinite Interval<br />
✬<br />
✫<br />
Numerical Method for the Blasius Equation on an Infinite Interval ∗<br />
A.I. Zadorin<br />
Omsk Branch <strong>of</strong> Sobolev <strong>Institut</strong>e <strong>of</strong> Mathematics,<br />
Siberian Branch <strong>of</strong> Russian Academy <strong>of</strong> Sciences, Omsk, Russia<br />
zadorin@iitam.omsk.net.ru<br />
The Blasius equation on a semi-infinite interval is considered. This problem can be considered<br />
as a model problem for constructing a numerical method for problems in unbo<strong>und</strong>ed domains.<br />
The Blasius problem have been investigated in many papers. For example, G.I. Shishkin [1]<br />
studied the asymptotic behavior <strong>of</strong> differential and difference solutions to get a difference scheme<br />
with a finite number <strong>of</strong> mesh points for a sufficiently long interval. We apply the method <strong>of</strong><br />
separation <strong>of</strong> the set <strong>of</strong> solutions that satisfy the limit bo<strong>und</strong>ary condition at infinity to transform<br />
the problem to a problem on a finite interval (see, e.g., [2, 3]). Difficulties are concerned with<br />
the nonlinearity <strong>of</strong> the differential equation and with an unbo<strong>und</strong>ed coefficient multiplying the<br />
second derivative. We propose to make a transformation <strong>of</strong> the independent variable to avoid<br />
the last problem.<br />
So, consider the Blasius problem<br />
u ′′′ (x) + u(x)u ′′ (x) = 0,<br />
u(0) = 0, u ′ (0) = 0, lim<br />
x→∞ u′ (x) = 1.<br />
Let u(x) = v(x) + x, w(x) = v ′ (x). Then problem (1) take the form<br />
v ′ (x) = w(x), v(0) = 0,<br />
w ′′ (x) + [v(x) + x]w ′ (x) = 0, w(0) = −1, lim w(x) = 0.<br />
x→∞<br />
To transfer the limit condition at infinity to a finite point, consider the linear problem<br />
εu ′′ (x) + [a(x) + x]u ′ (x) = f(x),<br />
u(0) = A, lim u(x) = 0.<br />
x→∞<br />
Suppose that there is a unique solution <strong>of</strong> (3), ε > 0, ∃ lim a(x), lim f(x) = 0. To avoid the<br />
x→∞ x→∞<br />
difficulty with unbo<strong>und</strong>edness <strong>of</strong> the coefficient multiplying the first derivative, we use the new<br />
variable t = x2 /2. Then problem (3) can be written in the form<br />
where<br />
εu ′′ (t) + b(t)u ′ (t) = F(t), u(0) = A, lim<br />
t→∞ u(t) = 0, (4)<br />
b(t) = a(√ 2t)<br />
√ 2t + 1 + 1<br />
2t , F(t) = f(√ 2t)/(2t).<br />
By the next equation we can restrict the set <strong>of</strong> solutions <strong>of</strong> the differential equation (4) satisfying<br />
the limit condition at infinity:<br />
εu ′ (t) + g(t)u(t) = β(t), (5)<br />
∗ Supported by the Russian Fo<strong>und</strong>ation for Basic Research <strong>und</strong>er grant No. 04-01-00578.<br />
Speaker: ZADORIN, A.I. 61 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
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(2)<br />
(3)<br />
✩<br />
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A.I. ZADORIN: Numerical Method for the Blasius Equation on an Infinite Interval<br />
✬<br />
✫<br />
where g(t), β(t) are solutions <strong>of</strong> auxiliary singular Cauchy problems and can be fo<strong>und</strong> as series<br />
in (2t) −0.5 with a given accuracy. We can use equation (5) as the exact bo<strong>und</strong>ary condition for<br />
a finite interval. Then we return to the variable x and get the exact restriction <strong>of</strong> problem (3)<br />
to a finite interval as follows:<br />
εu ′′ (x) + [a(x) + x]u ′ (x) = f(x),<br />
u(0) = A,<br />
ε<br />
L u′ (L) + g(L)u(L) = β(L).<br />
Return to problem (2). Consider the iterative method<br />
v ′ n(x) = wn−1(x), vn(0) = 0,<br />
w ′′<br />
n(x) + [vn(x) + x]w ′ n(x) = 0, wn(0) = −1, lim<br />
x→∞ wn(x) = 0.<br />
It is proved that method (7) has the property <strong>of</strong> convergence. At each iteration, we can transform<br />
problem (7) to a problem for a finite interval, as it was done for a linear problem. One can use<br />
a difference scheme to solve the problem obtained on a finite interval. Theoretical results are<br />
confirmed by results <strong>of</strong> numerical experiments.<br />
References<br />
[1] G.I. Shishkin, “Grid approximation <strong>of</strong> the solution to the Blasius Equation and <strong>of</strong> its Derivatives”,<br />
Computational Mathematics and Mathematical Physics, 41 (1), 37–54 (2001).<br />
[2] A.A. Abramov, N.B. Konyukhova, “Transfer <strong>of</strong> admissible bo<strong>und</strong>ary conditions from a singular<br />
point <strong>of</strong> linear ordinary differential equations”, Sov. J. Numer.Anal. Math. Modelling,<br />
1, (4), 245–265 (1986).<br />
[3] A.I. Zadorin, “The transfer <strong>of</strong> the bo<strong>und</strong>ary condition from the infinity for the numerical<br />
solution <strong>of</strong> second order equations with a small parameter” (in Russian), Siberian Journal<br />
<strong>of</strong> Numerical Mathematics, 2 (1), 21–36 (1999).<br />
Speaker: ZADORIN, A.I. 62 <strong>BAIL</strong> <strong>2006</strong><br />
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P. ZEGELING: An Adaptive Grid Method for the Solar Coronal Loop Model<br />
✬<br />
✫<br />
An Adaptive Grid Method for the Solar Coronal Loop Model<br />
Paul Zegeling<br />
Department <strong>of</strong> Mathematics, Faculty <strong>of</strong> Science, Utrecht University, Utrecht, The Netherlands<br />
zegeling@math.uu.nl<br />
Many interesting phenomena in plasma fluid dynamics can be described within the framework<br />
<strong>of</strong> magnetohydrodynamics. Numerical studies in plasma flows frequently involve simulations<br />
with highly varying spatial and temporal scales. As a consequence, numerical methods on<br />
uniform grids are inefficient to be used, since (too) many grid points are needed to resolve the<br />
spatial structures, such as bo<strong>und</strong>ary and internal layers, shocks, discontinuities, shear layers, or<br />
current sheets. For the efficient study <strong>of</strong> these phenomena, adaptive grid methods are needed<br />
which automatically track and spatially resolve one or more <strong>of</strong> these structures. An interesting<br />
application within this framework can be fo<strong>und</strong> in and aro<strong>und</strong> our sun. There are several cases<br />
for which we can expect steep bo<strong>und</strong>ary and internal layers (see figure 1).<br />
The first one deals with the expulsion <strong>of</strong> the magnetic flux by eddies in a solar magnetic<br />
field model. This model addresses the role <strong>of</strong> the magnetic field in a convecting plasma and the<br />
distortion <strong>of</strong> the field by cellular convection patterns for various (small) values <strong>of</strong> the resistivity<br />
(magnetic diffusion coefficient). This situation is <strong>of</strong> importance aro<strong>und</strong> convection cells just<br />
below the solar photosphere. Steep bo<strong>und</strong>ary and internal layers are formed when the magnetic<br />
induction reaches a steady-state configuration.<br />
In this presentation we discuss another phenomenon that takes place a little bit farther from<br />
the solar interior, viz., in the solar corona. It is known that the temperature gradually decreases<br />
from the center <strong>of</strong> the sun down to values <strong>of</strong> aro<strong>und</strong> 10 4 degrees Kelvin at the foot <strong>of</strong> the corona<br />
(see figure 2). From that point, however, it surprisingly increases dramatically again up to several<br />
millions <strong>of</strong> degrees Kelvin forming a non-trivial transition zone (bo<strong>und</strong>ary layer) between the<br />
photosphere and the chromosphere. Moreover, because <strong>of</strong> the extreme temperatures, the solar<br />
corona is highly structured with closed magnetic structures which are generally known as coronal<br />
loops. It can be derived that the temperature T and pressure distribution P in the loop as a<br />
function <strong>of</strong> a mass-coordinate z satisfy the following PDE model:<br />
5 P<br />
2 T<br />
∂T ∂P P ∂ 3<br />
− = ɛ (T 2P<br />
∂t ∂t T ∂z ∂T<br />
∂z ) + EH − P 2 χ(T), (1)<br />
where P(z,t) = P0(t) − µz, EH is a heating function, χ(T) the radiative loss function and<br />
ɛ a small parameter representing the thermal conductivity in the loop. Near the base <strong>of</strong> the<br />
loop there are two adjacent bo<strong>und</strong>ary layers where the temperature increases very quickly when<br />
moving upward in the loop; in these thin layers the pressure in nearly constant. We will examine<br />
the nature <strong>of</strong> this special bo<strong>und</strong>ary layer via the theory <strong>of</strong> significant degenerations and also in<br />
terms <strong>of</strong> a dynamical system <strong>of</strong> the steady-state <strong>of</strong> PDE (1) in which a non-trivial saddle-center<br />
connection occurs. A complicating factor is the fact that we also need to take into account the<br />
so-called loop-condition:<br />
� 1 T<br />
L = 2MR<br />
0 P<br />
dz = constant, (2)<br />
with gasconstant R, total mass in the loop M and (half) looplength L.<br />
To support and confirm the theory, we have applied an adaptive grid technique, based on<br />
an equidistribution principle with additional smoothing properties, to numerically simulate the<br />
forming <strong>of</strong> the thin bo<strong>und</strong>ary layer.<br />
Speaker: ZEGELING, P. 63 <strong>BAIL</strong> <strong>2006</strong><br />
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P. ZEGELING: An Adaptive Grid Method for the Solar Coronal Loop Model<br />
✬<br />
✫<br />
Convection cells<br />
Coronal loops<br />
Figure 1: Convection cells and coronal loops in, and on top <strong>of</strong>, the sun in the form <strong>of</strong> magnetic<br />
field lines.<br />
Figure 2: The temperature distribution and the steep transition zone in the outer layers <strong>of</strong> the<br />
sun.<br />
References<br />
[1] P.A. Davidson, An introduction to magneto-hydrodynamics, Cambridge Univ. Press (2001).<br />
[2] J.W. Pakkert, P.C.H. Martens and F. Verhulst, The thermal stability <strong>of</strong> coronal loops by<br />
nonlinear diffusion asymptotics, Astron. Astrophys., 179, 285-293 (1987).<br />
[3] F. Verhulst and P.A. Zegeling, An asymptotic-numerical approach to the coronal loop problem,<br />
Math. Meth. in the Appl. Sciences, 13, 431-439 (1990).<br />
[4] N.O. Weiss, The expulsion <strong>of</strong> magnetic flux by eddies, Proc. <strong>of</strong> Roy. Soc. A, 293, 310-328<br />
(1966).<br />
[5] P.A. Zegeling, On resistive MHD models with adaptive moving meshes, J. <strong>of</strong> Scientific<br />
Computing, 24, 263-284 (2005).<br />
[6] P.A. Zegeling and R. Keppens, Adaptive method <strong>of</strong> lines for magnetohydrodynamic PDE<br />
models, Chapter 4, 117-137, in Adaptive method <strong>of</strong> lines, Chapman & Hall/CRC Press<br />
(2001).<br />
Speaker: ZEGELING, P. 64 <strong>BAIL</strong> <strong>2006</strong><br />
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Contributed Presentations
F. ALIZARD, J.-CH. ROBINET: Two-dimensional temporal modes in nonparallel<br />
flows<br />
✬<br />
✫<br />
Two-dimensional temporal modes in nonparallel flows<br />
F. Alizard and J.-Ch. Robinet<br />
SINUMEF Laboratory, ENSAM-PARIS 151, Boulevard de l’Hôpital, 75013 PARIS, FRANCE<br />
Frederic.Alizard@paris.ensam.fr,<br />
1. Introduction<br />
To describe the evolution <strong>of</strong> a two-dimensional wavepacket in flow such as growing bo<strong>und</strong>ary<br />
layer, the classical stability approach is based on the assumption <strong>of</strong> locally parallel or weakly non<br />
parallel base flow. These approach was used by Gaster (1982) to characterize the spatio-temporal<br />
dynamic <strong>of</strong> a perturbation in a bo<strong>und</strong>ary layer. However this approach could failed if a wave<br />
length <strong>of</strong> any perturbation is larger than a characteristic length <strong>of</strong> the spatial inhomogeneity <strong>of</strong><br />
the base flow. Consequently a more general eigenvalue problem was developed by some authors<br />
as Lin & Malik (1995), The<strong>of</strong>ilis et al. (2000) and Erhenstein & Gallaire (2005) where two spatial<br />
directions are inhomogeneous. In this abstract we will focus on two-dimensional modes for a<br />
convectively unstable attached bo<strong>und</strong>ary layer. After the description <strong>of</strong> the numerical method,<br />
preliminary results on temporal linear stability modes depending on two space directions are<br />
computed for a bo<strong>und</strong>ary layer flow along a flat plat.<br />
2. Generalities and Basic Flow<br />
At the conference we will be interested exclusively in computations <strong>of</strong> convective instabilities<br />
in nonparallel flows. Two types <strong>of</strong> flows will be studied: a flat plate bo<strong>und</strong>ary-layer without<br />
pressure gradient, shown as a preliminary result and a separated bo<strong>und</strong>ary-layer. The twodimensional<br />
Navier-Stokes equations for incompressible fluids in the stream function-vorticity<br />
formulation are considered:<br />
∂ω<br />
∂ω 1<br />
+ u∂ω + v =<br />
∂t ∂x ∂y Re<br />
�<br />
∂2ω ∂x2 + ∂2ω ∂y2 �<br />
and ∆ψ = ω, (1)<br />
where ω and ψ are the vorticity and the stream function respectively. System (1) is closed<br />
by classical bo<strong>und</strong>ary conditions on ψ and ω (Briley (1971)). A second order finite differences<br />
scheme was used for the vorticity transport equation as well as the poisson equation <strong>of</strong> stream<br />
function. An A.D.I algorithm has been employed to solve the transport equation and the poisson<br />
equation. Preliminary results, shown on part 4, are realized on an attached bo<strong>und</strong>ary layer at<br />
Re=610, with a grid (450x200).<br />
3. Linearized Perturbed Flow and Numerical Procedure<br />
The proposed stability analysis is based on the classical perturbations technique where the<br />
instantaneous flow (q) is the superposition <strong>of</strong> the basic flow (Q), data <strong>of</strong> this problem, and<br />
unknown fluctuations (ˆq): q(x, y, t) =Q(x, y)+ˆq(x, y)exp(−iΩt), where Ω is the circular global<br />
frequency <strong>of</strong> the fluctuation. The two-dimensional generalized eigenvalue problem is obtained<br />
by the linearized Navier Stokes equations:<br />
� �<br />
∆2d<br />
div(û) = 0 and − U.grad û − gradU.û − gradˆp + iΩû =0, (2)<br />
Re<br />
1<br />
Speaker: ALIZARD, F. 67 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
F. ALIZARD, J.-CH. ROBINET: Two-dimensional temporal modes in nonparallel<br />
flows<br />
✬<br />
✫<br />
Figure 1: Discrete global spectrum from a convectively<br />
instable bo<strong>und</strong>ary layer. The real<br />
part <strong>of</strong> the eigenvalue is represented on the Xaxis<br />
and the imaginary part on the Y-axis.<br />
Figure 2: Real part <strong>of</strong> the horizontal velocity<br />
eigenfunction <strong>of</strong> a discrete eigenvalue from the<br />
spectrum ( Fig. 1).<br />
with U(x, y) =[U, V ] t and û(x, y) =[û, ˆv] t . The bo<strong>und</strong>ary conditions on velocity disturbances<br />
and constraints on pressure (T. N. Phillips & G. W. Roberts (1993), C. Canuto et al. (1988))<br />
complete the eigenvalue value problem. The partial differential stability equations (2) are discretized<br />
using an algorithm based on the collocation method based on Chebyshev Gauss-Lobatto<br />
grid. The algebraic eigenvalue problem (A − ΩB) X = 0 is solved by the QZ algorithm.<br />
4. Two-Dimensional Temporal Modes, results and perspectives<br />
The figure 1 represents a global spectrum <strong>of</strong> the bo<strong>und</strong>ary layer. The stable discrete eigenvalues<br />
appear in concordance with the fact a bo<strong>und</strong>ary layer is globally stable. These discrete values<br />
represent spatio-temporal convective modes as it can been shown fig. 2 (structure similar to a<br />
spatial exponential growth). At the conference, this analysis will be also applied on a separated<br />
incompressible bo<strong>und</strong>ary layer which is not absolutely unstable but only convectively unstable.<br />
References<br />
[1] M. Gaster , “The development <strong>of</strong> a two-dimensional wavepacket in a growing bo<strong>und</strong>ary<br />
layer ”, Proc. R. Soc. London, 3, 317–332 (1982).<br />
[2] Lin R.S. and Malik M.R , “On the stability <strong>of</strong> attachment-line bo<strong>und</strong>ary layers. ”, J. Fluid<br />
Mech., 3,239–255 (1995).<br />
[3] The<strong>of</strong>ilis V. Hein S and Dallmann U , “On the origins <strong>of</strong> unsteadiness and three dimensionality<br />
in a laminar separation bubble ”, Proc. R. Soc. London, 3,3229–3246 (2000).<br />
[4] U. Ehrenstein and F. Gallaire , “On two dimensional temporal modes in spatially evolving<br />
open flows: the flat-plate bo<strong>und</strong>ary layer ”, J. Fluid Mech., (2005).<br />
[5] Briley WR., “A numerical study <strong>of</strong> laminar separation bubbles using the Navier-Stokes<br />
equations.”, J. Fluid Mech., 3,713–736 (1971).<br />
[6] Timothy N. Phillips and Gareth W.Roberts, “The Treatment <strong>of</strong> Spurious Pressure Modes in<br />
Spectral Incompressible Flow Calculations.”, Journal <strong>of</strong> Computational Physics, 3,150–164<br />
(1993).<br />
[7] C. Canuto and M. Y. Hussaini and A. Quarteroni and T. A. Zang, “Spectral Methods in<br />
Fluids Dynamics”, Springer, (1988).<br />
Speaker: ALIZARD, F. 68 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
TH. ALRUTZ, T. KNOPP: Near-wall grid adaptation for wall functions<br />
✬<br />
✫<br />
Near-wall grid adaptation for wall-functions<br />
Th. Alrutz, T. Knopp<br />
<strong>Institut</strong>e <strong>of</strong> Aerodynamics and Flow Technology<br />
DLR (German Aerospace Center)<br />
Bunsenstr. 10, 37073 Göttingen, Germany<br />
Thomas.Alrutz@dlr.de<br />
A near-wall grid adaptation method for RANS turbulence modelling using wall-functions is proposed.<br />
Universal wall functions allow a considerable acceleration <strong>of</strong> the flow solver, but their predictions<br />
may deviate from the results with near-wall integration in flow situations which are beyond the <strong>und</strong>erlying<br />
modelling assumptions <strong>of</strong> wall-functions. In aerodynamic flows these include (i) stagnation points<br />
(flow impingement) and subsequent transition from laminar to turbulent flow, (ii) large surface curvature<br />
in conjunction with strong pressure gradients (as can be observed aro<strong>und</strong> leading edge <strong>of</strong> an airfoil), (iii)<br />
strong adverse pressure gradients leading to separation, and (iv) regions <strong>of</strong> separated flow. Bo<strong>und</strong>ary<br />
layer theory shows that the deviation from the universal wall-law becomes more significant as the walldistance<br />
<strong>of</strong> the first node above the wall is increased. But close agreement with the universal wall-law<br />
can be achived if the first node is close enough to the wall.<br />
To reduce the modelling error <strong>of</strong> universal wall-functions, a near-wall grid-adaptation technique is pro-<br />
Ýposed. �Ý<br />
Regions <strong>of</strong> strong surface curvature, large pressure gradients and recirculating flow are detected<br />
by a flow and geometry based sensor. Then in critical regions, the nodes <strong>of</strong> the prismatic nearwall<br />
grid are shifted towards the wall so that a user-specified target value forÝ is ensured, where<br />
Ù���with wall-distance <strong>of</strong> the first nodeÝ , friction velocityÙ�and viscosity�. This<br />
approach is applied to a transonic airfoil flow with shock induced separation [5] and to a subsonic highlift<br />
airfoil close to stall [6]. Thereby, the predictions aro<strong>und</strong> the leading edge (suction peak) and <strong>of</strong> the<br />
separation point and the recirculation region can be improved significantly.<br />
y +<br />
100<br />
80<br />
60<br />
40<br />
20<br />
y + (1) = 20<br />
y + (1) = 40<br />
y + (1) = 60<br />
0<br />
0 0.25 0.5 0.75 1<br />
x/c<br />
y +<br />
60<br />
40<br />
20<br />
y + (1) = 20<br />
y + (1) = 40<br />
y + (1) = 60<br />
0<br />
0 0.25 0.5 0.75 1<br />
x/c<br />
Figure 1: RAE2822 case 10 [5]: Distribution <strong>of</strong>Ý for Menter SST model [4] without adaptation<br />
(left) and withÝ-adaptation <strong>of</strong> the structured (prismatic) near-wall grid (right).<br />
References<br />
[1] T. Knopp, T. Alrutz and D. Schwamborn, “A grid and flow adaptive wall-function method for RANS<br />
turbulence modelling”, Journal <strong>of</strong> Computational Physics (submitted).<br />
Speaker: ALRUTZ, TH 69 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
TH. ALRUTZ, T. KNOPP: Near-wall grid adaptation for wall functions<br />
✬<br />
✫<br />
0.006 exp.<br />
low-Re<br />
y + (1) = 1<br />
y + (1) = 20<br />
0.004<br />
c f<br />
0.002<br />
0<br />
y + (1) = 40<br />
y + (1) = 60<br />
c f = 0<br />
0 0.25 0.5 0.75 1<br />
x/c<br />
0.006 exp.<br />
low-Re<br />
y + (1) = 1<br />
y + (1) = 20<br />
0.004<br />
c f<br />
0.002<br />
0<br />
y + (1) = 40<br />
y + (1) = 60<br />
c f = 0<br />
0 0.25 0.5 0.75 1<br />
x/c<br />
Figure 2: RAE2822 case 10 [5]: Prediction for skin friction coefficient�for Spalart-Allmaras-Edwards<br />
model [3] without adaptation (left) and withÝ -adaptation <strong>of</strong> the prismatic near-wall grid (right).<br />
c p<br />
-4.2<br />
-3.8<br />
-3.4<br />
-3<br />
exp.<br />
low-Re<br />
y + (1) = 12<br />
y + (1) = 24<br />
y + (1) = 40<br />
y + (1) = 80<br />
0 0.05 0.1 0.15<br />
x/c<br />
Ý ÆÝ Ü×�Ô� Ü×�Ô�<br />
SA-Edwards Menter SST<br />
low-Re 33 0.771 0.866<br />
1 33 0.770 0.866<br />
4 28 0.755 0.863<br />
7 26 0.759 0.868<br />
12 24 0.761 0.861<br />
24 21 0.787 0.861 (0.864)<br />
50 19 (0.771) 0.881 (0.873)<br />
70 17 (0.788) 0.903 (0.867)<br />
Figure 3: A-airfoil [6]: Detail <strong>of</strong> pressure coefficientÔfor SST model [4] on adapted grid (left). Right:<br />
Prediction <strong>of</strong> the separation point without adaptation and withÝ -adaptation (values in brackets).<br />
[2] Th. Alrutz, “Hybrid grid adaptation in TAU”, In: MEGAFLOW - Numerical flow simulation for<br />
aircraft design, Notes on Numerical Fluid Mechanics and Multidisciplinary Design. N. Kroll and<br />
J.K. Fassbender, Eds., (2005).<br />
[3] J.R. Edwards and S. Chandra, “Comparison <strong>of</strong> eddy viscosity-transport turbulence models for threedimensional,<br />
shock separated flowfields”, AIAA Journal, 34, 756–763 (1996).<br />
[4] F.R. Menter, “Zonal two equation�/�turbulence models for aerodynamic flows”, AIAA Paper<br />
1993-2906, (1993).<br />
[5] P. H. Cook, M. A. McDonald and M.C.P. Firmin, “Aer<strong>of</strong>oil RAE 2822 - Pressure distributions and<br />
bo<strong>und</strong>ary layer and wake measurements”, AGARD Advisory Report AR-138, A6.1-A6.77 (1979).<br />
[6] Ch. Gleyzes, “Opération décrochage - Résultats de la 2ème campagne d’essais à F2 – Mesures de<br />
pression et vélocimétrie laser”, RT-DERAT 55/5004 DN, ONERA, (1989).<br />
Speaker: ALRUTZ, TH 70 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
TH. APEL, G. MATTHIES: A family <strong>of</strong> non-conforming finite elements <strong>of</strong> arbitrary<br />
order for the Stokes problem on anisotropic quadrilateral meshes<br />
✬<br />
✫<br />
A family <strong>of</strong> non-conforming finite elements <strong>of</strong> arbitrary order for the Stokes<br />
problem on anisotropic quadrilateral meshes<br />
Thomas Apel 1 and Gunar Matthies 2<br />
1 <strong>Institut</strong> <strong>für</strong> Mathematik <strong>und</strong> Bauinformatik, Universität der B<strong>und</strong>eswehr München<br />
2 Fakultät <strong>für</strong> Mathematik, Ruhr-Universität Bochum,<br />
The solution <strong>of</strong> the Stokes problem in polygonal or polyhedral domains shows in general a<br />
singular behaviour near corners and edges <strong>of</strong> the domain. Both edge singularities and layers<br />
are anisotropic phenomena since the solution changes only slightly in one direction while the<br />
derivatives in the perpendicular direction(s) are large. These anisotropic behaviour can be well<br />
approximated on anisotropic triangulations.<br />
Let Ω ⊂ R 2 be a bo<strong>und</strong>ed polygonal domain. We consider the Stokes problem<br />
−△u + ∇p = f in Ω,<br />
div u = 0 in Ω,<br />
u = 0 on ∂Ω,<br />
where u and p are the velocity and the pressure, respectively, while f is a given force.<br />
We solve this problem by using finite element methods on triangulations with special properties.<br />
Let the domain Ω be partitioned by an admissible triangulation which consists <strong>of</strong> shape<br />
regular and isotropic macro-cells. Each macro-cell is further refined by applying admissible<br />
patches which are adapted to bo<strong>und</strong>ary layers and corner singularities, respectively. For a<br />
detailed description <strong>of</strong> such meshes, we refer to [1].<br />
We are interested in solving the Stokes problem by non-conforming finite element methods<br />
<strong>of</strong> higher order. To this end, we use the families with finite element pairs <strong>of</strong> arbitrary order<br />
which were given recently in [2]. Each pair consists <strong>of</strong> a non-conforming space <strong>of</strong> order r for<br />
approximating the velocity and a discontinuous, piecewise polynomial pressure approximation<br />
<strong>of</strong> order r − 1.<br />
For the stability <strong>of</strong> finite element methods for solving the Stokes problem and its relatives, it<br />
is necessary that the discrete spaces for the velocity and the pressure fulfil an inf-sup condition.<br />
In order to get error estimates with constants which are independent <strong>of</strong> the aspect ratio <strong>of</strong> the<br />
<strong>und</strong>erlying mesh, it is important that on the one hand the inf-sup constant is independent <strong>of</strong><br />
the aspect ratio and that on the other hand the approximation error and the consistency error<br />
can be bo<strong>und</strong>ed by expressions whose constants don’t depend on the aspect ratio.<br />
Considering the families given in [2], we will show that we obtain for one family optimal<br />
error estimates on anisotropic meshes, i.e., the constant are independent <strong>of</strong> the aspect ratio.<br />
The other families give only error estimates with constant which depend on the aspect ratio,<br />
i.e., the constants blow up with increasing aspect ratio.<br />
We will show by means <strong>of</strong> numerical results how the inf-sup constant behaves on special<br />
families <strong>of</strong> triangulation with increasing aspect ratio.<br />
References<br />
[1] Th. Apel, S. Nicaise, The inf-sup condition for low order elements on anisotropic meshes,<br />
CALCOLO, 41, 89–113 (2004).<br />
[2] G. Matthies, Inf-sup stable nonconforming finite elements <strong>of</strong> higher order on quadrilaterals<br />
and hexahedra. Bericht Nr. 373, Fakultät <strong>für</strong> Mathematik, Ruhr-Universität Bochum<br />
(2005).<br />
Speaker: MATTHIES, G. 71 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
M. BAUSE: Aspects <strong>of</strong> SUPG/PSPG and GRAD-DIV Stabilized Finite Element<br />
Approximation <strong>of</strong> Compressible Viscous Flow<br />
✬<br />
✫<br />
Aspects <strong>of</strong> SUPG/PSPG and GRAD-DIV Stabilized<br />
Finite Element Approximation <strong>of</strong> Compressible Viscous Flow<br />
Markus Bause<br />
<strong>Institut</strong> <strong>für</strong> Angewandte Mathematik, Universität Erlangen-Nürnberg<br />
Martensstr. 3, 91058 Erlangen<br />
bause@am.uni-erlangen.de<br />
In this contribution various aspects <strong>of</strong> a theoretical analysis and numerical study <strong>of</strong><br />
SUPG/PSPG and grad-div stabilized finite element approximations (cf. [3]) <strong>of</strong> steady<br />
and unsteady compressible isothermal viscous flow are addressed. After temporal discretization<br />
<strong>of</strong> the time variable by means <strong>of</strong> the implicit Euler method, the equations <strong>of</strong><br />
compressible viscous flow are solved by an iteration between a generalized Oseen problem<br />
for the velocity and a hyperbolic transport equation for the perturbation from the mean<br />
density (cf. [1]). Such a splitting-type approach seems attractive for computations because<br />
it <strong>of</strong>fers a reduction to simpler problems for which highly refined numerical methods either<br />
are known or can be built from existing discretization techniques for similar equations,<br />
and because <strong>of</strong> the guidance that can be drawn from an existence theory based on it.<br />
In the case <strong>of</strong> steady motions <strong>of</strong> a compressible viscous gas, decribed by the equations<br />
∇ · (ρv) = 0 , ρv · ∇v − µ∆v − (λ + µ)∇∇ · v + ∇p = ρf ,<br />
p = kρ , v|∂Ω = 0 ,<br />
�<br />
Ω ρ dx = M<br />
the iteration for solving this system reads as: Let ρ = 1 + σ. Put v0 = 0, σ0 = 0. For<br />
given vn, σn compute vn+1, σn+1 by<br />
(i) solving the generalized Oseen-system<br />
∇ · vn+1 = −∇ · (σnvn) ,<br />
(1 + σn)vn · ∇vn+1 + 1<br />
2 ∇ · ((1 + σn)vn)vn+1 − µ∆vn+1 + ∇πn+1 = (1 + σn)f ,<br />
vn+1|∂Ω = 0,<br />
�<br />
Ω πn+1 dx = 0<br />
(ii) and, then, solving the hyperbolic transport equation<br />
kσn+1 + (λ + 2µ)∇ · (σn+1vn+1) = πn+1 − µ∇ · vn+1 .<br />
For the approximation <strong>of</strong> the separated Oseen problem, SUPG/PSPG and grad-div stabilized<br />
higher order finite techniques based on LBB-stable elements are used and analyzed.<br />
The transport equation is discretized by SUPG stabilized finite element methods. Error<br />
estimates are provided. Numerical results for realistic steady and unsteady benchmark<br />
problems (driven cavity flow, flow over a backward facing step and DFG-benchmark) are<br />
given for a large scale <strong>of</strong> Reynolds numbers.<br />
References<br />
[1] M. Bause, J. G. Heywood, A. Novotny and M. Padula, On some approximation schemes<br />
for steady compressible viscous flow, J. Math. Fluid Mech., 5 (2003), pp. 201–230.<br />
[2] M. Bause, Stabilized finite element approximation <strong>of</strong> compressible viscous flow, to appear, <strong>2006</strong>.<br />
[3] T. Gelhard et al., Stabilized finite element schemes with LBB-stable elements for incompressible<br />
flow, J. Comput. Appl. Math. 177 (2005), pp. 243–267.<br />
Speaker: BAUSE, M. 72 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
L. BOGUSLAWSKI: Sheare Stress Distribution on Sphere Surface at Different Inflow<br />
Turbulence<br />
✬<br />
✫<br />
<strong>BAIL</strong> <strong>2006</strong><br />
SHEARE STRESS DISTRIBUTION ON SPHERE SURFACE AT DIFFERNT INFLOW<br />
TURBULENCE<br />
L. Bogusławski<br />
Poznań University <strong>of</strong> Technology, Chair <strong>of</strong> Thermal Engineering, 60 965 Poznań, Poland;<br />
e-mail: leon.boguslawski@put.poznan.pl<br />
Momentum and heat transfer processes on surfaces are sensitive on intensity <strong>of</strong> turbulence <strong>of</strong> flow<br />
above surface. Descriptions <strong>of</strong> share stress or heat transfer distributions usually assume certain level <strong>of</strong><br />
intensity <strong>of</strong> turbulence <strong>of</strong> free flow which overflows surface. When structure <strong>of</strong> flow is formed as<br />
developed flow for typical channels one can assume that turbulence level and structure <strong>of</strong> turbulent<br />
flow is repeated. In such case detailed knowledge <strong>of</strong> flow turbulence is not necessary because<br />
Reynolds number indicated average flow similarity and similarity <strong>of</strong> turbulence by the way.<br />
Unfortunately for most technical applications level <strong>of</strong> turbulence and its structure can vary in wide<br />
borders. More over this level is difficult to prediction based on channel geometry especially when any<br />
promoters <strong>of</strong> turbulence occur. Experimental data indicate that increase <strong>of</strong> turbulence intensity cause<br />
increasing heat and momentum transfer coefficients even when average flow velocity does not change.<br />
To estimate influence <strong>of</strong> turbulence on local distribution <strong>of</strong> shear stress a sphere was chosen as the<br />
simplest, repeatable geometry. Flow was generated by a free ro<strong>und</strong> jet. Level <strong>of</strong> turbulence, in the jet<br />
axis, change from about 0.5% near the nozzle outlet till about 20% far away from the nozzle.<br />
Changing <strong>of</strong> the average flow velocity at the nozzle outlet it is possible to keep constant value <strong>of</strong><br />
velocity at different distances from the nozzle outlet. Turbulent fluctuations <strong>of</strong> a flow velocity were<br />
measured by means <strong>of</strong> a constant temperature anemometer. The local shear stress distribution on<br />
sphere surface was measured by used a surface sensor connected to the constant temperature<br />
anemometer as well.<br />
For low level <strong>of</strong> turbulence the shear stress distribution was similar to literature data. Increase <strong>of</strong><br />
turbulence cause increase <strong>of</strong> a local value <strong>of</strong> shear stress. The local share stress distributions and its<br />
turbulent fluctuations for two chosen turbulence level are presented in figure 1 as an example. The<br />
Reynolds number <strong>of</strong> average flow was the some for both cases. Increasing <strong>of</strong> inflow turbulence level<br />
cause increasing <strong>of</strong> local, average shear stress distributions and equalizing distribution <strong>of</strong> ‘rms’ <strong>of</strong><br />
turbulent fluctuations on rather high level.<br />
o<br />
3.0<br />
2.5<br />
2.0<br />
1.5<br />
1.0<br />
0.5<br />
d = 0.03 m, Re = 3 10 4 , Tu = 2.5 %<br />
0.0<br />
0.0<br />
0 30 60 90 120 150 180<br />
φ<br />
3.5<br />
3.0<br />
2.5<br />
2.0<br />
1.5<br />
1.0<br />
0.5<br />
' rms / ' orms<br />
0.0<br />
0.0<br />
0 30 60 90 120 150 180<br />
Figure 1. Distribution <strong>of</strong> the local average shear stress and its turbulent fluctuations on the sphere<br />
surface at different inflow turbulence level.<br />
o<br />
3.0<br />
2.5<br />
2.0<br />
1.5<br />
1.0<br />
0.5<br />
d = 0.03 m, Re = 3 10 4 , Tu = 12.3 %<br />
Speaker: BOGUSLAWSKI, L. 73 <strong>BAIL</strong> <strong>2006</strong><br />
φ<br />
3.5<br />
3.0<br />
2.5<br />
2.0<br />
1.5<br />
1.0<br />
0.5<br />
' ms / ' orms<br />
✩<br />
✪
L. BOGUSLAWSKI: Sheare Stress Distribution on Sphere Surface at Different Inflow<br />
Turbulence<br />
✬<br />
✫<br />
External turbulence <strong>of</strong> inflow jet increasing flow turbulence near sphere surface where flow<br />
accelerate. This cause increase <strong>of</strong> local shear stress and its fluctuations. Increasing <strong>of</strong> shear stress<br />
transfer fluctuations indicated that turbulence <strong>of</strong> external flow intensify momentum processes near the<br />
wall <strong>of</strong> sphere. In flow deceleration zone <strong>of</strong> flow >90 o for both presented in figure 1 turbulence levels<br />
the time average value and its fluctuations rise in this some way. Both runs near parallel. For<br />
acceleration zone <strong>of</strong> flow near sphere ( ~60 o ) shear stress reach maximum value. In this some region<br />
<strong>of</strong> flow the flow acceleration reduced turbulent fluctuations <strong>of</strong> momentum transfer generated by<br />
external flow turbulence.<br />
Distributions for different level <strong>of</strong> turbulence without average velocity change will be presented and<br />
discussed. For such conditions only influence <strong>of</strong> turbulence are indicated.<br />
Analysis <strong>of</strong> the power spectrum <strong>of</strong> turbulent fluctuations <strong>of</strong> shear stress on sphere surfaces for<br />
different flow intensity at chosen locations will be presented and will be compared with the power<br />
spectrum <strong>of</strong> inflow turbulence.<br />
References<br />
[1] S.Whitaker. Forced convection heat transfer correlation for flow in pipes, past flat plates, single<br />
cylinders, single spheres and flow in packed beds and tube b<strong>und</strong>les, J. <strong>of</strong> AICHE, vol. 18, 361-<br />
371, 1972.<br />
[2] L. Bogusławski. Losses <strong>of</strong> heat from sphere surface at different inflow conditions (in polish),<br />
XVI Thermodinamics Conference, Kołobrzeg , vol. 1, 135-140, 1996.<br />
[3] L. Bogusławski. Measurements technique <strong>of</strong> stagnation point heat transfer and its<br />
fluctuations by means <strong>of</strong> a constant temperature sensor, Proceedings <strong>of</strong> Turbulent Heat<br />
Transfer Conference, 1-6, San Diego, May 1996.<br />
[4] H. Giedt. Trans. ASME, 71, 375, 1949<br />
Speaker: BOGUSLAWSKI, L. 74 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
A.CANGIANI, E.H.GEORGOULIS, M. JENSEN: Continuous-Discontinuous Finite<br />
Element Methods for Convection-Diffusion Problems<br />
✬<br />
✫<br />
Continuous-Discontinuous Finite Element Methods for<br />
Convection-Diffusion Problems<br />
Abstract<br />
Andrea Cangiani, Emmanuil H. Georgoulis and Max Jensen<br />
February 14, <strong>2006</strong><br />
Standard (conforming) finite element approximations <strong>of</strong> convection-dominated convection-diffusion<br />
problems <strong>of</strong>ten exhibit poor stability properties that manifest themselves as non-physical oscillations<br />
polluting the numerical solution. Various techniques have been proposed for the stabilisation <strong>of</strong> finite<br />
element methods (FEMs) for convection-diffusion problems, see for example, Morton [12] and Roos,<br />
Stynes and Tobiska [14] for a complete survey. Common techniques are Petrov-Galerkin methods,<br />
like the streamline upwind Petrov-Galerkin (SUPG) method introduced by Hughes and Brooks [8],<br />
exponential fitting [13], ad hoc meshing, like graded meshes [15] and Shishkin type meshes [11], and<br />
adaptive mesh refinement (see, e.g., [5] and [6]). More recently, the residual-free bubble method <strong>of</strong><br />
Brezzi et al [2], [1], [4] and the variational multiscale method <strong>of</strong> Hughes and co-authors [9],[10].<br />
During the last decade, families <strong>of</strong> discontinuous Galerkin finite element methods (DGFEMs)<br />
have been proposed for the numerical solution <strong>of</strong> convection-diffusion problems, due to many attractive<br />
properties they exhibit. In particular, DGFEMs admit good stability properties, they <strong>of</strong>fer<br />
flexibility in the mesh design (irregular meshes are admissible) and in the imposition <strong>of</strong> bo<strong>und</strong>ary<br />
conditions (Dirichlet bo<strong>und</strong>ary conditions are weakly imposed), and they are increasingly popular<br />
in the context <strong>of</strong> hp-adaptive algorithms.<br />
The above mentioned attractive features <strong>of</strong> DGFEMs come at the price <strong>of</strong> the higher number<br />
<strong>of</strong> degrees <strong>of</strong> freedom used. For instance, for piece-wise linear approximations in d-dimensions,<br />
DGFEMs require 2 d times more degrees <strong>of</strong> freedom than conforming FEMs and their stabilised<br />
variants. The relative difference in the number <strong>of</strong> degrees <strong>of</strong> freedom reduces when considering<br />
higher order local polynomial degree in the approximations; nevertheless, the conforming FEMs<br />
always require less degrees <strong>of</strong> freedom than their DGFEM counterparts.<br />
The issue <strong>of</strong> the number <strong>of</strong> degrees <strong>of</strong> freedom required by DGFEMs has recently been addressed<br />
by T.J.R. Hughes and co-workers in [7], where the Multiscale Discontinuous Galerkin (MDG) finite<br />
element method framework is introduced. MDG uses local, element-wise problems to develop a<br />
transformation between the degrees <strong>of</strong> freedom <strong>of</strong> the discontinuous space and a related, smaller,<br />
continuous space. The transformation enables a direct construction <strong>of</strong> the global matrix problem<br />
in terms <strong>of</strong> the degrees <strong>of</strong> freedom <strong>of</strong> the continuous space. It is proved that the method has the<br />
accuracy and stability <strong>of</strong> the original DGFEM. The drawback <strong>of</strong> this approach is the computational<br />
overhead <strong>of</strong> the solution <strong>of</strong> the local element-wise problems.<br />
We propose a numerical scheme for linear convection-diffusion problems which couples continuous<br />
and discontinuous Galerkin finite elements (CG-DG) in a different manner. Depending on the<br />
local variation <strong>of</strong> the solution, the scheme locally uses either the computationally less expensive<br />
continuous finite elements or the computationally more costly but also more stable discontinuous<br />
Galerkin discretisation. Given that good stability properties are required near features <strong>of</strong> almost<br />
(d − 1)-dimensional character (such as bo<strong>und</strong>ary and/or interior layers) discontinuous Galerkin<br />
discretisation is only used in the neighborhoods <strong>of</strong> such features, whereas standard conforming FEM<br />
is used away from the layers. Thus, the increased overhead from the use <strong>of</strong> DGFEMs is balanced by<br />
their minimal use, limited to the neighborhoods <strong>of</strong> layers.<br />
This work introduces the continuous-discontinuous Galerkin (CG-DG) finite element method,<br />
and presents the first results in the analysis <strong>of</strong> this approach. In particular, we derive an a-priori<br />
error analysis <strong>of</strong> the CG-DG blending technique, along with numerical experiments that evaluate<br />
the accuracy and efficiency <strong>of</strong> the CG-DG approach in practice.<br />
Speaker: GEORGOULIS, E.H. 75 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
A.CANGIANI, E.H.GEORGOULIS, M. JENSEN: Continuous-Discontinuous Finite<br />
Element Methods for Convection-Diffusion Problems<br />
✬<br />
✫<br />
References<br />
[1] Brezzi, F., Marini, D., and Süli, E. Residual-free bubbles for advection-diffusion problems:<br />
the general error analysis. Numer. Math. 85, 1 (2000), 31–47.<br />
[2] Brezzi, F., and Russo, A. Choosing bubbles for advection-diffusion problems. Math. Models<br />
Methods Appl. Sci. 4, 4 (1994), 571–587.<br />
[3] Brooks, A. N., and Hughes, T. J. R. Streamline upwind/Petrov-Galerkin formulations<br />
for convection dominated flows with particular emphasis on the incompressible Navier-Stokes<br />
equations. Comput. Methods Appl. Mech. Engrg. 32, 1-3 (1982), 199–259. FENOMECH ’81,<br />
Part I (Stuttgart, 1981).<br />
[4] Cangiani, A., and Süli, E. Enhanced RFB method. Numer. Math. 101(2) (2005), 273–308.<br />
[5] Eriksson, K., Estep, D., Hansbo, P., and Johnson, C. Introduction to adaptive methods<br />
for differential equations. In Acta numerica, 1995, Acta Numer. Cambridge Univ. Press,<br />
Cambridge, 1995, pp. 105–158.<br />
[6] Giles, M. B., and Süli, E. Adjoint methods for PDEs: a posteriori error analysis and<br />
postprocessing by duality. In Acta numerica, 2002, vol. 11 <strong>of</strong> Acta Numer. 2002, pp. 145–236.<br />
[7] Hughes, Thomas J. R.and Scovazzi, G., Bochev, P. B., and Buffa, A. A multiscale<br />
discontinuous Galerkin method with the computational structure <strong>of</strong> a continuous galerkin<br />
method. ICES Report 05-16 (2005).<br />
[8] Hughes, T. J. R., and Brooks, A. A multidimensional upwind scheme with no crosswind<br />
diffusion. In Finite element methods for convection dominated flows (Papers, Winter Ann.<br />
Meeting Amer. Soc. Mech. Engrs., New York, 1979), vol. 34 <strong>of</strong> AMD. Amer. Soc. Mech. Engrs.<br />
(ASME), New York, 1979, pp. 19–35.<br />
[9] Hughes, T. J. R., Feijóo, G. R., Mazzei, L., and Quincy, J.-B. The variational multiscale<br />
method—a paradigm for computational mechanics. Comput. Methods Appl. Mech. Engrg.<br />
166, 1-2 (1998), 3–24.<br />
[10] Hughes, T. J. R., and Stewart, J. R. A space-time formulation for multiscale phenomena.<br />
J. Comput. Appl. Math. 74, 1-2 (1996), 217–229.<br />
[11] Madden, N., and Stynes, M. Efficient generation <strong>of</strong> shishkin meshes in solving convectiondiffusion<br />
problems. Preprint <strong>of</strong> the Department <strong>of</strong> Mathematics, University College, Cork,<br />
Ireland no. 1995-2 (1995).<br />
[12] Morton, K. W. Numerical solution <strong>of</strong> convection-diffusion problems, vol. 12 <strong>of</strong> Applied Mathematics<br />
and Mathematical Computation. Chapman & Hall, London, 1996.<br />
[13] O’Riordan, E., and Stynes, M. A globally uniformly convergent finite element method for<br />
a singularly perturbed elliptic problem in two dimensions. Math. Comp. 57, 195 (1991), 47–62.<br />
[14] Roos, H.-G., Stynes, M., and Tobiska, L. Numerical Methods for Singularly Perturbed<br />
Differential Equations. Springer-Verlag, Berlin, 1996. Convection-diffusion and flow problems.<br />
[15] Schwab, C., and Suri, M. The p and hp versions <strong>of</strong> the finite element method for problems<br />
with bo<strong>und</strong>ary layers. Math. Comp. 65, 216 (1996), 1403–1429.<br />
2<br />
Speaker: GEORGOULIS, E.H. 76 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
C. CLAVERO, J.L. GRACIA, F. LISBONA: A second order uniform convergent<br />
method for a singularly perturbed parabolic system <strong>of</strong> reaction-diffusion type<br />
✬<br />
✫<br />
A second order uniform convergent method for a singularly perturbed<br />
parabolic system <strong>of</strong> reaction–diffusion type ∗<br />
C. Clavero, J.L. Gracia and F. Lisbona<br />
Department <strong>of</strong> Applied Mathematics<br />
University <strong>of</strong> Zaragoza. Spain<br />
clavero@unizar.es, jlgracia@unizar.es, lisbona@unizar.es<br />
Abstract<br />
In this work we are interested in solving singularly perturbed parabolic bo<strong>und</strong>ary value problems<br />
given by<br />
⎧<br />
⎪⎨ L�ε�u ≡<br />
⎪⎩<br />
∂�u<br />
∂t + Lx,�ε�u = � f, (x, t) ∈ Q = Ω × (0, T ] = (0, 1) × (0, T ],<br />
�u(0, t) = �g0(t), �u(1, t) = �g1(t), ∀t ∈ [0, T ],<br />
(1)<br />
�u(x, 0) = �0, ∀x ∈ Ω,<br />
where<br />
Lx,�ε ≡<br />
�<br />
−ε1 ∂2<br />
∂x 2<br />
−ε2 ∂2<br />
∂x 2<br />
�<br />
� �<br />
a11(x) a12(x)<br />
+ A, A =<br />
,<br />
a21(x) a22(x)<br />
with 0 < ε1 ≤ ε2 ≤ 1. The components <strong>of</strong> the functions �g0(t), �g1(t), the right hand side<br />
�f(x, t) = (f1(x, t), f2(x, t)) T and the matrix A are supposed smooth enough. The positivity<br />
condition<br />
ai1 + ai2 ≥ αi > 0, aii > 0, i = 1, 2, aij ≤ 0 if i �= j, (2)<br />
is satisfied by matrix A. Otherwise, we consider the transformation �v(x, t) = �u(x, t)e −α0t with<br />
α0 > 0 sufficiently large so that (2) holds.<br />
This problem is a simple model <strong>of</strong> the classical linear double–diffusion model for saturated<br />
flow in fractures porous media (Barenblatt system) developed in [1]. The first equation describes<br />
the flow in the matrix and the second one the flow in the fracture system. The coupling terms<br />
are given by the matrix<br />
� �<br />
1 −1<br />
A =<br />
,<br />
−1 1<br />
which describes the interchange <strong>of</strong> fluid between the two systems. The permeabilities ε1 and ε2<br />
in these equations could be very small and also they can have different magnitudes.<br />
It is well known that the exact solution <strong>of</strong> these problems has a multiscale character, i.e.,<br />
there are narrow regions (the bo<strong>und</strong>ary layer regions) where the solution has strong gradients<br />
and in the rest <strong>of</strong> the domain the solution varies smoothly. Therefore, it is necessary to dispose<br />
<strong>of</strong> efficient numerical methods (uniformly convergent methods) to approximate the solution<br />
independently <strong>of</strong> the values <strong>of</strong> the diffusion parameters ε1 and ε2.<br />
Recently some papers study uniform convergent numerical methods to solve singularly perturbed<br />
elliptic linear systems on a special piecewise uniform Shishkin mesh. In the analysis <strong>of</strong><br />
these type <strong>of</strong> problems the three following different cases can be distinguished depending on the<br />
relation between the singular perturbation parameters ε1 and ε2:<br />
[i.] ε1 = ε, ε2 = 1, [ii.] ε1 = ε2 = ε [iii.] ε1, ε2 arbitrary.<br />
∗ This research will be partially supported by the project MEC/FEDER MTM 2004-01905 and the Diputación<br />
General de Aragón.<br />
1<br />
Speaker: CLAVERO, C. 77 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
C. CLAVERO, J.L. GRACIA, F. LISBONA: A second order uniform convergent<br />
method for a singularly perturbed parabolic system <strong>of</strong> reaction-diffusion type<br />
✬<br />
✫<br />
In [7] and [6] it was developed a first order uniformly convergent method in cases [ii.] and [iii.]<br />
respectively. In [8], [4] and [5] a second order uniformly convergent scheme was obtained for<br />
cases [i.], [ii.] and [iii.] respectively.<br />
In [3] a decomposition <strong>of</strong> the exact solution <strong>of</strong> problem (1), into its regular and singular<br />
components, was given. From this decomposition it follows which is the asymptotic behaviour<br />
<strong>of</strong> each one <strong>of</strong> these components with respect to the singular perturbation parameters ε1 and ε2.<br />
Moreover, in that work a first order in time and second order in space (except by a logarithmic<br />
factor) uniformly convergent method was developed, using the classical Euler and central differences<br />
discretizations respectively. In order to increase the order <strong>of</strong> uniform convergence <strong>of</strong> this<br />
numerical scheme, here we replace the Euler scheme by the Crank-Nicolson method in the time<br />
discretization. This method has been used in the framework <strong>of</strong> singularly perturbed problem; for<br />
instance, in [2] to solve 1D evolutionary problems <strong>of</strong> convection–diffusion type. Some numerical<br />
experiments will be showed, which illustrate in practice the improvement in the uniform order<br />
<strong>of</strong> convergence <strong>of</strong> the new scheme.<br />
Keywords: Singular perturbation, reaction-diffusion problems, uniform convergence, coupled<br />
system, Shishkin mesh.<br />
AMS classification: 65N12, 65N30, 65N06<br />
References<br />
[1] G.I. Barenblatt, I.P. Zheltov and I.N. Kochina, “Basic concepts in the theory <strong>of</strong> seepage <strong>of</strong><br />
homogeneous liquids in fissured rocks”, J. Appl. Math. and Mech., 24, 1286–1303 (1960).<br />
[2] C. Clavero, J.L. Gracia and J.C. Jorge, “Second order numerical methods for one–<br />
dimensional parabolic singularly perturbed problems with regular layers”, Numerical Methods<br />
for Partial Differential Equations, 21 149–169 (2005).<br />
[3] J.L. Gracia and F. Lisbona “A uniformly convergent scheme for a system <strong>of</strong> reaction–<br />
diffusion equations”, submitted.<br />
[4] T. Linß and N. Madden, “An improved error estimate for a numerical method for a system<br />
<strong>of</strong> coupled singularly perturbed reaction–diffusion equations”, Comp. Meth. Appl. Math. 3<br />
417–423 (2003).<br />
[5] T. Linß and N. Madden, “Accurate solution <strong>of</strong> a system <strong>of</strong> coupled singularly perturbed<br />
reaction-diffusion equations”, Computing, 73, 121–133 (2004).<br />
[6] N. Madden and M. Stynes, “A uniformly convergent numerical method for a coupled system<br />
<strong>of</strong> two singularly perturbed linear reaction-diffusion problems“, IMA J. Numer. Anal., 23,<br />
627–644 (2003).<br />
[7] S. Matthews, J.J.H. Miller, E. O’Riordan, G.I. Shishkin, A parameter robust numerical<br />
method for a system <strong>of</strong> singularly perturbed ordinary differential equations, in: Analytical<br />
and Numerical Methods for Convection–Dominated and Singularly Perturbed Problems<br />
(J.J.H. Miller, G.I. Shishkin and L. Vulkov, eds.), Nova Science Publishers, New York, 2000,<br />
219–224.<br />
[8] S. Matthews, E. O’Riordan and G.I. Shishkin, “A nunerical method for a system <strong>of</strong> singularly<br />
perturbed reaction–diffusion equations“, J. Comput. Appl. Math., 145, 151–166<br />
(2002).<br />
2<br />
Speaker: CLAVERO, C. 78 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
B. EISFELD: Computation <strong>of</strong> complex compressible aerodynamic flows with a<br />
Reynolds stress turbulence model<br />
✬<br />
✫<br />
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Speaker: EISFELD, B. 79 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
B. EISFELD: Computation <strong>of</strong> complex compressible aerodynamic flows with a<br />
Reynolds stress turbulence model<br />
✬<br />
✫<br />
���� ��������� ���� ���������� ����������� ��� ������������ ��������� ����� �� ��������� �������<br />
������� �������������� ��� ���� �� �� � ���������� ����������� ������� ������ ������ ���<br />
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��<br />
Speaker: EISFELD, B. 80 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
A. FIROOZ, M. GADAMI: Turbulence Flow for NACA 4412 in Unbo<strong>und</strong>ed Flow and<br />
Gro<strong>und</strong> Effect with Different Turbulence Models and Two Gro<strong>und</strong> Conditions: Fixed<br />
and Moving Gro<strong>und</strong> Conditions<br />
✬<br />
✫<br />
Turbulence Flow for NACA 4412 in Unbo<strong>und</strong>ed Flow and Gro<strong>und</strong> Effect with<br />
Different Turbulence Models and Two Gro<strong>und</strong> Conditions: Fixed and<br />
Moving Gro<strong>und</strong> Conditions<br />
Abdolhamid Firooz, Academic board<br />
(ahfirooz@hamoon.usb.ac.ir)<br />
Mojgan Gadami, B.S. student<br />
(mozhgan_gadami@yahoo.com)<br />
Mechanical Engineering Department, University <strong>of</strong> Sistan & Baloochestan, Zahedan, Iran.<br />
Abstarct<br />
In this paper, the turbulence fluid flow aro<strong>und</strong> a<br />
two dimensional 4412 airfoil on different angles <strong>of</strong><br />
attack near and far from the gro<strong>und</strong> with the RANS<br />
(Reynolds averaged Navier-stokes) equations is<br />
calculated. Realizable K−ε turbulence model with<br />
Enhanced wall treatment and Spalart-Allmaras model<br />
are used (Re=2 × 10 6<br />
). Equations are approximated<br />
by finite volumes method, and they are solved by<br />
segregated method. The second order upwind method<br />
is used for the convection term, also for pressure<br />
interpolation the PRESTO method is used, and the<br />
relation between pressure and velocity with SIMPLEC<br />
algorithm is calculated.<br />
The computational domain extended 3C upstream<br />
<strong>of</strong> the leading edge <strong>of</strong> the airfoil 5C, downstream from<br />
the trailing edge, and 4C above the pressure surface.<br />
Distance from below the airfoil was defined with H/C<br />
where C is chord, and H is gro<strong>und</strong> distance to the<br />
trailing edge.<br />
Velocity inlet bo<strong>und</strong>ary condition was applied<br />
upstream with speed <strong>of</strong> (U ∞ =29.215) and outflow<br />
bo<strong>und</strong>ary condition was applied downstream. The<br />
pressure and suction side <strong>of</strong> the airfoil and above and<br />
below's bo<strong>und</strong>aries <strong>of</strong> domain were defined<br />
independently with no slip wall bo<strong>und</strong>ary condition.<br />
Moving wall with speed <strong>of</strong> (U ∞ =29.215) for above,<br />
and fixed or moving wall for below the airfoil was<br />
used.<br />
An unstructured mesh arrangement with<br />
quadrilateral elements was adopted to map the flow<br />
domain in gro<strong>und</strong> effect and unbo<strong>und</strong>ed flow. A<br />
considerably fine C-type mesh was applied to achieve<br />
sufficient resolution <strong>of</strong> the airfoil surface and bo<strong>und</strong>ary<br />
layer region. Particular attention was directed to an<br />
<strong>of</strong>fset 'inner region' encompassing the airfoil, and also<br />
C-type mesh was applied on near the airfoil at above<br />
and bottom, which it’s domain depends on the H/C in<br />
gro<strong>und</strong> effects condition. Continuing downstream from<br />
leading edge and continuing far from above the airfoil<br />
H-type mesh was applied.<br />
Distance from the wall-adjacent cells must be<br />
determined by considering the range over which the<br />
log-law is valid. The distance is usually measured in<br />
the wall unit, y + (= ρu τ y / µ ). By increasing the<br />
grid numbers and changing the type <strong>of</strong> arranging mesh,<br />
adapting, aro<strong>und</strong> the airfoil a proper y + value, is<br />
obtained, and with this value solution results have good<br />
agreement with experimental data. Fig (1), Fig (2).<br />
The aerodynamic characteristic <strong>of</strong> an airfoil in<br />
gro<strong>und</strong> proximity is known to be much different from<br />
that <strong>of</strong> unbo<strong>und</strong>ed flow. The condition <strong>of</strong> the wind<br />
tunnel bottom, I. e., moving or fixed relative to the<br />
airfoil would influence the performance <strong>of</strong> the airfoil in<br />
gro<strong>und</strong> effect. The presence <strong>of</strong> bo<strong>und</strong>ary layer when air<br />
is flowing over bottom <strong>of</strong> the wind tunnel would be<br />
different from the real situation for a flying WIG.<br />
Proper velocity in moving gro<strong>und</strong> bo<strong>und</strong>ary<br />
condition is considered with moving gro<strong>und</strong>, and<br />
bo<strong>und</strong>ary layer is considered with fixed gro<strong>und</strong>, and in<br />
the moving gro<strong>und</strong> the bo<strong>und</strong>ary layer's effect is<br />
omitted, and so is the proper velocity in the fix gro<strong>und</strong>.<br />
A grid independence analysis was conducted using<br />
some meshes <strong>of</strong> varying cell number. Each mesh was<br />
processed using the Realisable K-ε turbulence model<br />
with Enhanced wall treatment and Spalart-Allmaras<br />
model. Application <strong>of</strong> each mesh generally produces<br />
accurate predictions <strong>of</strong> the lift coefficients with<br />
comparison to the experimental data. It can be seen<br />
that the error associated with the predicated lift<br />
coefficient decreases with mesh refinement.<br />
In order to validate the present numerical data the<br />
computational results for NACA 4412 in unbo<strong>und</strong>ed<br />
flow is compared with published numerical results and<br />
experimental data. Fig (3).<br />
Fig (4) shows Cp variation on surface <strong>of</strong> the airfoil<br />
at four relative gro<strong>und</strong> high computed (α =8). As the<br />
Speaker: FIROOZ, A. 81 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
A. FIROOZ, M. GADAMI: Turbulence Flow for NACA 4412 in Unbo<strong>und</strong>ed Flow and<br />
Gro<strong>und</strong> Effect with Different Turbulence Models and Two Gro<strong>und</strong> Conditions: Fixed<br />
and Moving Gro<strong>und</strong> Conditions<br />
✬<br />
✫<br />
wing approaches the gro<strong>und</strong>, the pressure on the<br />
pressure side <strong>of</strong> wing gradually increases due to slowdown<br />
<strong>of</strong> flow in region, while the pressure on the<br />
suction side <strong>of</strong> wing gradually decreases resulting in<br />
Lift increase that is regarded as the advantage <strong>of</strong> the<br />
WIG vehicle.<br />
The velocity fields aro<strong>und</strong> this section in gro<strong>und</strong><br />
effect with H/C=.2 for two different gro<strong>und</strong> conditions<br />
at α =8 are shown in Fig (5) and (6). The different in<br />
the velocity field near the wing surface due to the<br />
bottom condition differences can not be clearly seen in<br />
Fig (5) and (6), but a bo<strong>und</strong>ary layer developed on the<br />
fix gro<strong>und</strong> can be clearly seen in Fig (6), on the other<br />
hand, for the moving gro<strong>und</strong> with oncoming<br />
<strong>und</strong>isturbed velocity as seen in Fig (6), the velocity<br />
decreases with increasing high.<br />
Meanwhile the difference in the Lift simulated by<br />
the fixed and moving bottom conditions is negligible<br />
but the Drag force simulated by the moving bottom is<br />
to some extent larger than that <strong>of</strong> the fixed one. Also it<br />
is concluded that on different angles <strong>of</strong> attack Lift<br />
force <strong>of</strong> the airfoil increases as it approaches the<br />
gro<strong>und</strong>, and the Drag force decreases.<br />
Figure (2): adapted C-grid for unbo<strong>und</strong>ed flow (α =5) Figure (1): C-grid for bo<strong>und</strong>ed flow ( α =5)<br />
Figure (3): CL vs. angel <strong>of</strong> attack<br />
(Experimental data ( Abbott, I.H., and von Doenh<strong>of</strong>f, A.E.,<br />
Theory <strong>of</strong> Wing Sections, Dover, New York, 1959.)<br />
Speaker: FIROOZ, A. 82 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
A. FIROOZ, M. GADAMI: Turbulence Flow for NACA 4412 in Unbo<strong>und</strong>ed Flow and<br />
Gro<strong>und</strong> Effect with Different Turbulence Models and Two Gro<strong>und</strong> Conditions: Fixed<br />
and Moving Gro<strong>und</strong> Conditions<br />
✬<br />
✫<br />
Figure (4): Surface pressure distributions for NACA 4412 at the different gro<strong>und</strong> clearance<br />
(α =8, R=2× 10 6 )<br />
Figure (5): Velocity vector field for NACA 4412 in gro<strong>und</strong> effect<br />
(α=8, Re=2×10 6 , H/C=.2, moving gro<strong>und</strong>)<br />
Figure (6): Velocity vector field for NACA 4412 in gro<strong>und</strong> effect<br />
6<br />
(α =8, Re = 2 × 10 , H/C=.2, fix gro<strong>und</strong> )<br />
Speaker: FIROOZ, A. 83 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
A. FIROOZ, M. GADAMI: Turbulence Flow for NACA 4412 in Unbo<strong>und</strong>ed Flow and<br />
Gro<strong>und</strong> Effect with Different Turbulence Models and Two Gro<strong>und</strong> Conditions: Fixed<br />
and Moving Gro<strong>und</strong> Conditions<br />
✬<br />
✫<br />
EFERENCES<br />
Chawal M. D., Edwards L. C. and Franke M,<br />
E 1990 Wind Tunnel Investigation <strong>of</strong> Wing<br />
–in Gro<strong>und</strong> Effect, Journal <strong>of</strong> Aircraft, Vol<br />
27 ,No.4, pp.289-293<br />
Chorin A. J., 1967 A Numerical Method for<br />
Solving Incompressible Viscous Flow<br />
Problems, Journal Computational Physics<br />
Vol.2 No.2, pp,14-23<br />
Chun H. H., Chang C. H. and Paik K. J.,1999,<br />
Longitudinal Stability <strong>of</strong> a Wing in Gro<strong>und</strong><br />
Effect Craft, J. <strong>of</strong> The Society <strong>of</strong> Naval<br />
Architects <strong>of</strong> Korea, Vol.36,No.3,pp.60-70<br />
RINA, London, U., total <strong>of</strong> 19 papers include<br />
machines 2000, Saint Petersburg State Marine<br />
Technical University , Russia<br />
Sowdon A., 1995 A Simple Method to remove the<br />
Bo<strong>und</strong>ary Layer on a Gro<strong>und</strong> Plate, Papers <strong>of</strong><br />
Ship Research <strong>Institut</strong>e Japan , Vol.32 Vo.2, pp.<br />
53-78<br />
Stinton D. 1998 The Anatomy <strong>of</strong> the Aeroplan ,<br />
2nd Edition published Blacewell Science, pp.<br />
86-92<br />
Staufenbiel, D, 1996 Comment on Aerodynamic<br />
Characteristics <strong>of</strong> a Two Dimensional Airfoil<br />
with Gro<strong>und</strong> Effect, Journal <strong>of</strong> Aircraft<br />
Aerodynamic <strong>of</strong> Wing-In-Gro<strong>und</strong> Effect Vehicles<br />
Rheinisch-West-falische Technische<br />
Hochschule, project Rept. 78/1, Aachen,<br />
Germany, 1978<br />
Steinbach, D 1996 Comment on Aerodynamic<br />
Characteristics <strong>of</strong> a Two-Dimensional Airfoil<br />
with Gro<strong>und</strong> Effect , Journal <strong>of</strong> Aircraft,<br />
Vol.34, No.3, pp.455-456<br />
Thomas J. L., Paulson J,w. and Margason R, J.,<br />
1979 Powered Low-Aspect-ratio Wing in<br />
Gro<strong>und</strong> Effect (WIG) Aerodynamic<br />
Characteristics, NASA TM78793<br />
Turner T. R., 1966 Endless-Belt Technique for<br />
Gro<strong>und</strong> Simulation, NASA SP-116<br />
Speziale, C.G., Abid, R. & Anderson, E.C. 1992,<br />
.Critical Evaluation <strong>of</strong> Two-Equation Models<br />
for Near-Wall Turbulence., AIAA J., Vol. 30<br />
No. 2, pp. 324-331.<br />
Wilcox, D.C. 1988, .Reassessment <strong>of</strong> the scaledetermining<br />
equation for advanced turbulence<br />
models., AIAA J., Vol. 26 No. 11, pp. 1299-<br />
1310.<br />
Pajayakrit, P. & Kind, R.J. 2000, .Assessment and<br />
Modification <strong>of</strong> Two-Equation Turbulence<br />
Models., AIAA J., Vol. 38 No. 6, pp. 955-963.<br />
Gorski, J. & Nguyen, P. 1991, .Navier-Stokes<br />
Analysis <strong>of</strong> Turbulent Bo<strong>und</strong>ary Layer Wake<br />
for Two-Dimensional Lifting<br />
Bodies.,Eighteenth Symposium on Naval<br />
Hydrodynamics, Ann Abor, USA, pp. 633-643.<br />
Gersten, K. & Schlichting, H. 2000, .Bo<strong>und</strong>ary<br />
Layer Theory., 8th Ed., Springer-Verlag,<br />
Berlin, Germany.<br />
Abbott, I.H., and von Doenh<strong>of</strong>f, A.E., Theory <strong>of</strong><br />
Wing Sections, Dover, New York, 1959.<br />
Akimoto, H. and Kubo, S., 1998 Characteristics<br />
Study <strong>of</strong> Twp-dimensional in Surface Effect by<br />
CFD Simulation, Journal <strong>of</strong> the Society <strong>of</strong><br />
Naval Architects <strong>of</strong> Japan, Vol. 184,pp.a7-54<br />
Bagley J. A., 1961 The Pressure Distribution<br />
on Two-Dimensional Wings Near Gro<strong>und</strong>,<br />
Ministry <strong>of</strong> Aviation Aeronautical<br />
Research Council R&M, NO,3238,40<br />
pages<br />
Chang R, H 2000 Numerical Simulation <strong>of</strong><br />
Turbulent Flow aro<strong>und</strong> Two-Dimensional<br />
Wings In Gro<strong>und</strong> Effect Wing Different<br />
Gro<strong>und</strong> Bo<strong>und</strong>ary Condition, MSc Thesis,<br />
Dept <strong>of</strong> Naval Architecture & ocean<br />
Engineering Pusan National University,<br />
Korea<br />
Speaker: FIROOZ, A. 84 <strong>BAIL</strong> <strong>2006</strong><br />
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S.A. GAPONOV, G.V. PETROV, B.V. SMORODSKY: Bo<strong>und</strong>ary layer intercation with<br />
external disturbances<br />
✬<br />
✫<br />
BOUNDARY LAYER INTERACTION WITH EXTERNAL DISTURBANCES<br />
S.A.Gaponov, G.V.Petrov, B.V.Smorodsky<br />
<strong>Institut</strong>e <strong>of</strong> Theoretical and Applied Mechanics SB RAS, Novosibirsk 630090,<br />
Russia; E-mail: gaponov@itam.nsc.ru, Fax:+7(3832)342268<br />
Generation <strong>of</strong> initial unstable eigen disturbances inside the bo<strong>und</strong>ary layer (BL) by external<br />
perturbations is an actual problem nowadays in the investigation <strong>of</strong> laminar-turbulent transition.<br />
Morkovin [1] was the first who has formulated so called BL receptivity problem. Up to now a lot <strong>of</strong><br />
experimental and theoretical works studying subsonic BL has been performed. The detailed review <strong>of</strong><br />
these efforts can be fo<strong>und</strong> in [2,3]. The knowledge about the supersonic BL is much shorter at the<br />
present moment. The existing papers are devoted mainly to the investigation <strong>of</strong> external acoustic field<br />
interaction with a supersonic BL on a smooth flat plate [4-6]. However an oncoming supersonic flow<br />
always comprises not only acoustic but also vortical and thermal (entropy) perturbations [7]. This<br />
paper presents results concerning irrotational external disturbances with zero damping in the direction<br />
<strong>of</strong> the main flow. Present paper is devoted to the investigation <strong>of</strong> disturbance excitation in sub- and<br />
supersonic BL by external vortical and thermal waves. Interaction <strong>of</strong> the acoustic waves with the BL<br />
on the non-smooth surface has also been investigated and is reported here.Studies were conducted<br />
both in an approaching <strong>of</strong> parallel basic flow and taken in consideration dependence <strong>of</strong> the main flow<br />
in bo<strong>und</strong>ary layer on longitudinal coordinate. In the second case were used <strong>of</strong> an equation <strong>of</strong> stability<br />
<strong>of</strong>fered in [8].<br />
For the acoustic field we distinguish two different kinds <strong>of</strong> interaction with the BL. In the first case<br />
the incidence angle <strong>of</strong> the acoustic wave onto the BL is finite. In the second case the incidence angle is<br />
zero. If the incidence angle is equal to zero, then in the result <strong>of</strong> the interaction the normal to the-wall<br />
disturbance velocity at the BL outer edge is non-zero and it is an additional source <strong>of</strong> the streamwise<br />
acoustic field. Such interaction leads to a very fast amplification <strong>of</strong> initial wave. For nonzero incidence<br />
angles we have performed computations <strong>of</strong> the reflection coefficient. It is important to note here that<br />
in some cases such reflectance is greater than unity. The amplitude <strong>of</strong> mass flux perturbation inside the<br />
BL excited by an external acoustic wave is practically always an order <strong>of</strong> magnitude larger than the<br />
initial wave amplitude in the free stream. Comparison <strong>of</strong> theoretical results with the experiment [6]<br />
leads authors to necessary to consider the problem <strong>of</strong> diffraction <strong>of</strong> acoustic waves on a plate leading<br />
edge. Using Fourier transformation and the equations <strong>of</strong> gas dynamics, one can show, that mass flux<br />
fluctuations along the plate could be completely determined by means <strong>of</strong> the jump <strong>of</strong> normal-to-thewall<br />
disturbance velocity at the plate leading edge. The normal velocity disturbance upstream <strong>of</strong> the<br />
plate leading edge ( x < 0 ) is determined by the distribution <strong>of</strong> the mass flux. The obtained formulas<br />
give the relations <strong>of</strong> the mass flux in the region x > 0 with its distribution at x < 0 . It was shown that<br />
intensity <strong>of</strong> the mass flux fluctuation is reduced with distance from the leading edge and is dependent<br />
<strong>of</strong> the orientation <strong>of</strong> the incident wave.<br />
Tollmien-Schlichting (TS) wave excitation in the supersonic BL by a pair <strong>of</strong> acoustic waves has<br />
been also investigated theoretically. The receptivity coefficient and the range <strong>of</strong> wave parameters<br />
where TS-wave generation takes place have been computed. It was obtained, that at enough large<br />
values <strong>of</strong> a Reynold's number, in narrow range <strong>of</strong> the acoustic wave numbers, the excited disturbances<br />
practically do not differ from an own increasing disturbance. Outside <strong>of</strong> this range the TS wave is not<br />
excited. The parameters <strong>of</strong> excited disturbances hardly differ from TS wave parameters near a neutral<br />
point, the coincidence is observed only at essential move away from neutral area downstream<br />
Beside in the paper investigation <strong>of</strong> the so<strong>und</strong> interaction with BL on the flat plate with roughness<br />
is consider also. The problem <strong>of</strong> the disturbance generation by small amplitude spatially periodic wall<br />
roughness has been formulated and solved in the linear approximation. The parameters <strong>of</strong> so<strong>und</strong><br />
irradiated by the model with roughness in the supersonic flow have been computed. The peculiarities<br />
<strong>of</strong> the disturbances in the case when the angle between the wave fronts and the mean flow is close to<br />
the Mach angle have been investigated specially. It has been shown that the amplitude <strong>of</strong> the<br />
disturbance streamline inside the BL is greatly reduced in the near-wall sub-layer. At M = 1 mass<br />
flux perturbations in the main part <strong>of</strong> the BL are close to zero also. Considerable reduction <strong>of</strong> the<br />
Speaker: GAPONOV, S.A. 85 <strong>BAIL</strong> <strong>2006</strong><br />
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S.A. GAPONOV, G.V. PETROV, B.V. SMORODSKY: Bo<strong>und</strong>ary layer intercation with<br />
external disturbances<br />
✬<br />
✫<br />
M where M = M cos χ and<br />
disturbance amplitude takes place for oblique roughness at = 1<br />
χ is the angle between the roughness wave front and the plate leading edge. At the BL outer edge the<br />
disturbance amplitude is almost zero because it is already damped inside the BL. The problem <strong>of</strong><br />
nonlinear interactions <strong>of</strong> the disturbances induced by so<strong>und</strong> and roughness was investigated. It has<br />
been fo<strong>und</strong> that the parameter, which defines the ability to the instability wave excitation (receptivity<br />
coefficient) is strongly dependent <strong>of</strong> the acoustics incidence angle and the roughness wave front<br />
orientation. Computations show that even at high subsonic external flow velocities the receptivity is<br />
strongly dependent also on the direction <strong>of</strong> so<strong>und</strong> propagation. At M > 1 the instability could be<br />
excited by disturbances with the wavelength much smaller than TS wave wavelength. Maximal<br />
receptivity corresponds to the case when the angle between the roughness wave front and the mean<br />
flow is close to the Mach angle.<br />
The paper presents results <strong>of</strong> the detailed investigation <strong>of</strong> the interaction <strong>of</strong> supersonic BL with<br />
external vortical and thermal perturbations. The bo<strong>und</strong>ary conditions for the disturbance at the BL<br />
outer edge are <strong>und</strong>er special consideration. It has been fo<strong>und</strong> that inside the BL the streamwise<br />
velocity and mass flux perturbations can exceed much the amplitude <strong>of</strong> the external vorticity waves.<br />
The disturbance excitation rate is reducing with increasing Mach number. The influence <strong>of</strong> the<br />
external thermal wave onto the flow inside the BL is considerably The results <strong>of</strong> the computations <strong>of</strong><br />
the intensity and the spatial dimensions <strong>of</strong> the streamwise streaky structures in the BL are in<br />
agreement with measurements [9].<br />
This work has been performed <strong>und</strong>er the financial support <strong>of</strong> RFBR and the Russian Federation<br />
President Council (projects 05-01-00079-a, NSh-9642003.1).<br />
References<br />
1. Morkovin M.V. Critical evaluation <strong>of</strong> transition from laminar to turbulent shear layer with<br />
emphasis on hypersonically trevelling bodies. Tech. Rep. AFFDL № 68-149, 1969.<br />
2. Kachanov Yu.S. Physical mechanisms <strong>of</strong> laminar-bo<strong>und</strong>ary-layer transition. Annu.Rev.Fluid<br />
Mech., Vol.26, 1994, p.411.<br />
3. Boyko A.V., Greek G.R., Dovgal A.V., Kozlov V.V. Turbulence origin in near-wall flows.<br />
Novosibirsk: Science, 1999 (in Russian).<br />
4. Gaponov S.A. On the interaction <strong>of</strong> a supersonic bo<strong>und</strong>ary layer with acoustic disturbances.<br />
Thermophysics and Aeromechanics, Vol.2, №3, 1995, pp.181-188.<br />
5. Fedorov A.V., Hohlov A.P. Excitation <strong>of</strong> unstable modes in a supersonic bo<strong>und</strong>ary layer by<br />
acoustic waves. Fluid Dynamics, №4, 1991, pp.67-71 (in Russian).<br />
6. Semionov N.V., Kosinov A.D., Maslov A.A. Experimental investigation <strong>of</strong> supersonic bo<strong>und</strong>ary<br />
layer receptivity. Transitional bo<strong>und</strong>ary layers in aeronautics, edited by R.A.W.M.Henkes and<br />
J.L. van Ingen. North-Holland, Amsterdam, 1996, pp.413-420.<br />
7. Kovasznay L.S.G. Turbulence in supersonic flow. J.Aeron.Sci., Vol.20, №10, 1953, pp.657-674.<br />
8. Petrov G.V. New parabolized system <strong>of</strong> equations <strong>of</strong> stability <strong>of</strong> a compressible bo<strong>und</strong>ary<br />
layer. J. Appl.Mech. Techn. Phys. Vol.41, №1, 2000, p. 55-61.<br />
9. Westin K.J.A., BakchinovA.A., Kozlov V.V., Alfredsson P.H. Experiments on localized<br />
disturbances in a flat plate bo<strong>und</strong>ary layer. Pt 1: The receptivity and evolution <strong>of</strong> a localized free<br />
stream disturbances. Europ. J. Mech., B. Fluids, Vol.17, №6, 1998, pp.823-846.<br />
Speaker: GAPONOV, S.A. 86 <strong>BAIL</strong> <strong>2006</strong><br />
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Z.HAMMOUCH: Similarity solutions <strong>of</strong> a power-law non-Newtonian laminar bo<strong>und</strong>ary<br />
layer flows<br />
✬<br />
✫<br />
Similarity solutions <strong>of</strong> a power-law non-Newtonian laminar bo<strong>und</strong>ary<br />
layer flows<br />
Z. Hammouch<br />
LAMFA, CNRS UMR 6140, Université de Picardie Jules Verne,<br />
Faculté de Mathématiques et d’Informatique, 33, rue Saint-Leu 80039 Amiens, France<br />
Abstract<br />
A steady–state laminar bo<strong>und</strong>ary layer flow, governed by the Ostwald-de Waele power–law model <strong>of</strong> a non–Newtonian<br />
fluid past a semi-infinite plate is considered. The Blasius method is used to find similarity solutions. Under appropriate<br />
assumptions, partial differential equations are transformed into an autonomous third–order nonlinear degenerate ordinary<br />
differential equation with bo<strong>und</strong>ary conditions. We establish the existence <strong>of</strong> an infinite family <strong>of</strong> unbo<strong>und</strong>ed global<br />
solutions. The asymptotic behavior is also discussed. Some properties <strong>of</strong> those solutions depend on the power–law index.<br />
Keywords: Bo<strong>und</strong>ary–layer; Power–law fluid; Degenerate differential equation; Global existence; Asymptotic behavior; Similarity<br />
solutions.<br />
MSC: 34B15; 34B40; 76D10; 76M55 .<br />
PACS: 47.15, 47.27 Te .<br />
Speaker: HAMMOUCH, Z. 87 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
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M. HAMOUDA, R. TEMAM: Bo<strong>und</strong>ary layers for the Navier-Stokes equations :<br />
asymptotic analysis<br />
✬<br />
✫<br />
Bo<strong>und</strong>ary layers for the Navier-Stokes equations : asymptotic<br />
analysis.<br />
M. Hamouda ♯ and R. Temam ∗♯<br />
∗ Laboratoire d’Analyse Numérique, Université de Paris–Sud, Orsay, France.<br />
♯ The <strong>Institut</strong>e for Scientific Computing and Applied Mathematics,<br />
Indiana University, Bloomington, IN, USA.<br />
Abstract<br />
In this talk, we consider the asymptotic analysis <strong>of</strong> the solutions <strong>of</strong> the Navier-<br />
Stokes problem, when the viscosity goes to zero; we consider the flow in a channel <strong>of</strong><br />
R 3 , in the non-characteristic bo<strong>und</strong>ary case. More precisely, a complete asymptotic<br />
expansion, at all orders, is given in the linear case. For the full nonlinear Navier-Stokes<br />
solution, we give a convergence theorem up to order 1, thus improving and simplifying<br />
the results <strong>of</strong> [TW].<br />
MSC : 76D05, 76D10, 35C20.<br />
We consider the Navier-Stokes equations in a channel Ω∞ = R 2 × (0, h) with a permeable<br />
bo<strong>und</strong>ary, making the bo<strong>und</strong>aries z = 0, h, non-characteristic. More precisely we<br />
have<br />
⎧<br />
⎪⎨<br />
⎪⎩<br />
which is equivalent to<br />
⎧<br />
⎪⎨<br />
⎪⎩<br />
∂u ε<br />
∂t − ε∆uε + (u ε .∇) u ε + ∇p ε = f, in Ω∞,<br />
div u ε = 0, in Ω∞,<br />
u ε = (0, 0, −U), on Γ∞,<br />
u ε is periodic in the x and y directions with periods L1, L2,<br />
u ε | t=0 = u0,<br />
∂v ε<br />
∂t − ε∆vε − UD3v ε + (v ε .∇) v ε + ∇p ε = f, in Ω∞,<br />
div v ε = 0, in Ω∞,<br />
v ε = 0, on Γ∞,<br />
v ε is periodic in the x and y directions with periods L1, L2,<br />
v ε | t=0 = v0.<br />
Here Γ∞ = ∂Ω∞ = R 2 × {0, h} and we introduce also Ω and Γ :<br />
Ω = (0, L1) × (0, L2) × (0, h), Γ = (0, L1) × (0, L2) × {0, h}.<br />
Speaker: HAMOUDA, M. 88 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
(0.1)<br />
(0.2)<br />
✩<br />
✪
M. HAMOUDA, R. TEMAM: Bo<strong>und</strong>ary layers for the Navier-Stokes equations :<br />
asymptotic analysis<br />
✬<br />
✫<br />
We assume that f and u0 are given functions as regular as necessary in the channel<br />
Ω∞, and that U is a given constant; at the price <strong>of</strong> long technicalities, we can also consider<br />
the case where U is nonconstant everywhere.<br />
Theorem 0.1 For each N ≥ 1, there exists C > 0 and for all k ∈ [0, N] an explicit given<br />
function θ k,ε such that :<br />
�v ε N�<br />
− ε k (v k + θ k,ε �L∞ (0,T ;L2 (Ω)) ≤ C ε N+1 , (0.3)<br />
�v ε −<br />
k=0<br />
N�<br />
k=0<br />
ε k (v k + θ k,ε � L 2 (0,T ;H 1 (Ω)) ≤ C ε N+1/2 , (0.4)<br />
where L 2 (Ω) = (L 2 (Ω)) 3 , H 1 (Ω) = (H 1 (Ω)) 3 , and C denotes a constant which depends<br />
on the data (and N) but not on ε. Here v ε denotes the solution <strong>of</strong> the linearized problem<br />
<strong>of</strong> (0.2) and v k the ones <strong>of</strong> the limit problems (ε = 0) at all orders.<br />
The second result concerns the solution <strong>of</strong> the full nonlinear problem (0.2) :<br />
Theorem 0.2 For v ε solution <strong>of</strong> the Navier-Stokes problem (0.2), there exist a time T∗ ><br />
0, correctors function θ 0,ε and θ 1,ε explicitly given, and a constant κ > 0 depending on the<br />
data but not on ε, such that :<br />
�v ε − (v 0 + θ 0,ε ) − ε(v 1 + θ 1,ε )� L ∞ (0,T∗; L 2 (Ω)) ≤ κ ε 2 , (0.5)<br />
�v ε − (v 0 + θ 0,ε ) − ε(v 1 + θ 1,ε )� L 2 (0,T∗; H 1 (Ω)) ≤ κ ε 3/2 . (0.6)<br />
We recall here the limit problem which is the Euler problem and its solution v0 satisfies :<br />
⎧<br />
∂v<br />
⎪⎨<br />
⎪⎩<br />
0<br />
∂t − UD3v 0 + (v 0 .∇) v 0 + ∇p 0 = f, in Ω∞,<br />
div v 0 = 0, in Ω∞,<br />
v 0 3 = 0, on Γ0,<br />
v 0 = 0, on Γh,<br />
v 0 (0.7)<br />
is periodic in the x and y, directions with periods L1, L2.<br />
It is obvious that we can not expect a convergence result between v ε and v 0 (in H 1 (Ω) for<br />
example) and more precisely we are leading with a bo<strong>und</strong>ary layer problem close to some<br />
parts <strong>of</strong> the bo<strong>und</strong>ary Γ. This is the main object <strong>of</strong> our work.<br />
At the following order v 1 is solution <strong>of</strong><br />
⎧<br />
⎪⎨<br />
⎪⎩<br />
∂v 1<br />
∂t − UD3v 1 + (v 1 .∇) v 0 + (v 0 .∇) v 1 + ∇p 1<br />
= − ∂ϕ0<br />
∂t + UD3ϕ 0 − (v 0 .∇) ϕ 0 − (ϕ 0 .∇) v 0 + ∆v 0 , in Ω∞,<br />
div v 1 = 0, in Ω∞,<br />
v 1 3 = 0, on Γ0,<br />
v 1 = 0, on Γh,<br />
v 1 is periodic in the x and y, directions with periods L1, L2.<br />
The function ϕ 0 is a known function at this level.<br />
2<br />
Speaker: HAMOUDA, M. 89 <strong>BAIL</strong> <strong>2006</strong><br />
(0.8)<br />
✩<br />
✪
M. HAMOUDA, R. TEMAM: Bo<strong>und</strong>ary layers for the Navier-Stokes equations :<br />
asymptotic analysis<br />
✬<br />
✫<br />
References<br />
[F] K.O. Friedrichs, The mathematical strucure <strong>of</strong> the bo<strong>und</strong>ary layer problem in Fluid<br />
Dynamics (R. von Mises and K.O. Friedrichs, eds), Brown Univ., Providence, RI<br />
(reprinted by Springer-Verlag, New York, 1971). pp. 171-174.<br />
[Li2] J. L. Lions, Problèmes aux limites dans les équations aux dérivées partielles. Les<br />
Presses de l’Université de Montréal, Montreal, Que., 1965. Reedited in [?].<br />
[O] R. E. O’Malley, Singular perturbation analysis for ordinary differential equations.<br />
Communications <strong>of</strong> the Mathematical <strong>Institut</strong>e, Rijksuniversiteit Utrecht, 5. Rijksuniversiteit<br />
Utrecht, Mathematical <strong>Institut</strong>e, Utrecht, 1977.<br />
[TW] R. Temam and X. Wang, Bo<strong>und</strong>ary layers associated with incompressible Navier-<br />
Stokes equations: the noncharacteristic bo<strong>und</strong>ary case. J. Differential Equations 179<br />
(2002), no. 2, 647–686.<br />
[VL] M.I. Vishik and L.A. Lyusternik, Regular degeneration and bo<strong>und</strong>ary layer for linear<br />
differential equations with small parameter, Uspekki Mat. Nauk, 12 (1957), 3-122.<br />
3<br />
Speaker: HAMOUDA, M. 90 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
M. HÖLLING, H. HERWIG: Computation <strong>of</strong> turbulent natural convection at vertical<br />
walls using new wall functions<br />
✬<br />
✫<br />
Computation <strong>of</strong> turbulent natural convection at vertical walls using new wall<br />
functions<br />
M. Hölling, H. Herwig<br />
Technical Thermodynamics<br />
Hamburg University <strong>of</strong> Technology<br />
Denickestraße 15, 21073 Hamburg, Germany<br />
m.hoelling@tu-harburg.de<br />
h.herwig@tu-harburg.de<br />
Turbulent natural convection at vertical walls has been <strong>und</strong>er investigation in the last decades<br />
but is still not sufficiently <strong>und</strong>erstood. The viscous sublayer, i.e. the region very close to the wall,<br />
can be described properly, see e.g. Tsuji and Nagano [1], since there the turbulent fluctuations<br />
are damped by the wall and the governing equations can be solved directly. But in the more<br />
interesting region in which turbulence dominates, the flow cannot be described properly. George<br />
and Capp [2] <strong>of</strong>fer analytical temperature and velocity pr<strong>of</strong>iles which have become a kind <strong>of</strong><br />
standard for natural convection. But, it was shown by Versteegh and Nieuwstadt [3] and by<br />
Henkes and Hoogendoorn [4] that at least the velocity pr<strong>of</strong>ile is erroneous. We employ a different<br />
approach presented in Hölling and Herwig [5] to describe the turbulence affected region <strong>of</strong> the<br />
flow field.<br />
The starting point for the analysis is a channel with a hot and a cold wall <strong>of</strong> infinite extent<br />
as used by Versteegh and Nieuwstadt [3] for their DNS study. The governing equations then<br />
reduce to:<br />
0 = ∂<br />
�<br />
∂y<br />
0 = ∂<br />
∂y<br />
∂y − v′ T ′<br />
�<br />
a ∂T<br />
�<br />
ν ∂u<br />
∂y − u′ v ′<br />
�<br />
+ gβ � �<br />
T − T0<br />
It is fo<strong>und</strong> that the temperature field consists <strong>of</strong> a viscosity influenced wall layer and a fully<br />
turbulent outer layer. The temperature pr<strong>of</strong>ile is obtained by matching <strong>of</strong> gradients between<br />
these layers that reveals a logarithmic pr<strong>of</strong>ile. It is in good agreement with DNS as well as<br />
experimental temperature pr<strong>of</strong>iles from various studies.<br />
For the velocity pr<strong>of</strong>ile a different approach is chosen; the pr<strong>of</strong>ile is not obtained by matching<br />
<strong>of</strong> gradients. Instead the momentum equation (2) is rewritten in such a way that the temperature<br />
pr<strong>of</strong>ile and the Reynolds stresses are expressed as a function <strong>of</strong> the wall distance. The Reynolds<br />
stresses are modelled using the eddy viscosity approach. A constant turbulent Prandtl number<br />
is assumed as can be concluded from DNS data. Then the eddy viscosity is directly linked to the<br />
turbulent thermal diffusivity and therefore is a linear function <strong>of</strong> wall distance. Once all terms<br />
are expressed as a function <strong>of</strong> wall distance the momentum equation can be integrated and a<br />
velocity pr<strong>of</strong>ile emerges. This pr<strong>of</strong>ile is in good agreement with DNS and experimental data.<br />
Straightforward numerical solutions without adequate near wall treatment, like with FLU-<br />
ENT 6.2, to reproduce the DNS data <strong>of</strong> Versteegh and Nieuwstadt [3] for Ra = 5.0 · 10 6 show<br />
that even with fine grids also in the viscous sublayer only poor agreement can be achieved.<br />
Thus, we conclude that it would be diserable to have a new approach and improved near wall<br />
treatment.<br />
Therefore, we apply the new universal pr<strong>of</strong>iles as wall functions for CFD calculations. They<br />
are implemented in the two dimensional CAFFA code <strong>of</strong> Ferziger and Peric [6] that uses the kω-turbulence<br />
model and the Boussinesq-approximation. The standard k-ω model is used inspite<br />
Speaker: HÖLLING, M. 91 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
(1)<br />
(2)<br />
✩<br />
✪
M. HÖLLING, H. HERWIG: Computation <strong>of</strong> turbulent natural convection at vertical<br />
walls using new wall functions<br />
✬<br />
✫<br />
T in K<br />
380<br />
370<br />
360<br />
350<br />
340<br />
330<br />
8×200<br />
4×200<br />
DNS<br />
320<br />
0 0.05<br />
y in m<br />
0.1<br />
u in m/s<br />
0.25<br />
0.2<br />
0.15<br />
0.1<br />
0.05<br />
0<br />
−0.05<br />
−0.1<br />
−0.15<br />
−0.2<br />
8×200<br />
4×200<br />
DNS<br />
−0.25<br />
0 0.05<br />
y in m<br />
0.1<br />
Figure 1: Temperature and velocity pr<strong>of</strong>ile <strong>of</strong> Versteegh and Nieuwstadt [3] for Ra = 5.0 · 10 6<br />
compared to results <strong>of</strong> the modified CAFFA code using two grid sizes.<br />
that it is inadequate for natural convection. Instead <strong>of</strong> trying to find another modification <strong>of</strong><br />
an existing turbulence model, the deficiences could be compensated by modifying the bo<strong>und</strong>ary<br />
conditions for k and ω.<br />
The results are again compared to the DNS data <strong>of</strong> Versteegh and Nieuwstadt [3] and good<br />
agreement is fo<strong>und</strong>. Figure 1 shows the temperature and velocity pr<strong>of</strong>ile for Ra = 5.0 · 10 6<br />
together with the results <strong>of</strong> the modified CAFFA code. Two different grid sizes were used and<br />
despite the very few control volumes (8 and 4 CVs) across the channel width the pr<strong>of</strong>iles are<br />
matched very well. Also the wall gradients, i.e. the Nusselt number and the shear stress, are<br />
correct within 4 %.<br />
References<br />
[1] T. Tsuji and Y. Nagano, “Characteristics <strong>of</strong> a turbulent natural convection bo<strong>und</strong>ary layer<br />
along a vertical flat plate”, Int. J. Heat Mass Transfer 31, 1723–1734 (1989).<br />
[2] W.K. George and S.P. Capp, “A theory for natural convection turbulent bo<strong>und</strong>ary layers<br />
next to heated vertical surfaces”, Int. J. Heat Mass Transfer 22, 813–826 (1979).<br />
[3] T.A.M. Versteegh and F.T.M. Nieuwstadt, “A direct numerical simulation <strong>of</strong> natural convection<br />
between two infinite vertical differentially heated walls: scaling laws and wall functions”,<br />
Int. J. Heat Mass Transfer 42, 3673–3693 (1999).<br />
[4] R.A.W.M. Henkes and C.J. Hoogendoorn, “Numerical determination <strong>of</strong> wall functions for<br />
the turbulent natural convection bo<strong>und</strong>ary layer”, Int. J. Heat Mass Transfer 33, 1087–<br />
1097 (1990).<br />
[5] M. Hölling and H. Herwig, “Asymptotic analysis <strong>of</strong> the near wall region <strong>of</strong> turbulent natural<br />
convection flows”, J. Fluid Mech. 541, 383–397 (2005).<br />
[6] J.H. Ferziger and M. Peric, “Computational methods for fluid dynamics”, 2nd ed., Springer,<br />
Berlin (1999).<br />
Speaker: HÖLLING, M. 92 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
A.-M. IL’IN, B.I. SULEIMANOV: The coefficients <strong>of</strong> inner asymptotic expansions for<br />
solutions <strong>of</strong> some singular bo<strong>und</strong>ary value problems<br />
✬<br />
✫<br />
���������� ��������������<br />
��� ���������� �� ����� ���������� ����������<br />
��� ��������� �� ���� �������� �������� ����� ��������<br />
��� ������� ��������� �� �������� ����������� ���������<br />
ux + u 3 − tu − x = 0, (1)<br />
uxx = u 3 − tu − x (2)<br />
��� ����������� ��� ������� ��������� ��� ���������� ���� ��� ��������� �� � ���� ����� ��<br />
��������� �� ������� ����������� ��������� ���� ����� ��������� �� ��� ���� ��� ����� ���������<br />
���� ������ �� ������<br />
��� ������� �������� �� ��������<br />
ε 2 (Ux1x1 + Ux2x2) + εbUx1 + f(x1, x2, U) = 0,<br />
����� ����� �������� f(x1, x2, U) = 0 ��� ���� ����� Uj(x1, x2). �� ��� ������� ���� ����<br />
�������� ��� ����� ������ ��� ������ �� ��� ���� ������ U0(0, 0) = 0 ��� f(x1, x2, U) =<br />
x1 + x2U − U 3 + · · · . ����� �� ��� ������ ���� �� x2 < 0 ��� ����� ��� ��� ������ ����� ���<br />
��� �������� ���� �� x2 > 0.<br />
�� ��� ������������ �� ������ �� ������ ���������� �� b �= 0 ����<br />
z = x1<br />
,<br />
ε3/5 x2<br />
t = ,<br />
ε2/5 U<br />
w = .<br />
ε1/5 �� ���� ���� ��� �������� ��� ��� ��������� ���� ��� ��� ���� bwz = w3 − tw − z<br />
���������� �� �������� ����<br />
����� ��<br />
�� b = 0 ����<br />
z = x1 x2 U<br />
, t = , v =<br />
ε3/4 ε1/2 ε1/4 ��� ��� �������� ��� ��� ��������� ���� ��� ��� ���� wzz = w3 − tw − z ����� �� ����������<br />
�� �������� ����<br />
��� ���� ��� �� �� ��������� ��� ����������� ����������� �� ��� ��������� �� ���������<br />
��� ��� ��� �� ��� ������ ����� ������<br />
�� �� ������� �� ������ ���� ��������� ���� �� ������ �� ������� ���� �������� H(x, t)<br />
H 3 − tH − x = 0 (3)<br />
�� x 2 + t 2 → ∞. �� �� ������ ������ ��� ����� ����� ���� ����� ����� ����������� �� ���������<br />
���� ��������� �������� ������������ ����������� ��� ������� t ��� ���������� �������<br />
������� �� ��� ����� ���� t ����� ����� ������ �������� ���������� �������� �� ���<br />
����������� �������� ��� ��� u(x, t) − H(x, t) → 0 �� x → ∞.<br />
u(x, t) = as x 1/3 (1 +<br />
∞�<br />
cj(t)x −j/3 ), x → ∞.<br />
j=2<br />
���� ���������� ��������� �� ������� �� |t| < T ��� �� �� ��� ������� �� ����� �����<br />
(x, t).<br />
������� �� ��� t → −∞ ��� �������� u(x, t) ��� ��� ��������� ������� ����������<br />
����������<br />
u(x, t) = |t| 1/2<br />
�<br />
f(s) +<br />
�<br />
∞�<br />
j=1<br />
vj(s)<br />
t4j �<br />
,<br />
Speaker: IL’IN, A.M. 93 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
A.-M. IL’IN, B.I. SULEIMANOV: The coefficients <strong>of</strong> inner asymptotic expansions for<br />
solutions <strong>of</strong> some singular bo<strong>und</strong>ary value problems<br />
✬<br />
✫<br />
�����<br />
s = x|t| −3/2 , f 3 (s) + f(s) − s = 0.<br />
�� t → ∞ ����������� �� ��� �������� u(x, t) �� ���� ������������<br />
������� �� ���������� ���������<br />
�����<br />
u(x, t) = t 1/2<br />
� ∞�<br />
g(s) + t −4j ∞�<br />
vj(s) + t −2k �<br />
wk(ξ)<br />
j=1<br />
s = x|t| −3/2 , g(s) 3 − g(s) − s = 0, w0(ξ) = −1 + tanh ξ<br />
√ 2 , ξ = st 2<br />
�� ��������� ����� �� t > T > 0. ��� �������������� ����� ����� �������� ��� ���� ���������<br />
�� ����<br />
��� ������� ������� �� ��� ���� ����� ���� �������� ����<br />
����������� �� ��� �������� �� ���� �������� �� ���� ����������� ���� ����������� ���<br />
������ ����� ���������<br />
��� �� ��������� H(x, t) �� �������<br />
�� �� �������� �� ��� �������� ��� �� t � 0�<br />
�������� H(x, t) �� �������� ���������� �������� �� ��� �������� ��� ��<br />
k=0<br />
t > 0, x < xc(t) = 2<br />
√ 27 t 3/2<br />
��� �������� ���������� �������� �� ��� �������� ��� ��<br />
t > 0, x > xc(t).<br />
��� ���������� �������� �� ��� �������� ��� �� ����� �� ���� �������� H(x, t) �� �������<br />
���������� ������ ��� ������ ������ ������ ��� ���� x = xc(t).<br />
����������� �� ��� ���� �������� ��� �� t → −∞ ��� ��� �� ��� ������������ �� ����<br />
x = xc(t) �� ������� �� ��� ����������� �� ��� �������� ��� ���������� ������ u(x, t) =<br />
v(s, t)|t| 1/2 ����� s = x |t| −3/2 ,<br />
∞�<br />
v(s, t) = |t|<br />
k=0<br />
−5k/2 v −<br />
k (s).<br />
���� ��� ���� s = 2 √ �� �� ��������� �� ����������� ��� �������� ������� ��� ���������<br />
27<br />
��������� �� ��� ���� �������� ����� ��� ��� ����������<br />
z = (s − s∗)t 5/3 , r = ( 1<br />
√ 3 + v(s, t))t 5/6 .<br />
��� ��������� ��������� �� ��� ������ �������� ����� ��� ��� ����������<br />
(z − z0) = ηt −5/6 , w = r(z)t −5/6 = (v(s) + 1/ √ 3)<br />
����� z0 �� ��� ���� �� ���� �������� Ai(−3 1/6 z)�<br />
���� �� ���� ������� ���������� ���������� �� ��� ������� ���������� �� ��� ����� ������<br />
1. u(x, t) = as t 1/2<br />
∞�<br />
k=0<br />
2. u(x, t) = as t 1/2 [− 1<br />
√ 3 + t −5/6<br />
�<br />
|t| −5k/2 v +<br />
k (s),<br />
�<br />
∞�<br />
r0(z) + t −5j/6 �<br />
rj(z) ]<br />
Speaker: IL’IN, A.M. 94 <strong>BAIL</strong> <strong>2006</strong><br />
j=1<br />
✩<br />
✪
A.-M. IL’IN, B.I. SULEIMANOV: The coefficients <strong>of</strong> inner asymptotic expansions for<br />
solutions <strong>of</strong> some singular bo<strong>und</strong>ary value problems<br />
✬<br />
✫<br />
���<br />
3. u(x, t) = as t 1/2 [− 1<br />
√ 3 +<br />
∞�<br />
t −5k/6 wk(ln t, η)].<br />
��� ���������� �� ��� ���������� ���������� �� � �� ���� �� ����������� ��� �����<br />
���������� ���� �� ������� �� ��� ����� ������������<br />
��� ��������� ��� ��������������� ������ �� ��������� �������� ���������� ��������� ���� �<br />
���� ������������� ��������������� ������� ������ ����� ������� ������� ������� �� ��������<br />
����������� ������ ��������� �������<br />
Speaker: IL’IN, A.M. 95 <strong>BAIL</strong> <strong>2006</strong><br />
�<br />
k=0<br />
✩<br />
✪
W.S. ISLAM, V.R. RAGHAVAN: Numerical Simulation <strong>of</strong> High Sub-critical Reynolds<br />
Number Flow Past a Circular Cylinder<br />
✬<br />
✫<br />
Numerical Simulation <strong>of</strong> High Sub-critical Reynolds Number Flow<br />
Past a Circular Cylinder<br />
Wan Saiful Islam* and Vijay R. Raghavan**<br />
Faculty <strong>of</strong> Mechanical Engineering<br />
Kolej Universiti Teknologi Tun Hussein Onn<br />
86400 Parit Raja, Malaysia<br />
*wsaiful@kuittho.edu.my<br />
**vijay@kuittho.edu.my<br />
ABSTRACT<br />
Few areas in fluid mechanics have received more attention than that <strong>of</strong> flow past a bluff body. In<br />
particular, flow across a circular cylinder in unconfined and confined flow is a classical problem,<br />
and has been studied experimentally, visually and numerically [1-6]. Although the geometry is<br />
apparently simple, this problem has not yielded to closed form analytical solution except at very<br />
low Reynolds numbers because <strong>of</strong> the complexity associated with adverse pressure gradients,<br />
separation, eddy shedding, recirculation and reattachment. There are a very large number <strong>of</strong><br />
attempts reported in the literature using a variety <strong>of</strong> numerical approaches viz., finite difference,<br />
finite element and finite volume methods. However, there is room for improvement in the<br />
agreement with experiments that has been obtained hitherto [5,6]. A numerical solution that gives<br />
good agreement is also likely to be useful for benchmarking existing codes and new ones that<br />
may be written. The purpose <strong>of</strong> the present study is to find a satisfactory solution in the entire<br />
range <strong>of</strong> sub-critical Reynolds numbers for flow over a circular cylinder.<br />
In earlier attempts to establish benchmark solutions and to obtain agreement with published data<br />
over a range <strong>of</strong> Reynolds numbers, various turbulence models including large eddy simulation<br />
(LES) had been considered and both 2-D and 3-D had been tried [4-6]. The results were obtained<br />
in the form <strong>of</strong> general appearance <strong>of</strong> the wake flow, examination <strong>of</strong> the velocity magnitudes in<br />
the near-field and far-field, eddy frequencies, Strouhal numbers and detailed local distributions <strong>of</strong><br />
pressure. However, most <strong>of</strong> these authors have carried out their work in the more convenient<br />
Speaker: ISLAM, W.S. 96 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
W.S. ISLAM, V.R. RAGHAVAN: Numerical Simulation <strong>of</strong> High Sub-critical Reynolds<br />
Number Flow Past a Circular Cylinder<br />
✬<br />
✫<br />
Reynolds number range <strong>of</strong> 40 to 1000 [2,3]. As one goes to higher Re ranges, results are seen to<br />
deviate progressively more widely from experimental results.<br />
In the present study simulations are performed for unsteady, two-dimensional (2-D) flow past a<br />
circular cylinder in a confined duct with appropriate blockage ratios. At Reynolds numbers as<br />
high as 100,000 the numerical solutions obtained agree remarkably well with experiments, not<br />
only in the global sense in the form <strong>of</strong> CD, but also locally in terms <strong>of</strong> pressure distribution. The<br />
paper describes how the agreement was obtained and these results might serve as a benchmark for<br />
validating CFD codes.<br />
REFERENCES<br />
1. Achenbach, E., “Distribution <strong>of</strong> Local Pressure and Skin Friction Aro<strong>und</strong> a Circular<br />
Cylinder in Cross-Flow up to Re = 5×10 6 ”, Journal <strong>of</strong> Fluid Mechanics, 34, 4, 625-<br />
639, 1968.<br />
2. Son, J.S. and Hanratty, T.J., “Numerical Solution for the Flow aro<strong>und</strong> a Cylinder at<br />
Reynolds Numbers <strong>of</strong> 40, 200 and 500”, Journal <strong>of</strong> Fluid Mechanics, 35, 2, 369-386,<br />
1969.<br />
3. Fornberg, B., “Steady Viscous Flow Past a Circular Cylinder up to Reynolds<br />
Number 600”, Journal <strong>of</strong> Computational Physics, 61, 297-320, 1985.<br />
4. Chou, M.-H. and Huang, W., “Numerical Study <strong>of</strong> High-Reynolds-Number Flow<br />
Past a Bluff Object”, International Journal for Numerical Methods in Fluids, 23, 711-<br />
732, 1996.<br />
5. Selvam, R.P., “Finite Element Modeling <strong>of</strong> Flow Aro<strong>und</strong> a Circular Cylinder using<br />
LES”, Journal <strong>of</strong> Wind Engineering and Industrial Aerodynamics, 67&68, 129-139,<br />
1997.<br />
6. Breuer, M., “Numerical and Modeling Influences on Large Eddy Simulations for the<br />
Flow Past a Circular Cylinder”, International Journal <strong>of</strong> Heat and Fluid Flow, 19,<br />
512-521, 1998<br />
Speaker: ISLAM, W.S. 97 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
D. KACHUMA, I. SOBEY: Fast waves during transient flow in an asymmetric channel<br />
✬<br />
✫<br />
Abstract<br />
Fast waves during transient flow in an asymmetric channel<br />
Dick Kachuma & Ian Sobey<br />
Oxford University Computing Laboratory<br />
Wolfson Building, Parks Road,<br />
Oxford UK OX1 3QD<br />
dick.kachuma@comlab.ox.ac.uk<br />
ian.sobey@comlab.ox.ac.uk<br />
The use <strong>of</strong> stepped channels together with unsteady laminar flow provides a powerful mixing mechanism<br />
that is particularly applicable to processes where the fluid contains delicate elements, for example, applications<br />
involving mass transfer in blood or in a cell culture. In such channel flows there are parameter<br />
regimes where the flow is described by the two-dimensional unsteady Navier–Stokes equations. Sobey<br />
(1985) showed both experimentally and numerically that a standing wave <strong>of</strong> separated regions developed<br />
behind a channel step during oscillatory flow and called the resulting flow a vortex wave. Included in his<br />
experimental observations were vortex waves <strong>of</strong> extreme longitudinal extent and he conjectured that the<br />
wave formed was, <strong>und</strong>er the correct parameter conditions, virtually <strong>und</strong>amped in the streamwise direction.<br />
We have <strong>und</strong>ertaken calculations in a slightly different parameter region and find that a sequence <strong>of</strong><br />
two events occurs: one is the formation <strong>of</strong> a vortex wave <strong>of</strong> finite extent (typically 3-5 vortices alternating<br />
on the two walls behind the step), the second is a subsequent rapidly propagating wave <strong>of</strong> regular but<br />
slightly smaller vortices. The speed <strong>of</strong> propagation <strong>of</strong> this second wave is such that its resolution would<br />
have been beyond that <strong>of</strong> the apparatus used in Sobey (1985). In describing these waves we shall refer to<br />
the vortex wave as a V-wave and the second wave as a KH-wave. An example <strong>of</strong> the waves is illustrated<br />
in Figure 1 where contours <strong>of</strong> a flow are shown.<br />
V-wave KH-wave<br />
Figure 1: Instantaneous streamlines<br />
In order to <strong>und</strong>erstand the genesis <strong>of</strong> KH-waves we have <strong>und</strong>ertaken a study <strong>of</strong> starting flows in<br />
which the fluid is accelerated from rest to either steady channel flux or a flux with a small oscillatory<br />
component. We have tested two hypotheses: one that the KH-wave results from the evolution <strong>of</strong> an<br />
inviscid rotational core flow that is described by an evolutionary linearised Kortweg-de Vries (KdV)<br />
equation. That this might be a plausible hypothesis comes from results by Tutty and Pedley (1994)<br />
which show the evolution <strong>of</strong> waves in solutions <strong>of</strong> an evolutionary KdV equation that models such a core<br />
flow. The second hypothesis is that the KH-wave results from an Orr-Sommerfeld type instability <strong>of</strong><br />
nearly parallel but non-Poiseuille like flow. This has lead us to study stability <strong>of</strong> a base flow<br />
u0(y) = (1 − σy)(1 − y 2 ), −1 ≤ y ≤ 1,<br />
where σ = 0 is Poiseuille flow and σ > 1 indicates reverse flow near one wall.<br />
The development <strong>of</strong> KH-waves has been considered in channels with smoothly varying and sharp<br />
corners and using different numerical methods, as well as with different numerical resolution. The paper<br />
is divided into four sections.<br />
Speaker: KACHUMA, D. 98 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
D. KACHUMA, I. SOBEY: Fast waves during transient flow in an asymmetric channel<br />
✬<br />
✫<br />
(1) We describe the numerical solution <strong>of</strong> the unsteady Navier–Stokes equations and illustrate the<br />
development <strong>of</strong> a KH-wave.<br />
(2) We integrate velocities in time to obtain particle paths and use these to help interpret the development<br />
<strong>of</strong> the flows.<br />
(3) We describe solutions <strong>of</strong> an evolutionary linearised KdV equation and their interpretation.<br />
(4) We consider solutions <strong>of</strong> an Orr-Sommerfeld equation as the extent <strong>of</strong> a reverse flow region is<br />
varied and investigate the consequences <strong>of</strong> instability in the base flow on subsequent flow development.<br />
The results we have indicate that it is unlikely that the KH-wave is the result <strong>of</strong> evolution <strong>of</strong> an<br />
inviscid rotational core flow and instead, that it is more likely the result <strong>of</strong> a linear instability mechanism<br />
described by an Orr–Sommerfeld equation but with growth rates that are orders <strong>of</strong> magnitude greater<br />
than those for disturbances to symmetric Poiseuille flow and with instability occuring at relatively low<br />
Reynolds number. The complexity <strong>of</strong> unsteady flows calculated from the full Navier–Stokes equations<br />
is remarkable and it is likely that flows in other parameter regimes are dominated by entirely different<br />
mechanisms.<br />
References<br />
Sobey I.J. (1985). Observation <strong>of</strong> waves during oscillatory channel flow. J. Fluid Mech., 151:395–426.<br />
Tutty O.R. and Pedley T.J. (1994). Unsteady flow in a nonuniform channel: A model for wave generation.<br />
Phys. Fluids, 6:199–208.<br />
Speaker: KACHUMA, D. 99 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
A. KAUSHIK, K.K. SHARMA: A Robust Numerical Approach for Singularly Perturbed<br />
Time Delayed Parabolic Partial Differential Equations<br />
✬<br />
✫<br />
A Robust Numerical Approach for Singularly<br />
Perturbed Time Delayed Parabolic Partial<br />
Differential Equations<br />
Aditya Kaushik † Kapil K. Sharma ‡<br />
† Department <strong>of</strong> Mathematics, Kurukshetra University, Kurukshetra-136 119, India<br />
‡ MAB, University Bourdauex 1, 351 Cours de Libration F-33405, Cedex Talence, France<br />
[ † a-kaushik@lycos.com ‡ sharmal@math.u-bordeaux1.fr ]<br />
Summary<br />
In this paper a numerical study for a class <strong>of</strong> initial bo<strong>und</strong>ary value problems for<br />
singularly perturbed unsteady parabolic partial differential equation with variable coefficients<br />
having time delayed reaction term, is initiated on a rectangular domain. Such<br />
problems arise in diverse area <strong>of</strong> science and engineering that take into account not just<br />
the present state <strong>of</strong> physical systems but also its past history. These models are described<br />
by certain class <strong>of</strong> functional differential equations <strong>of</strong>ten called delay differential equation<br />
and from mathematical perspective they are singularly perturbed. In most application in<br />
the life sciences, a delay is introduced when there are some hidden variables and processes<br />
which are not well <strong>und</strong>erstood but are known to cause a time lag. The delay differential<br />
is versatile in mathematical modeling <strong>of</strong> processes in various application field, where they<br />
provide the best and sometimes the only realistic simulation <strong>of</strong> observed phenomena. The<br />
singularly perturbed differential difference equation with delay arises in general in the<br />
modeling <strong>of</strong> various real life phenomena’s, for instance, in studying heat or mass transfer<br />
process in composite materials with small heat conduction or diffusion, in drift diffusion<br />
model <strong>of</strong> semiconductor devices, in fluid flow problems, physiological kinetics, in various<br />
branches <strong>of</strong> biosciences and population dynamics, control theory, chemical kinetics, etc.<br />
Some modelers ignore the ”lag” effect and use an differential equations model as a substitute<br />
for a delay differential equation model. Kuang [1], comments <strong>und</strong>er the heading<br />
”Small delays can have large effects” on the dangers that researchers risk if they ignore<br />
lags which they think are small. There are inherent qualitative differences between delay<br />
differential equations and finite systems <strong>of</strong> differential equations that make such a strategy<br />
risky.<br />
The concept <strong>of</strong> singular perturbation is not new, indeed, it has been a formidable tool in<br />
the solution <strong>of</strong> some important applied mathematical problems. A singular perturbation<br />
is a modification <strong>of</strong> partial differential equation by adding a multiple ǫ times a higher<br />
order term. In accordance with the informal principle that the behavior <strong>of</strong> solutions is<br />
governed primarily by the highest order terms, a solution u ǫ <strong>of</strong> the perturbed problem will<br />
<strong>of</strong>ten behave analytically quite differently from a solution <strong>of</strong> the original equation, and<br />
exhibits bo<strong>und</strong>ary or the transition layers in the outflow bo<strong>und</strong>ary reasons when the perturbation<br />
parameter specifying the problem tends to zero [2]. Due to the presence <strong>of</strong> the<br />
perturbation parameter and in particular time delay, the primary mathematical methods<br />
fails to provide the desired results. Thus, the quest for some new numerical techniques<br />
Speaker: KAUSHIK, A. 100 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
A. KAUSHIK, K.K. SHARMA: A Robust Numerical Approach for Singularly Perturbed<br />
Time Delayed Parabolic Partial Differential Equations<br />
✬<br />
✫<br />
to handle the difficulties occurring due to presence <strong>of</strong> these two parameters and development<br />
<strong>of</strong> a robust numerical method to solve such type <strong>of</strong> problem, has fo<strong>und</strong> special<br />
relevance. To sort out both the difficulties, a numerical method consisting <strong>of</strong> standard<br />
finite difference operator on a uniform mesh is constructed. The first step in this direction<br />
consists <strong>of</strong> discretizing the time variable with the backward Euler’s method with constant<br />
time step. This produces a set <strong>of</strong> stationary singularly perturbed semidiscrete problem<br />
which is further discretized in space using standard finite difference operator on a uniform<br />
mesh. An extensive amount <strong>of</strong> analysis is carried out in order to establish the convergence<br />
and stability <strong>of</strong> the method proposed. A set <strong>of</strong> numerical experiment is carried out in<br />
support <strong>of</strong> the predicted theory and to show the effect <strong>of</strong> delay on the bo<strong>und</strong>ary layer<br />
behavior <strong>of</strong> the solution for the initial bo<strong>und</strong>ary value problem considered which validates<br />
computationally the theoretical results.<br />
[1] Y. Kuang, Delay differntial equations with applications in population dynamics, Academic<br />
Press Inc.,(1993).<br />
[2] H. G. Roos, M. Stynes, and L. Tobiska, Numerical Methods for Singularly Perturbed<br />
Di.erential Equa- tions. Convection-Di.usion and Flow Problems, Springer-Verlag, Berlin,<br />
1996.<br />
Speaker: KAUSHIK, A. 101 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
P. KNOBLOCH: On methods diminishing spurious oscillations in finite element<br />
solutions <strong>of</strong> convection-diffusion equations<br />
✬<br />
✫<br />
On methods diminishing spurious oscillations<br />
in finite element solutions <strong>of</strong> convection–diffusion equations<br />
Petr Knobloch<br />
Charles University, Faculty <strong>of</strong> Mathematics and Physics, Department <strong>of</strong> Numerical Mathematics,<br />
Sokolovská 83, 186 75 Praha 8, Czech Republic<br />
e-mail: knobloch@karlin.mff.cuni.cz<br />
We discuss the application <strong>of</strong> the finite element method to the numerical solution <strong>of</strong> the scalar<br />
convection–diffusion equation<br />
−ε∆u + b · ∇u = f in Ω, u = ub on Γ D , ε ∂u<br />
∂n = g on ΓN . (1)<br />
Here Ω is a bo<strong>und</strong>ed two–dimensional domain with a polygonal bo<strong>und</strong>ary ∂Ω, Γ D and Γ N are disjoint<br />
and relatively open subsets <strong>of</strong> ∂Ω satisfying meas1(Γ D ) > 0 and Γ D ∪ Γ N = ∂Ω, n is the outward unit<br />
normal vector to ∂Ω, f is a given outer source <strong>of</strong> the unknown scalar quantity u, ε > 0 is the constant<br />
diffusivity, b is the flow velocity, and ub, g are given functions.<br />
Despite the apparent simplicity <strong>of</strong> problem (1), its numerical solution is by no means easy if convection<br />
is strongly dominant (i.e., if ε ≪ |b|). In this case, the solution <strong>of</strong> (1) typically possesses interior and<br />
bo<strong>und</strong>ary layers whose widths are usually significantly smaller than the mesh size and hence the layers<br />
cannot be resolved properly. In particular, it is well known that the classical Galerkin finite element<br />
discretization <strong>of</strong> (1) is inappropriate in the convection–dominated regime since the discrete solution is<br />
typically globally polluted by spurious oscillations. Although, during the last three decades, an extensive<br />
research has been devoted to the development <strong>of</strong> methods which diminish spurious oscillations in<br />
the discrete solutions <strong>of</strong> (1), the numerical solution <strong>of</strong> (1) is still a challenge when convection strongly<br />
dominates diffusion. The broad interest in solving problem (1) is caused not only by its actual physical<br />
meaning but also by the fact that it represents a simple model problem for convection–diffusion effects<br />
which appear in many more complicated problems arising in applications.<br />
Initially, stabilizations <strong>of</strong> the Galerkin discretization <strong>of</strong> (1) imitated upwind finite difference techniques.<br />
However, like in the finite difference method, the upwind finite element discretizations remove<br />
the unwanted oscillations but the accuracy attained is <strong>of</strong>ten poor since too much numerical diffusion<br />
is introduced. According to our experiences, one <strong>of</strong> the most successful upwinding techniques is the<br />
improved Mizukami–Hughes method, see Knobloch [9]. It is a nonlinear Petrov–Galerkin method for<br />
conforming linear triangular finite elements P1 which satisfies the discrete maximum principle on weakly<br />
acute meshes. In contrast with many other upwinding methods for P1 elements satisfying the discrete<br />
maximum principle, the improved Mizukami–Hughes method adds much less numerical diffusion and<br />
provides rather accurate solutions, cf. Knobloch [10].<br />
One <strong>of</strong> the most efficient procedures is the streamline upwind/Petrov–Galerkin (SUPG) method developed<br />
by Brooks and Hughes [2] which is a higher–order method possessing good stability properties<br />
achieved by adding artificial diffusion in the streamline direction. Unfortunately, the SUPG method<br />
does not preclude spurious oscillations localized in narrow regions along sharp layers. Although these<br />
oscillations are usually small in magnitude, they are not permissible in many applications (e.g., chemically<br />
reacting flows, free–convection computations, two–equations turbulence models, compressible<br />
flow problems with shocks). Therefore, various terms introducing artificial crosswind diffusion in the<br />
neighborhood <strong>of</strong> layers have been proposed to be added to the SUPG formulation in order to obtain a<br />
method which is monotone or which at least reduces the local oscillations (cf. e.g. [3, 4] and the references<br />
there). This procedure is <strong>of</strong>ten referred to as discontinuity capturing (or shock capturing). These<br />
discontinuity–capturing methods can be divided into three groups according to whether the additional<br />
artificial diffusion is isotropic, or orthogonal to streamlines, or based on edge stabilizations. We have<br />
demonstrated for P1 finite elements in [7] that the edge stabilization methods add too much artificial<br />
diffusion. Among the remaining two groups <strong>of</strong> methods, the best methods for P1 finite elements seem<br />
Speaker: KNOBLOCH, P. 102 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
P. KNOBLOCH: On methods diminishing spurious oscillations in finite element<br />
solutions <strong>of</strong> convection-diffusion equations<br />
✬<br />
✫<br />
to be the methods <strong>of</strong> do Carmo and Galeão [5], <strong>of</strong> Almeida and Silva [1] and slight modifications <strong>of</strong> the<br />
methods <strong>of</strong> Codina [6] and <strong>of</strong> Burman and Ern [3], see also John and Knobloch [8].<br />
Our aim is to continue the discussion <strong>of</strong> properties <strong>of</strong> the various methods diminishing spurious<br />
oscillations in finite element solutions <strong>of</strong> (1) mentioned above. We would like to concentrate on three<br />
aspects:<br />
• properties <strong>of</strong> methods <strong>of</strong> Mizukami–Hughes type satisfying the discrete maximum principle where<br />
we mention the improved Mizukami–Hughes method <strong>of</strong> [9] for P1 finite elements and will discuss<br />
its generalization to other types <strong>of</strong> finite elements;<br />
• comparison <strong>of</strong> the above–mentioned discontinuity–capturing methods for higher order finite elements;<br />
• choice <strong>of</strong> stabilization parameters where we will present a novel approach to the choice <strong>of</strong> the<br />
SUPG stabilization parameter in outflow bo<strong>und</strong>ary layers.<br />
The above described discussion will be performed for the two–dimensional case and the results obtained<br />
in three–dimensions will be mentioned only briefly.<br />
References<br />
[1] R.C. Almeida, R.S. Silva, A stable Petrov–Galerkin method for convection–dominated problems,<br />
Comput. Methods Appl. Mech. Eng. 140 (1997) 291–304.<br />
[2] A.N. Brooks, T.J.R. Hughes, Streamline upwind/Petrov–Galerkin formulations for convection<br />
dominated flows with particular emphasis on the incompressible Navier–Stokes equations, Comput.<br />
Methods Appl. Mech. Eng. 32 (1982) 199–259.<br />
[3] E. Burman, A. Ern, Nonlinear diffusion and discrete maximum principle for stabilized Galerkin<br />
approximations <strong>of</strong> the convection–diffusion–reaction equation, Comput. Methods Appl. Mech.<br />
Eng. 191 (2002) 3833–3855.<br />
[4] E.G.D. do Carmo, G.B. Alvarez, A new stabilized finite element formulation for scalar convection–<br />
diffusion problems: The streamline and approximate upwind/Petrov–Galerkin method, Comput.<br />
Methods Appl. Mech. Eng. 192 (2003) 3379–3396.<br />
[5] E.G.D. do Carmo, A.C. Galeão, Feedback Petrov–Galerkin methods for convection–dominated<br />
problems, Comput. Methods Appl. Mech. Eng. 88 (1991) 1–16.<br />
[6] R. Codina, A discontinuity–capturing crosswind–dissipation for the finite element solution <strong>of</strong> the<br />
convection–diffusion equation, Comput. Methods Appl. Mech. Eng. 110 (1993) 325–342.<br />
[7] V. John, P. Knobloch, A comparison <strong>of</strong> spurious oscillations at layers diminishing (SOLD) methods<br />
for convection–diffusion equations: Part I, Preprint Nr. 156, FR 6.1 – Mathematik, Universität des<br />
Saarlandes, Saarbrücken, 2005.<br />
[8] V. John, P. Knobloch, On discontinuity–capturing methods for convection–diffusion equations, submitted<br />
to the Proceedings <strong>of</strong> the conference ENUMATH 2005, Santiago de Compostela, July 18–22,<br />
2005.<br />
[9] P. Knobloch, Improvements <strong>of</strong> the Mizukami–Hughes method for convection–diffusion equations,<br />
Preprint No. MATH–knm–2005/6, Faculty <strong>of</strong> Mathematics and Physics, Charles University,<br />
Prague, 2005.<br />
[10] Knobloch, P.: Numerical solution <strong>of</strong> convection–diffusion equations using upwinding techniques<br />
satisfying the discrete maximum principle. Submitted to the Proceedings <strong>of</strong> the Czech–Japanese<br />
Seminar in Applied Mathematics 2005, Kuju Training Center, Oita, Japan, September 15–18, 2005.<br />
Speaker: KNOBLOCH, P. 103 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
T. KNOPP: Model-consistent universal wall-functions for RANS turbulence modelling<br />
✬<br />
✫<br />
Model-consistent universal wall-functions for RANS turbulence modelling<br />
T. Knopp<br />
<strong>Institut</strong>e <strong>of</strong> Aerodynamics and Flow Technology<br />
DLR (German Aerospace Center)<br />
Bunsenstr. 10, 37073 Göttingen, Germany<br />
Tobias.Knopp@dlr.de<br />
Ý<br />
A model-consistent universal wall-function method for RANS turbulence modelling [1] is presented,<br />
which gives solutions almost independent <strong>of</strong> the spacing <strong>of</strong> the first grid node above the wall (denoted by<br />
in plus-units) and allows a considerable solver acceleration and reduction <strong>of</strong> memory consumptions.<br />
Model-consistent wall-functions are turbulence model specific, ensuring almost grid-independent<br />
predictions for bo<strong>und</strong>ary layer flows at zero pressure gradient, e.g. the flow by Wieghardt [5].<br />
0.0035<br />
C f<br />
0.0025<br />
1 2 3 4<br />
x<br />
Exp.<br />
low Re<br />
y + (1) = 1<br />
y + (1) = 4<br />
y + (1) = 9<br />
y + (1) = 17<br />
y + (1) = 23<br />
y + (1) = 40<br />
0.0035<br />
C f<br />
0.0025<br />
1 2 3 4<br />
x<br />
Exp.<br />
low Re (fine grid)<br />
y + (1) = 1<br />
y + (1) = 4<br />
y + (1) = 9<br />
y + (1) = 17<br />
y + (1) = 23<br />
y + (1) = 40<br />
Figure 1: Skin friction �for equilibrium layer [5]. Almost grid-independent prediction for Spalart-<br />
Allmaras (SA) model with Edwards modification [3] (left) and for Menter baseline�-�model [4] (right).<br />
The <strong>und</strong>erlying approximations, i.e., (i) one-dimensional bo<strong>und</strong>ary-layer flow and (ii) near-wall equilibrium<br />
stress balance by neglecting the streamwise pressure gradient, are assessed by investigation <strong>of</strong> a flat<br />
plate turbulent bo<strong>und</strong>ary flow with adverse pressure gradient and separation devised by [2].<br />
p +<br />
0.1<br />
0.05<br />
p + 3<br />
= v / (rho ut ) * dp / dx<br />
p + = 0<br />
station 1 at x1 = 1.3<br />
station 2 at x2 = 1.6<br />
station 3 at x3 = 1.9<br />
station 4 at x4 = 2.2<br />
station 5 at x = 2.4 5<br />
station 6 at x = 2.5 6<br />
station 7 at x = 2.6 7<br />
station 8 at x = 2.7 8<br />
station 9 at x = 2.76<br />
9<br />
station 10 at x = 2.8<br />
10<br />
0<br />
0 1 2<br />
x<br />
y +<br />
10 0<br />
10 1<br />
10 2<br />
Ù �Ù�Ù�vs.Ý Figure 2: Pressure gradient parameterÔ ����Ù��Ô��Ü(left) and corresponding velocity pr<strong>of</strong>iles<br />
�ÝÙ���for the adverse pressure gradient flow by Kalitzin et al. [2].<br />
u +<br />
25<br />
20<br />
15<br />
10<br />
5<br />
RANS station 4<br />
RANS station 6<br />
RANS station 7<br />
RANS station 8<br />
RANS station 9<br />
RANS station 10<br />
RANS ZPG bou. layer<br />
The method is then applied successfully to aerodynamic flows with separation including a transonic flow<br />
Speaker: KNOPP, T. 104 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
T. KNOPP: Model-consistent universal wall-functions for RANS turbulence modelling<br />
✬<br />
✫<br />
c p<br />
-1<br />
-0.5<br />
0<br />
0.5<br />
exp.<br />
low-Re<br />
y + (1) = 1<br />
y + (1) = 20<br />
y + (1) = 40<br />
y + (1) = 60<br />
1<br />
0 0.25 0.5<br />
x/c<br />
0.75 1<br />
0.006<br />
0.004<br />
c f<br />
0.002<br />
0<br />
exp.<br />
low-Re<br />
y + (1) = 1<br />
y + (1) = 20<br />
y + (1) = 40<br />
y + (1) = 60<br />
c f = 0<br />
0 0.25 0.5 0.75 1<br />
x/c<br />
Figure 3: Distribution <strong>of</strong>Ô(left) and�(right) for SA-Edwards model [3] for RAE2822 case 10 [6].<br />
0.006<br />
0.004<br />
c f<br />
0.002<br />
0<br />
0.25 0.5 0.75<br />
x/c<br />
exp.<br />
low-Re<br />
y + (1) = 1<br />
y + (1) = 4<br />
y + (1) = 7<br />
y + (1) = 10<br />
c f = 0<br />
0.006<br />
0.004<br />
c f<br />
0.002<br />
0<br />
0.25 0.5 0.75<br />
x/c<br />
exp.<br />
low-Re<br />
y + (1) = 1<br />
y + (1) = 20<br />
y + (1) = 40<br />
y + (1) = 80<br />
c f = 0<br />
Figure 4: Prediction for�on grids with varying near-wall spacing for SST model [4] for A-airfoil [7].<br />
with shock induced separation [6] and a subsonic highlift airfoil close to stall [7].<br />
References<br />
[1] T. Knopp, T. Alrutz and D. Schwamborn, “A grid and flow adaptive wall-function method for RANS<br />
turbulence modelling”, Journal <strong>of</strong> Computational Physics (submitted).<br />
[2] G. Kalitzin, G. Medic, G. Iaccarino and P. Durbin, “Near-wall behaviour <strong>of</strong> RANS turbulence models<br />
and implications for wall functions”, Journal <strong>of</strong> Computational Physics, 204, 265-291 (2005).<br />
[3] J.R. Edwards and S. Chandra, “Comparison <strong>of</strong> eddy viscosity-transport turbulence models for threedimensional,<br />
shock separated flowfields”, AIAA Journal, 34, 756–763 (1996).<br />
[4] F.R. Menter, “Zonal two equation�/�turbulence models for aerodynamic flows”, AIAA Paper<br />
1993-2906 (1993).<br />
[5] D. E. Coles and E. A. Hirst (Eds.), Computation <strong>of</strong> Turbulent Bo<strong>und</strong>ary Layers - 1968 AFOSR-IFP-<br />
Stanford Conference, Stanford (1969).<br />
[6] P. H. Cook, M. A. McDonald and M.C.P. Firmin, “Aer<strong>of</strong>oil RAE 2822 - Pressure distributions and<br />
bo<strong>und</strong>ary layer and wake measurements”, AGARD Advisory Report AR-138, A6.1-A6.77 (1979).<br />
[7] Ch. Gleyzes, “Opération décrochage - Résultats de la 2ème campagne d’essais à F2 – Mesures de<br />
pression et vélocimétrie laser”, RT-DERAT 55/5004 DN, ONERA (1989).<br />
Speaker: KNOPP, T. 105 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
J.-S. LEU, J.-Y. JANG, Y.-C. CHOU: Evaporating cooling <strong>of</strong> liquid film along an<br />
inclined plate coverd with a porous layer<br />
✬<br />
✫<br />
Evaporating cooling <strong>of</strong> liquid film along an inclined plate covered with a<br />
porous layer<br />
ABSTRACT<br />
Jin-Sheng Leu<br />
Department <strong>of</strong> Mechanical Engineering<br />
Air Force <strong>Institut</strong>e <strong>of</strong> Technology<br />
Kaohsiung, Taiwan 82042<br />
Jiin-Yuh Jang* and Yin Chou<br />
Department <strong>of</strong> Mechanical Engineering,<br />
National Cheng-Kung University<br />
Tainan, Taiwan 70101<br />
The purpose <strong>of</strong> this work is to evaluate the heat and mass enhancement <strong>of</strong> liquid film<br />
evaporation by covering a porous layer on the plate (as shown in Fig. 1). There is an extensive<br />
literature for liquid film evaporating flow based on simplified 1-D and 2-D mathematical models.<br />
Wassel and Mills [1] illustrated a 1-D design methodology for a counter-current falling film<br />
evaporative cooler. Yan and Soong [2] presented their numerical solution for convective heat and<br />
mass transfer along an inclined heated plate with film evaporation with more rigorous treatments <strong>of</strong><br />
the equations governing the liquid film and liquid-gas interface. The complete two-dimensional<br />
bo<strong>und</strong>ary layer model for the evaporating liquid and gas flows along an inclined plate was studied<br />
recently by Mezaache and Daguenet [3]. Their parametric study focused on the effects <strong>of</strong> inlet<br />
conditions such as gas velocity, liquid mass flow rate and inclined angles and their interaction with<br />
both isothermal and heated walls. Zhao [4] studied the coupled heat and mass transfer in a stagnation<br />
point flow <strong>of</strong> air through a heated porous bed with thin liquid film evaporation.<br />
Until now, there seems to be no related theoretical analysis to evaluate the feasibility <strong>of</strong><br />
utilizing porous materials for the heat transfer enhancement <strong>of</strong> falling liquid evaporation. This has<br />
motivated the present investigation. The present study analyzes the liquid film evaporation flow along<br />
a vertical isothermal plate covered with a thin liquid-saturated porous layer. Liquid and gas streams<br />
are approached by two coupled laminar bo<strong>und</strong>ary layers. The non-Darcian inertia and bo<strong>und</strong>ary effects<br />
are included to describe the hydraulic characteristic <strong>of</strong> the liquid-saturated porous medium. Then, the<br />
governing equations (tabulated in Table1) are discretized to a fully implicit difference representation,<br />
in which the upwind scheme is used to model the axial convective terms, while second-order central<br />
difference schemes are employed for the transverse convection and diffusion terms. Newton<br />
linearization procedure is used to linearize the nonlinear terms <strong>of</strong> governing equation.The numerical<br />
solution is obtained by utilizing a fully implicit finite difference method and examined in detail for the<br />
effects <strong>of</strong> porosity ε, porous layer thickness δ, ambient relative humidity φ and Lewis number Le on<br />
the average heat and mass transfer performance.<br />
The numerical results conclude that the latent heat flux is the dominant mode for the<br />
present study. The cases for lower ε and δ would produce higher interfacial temperature and mass<br />
concentration, and thus enhance the �heat and mass transfer performances across the film interface. The<br />
influence <strong>of</strong> ε on the Nusselt number (Nu) and Sherwood number(Sh) is gradually more significant<br />
as δ is increased. An applicable range <strong>of</strong> porous layer thickness δ=0.001~0.005 is suggested for the<br />
practical application (as shown in Fig. 2). For the effect <strong>of</strong> ambient relative humidity φ, it is observed<br />
that a lower φ leads to a higher Nu but lower Sh. However, the influence on Nu and Sh appears to be<br />
less significant than those <strong>of</strong> ε and δ. In addition, as the Lewis number is increased(Le>1), a larger<br />
heat transfer rate is achieved.<br />
* Pr<strong>of</strong>essor, author to whom correspondence should be addressed<br />
Tel: 886-6-2088573 Fax: 886-6-2342232<br />
1<br />
E-mail: jangjim@mail.ncku.edu.tw<br />
Speaker: JANG, J.-Y. 106 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
J.-S. LEU, J.-Y. JANG, Y.-C. CHOU: Evaporating cooling <strong>of</strong> liquid film along an<br />
inclined plate coverd with a porous layer<br />
✬<br />
✫<br />
REFERRENCE<br />
[1]. Wassel, A. T., and Mills, A. F., "Design Methodology for a Counter-current Falling Film<br />
Evaporative Condenser". ASME J. <strong>of</strong> Heat Transfer, Vol. 109, pp.784-787, 1987.<br />
[2] Yan, W. M., and Soong, C. Y., “Convection heat and mass transfer along an inclined heated plate<br />
with film evaporation”, Int. J. Heat Mass Transfer, Vol.38, pp.1261-1269, 1995.<br />
[3] Mezaache, E., and Daguenet, M., “Effects <strong>of</strong> Inlet Conditions on Film Evaporation along an<br />
Inclined Plate”, Solar Energy, Vol. 78, pp.535-542, 2005.<br />
[4]. Zhao, T. S., “Coupled Heat and Mass Transfer <strong>of</strong> a Stagnation Point Flow in a Heated Porous Bed<br />
with Liquid Film Evaporation”, Int. J. Heat Mass Transfer, Vol.42, pp.861-872, 1999.<br />
Table 1: The governing equations for liquid film<br />
and gas steam regions<br />
Liquid<br />
film<br />
region<br />
Gas<br />
stream<br />
region<br />
2<br />
µ l ∂ u l µ l ρlC<br />
2<br />
0 = ρlg<br />
cos ϕ + − u<br />
2 l − u l<br />
ε ∂y<br />
K K<br />
2<br />
∂Tl<br />
∂ Tl<br />
u l = αe<br />
∂x<br />
2<br />
∂y<br />
∂u<br />
g ∂v<br />
g<br />
+ = 0<br />
∂x<br />
∂y<br />
2<br />
∂u<br />
g ∂u<br />
g ∂ u g<br />
u g + vg<br />
= ν g<br />
∂x<br />
∂y<br />
2<br />
∂y<br />
2<br />
∂Tg<br />
∂Tg<br />
∂ Tg<br />
ug<br />
+ vg<br />
= αg<br />
∂x<br />
∂y<br />
2<br />
∂y<br />
2<br />
∂ω<br />
∂ω<br />
∂ ω<br />
ug<br />
+ vg<br />
= D<br />
∂x<br />
∂y<br />
2<br />
∂y<br />
where the subscript “l”, “g” represents the<br />
variables <strong>of</strong> the liquid and gas stream,<br />
respectively. ω, ρ ,ν ,α and D are the mass<br />
concentration, density, kinematic viscosity,<br />
thermal diffusivity and mass diffusivity <strong>of</strong> the<br />
gas. ε and K is the porosity and permeability <strong>of</strong><br />
the porous medium, C is the flow inertia<br />
parameter.<br />
Nu<br />
600<br />
500<br />
400<br />
300<br />
200<br />
δ =0.001<br />
0.002<br />
0.005<br />
0.01<br />
0.02<br />
100<br />
0.2 0.4 0.6<br />
ε<br />
0.8 1<br />
2<br />
liquid<br />
film<br />
X = 0<br />
X<br />
Tw<br />
air<br />
Y<br />
Tl<br />
Ti a T<br />
porous layer<br />
Figure 1 Schematic diagram <strong>of</strong> the physical system<br />
Sh<br />
35<br />
30<br />
25<br />
20<br />
15<br />
10<br />
= 0.001<br />
0.002<br />
0.005<br />
0.01<br />
0.02<br />
5<br />
0.2 0.4 0.6<br />
ε<br />
0.8 1<br />
(a) (b)<br />
Figure 2 The coupled effects <strong>of</strong> porosity ε and thickness δ on the average (a) Nusselt and<br />
(b)Sherwood numbers with Reg =50000 and φ=70%.<br />
Speaker: JANG, J.-Y. 107 <strong>BAIL</strong> <strong>2006</strong><br />
δ<br />
✩<br />
✪
V.D. LISEYKIN, Y.V. LIKHANOVA, D.V. PATRAKHIN, I.A. VASEVA: Application<br />
<strong>of</strong> bo<strong>und</strong>ary layer-type functions to comprehensive grid generation codes<br />
✬<br />
✫<br />
Liseykin V.D., Likhanova Yu.V, Patrakhin D.V., Vaseva I.A.<br />
Application <strong>of</strong> bo<strong>und</strong>ary layer-type functions to comprehensive<br />
grid generation codes<br />
The paper presents recent results related to the development<br />
<strong>of</strong> algorithms and codes for generating both structured and unstructured<br />
grids with the use <strong>of</strong> operator Beltrami [1]. Control <strong>of</strong><br />
grid properties is realized by monitor metrics formulated with the<br />
use <strong>of</strong> bo<strong>und</strong>ary layer-type functions. Formulas for the metrics<br />
providing generation <strong>of</strong> grids adapting to vector fields, gradients,<br />
and/or values <strong>of</strong> physical quantities are presented. Applications<br />
<strong>of</strong> adaptive grids to fluid dynamics and plasma related problems<br />
are demonstrated.<br />
The work over the paper is supported by CRDF (RU-M1-<br />
2579) and RFBR (06-01-00205) grants.<br />
[1] V.D. Liseikin ”A Computaional Differential Geometry Approach to<br />
Grid Generation”, 2004, Berlin, Springer.<br />
Speaker: LISEYKIN, V.D. 108 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
G. LUBE: A stabilized finite element method with anisotropic mesh refinement for the<br />
Oseen equations<br />
✬<br />
✫<br />
Int. Conference on Bo<strong>und</strong>ary and Interior Layers<br />
<strong>BAIL</strong> <strong>2006</strong><br />
G. Lube, G. Rapin (Eds)<br />
c○ University <strong>of</strong> Göttingen, Germany, <strong>2006</strong><br />
A stabilized finite element method<br />
with anisotropic mesh refinement for the Oseen problem<br />
G. Lube<br />
<strong>Institut</strong> <strong>für</strong> <strong>Numerische</strong> <strong>und</strong> Angewandte Mathematik,<br />
Georg-August-Universität Göttingen,<br />
Lotzestrasse 16-18, D-37083 Göttingen, Germany<br />
lube@math.uni-goettingen.de<br />
Nonstationary incompressible flow problems can be split into auxiliary problems <strong>of</strong> Oseen<br />
type. We start with a quasi-optimal error estimate <strong>of</strong> Cea-type for conforming stabilized Galerkin<br />
methods <strong>of</strong> SUPG/PSPG-type with equal-order interpolation <strong>of</strong> velocity/pressure on general<br />
meshes. Then we present some new results for this class <strong>of</strong> methods on hybrid meshes with<br />
structured anisotropic mesh refinement in bo<strong>und</strong>ary layers. The layer meshes are supposed to<br />
be <strong>of</strong> tensor-product type. In particular, we prove a modified inf-sup condition with a constant<br />
independent <strong>of</strong> the viscosity and <strong>of</strong> critical parameters <strong>of</strong> the mesh. Full pro<strong>of</strong>s <strong>of</strong> the main<br />
results can be fo<strong>und</strong> in [1].<br />
Some numerical tests for a laminar and a turbulent channel flow problem confirm the theoretical<br />
results. In Fig. 1, we show some results for the three-dimensional channel flow at Reτ = 395<br />
using an improved statististical turbulence model based on the unsteady Reynolds averaged<br />
Navier-Stokes model (URANS), the v 2 − f model by P. Durbin, see also [3]. The results are in<br />
good agreement with the DNS data in [2] and partly better than those reported in [3].<br />
Achnowledgement: This paper is based on joint work with Th. Apel (Neubiberg), T.<br />
Knopp (DLR Göttingen) and R. Gritzki (TU Dresden).<br />
References<br />
[1] Apel, Th., Knopp, T., Lube, G.: Stabilized finite element methods with anisotropic mesh<br />
refinement for the Oseen problem, submitted to Appl. Num. Math. <strong>2006</strong><br />
[2] Kim, J., Moin, P., Moser, R.: Turbulence statistics in fully developed channel flow at low<br />
Reynolds number, J. Fluid Mech. 177 (1987) 133–166.<br />
[3] Laurence, L.R., Uribe, J.C., Utyuzhnikov, S.V.: A robust formulation <strong>of</strong> the v2 − f model,<br />
J. Flow, Turbulence and Combustion 23 (2004) 169–185.<br />
Speaker: LUBE, G. 109 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
G. LUBE: A stabilized finite element method with anisotropic mesh refinement for the<br />
Oseen equations<br />
✬<br />
✫<br />
30 ParallelNS<br />
x Laurence<br />
25<br />
DNS<br />
U +<br />
20<br />
15<br />
10<br />
5<br />
0<br />
10 -1<br />
x x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x x<br />
x x<br />
y +<br />
10 0<br />
10 1<br />
10 2<br />
0.35 ParallelNS<br />
x Laurence<br />
0.3<br />
DNS<br />
0.25<br />
0.2<br />
ε +<br />
0.15<br />
0.1<br />
0.05<br />
x<br />
x<br />
x<br />
x xx xxx x x x x xx x x x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
y +<br />
x<br />
x<br />
x<br />
10 3<br />
x x x x<br />
0<br />
0 20 40 60 80 100<br />
k +<br />
v 2+<br />
6 ParallelNS<br />
x Laurence<br />
5<br />
DNS<br />
4<br />
3<br />
2<br />
1<br />
x<br />
x<br />
x<br />
x<br />
x<br />
xx x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
y +<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x x x<br />
0 x<br />
0 100 200 300 400<br />
2 ParallelNS<br />
x Laurence<br />
DNS<br />
1.5<br />
1<br />
0.5<br />
x<br />
x x x x<br />
x x<br />
x x<br />
x<br />
x<br />
x<br />
x<br />
x<br />
x x<br />
x<br />
x x<br />
x<br />
x x x x x<br />
x<br />
x<br />
x<br />
x<br />
x xx<br />
0<br />
0 100 200 300 400<br />
Figure 1: Plot <strong>of</strong> u + ,k + ,ǫ + ,(v 2 ) + vs. y + := yuτ<br />
ν compared to DNS-data in [2] and results in [3]<br />
Speaker: LUBE, G. 110 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
y +<br />
✩<br />
✪
H. LÜDEKE: Detached Eddy Simulation <strong>of</strong> Supersonic Shear Layer Wake Flows<br />
✬<br />
✫<br />
Detached Eddy Simulation <strong>of</strong> Supersonic Shear Layer Wake Flows<br />
Heinrich Lüdeke<br />
∗ DLR <strong>Institut</strong>e <strong>of</strong> Aerodynamics<br />
and Flow Technology<br />
Lilienthalplatz 7, D-38108 Braunschweig<br />
e-mail: heinrich.luedeke@dlr.de<br />
Tel. +49 (531) 295-3315<br />
Key words: detached-eddy simulation, axisymmetric base flow, compressible wake, turbulent<br />
separation<br />
One challenge <strong>of</strong> numerical investigations <strong>of</strong> unsteady super- and hypersonic flow fields is the<br />
study <strong>of</strong> the turbulent wake at complex vehicle configurations. A recent promising approach is the<br />
technique <strong>of</strong> detached-eddy simulation (DES) proposed by Spalart et.al. Detached-eddy simulation<br />
is a hybrid approach for the modelling <strong>of</strong> turbulent flow fields at complex geometries. The idea<br />
is to combine the best features <strong>of</strong> both, the Reynolds-averaged Navier-Stokes (RANS) and the<br />
large eddy simulation (LES) approach to predict massively separated unsteady flow fields at high<br />
Reynolds-numbers especially in the wake <strong>of</strong> Re-entry vehicles during descent. In this study the<br />
Spalart Allmaras one equation turbulence model is used as an accurate and efficient base for DES.<br />
The intention <strong>of</strong> the current work is an investigation <strong>of</strong> the shear flow in the wake <strong>of</strong> a blunt<br />
cylinder at M =2.4 at high Reynolds numbers. This is used as a basic configuration for re-entry<br />
vehicles with a blunt base. The typical time averaged flow field for this configuration is shown<br />
in fig. 1 with pressure contours and streamlines. The large turning angle behind the base causes<br />
separation and a region <strong>of</strong> reverse flow as visible in the wake. The point at the axis <strong>of</strong> symmetrie<br />
where the streamwise velocity is zero is considered to be the shear layer reattachment point. In<br />
this region the flow is forced to turn along the axis <strong>of</strong> symmetry causing a reattachment shock<br />
to be formed. The detailed experimental data base, provided by Herrin and Dutton [1], is used<br />
for comparison <strong>of</strong> numerically predicted and measured data. The practical applicability <strong>of</strong> the<br />
approach is demonstrated considering as example an axisymmetric re-entry capsule.<br />
All simulations were carried out by the hybrid structured-unstructured DLR Tau code which<br />
is extensively validated for sub- trans- and hypersonic cases [2]. For the axisymmetric cylinderconfiguration<br />
structured and unstructured grids have been generated at different resolution <strong>of</strong> the<br />
turbulent wake. They are designed with a similar resolution used by Forsythe and Sqires in [3].<br />
Especially the near wake <strong>of</strong> the cylinder is refined extensively. The results have shown good grid<br />
convergence for the cylinder cases for all averaged quantities, namely the velocity components and<br />
the pressure, as well as for the diagonal elements <strong>of</strong> the Reynolds stress tensor and the resolved<br />
turbulent kinetic energy in the free shear layer.<br />
In the wake the turbulent kinetic energy and turbulent intensities in radial and streamwise<br />
direction, computed by extracting the standard deviation <strong>of</strong> the velocitys over the time, was successffully<br />
compared with the measurements. Furthermore the pressure level along the base was<br />
compared with the experimental data <strong>of</strong> Herrin and Dutton [1]<br />
Finally simulations <strong>of</strong> the SARA capsule, a facility conceived to be a recovery orbital platform<br />
to perform orbital flights, are carried out to give a practical demonstratin <strong>of</strong> DES modelling for<br />
hypersonic flight [4]. To ensure turbulent wake flow the trajectory point at M =5.1, Re =20· 106 was chosen. The influence <strong>of</strong> unsteady loads, generated by the turbulent wake flow was investigated<br />
for this vehicle. A preliminary snapshot <strong>of</strong> the vorticity contours in the wake is shown in fig. 2.<br />
1<br />
Speaker: LÜDEKE, H. 111 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
H. LÜDEKE: Detached Eddy Simulation <strong>of</strong> Supersonic Shear Layer Wake Flows<br />
✬<br />
✫<br />
References<br />
[1] J.L. Herrin, J.C. Dutton: Supersonic Base flow Experiments in the Near Wake <strong>of</strong> aa Cylindrical<br />
Afterbody. AIAA Journal, Vol 32, No. 1, January 1994.<br />
[2] A. Mack, V. Hannemann: Validation <strong>of</strong> the unstructured DLR-TAU-Code for Hypersonic<br />
Flows, AIAA 2002-3111, 2002.<br />
[3] J.R. Forsythe, K.A. H<strong>of</strong>fmann, K.D. Squires: Detached-Eddy Simulation with compressibility<br />
Corrections Applied to a Supersonic Axisymmetric Base Flow. AIAA 02-0586, 2002.<br />
[4] Alessandro La Neve, Flávio de Azevedo Corrêa Junior: SARA Experiment Module Project:<br />
Using Skills to Enlarge Experiences. International conference on Engineering Education,<br />
Manchester, U.K., August 18-21, 2002<br />
Expansion Waves<br />
Separation Bubble<br />
Reattachment Shock<br />
cp: -0.18 -0.14 -0.10 -0.07 -0.03 0.01 0.05<br />
Figure 1: Flow topology and Cp contours <strong>of</strong><br />
the axisymmetric cylinder wake at M∞ =2.4,<br />
Re =1.4 · 10 6 .<br />
vorticity: 1600 2106 2773 3650 4804 6325 8326 10960 14427 18991 25000<br />
Figure 2: Instantanious vorticity contours in the<br />
SARA wake at M∞ =5.1, Re =20· 10 6 .<br />
Speaker: LÜDEKE, H. 112 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
K. MANSOUR: Bo<strong>und</strong>ary Layer Solution For laminar flow through a Loosely curved<br />
Pipe by Using Stokes Expansion<br />
✬<br />
✫<br />
Bo<strong>und</strong>ary Layer Solution For laminar flow through a<br />
Loosely curved Pipe by Using Stokes Expansion<br />
By Kamyar Mansour<br />
Department <strong>of</strong> Aerospace Engineering and New Technologies Research Center<br />
Amir Kabir University <strong>of</strong> Technology<br />
Tehran, Iran, 15875-4413<br />
mansour@aut.ac.ir<br />
And<br />
Flow Research and Engineering<br />
P.O. Box # 20543 Palo Alto, CA, 94309<br />
Keywords: Curved pipe, high Dean Number<br />
We consider fully developed steady laminar flow through a toroidal pipe <strong>of</strong> small curvature ratios<br />
.The solution is expanded up to 40 terms by computer in powers <strong>of</strong> Dean Number. The major<br />
conclusion <strong>of</strong> this investigation is that the friction ratio in a loosely coiled pipe grows<br />
asymptotically as the 1/4 power <strong>of</strong> the similarity parameter and not as the 1/2 power as previously<br />
deduced from bo<strong>und</strong>ary-layer analysis. This work confirmed the results obtained by [1]. The goal<br />
<strong>of</strong> this analysis is to provide as complete a description as possible <strong>of</strong> the flow. The analysis<br />
yields a solution for all values <strong>of</strong> Reynolds number from zero to infinity in a continuous fashion<br />
The paradox concerns the discrepancy between the solution obtained using the extended Stokes<br />
series method [1] and that obtained using bo<strong>und</strong>ary layer techniques [2],[3],[4],[5],[6]and<br />
experimental work <strong>of</strong> [7],[8],[9],[10]and numerical work <strong>of</strong> [11]for the ratio <strong>of</strong> the friction factors<br />
in coiled tubes to that in straight one in steady, fully developed laminar flow. . In the ensuing<br />
debates several papers <strong>of</strong>[12],[13].[14],[15],[16].[17],[18].[19],[20],[21],[22],[23] various<br />
explanations and new evidence have been given; however, the paradox , the resolution <strong>of</strong> which<br />
is important still remain as a open problem<br />
The author in [20] raise the possibility <strong>of</strong> cause <strong>of</strong> this paradox is the use <strong>of</strong> only 24 terms to<br />
estimate the asymptotic limit obtained by [1]. In this paper we extend the Stokes series from 24<br />
terms used by [1] to 40 terms. We confirm the major result <strong>of</strong> the friction ratio in a loosely coiled<br />
pipe grows asymptotically as the 1/4 power <strong>of</strong> the similarity parameter and not as the 1/2 power<br />
and that confirm the result <strong>of</strong> [1].<br />
What is particularly important in problems <strong>of</strong> this type is the presence <strong>of</strong> analyticity. Not every<br />
stokes expansion, for examples that <strong>of</strong> the flow past sphere as described by the full Navier-Stokes<br />
equation are analytic in Reynolds number. In this case, method <strong>of</strong> matched asymptotic expansions<br />
is required and can be automated<br />
An alternative explanation <strong>of</strong> the departure <strong>of</strong> the experiments from our curve might be that for<br />
more tightly coiled pipes the steady laminar flow is succeeded not by turbulent flow, but by an<br />
intermediate regime <strong>of</strong> unsteady laminar motion, with higher friction. Taylor [25] expressed the<br />
possibility that there may exist an intermediate flow regime between the laminar and turbulent<br />
ranges. He observed a transition from a steady laminar flow to a laminar vibrating flow as the<br />
speed increased. The onset <strong>of</strong> turbulence accrued only at a significantly higher speed.<br />
The effect <strong>of</strong> diameter ratios a/L on the relation between the friction factor and the Dean<br />
number has been investigated numerically by [16] and is fo<strong>und</strong> to be negligibly small. They<br />
concluded the friction factor ratio is relatively insensitive to the diameter ratios at a given Dean<br />
number. However in 1988 [18] for corresponding curved pipe problem tried to make experiment<br />
to match the series extension, would have to satisfy that is the flow be fully developed at high<br />
Dean number namely bigger than 500 and laminar as well as a/L less than .03. But his result adds<br />
another mystery to this paradox and they obtained data, which lay closer to the present method. In<br />
Speaker: MANSOUR, K. 113 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
K. MANSOUR: Bo<strong>und</strong>ary Layer Solution For laminar flow through a Loosely curved<br />
Pipe by Using Stokes Expansion<br />
✬<br />
✫<br />
this paper we have shown that what proposed by [20] as the cause <strong>of</strong> the discrepancy lies in the<br />
use <strong>of</strong> the only first 12 terms for corresponding curved problem is not correct. In this work we<br />
increase number <strong>of</strong> terms from 12 in [1] to 20 and still the major conclusion <strong>of</strong> the discrepancy<br />
between the solution obtained using the extended stoke series method and that obtained using<br />
other method persist as it was the case for the rotating pipe[26].<br />
REFERENCES<br />
[1] Van Dyke, M. 1978 Extended stokes series: laminar flow through a loosely coiled pipe. J.Fluid<br />
Mech.,86, 129-145<br />
[2] Adler,M.”Flow in curved tubes” Z.Angew.Math.1934 Mech.,14,257<br />
[3]Barua,S.N. 1963 On secondary flow in stationary curved pipes. Quart. J. Mech. Appl. Maths. 26. 61-77<br />
[4] Mori, Y. & Nakayama, W. 1965 study on forced convective heat transfer in curved pipes (1 st report,<br />
laminar region). Intl. J. <strong>of</strong> Heat Mass Transfer 8, 67-82<br />
[5] Ito, H., 1969 Laminar Flow in curved pipes Z. agnew. Math. Mech. 11. 653-663<br />
[6] Smith, F. T. 1976 Steady motion within a curved pipe. Proc. Roy. Soc. A 347, 345-370<br />
[7] White, C. M. 1929 Streamline flow through curved pipes. Proc. Roy. Soc. A 123, 845-663.<br />
[8] Hasson,D. 1955 “Streamline flow resistence in coils. Research 8(1) supplement p.S1<br />
[9] Trefethen, L. 1957b Flow in rotating radial ducts: report R55GL 350 on laminar flow in rotating,<br />
heated horizontal, and bent tubes, extended into transition and turbulent regions. Gen. Elec. Co.<br />
Rep. 55GL350-A.<br />
[10] Ito, H.,1959 Friction factors for turbulent flow in curved pipes.Trans.ASMEJ.BasicEngng.81,123-134<br />
[11] Collins, W. M. &Dennis, S. C. R. 1975 The steady motion <strong>of</strong> a viscous fluid in a curved tube.<br />
Quart. J. Mech. Appl. Maths. 28, 133-156.<br />
[12] Dennis, S.C.R. 1980 “Calculation <strong>of</strong> the steady flow through a curved tube using a new finite<br />
difference method. J.Fluid. Mech.,99, 449-467<br />
[13] Dennis, S.C.R. &Ng,M.C. 1982 “Dual solution for steady laminar flow through a curved tube.Q.J.<br />
Mech. Appl. Maths 35,305-324<br />
[14] Nandakumar, K. & Masliyah, J. H. 1982 Bifurcation in steady laminar flow through curved tubes.J.<br />
Fluid Mech. 119,475-490<br />
[15] Mansour, K. 1985 Laminar flow through a slowly rotating straight pipe. J. Fluid Mech. 150, 1-24.<br />
[16] Soh,W.Y.&Berger,S.A. 1987 “fully developed flow in a curved pipe <strong>of</strong> arbitrary<br />
curvature ratio.Intl J. Numer.Mech. Fluids 7,733<br />
[17] Winters,K.H. 1987 A bifurcation study <strong>of</strong> laminar flow in a curved<br />
tube <strong>of</strong> rectangular cross-section. J. Fluid Mech. 180, 343-369<br />
[18] Ramshankar, R. & Sreenvasan, K. R. 1988 A paradox concerning the extended Stokes series solution<br />
for the pressure drop in coiled pipes. Phys. Fluids, 1339-1347.<br />
[19] Van Dyke, M. 1989 some paradoxes in viscous flow theory. “Some unanswered question in fluid<br />
mechanics “ (ed. L. M. Trefethan & R. L. Panton).Appl. Mech. Rev. 43, 153-170<br />
[20] S. Jayanti & G.F. Hewitt. "On the paradox concerning friction factor ratio in laminar flow in coils",<br />
Proc. R. Soc. Lond. A (1991) 432, 291-299<br />
[21] Mansour, K. 1993 Using Stokes Expansion For Natural Convection inside a two-dimensional cavity.<br />
Fluid Dynamics Research, 1-33<br />
[22 ] Dennis,S.C.R. and Riley,N. 1993 ”On the fully developed flow in a curved pipe<br />
at large Dean number” Proc. Roy. Soc. A.434, 473-478<br />
[23] Ishigaki, H. "Analogy between laminar flows in curved pipes and orthogonal rotating pipes". J. Fluid<br />
Mech. (1994), vol.268, pp. 133-145<br />
[24] Dean, W.R. 1927 Note on the motion <strong>of</strong> fluid in a curved pipe. Phil.Mag. (7) 4,208-223<br />
[25] Taylor, G.I. 1929 The criterion for turbulence in curved piped. Proc. R. Soc. Lond. A 124, 243-249.<br />
[26] Mansour, K. 2002 Bo<strong>und</strong>ary layer solution using Stokes expansion for Laminar flow through a slow-<br />
rotating pipe, Proceedings <strong>of</strong> <strong>BAIL</strong> 2002 ,An international conference on bo<strong>und</strong>ary and interior layers<br />
computational & Asymptotic methods, Perth, Western Australia.<br />
Speaker: MANSOUR, K. 114 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
G. MATTHIES, L. TOBISKA: Mass conservation <strong>of</strong> finite element methods for coupled<br />
flow-transport problems<br />
✬<br />
✫<br />
Mass conservation <strong>of</strong> finite element methods for coupled flow-transport<br />
problems<br />
Gunar Matthies 1 and Lutz Tobiska 2<br />
1 Fakultät <strong>für</strong> Mathematik, Ruhr-Universität Bochum<br />
2 <strong>Institut</strong> <strong>für</strong> Analysis <strong>und</strong> Numerik, Otto-von-Guericke-Universität Magdeburg<br />
We consider a coupled flow-transport problem in a bo<strong>und</strong>ed domain Ω ⊂ R d , d = 2,3. The<br />
system is described by the instationary, incompressible Navier–Stokes equations<br />
and the time-dependent transport equation<br />
ut − ν△u + (u · ∇)u + ∇p = f in Ω × (0,T],<br />
div u = 0 in Ω × (0,T],<br />
u = ub on ∂Ω × (0,T],<br />
u(0) = u 0<br />
in Ω,<br />
ct − ε△c + u · ∇c = g in Ω × (0,T],<br />
(cu − ε∇c) · n = cI u · n on Γ− × (0,T],<br />
ε∇c · n = 0 on Γ+ × (0,T],<br />
c(0) = c 0<br />
in Ω.<br />
Here, u and p denote the velocity and the pressure <strong>of</strong> the fluid, respectively, ν and ε are small<br />
positive numbers, c is the concentration, cI the concentration at the inflow bo<strong>und</strong>ary Γ− :=<br />
{x ∈ ∂Ω : u · n < 0}, and Γ+ := ∂Ω \ Γ−. We assume that ub is the restriction <strong>of</strong> a divergence<br />
free function onto the bo<strong>und</strong>ary ∂Ω. Note that the velocity u from the Navier–Stokes equations<br />
enters the transport equation as a convection field.<br />
Due to incompressibility constraint, the weak solution c <strong>of</strong> (2) satisfies the global mass<br />
conservation property<br />
� � � �<br />
d<br />
cdx + cIu · ndγ + cu · ndγ = g dx. (3)<br />
dt Ω Γ−<br />
Γ+<br />
Ω<br />
It is well-known [1], that the finite element solutions satisfy in general the incompressibility<br />
constraint and the global mass conservation property (3) only approximately.<br />
Different discretisation methods [2, 3, 4] for the instationary, incompressible Navier–Stokes<br />
equations and stabilised schemes for the transport problem like SDFEM will be studied numerically.<br />
References<br />
[1] C. Dawson, S. Sun, M. F. Wheeler, Compatible algorithms for coupled flow and transport.<br />
Comput. Methods Appl. Mech. Engrg., 193, 2565–2580 (2004).<br />
[2] G. Matthies, L. Tobiska, The inf-sup condition for the mapped Qk/P disc<br />
k−1 element in arbitrary<br />
space dimensions. Computing, 69, 119–139 (2002).<br />
[3] G. Matthies, L. Tobiska, Inf-sup stable non-conforming finite elements <strong>of</strong> arbitrary order<br />
on triangles. Numer. Math., 102, 293–309 (2005).<br />
[4] G. Matthies, Inf-sup stable nonconforming finite elements <strong>of</strong> higher order on quadrilaterals<br />
and hexahedra. Bericht Nr. 373, Fakultät <strong>für</strong> Mathematik, Ruhr-Universität Bochum<br />
(2005).<br />
Speaker: MATTHIES, G. 115 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
(1)<br />
(2)<br />
✩<br />
✪
J. MAUSS, J. COUSTEIX: Global Interactive Bo<strong>und</strong>ary Layer (GIBL) for a Channel<br />
✬<br />
✫<br />
Global Interactive Bo<strong>und</strong>ary Layer (GIBL) for a Channel<br />
J. Mauss ♦ and J. Cousteix ♣<br />
♦ IMFT and UPS, 118 route de Narbonne, 31062 Toulouse Cedex - France<br />
Phone: 05 61 55 67 94 - mauss@cict.fr<br />
♣ ONERA and SUPAERO, 2 av. É. Belin, 31055 Toulouse Cedex - France<br />
Phone: 05 62 25 25 80 - Jean.Cousteix@onecert.fr<br />
We consider a laminar, steady, two-dimensional flow <strong>of</strong> an incompressible Newtonian fluid<br />
in a channel at high Reynolds number. When the walls are slightly deformed, adverse pressure<br />
gradients are generated and separation can occur. The analysis <strong>of</strong> the flow structure has been<br />
done essentially by Smith [4]. Later, a systematic asymptotic analysis has been performed by<br />
Saintlos and Mauss [3]. With the Successive Complementary Expansion Method, SCEM, we<br />
assume a uniformly valid approximation (UVA) based on generalised expansions. This method,<br />
developed by Cousteix and Mauss [1], has been used by Dechaume et al. [2].<br />
Navier-Stokes dimensionless equations can be written<br />
div −→ V =0, (grad −→ V ) · −→ V = − grad Π+ 1<br />
Re △ −→ V . (1)<br />
The basic plane Poiseuille flow is<br />
v (x) = u0 = y − y 2 , v (y) =0, Π=Π0 = − 2x<br />
Re + p0 . (2)<br />
The flow is perturbed, for instance, by indentations <strong>of</strong> the lower and upper walls such as<br />
yl = εF (x, ε) , yu =1− εG(x, ε) , (3)<br />
where ε is a small parameter. If we seek a solution in the form<br />
v (x) = u0(y)+εu(x, y, ε) , v (y) = εv(x, y, ε) , Π − p0 = − 2x<br />
the Navier-Stokes equations become<br />
+ εp(x, y, ε) ,<br />
Re<br />
(4)<br />
∂u ∂v<br />
+ = 0 , (5a)<br />
∂x ∂y<br />
�<br />
ε u ∂u<br />
�<br />
�<br />
∂u ∂u du0 ∂p 1 ∂2u + v + u0 + v = − +<br />
∂x ∂y ∂x dy ∂x Re ∂x2 + ∂2u ∂y2 �<br />
, (5b)<br />
�<br />
ε u ∂v<br />
�<br />
�<br />
∂v ∂v<br />
1 ∂2v + v + u0 = −∂p +<br />
∂x ∂y ∂x ∂y Re ∂x2 + ∂2v ∂y2 �<br />
. (5c)<br />
It is clear that, for high Reynolds numbers, the reduced equations are <strong>of</strong> first order leading<br />
to a singular perturbation. In the core flow, we are looking for approximations coming from<br />
asymptotic generalised expansions such as<br />
u = u1(x, y, ε)+··· , v = v1(x, y, ε)+··· , p = p1(x, y, ε)+··· . (6)<br />
Formally, neglecting terms <strong>of</strong> order O(ε, 1/Re) , for the core flow, we obtain<br />
∂u1<br />
∂x<br />
+ ∂v1<br />
∂y<br />
∂u1 du0<br />
u0 + v1<br />
∂x dy<br />
∂v1<br />
u0<br />
∂x<br />
1<br />
= 0 , (7a)<br />
= −∂p1<br />
∂x<br />
= −∂p1<br />
∂y<br />
, (7b)<br />
. (7c)<br />
Speaker: MAUSS, J. 116 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
J. MAUSS, J. COUSTEIX: Global Interactive Bo<strong>und</strong>ary Layer (GIBL) for a Channel<br />
✬<br />
✫<br />
It is very interesting to observe the singular behaviour <strong>of</strong> the solution <strong>of</strong> (7a–7c) as we<br />
approach the bo<strong>und</strong>aries. For instance, when y → 0, we have<br />
u1 = −2p10 ln y + c10 + ··· ,<br />
where p10 and c10 are functions <strong>of</strong> x and ε.<br />
The generalised asymptotic expansions for the velocity are given by<br />
v (x) = u0(y)+εu(x, y, ε)+··· , v (y) = εv(x, y, ε)+··· . (8)<br />
Using the SCEM, the problem consists <strong>of</strong> solving the continuity equation together with the<br />
momentum equation<br />
∂u ∂v<br />
+ = 0 , (9a)<br />
∂x ∂y<br />
�<br />
ε u ∂u<br />
�<br />
∂u ∂u du0<br />
+ v + u0 + v = −∂p1<br />
∂x ∂y ∂x dy ∂x + ε3 ∂2u . (9b)<br />
∂y2 But, now, we have to solve simultaneously (9a–9b) and the core equations (7a–7c). The same<br />
form as Prandtl’s equations is recovered if we let<br />
∂Π<br />
U = u0 + εu , V = εv ,<br />
∂x = −2ε3 + ε ∂p1<br />
, (10)<br />
∂x<br />
leading to<br />
U ∂U ∂U<br />
+ V = −∂Π<br />
∂x ∂y ∂x + ε3 ∂2U . (11)<br />
∂y2 The bo<strong>und</strong>ary conditions are now U = V = 0 on the walls. As four conditions must be satisfied,<br />
it is clear that the pressure gradient must be adjusted in order to ensure the global mass flow<br />
conservation in the channel. Calculations have been performed with a simplified model coming<br />
from the triple deck theory. An example is given in Fig. 1 which gives the evolution <strong>of</strong> the skinfriction<br />
coefficient along the lower and upper walls <strong>of</strong> a channel whose lower wall is deformed.<br />
References<br />
Cf<br />
upper<br />
wall<br />
0,0<br />
2 Re<br />
lower<br />
wall<br />
1.2<br />
1.0<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
R =10 3<br />
x/L<br />
-5 -4 -3 -2 -1 0 1 2 3 4 5<br />
Figure 1: Application <strong>of</strong> GIBL in a channel whose lower wall is deformed<br />
[1] J. Cousteix and J. Mauss. Approximations <strong>of</strong> the Navier-Stokes equations for high Reynolds<br />
number flows past a solid wall. Jour. Comp. and Appl. Math., 166(1):101–122, 2004.<br />
[2] A. Dechaume, J. Cousteix, and J. Mauss. An interactive bo<strong>und</strong>ary layer model compared to<br />
the triple deck theory. Eur. J. <strong>of</strong> Mechanics B/Fluids, 24:439–447, 2005.<br />
[3] S. Saintlos and J. Mauss. Asymptotic modelling for separating bo<strong>und</strong>ary layers in a channel.<br />
Int. J. Engng. Sci., 34(2):201–211, 1996.<br />
[4] F.T. Smith. On the high Reynolds number theory <strong>of</strong> laminar flows. IMA J. Appl. Math.,<br />
28(3):207–281, 1982.<br />
Speaker: MAUSS, J. 117 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
O. MIERKA, D. KUZMIN: On the implementation <strong>of</strong> turbulence models in incompressible<br />
flow solvers based on a finite element discretization<br />
✬<br />
✫<br />
On the implementation <strong>of</strong> turbulence models in incompressible<br />
flow solvers based on a finite element discretization<br />
1. Introduction<br />
O. Mierka and D. Kuzmin<br />
<strong>Institut</strong>e <strong>of</strong> Applied Mathematics (LS III), University <strong>of</strong> Dortm<strong>und</strong><br />
Vogelpothsweg 87, D-44227, Dortm<strong>und</strong>, Germany<br />
omierka@math.uni-dortm<strong>und</strong>.de<br />
kuzmin@math.uni-dortm<strong>und</strong>.de<br />
The numerical implementation <strong>of</strong> turbulence models involves many algorithmic components<br />
all <strong>of</strong> which may have a decisive influence on the quality <strong>of</strong> simulation results. In particular,<br />
a positivity-preserving discretization <strong>of</strong> the troublesome convective terms and nonlinear<br />
sources/sinks is an important prerequisite for the robustness <strong>of</strong> the numerical algorithm. This<br />
paper presents a detailed numerical study <strong>of</strong> several eddy viscosity models implemented in the<br />
open-source s<strong>of</strong>tware package FeatFlow (http://www.featflow.de) using algebraic flux correction<br />
to enforce the positivity constraint. The <strong>und</strong>erlying finite element discretization and<br />
iterative solution techniques are presented and relevant algorithmic details are revealed.<br />
2. Algebraic flux correction schemes<br />
The design <strong>of</strong> high-resolution finite element schemes for numerical simulation <strong>of</strong> turbulent incompressible<br />
flows on the basis <strong>of</strong> eddy viscosity models is addressed. A robust positivity-preserving<br />
algorithm is developed building on the algebraic flux correction paradigm for scalar transport<br />
problems [1]. It is explained how to get rid <strong>of</strong> nonphysical oscillations in the vicinity <strong>of</strong> steep<br />
gradients and to remove excessive artificial diffusion in regions where the solution is sufficiently<br />
smooth. To this end, the discrete operators resulting from a standard Galerkin discretization<br />
<strong>of</strong> convective terms are modified so as to enforce the desired matrix properies without violating<br />
mass conservation.<br />
3. Implementation <strong>of</strong> eddy viscosity models<br />
The developed algebraic flux correction techniques are applied to high Reynolds number flows<br />
that can be described by the incompressible Navier-Stokes equations coupled with an eddy<br />
viscosity model <strong>of</strong> turbulence. A global Multilevel Pressure Schur Complement (discrete projection)<br />
method is employed to enforce the incompressibility constraint at the discrete level [2].<br />
The turbulent eddy viscosity is introduced in several different ways using<br />
• the RANS approach as represented by various modifications <strong>of</strong> the k − ε model;<br />
• Large Eddy Simulation (LES) with explicit and implicit subgrid scale modelling.<br />
In particular, the advantages <strong>of</strong> Monotonically Integrated LES algorithms as compared to explicit<br />
subgrid scale models <strong>of</strong> Smagorinsky type are explored. The implementation <strong>of</strong> the standard k−ε<br />
model is based on a block-iterative algorithm featuring a positivity-preserving representation <strong>of</strong><br />
sink terms [2]. The main highlight <strong>of</strong> the present paper is a unified solution strategy for strongly<br />
coupled PDE systems which result from 2D/3D finite element discretizations <strong>of</strong> RANS and<br />
LES models on unstructured meshes. Special emphasis is laid on the near wall treatment and<br />
Speaker: MIERKA, O. 118 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
O. MIERKA, D. KUZMIN: On the implementation <strong>of</strong> turbulence models in incompressible<br />
flow solvers based on a finite element discretization<br />
✬<br />
✫<br />
implementation <strong>of</strong> initial/bo<strong>und</strong>ary conditions. A set <strong>of</strong> representative benchmark problems is<br />
employed to evaluate the performance <strong>of</strong> the turbulence models <strong>und</strong>er consideration as applied<br />
to incompressible flows at high Reynolds numbers.<br />
4. Numerical examples<br />
The first example deals with a 3D simulation <strong>of</strong> the turbulent incompressible flow past a backward<br />
facing step (Re = 44,000) using the standard k −ε model with logarithmic wall functions.<br />
The numerical solutions displayed in Figure 1 are in a good agreement with those published in<br />
the literature [3].<br />
Figure 1: Backward facing step simulation results (Re = 44,000). Contour lines <strong>of</strong> a),b) -<br />
turbulent kinetic energy; c),d) - turbulent eddy viscosity. a),c) - reference solution [3].<br />
A preliminary code validation for Chien’s low-Reynolds number modification was performed<br />
for a simple channel flow at Re = 13,750 and compared with Kim’s [4] DNS data in Figure 2.<br />
Numerical experiments using both versions <strong>of</strong> the k −ε model as well as Large Eddy Simulation<br />
with explicit and implicit subgrid scale modelling are currently <strong>und</strong>er way. The results <strong>of</strong> an<br />
in-depth comparative study will be reported at the Conference.<br />
Figure 2: Channel flow simulation results (Re = 13,750) compared with reference data [4].<br />
References<br />
[1] D. Kuzmin and M. Möller, Algebraic flux correction I. Scalar conservation laws. In: D.<br />
Kuzmin, R. Löhner and S. Turek (eds.) Flux-Corrected Transport: Principles, Algorithms,<br />
and Applications. Springer, 2005, 155-206.<br />
[2] S. Turek and D. Kuzmin, Algebraic flux correction III. Incompressible flow problems. In: D.<br />
Kuzmin, R. Löhner and S. Turek (eds.) Flux-Corrected Transport: Principles, Algorithms,<br />
and Applications. Springer, 2005, 251-296.<br />
[3] F. Ilinca, J.-F. Hétu and D. Pelletier, A Unified Finite Element Algorithm for Two-Equation<br />
Models <strong>of</strong> Turbulence. Comp. & Fluids 27-3 (1998) 291–310.<br />
[4] J. Kim, P. Moin and R. D. Moser, Turbulence statistics in fully developed channel flow at<br />
low Reynolds number. J. Fluid Mech. 177 (1987) 133–166.<br />
2<br />
Speaker: MIERKA, O. 119 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
K. MORINISHI: Rarefied Gas Bo<strong>und</strong>ary Layer Predicted with Continuum and Kinetic<br />
Approaches<br />
✬<br />
✫<br />
Ê�Ö�¬�� ��× �ÓÙÒ��ÖÝ Ä�Ý�Ö<br />
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ÃÝÓØÓ ÁÒ×Ø�ØÙØ� Ó� Ì� �ÒÓÐÓ�Ý<br />
Å�Ø×Ù��×��� Ë��ÝÓ �Ù ÃÝÓØÓ � � ���� Â�Ô�Ò<br />
�� � ��� � � � ���� � ��� � �<br />
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Ì�� ×� ÓÒ� �Ü�ÑÔÐ� �× � ×ÙÔ�Ö×ÓÒ� ÓÛ ÓÚ�Ö � �Ö ÙÐ�Ö ÝÐ�Ò��Ö �Ø � �Ö�� ×ØÖ��Ñ Å� �ÒÙÑ<br />
��Ö Ó� � �Ò� � ÃÒÙ�×�Ò ÒÙÑ��ÖÓ� � ���ÙÖ�× �Ò� ×�ÓÛ Ø�� ÓÑÔ�Ö�×ÓÒ Ó� Ø�Ò��ÒØ��Ð<br />
Ú�ÐÓ �ØÝ ��×ØÖ��ÙØ�ÓÒ �ÐÓÒ� Ø�� ÒÓÖÑ�Ð Ð�Ò�× �ÖÓÑ Ø�� ÝÐ�Ò��Ö ×ÙÖ�� � �Ø � � ��� �Ò�� � ��<br />
Ö�×Ô� Ø�Ú�ÐÝ Ì��Æ�Ú��Ö ËØÓ��× ÔÖ��� Ø�ÓÒ �× �Ò �ÓÓ� ��Ö��Ñ�ÒØ Û�Ø� Ø�� ��Ò�Ø� ÔÖ��� Ø�ÓÒ× �Ø<br />
Speaker: MORINISHI, K. 120 <strong>BAIL</strong> <strong>2006</strong><br />
Ì<br />
Ò<br />
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Ì<br />
×<br />
✩<br />
✪
K. MORINISHI: Rarefied Gas Bo<strong>und</strong>ary Layer Predicted with Continuum and Kinetic<br />
Approaches<br />
✬<br />
y<br />
__<br />
H<br />
0.20<br />
0.15<br />
0.10<br />
0.05<br />
Mw=0.2 , Kn=0.1<br />
Kinetic<br />
DSMC<br />
NS-Slip<br />
0.00<br />
0.00 0.05 0.10<br />
u / Uw<br />
0.15 0.20<br />
���ÙÖ� � �ÓÑÔ�Ö�×ÓÒ Ó� Ø�� Ú�ÐÓ �ØÝ ��×ØÖ�<br />
�ÙØ�ÓÒ �ÓÖ � ÔÐ�Ò� �ÓÙ�ØØ� ÓÛ<br />
y<br />
__<br />
D<br />
1.00<br />
0.75<br />
0.50<br />
0.25<br />
q = 90<br />
Kinetic<br />
DSMC<br />
NS-Slip<br />
0.00<br />
0.0 0.2 0.4<br />
u / U<br />
0.6 0.8<br />
���ÙÖ� � �ÓÑÔ�Ö�×ÓÒ Ó� Ø�Ò��ÒØ��Ð Ú�ÐÓ �ØÝ<br />
��×ØÖ��ÙØ�ÓÒ �Ø � � ��<br />
y<br />
__<br />
D<br />
1.00<br />
0.75<br />
0.50<br />
0.25<br />
q = 45<br />
Kinetic<br />
DSMC<br />
NS-Slip<br />
0.00<br />
0.0 0.2 0.4<br />
u / U<br />
0.6 0.8<br />
���ÙÖ� � �ÓÑÔ�Ö�×ÓÒ Ó� Ø�Ò��ÒØ��Ð Ú�ÐÓ �ØÝ<br />
��×ØÖ��ÙØ�ÓÒ �Ø � � ���<br />
Kinetic<br />
NS-Slip<br />
2.0<br />
2.0<br />
���ÙÖ� �� �ÓÑÔ�Ö�×ÓÒ Ó� Ø�ÑÔ�Ö�ØÙÖ� ÓÒ<br />
ØÓÙÖ×<br />
� � ��� Û��Ð� ×ÓÑ� ��× Ö�Ô�Ò Ý �× Ó�×�ÖÚ�� �Ø � � �� ���ÙÖ� � ÔÐÓØØ�� Ø�� Ø�ÑÔ�Ö�ØÙÖ�<br />
ÓÒØÓÙÖ× �ÖÓÙÒ� Ø�� �Ö ÙÐ�Ö ÝÐ�Ò��Ö Ì�� Ö�×ÙÐØ× Ó� Ø�� Æ�Ú��Ö ËØÓ��× �ÕÙ�Ø�ÓÒ× Û�Ø� Ø�� Ú�<br />
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�ÓÐØÞÑ�ÒÒ �ÕÙ�Ø�ÓÒ �Ò Ø�� �ÖÓÒØ Ö���ÓÒ �Ò ÐÙ��Ò� Ø�� ÔÓ×�Ø�ÓÒ Ó� �ÓÛ ×�Ó � Û��Ð� ��× Ö�Ô�Ò Ý<br />
�× Ó�×�ÖÚ�� �Ò Ø�� Û��� Ì�� ��Ò×�ØÝ �Ò Ø�� Û��� �×ÐÓÛ�Ö Ø��Ò Ø�� �Ö�� ×ØÖ��Ñ ��Ò×�ØÝ Ì��×<br />
Ð�Ö�� Ö�Ö��� Ø�ÓÒ �«� Ø Ð���× Ø�� Æ�Ú��Ö ËØÓ��× �ÕÙ�Ø�ÓÒ× ØÓ ���Ð ØÓ ÔÖ��� Ø Ø�� Û��� ÓÛ ¬�Ð�<br />
�ÙÐÐ ��× Ö�ÔØ�ÓÒ Ó� Ø�� ÒÙÑ�Ö� �Ð Ñ�Ø�Ó�× �Ò� �ÙÖØ��Ö ÒÙÑ�Ö� �Ð Ö�×ÙÐØ× ��ÓÙØ ×Ù�×ÓÒ� �Ò�<br />
×ÙÔ�Ö×ÓÒ� ÓÛ× �Ò ×Ð�Ô �Ò� ØÖ�Ò×�Ø�ÓÒ�Ð Ö���Ñ�× Û�ÐÐ �� ÔÖ�×�ÒØ�� �Ò Ø�� ¬Ò�Ð Ô�Ô�Ö<br />
✫<br />
Ê���Ö�Ò �×<br />
� ℄ ��Ö� � � ÅÓÐ� ÙÐ�Ö ��× �ÝÒ�Ñ� × ÇÜ�ÓÖ� ÍÒ�Ú�Ö×�ØÝ ÈÖ�×× ���<br />
� ℄ ��Ò Â �ÓÝ� Á � �Ò� ��� � È �ÓÑÔÙØ�Ø�ÓÒ Ó� Ê�Ö�¬�� ��× �ÐÓÛ× �ÖÓÙÒ� � Æ���<br />
��Ö�Ó�Ð �Á�� ÂÓÙÖÒ�Ð � � � � � �<br />
� ℄ ÅÓÖ�Ò�×�� à �Ò� Ç�Ù �� À � �ÓÑÔÙØ�Ø�ÓÒ�Ð Å�Ø�Ó� �Ò� ÁØ× �ÔÔÐ� �Ø�ÓÒ ØÓ �Ò�ÐÝ×�×<br />
Ó� Ê�Ö�¬�� ��× �ÐÓÛ× ÈÖÓ �Ø� ÁÒØ�ÖÒ�Ø�ÓÒ�Ð ËÝÑÔÓ×�ÙÑ ÓÒ Ê�Ö�¬�� ��× �ÝÒ�Ñ� ×<br />
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Speaker: MORINISHI, K. 121 <strong>BAIL</strong> <strong>2006</strong><br />
1.6<br />
1.6<br />
2.0<br />
1.2<br />
1.2<br />
1.6<br />
1.6<br />
1.2<br />
1.2<br />
✩<br />
✪
A. NASTASE: Qualitative Analysis <strong>of</strong> the Navier-Stokes Solutions in Vicinity <strong>of</strong> their<br />
Critical Lines<br />
✬<br />
✫<br />
QUALITATIVE ANALYSIS OF NAVIER-STOKES SOLUTIONS<br />
IN VICINITY OF THEIR CRITICAL LINES<br />
by Adriana Nastase<br />
Aerodynamik des Fluges, RWTH-Aachen, Germany<br />
Fax: 0049/241/809-2173, E-Mail: nastase@lafaero.rwth-aachen.de<br />
Own developed, zonal, spectral solutions for the compressible stationary<br />
Navier-Stokes layer (NSL) over flattened flying configurations (FCs), are here<br />
proposed. A new spectral coordinate η was introduced in the NSL :<br />
η = x3 − Z(x1, x2)<br />
(0 ≤ η ≤ 1) (1)<br />
δ(x1, x2)<br />
and the dimensionless axial, lateral and vertical velocities uδ, vδ and wδ, the<br />
density function R = lnρ and the absolute temperature T on the upper NSL<br />
(which is here only considered) are expressed in the following spectral forms,<br />
as in [1], [2], namely :<br />
N�<br />
ui η i<br />
N�<br />
vi η i<br />
N�<br />
wi η i<br />
,<br />
uδ = ue<br />
i=1<br />
, vδ = ve<br />
i=1<br />
N�<br />
R = Rw + (Re − Rw)<br />
i=1<br />
ri η i<br />
, wδ = we<br />
i=1<br />
N�<br />
, T = Tw + (Te − Tw)<br />
i=1<br />
ti η i<br />
. (2a-e)<br />
Hereby ue, ve, we, Re and Te are the edge values, which can be obtained<br />
from the outer potential flow, Rw and Tw are the given values <strong>of</strong> R and T on<br />
the wall <strong>of</strong> the FC and ui, vi, wi, ri and ti are the unknown spectral coefficients<br />
<strong>of</strong> the velocity’s components, which are used to fulfill the partial differential<br />
equations (PDEs) <strong>of</strong> the NSL. The first and the second derivatives <strong>of</strong> the velocity’s<br />
components uδ, vδ, wδ are linear functions versus the spectral coefficients<br />
ui, vi, wi <strong>of</strong> the velocity’s components.<br />
The impulse equations <strong>of</strong> the NSL, which are PDEs <strong>of</strong> second order, are<br />
now considered. If the spectral forms <strong>of</strong> the velocity’s components uδ, vδ and<br />
wδ are used, the impulse equations are reduced to three equivalent quadratical<br />
algebraic equations (QAEs) with slightly variable coefficients, versus the spectral<br />
coefficients ui, vi and wi, as in [1], [2]. In these equations the free terms<br />
are proportional to the gradients <strong>of</strong> the pressure p in the direction <strong>of</strong> the axis<br />
<strong>of</strong> coordinates O xi and, therefore, these terms have greater variations than<br />
the other coefficients <strong>of</strong> these equations. The influence <strong>of</strong> the variation <strong>of</strong> free<br />
terms and <strong>of</strong> one <strong>of</strong> coefficients <strong>of</strong> the linear term <strong>of</strong> the QAE over the existence<br />
<strong>of</strong> real values <strong>of</strong> the spectral coefficients and the performing <strong>of</strong> the qualitative<br />
analysis <strong>of</strong> the asymptotical behaviours <strong>of</strong> the three-dimensional PDEs <strong>of</strong> the<br />
compressible NSLs in the vicinity <strong>of</strong> their singular points and lines, are treated<br />
here by using the qualitative analysis <strong>of</strong> the equivalent QAEs.<br />
The visualizations <strong>of</strong> asymptotical behaviours <strong>of</strong> these equivalent QAEs are<br />
made in a here introduced ”Euclidian M-orthogonal space <strong>of</strong> the NSL’s free<br />
spectral coefficients”, which are here treated as variables.<br />
Further the assumption is made that all QAEs <strong>of</strong> the same type (elliptical<br />
Speaker: NASTASE, A. 122 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
A. NASTASE: Qualitative Analysis <strong>of</strong> the Navier-Stokes Solutions in Vicinity <strong>of</strong> their<br />
Critical Lines<br />
✬<br />
✫<br />
or hyperbolical), <strong>of</strong> the same size (same space dimension M), with the same<br />
number <strong>of</strong> positive eigenvalues, for which the free terms a are varied from<br />
−∞ to +∞ and all the other coefficients are maintained constant, have, in the<br />
vicinity <strong>of</strong> their singular points, qualitatively, similar asymptotical behaviours.<br />
The visualizations <strong>of</strong> the asymptotical behaviours <strong>of</strong> elliptical and hyperbolical<br />
QAEs with variable coefficients, are made versus their principal coordinates.<br />
Their critical points and lines are obtained by cancelling <strong>of</strong> their great<br />
determinants ∆i.<br />
The visualization <strong>of</strong> elliptical QAEs with variable free coefficients is represented,<br />
in two-dimensional cuts, in form <strong>of</strong> coaxial ellipses, which collapse, if<br />
the free term a is equal to the critical value ac , which is located in the common<br />
center C <strong>of</strong> the coaxial ellipses. If a < ac , the visualization <strong>of</strong> the elliptical<br />
QAEs in two-dimensional cuts are coaxial ellipses, which all approach the critical<br />
point a = ac , when the free term increases. If a = ac , the elliptical QAEs<br />
collapse in this critical point (black point). If a > ac , the elliptical QAEs have<br />
no more real solutions and the spectral velocity’s components are partially or<br />
totally imaginary for each value <strong>of</strong> M.<br />
The visualization <strong>of</strong> the hyperbolical QAEs in the vicinity <strong>of</strong> their critical<br />
point (b = bc) is totally different. If their free coefficients b < bc , the<br />
two-dimensional cuts are coaxial hyperbolas with two branches (for M = 2),<br />
which approach their common asymptotes, if b increases. Up M ≥ 3 break<br />
and rebreak <strong>of</strong> hyperhyperboloids occur. The two-dimensional cuts in hyperboloids<br />
(M = 3) or hyperhyperboloids (M > 3) are coaxial hyperbolas<br />
with two sheets or coaxial ellipses, because the hyperboloids and hyperhyperboloids<br />
can be with one or two sheets. If b = bc , the two-dimensional cuts in<br />
the hyperhyperboloids degenerate in their asymptotical lines. If b > bc , the<br />
two-dimensional cuts are coaxial hyperbolas with two sheets, which are jumping<br />
in the opposite double angles <strong>of</strong> their asymptotical lines or coaxial ellipses,<br />
which are approaching their critical point, located in their common center.<br />
The asymptotical behaviours <strong>of</strong> the elliptical and hyperbolical QAEs with<br />
variable values <strong>of</strong> the coefficients <strong>of</strong> their free terms and <strong>of</strong> one <strong>of</strong> their linear<br />
terms in the vicinity <strong>of</strong> their critical parabolas are also very different.<br />
The elliptical QAEs (for M = 2) are visualized in form <strong>of</strong> coaxial ellipses,<br />
which collapse in each point <strong>of</strong> their critical parabola and, inside this parabola,<br />
there are no more real solutions. A black parabolic hole occurs.<br />
The hyperbolic QAEs (for M = 2) degenerate in their asymptotes, in each<br />
point <strong>of</strong> their critical parabola. By crossing <strong>of</strong> this parabola, the hyperbolas<br />
approach their asymptotes in one <strong>of</strong> their double angles and, after jumping,<br />
they are going away from these asymptotes.<br />
The collapse points and lines <strong>of</strong> the elliptical QAE are useful for the determination<br />
<strong>of</strong> the position <strong>of</strong> detachment lines and for the beginning <strong>of</strong> transition.<br />
The saddle points and lines <strong>of</strong> the hyperbolical QAE are useful for the determination<br />
<strong>of</strong> the position <strong>of</strong> characteristic and shock surfaces and for the<br />
bifurcation.<br />
REFERENCES<br />
1. NASTASE, A., New Zonal, Spectral Solutions for the Navier-Stokes Partial Differential<br />
Equations, Proc. <strong>of</strong> the International Conference on Bo<strong>und</strong>ary and<br />
Interior Layers, ONERA Toulouse, 2004, France.<br />
2. NASTASE, A., Zonal, Spectral Solutions for Navier-Stokes Layer and Applications,<br />
4th European Congress on Computational Methods in Applied Sciences<br />
and Engineering (ECCOMAS), Jyvskyl, 2004, Finland.<br />
Speaker: NASTASE, A. 123 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
F. NATAF, G. RAPIN: Application <strong>of</strong> the Smith Factorization to Domain Decomposition<br />
Methods for the Stokes equations<br />
✬<br />
✫<br />
Application <strong>of</strong> the Smith Factorization to Domain<br />
Decomposition Methods for the Stokes Equations<br />
FRÉDÉRIC NATAF, GERD RAPIN<br />
Laboratoire J. L. Lions, Université Pierre et Marie Curie, 75252 Paris Cedex 05,<br />
France; nataf@ann.jussieu.fr<br />
Math. Dep., NAM, University <strong>of</strong> Göttingen, D-37083, Germany;<br />
grapin@math.uni-goettingen.de<br />
In this talk the Smith factorization is used systematically to derive a new domain decomposition<br />
method for the Stokes problem. In two dimensions the key idea is the<br />
transformation <strong>of</strong> the Stokes problem into a scalar bi-harmonic problem. We show,<br />
how a proposed domain decomposition method for the bi-harmonic problem leads to<br />
a domain decomposition method for the Stokes equations which inherits the convergence<br />
behavior <strong>of</strong> the scalar problem. Thus, it is sufficient to study the convergence <strong>of</strong><br />
the scalar algorithm. The same procedure can also be applied to the three dimensional<br />
Stokes problem.<br />
As transmission conditions for the resulting domain decomposition method <strong>of</strong> the<br />
Stokes problem we obtain natural bo<strong>und</strong>ary conditions. Therefore it can be implemented<br />
easily.<br />
A Fourier analysis and some numerical experiments show very fast convergence <strong>of</strong><br />
the proposed algorithm. Our algorithm shows a more robust behavior than Neumann-<br />
Neumann or FETI type methods.<br />
The last decade has shown, that Neumann-Neumann type algorithms, FETI, and<br />
BDDC methods are very efficient domain decomposition methods. Most <strong>of</strong> the early<br />
theoretical and numerical work has been carried out for scalar symmetric positive definite<br />
second order problems, see for example [8, 5]. Then, the method was extended<br />
to different other problems, like the advection-diffusion equations [1], plate and shell<br />
problems [12] or the Stokes equations [10, 11].<br />
In the literature one can also find other preconditioners for the Schur complement<br />
<strong>of</strong> the Stokes equations (cf. [11, 2]). A more complete list <strong>of</strong> domain decomposition<br />
methods for the Stokes equations can be fo<strong>und</strong> in [10, 13]. Also FETI [6] and BDDC<br />
methods [7] have been applied to the Stokes problem with success.<br />
Our work is motivated by the fact that in some sense the domain decomposition<br />
methods for Stokes are less optimal than the domain decompoition methods for scalar<br />
problems. Indeed, in the case <strong>of</strong> two subdomains consisting <strong>of</strong> the two half planes it<br />
is well known, that the Neumann-Neumann preconditioner is an exact preconditioner<br />
for the Schur complement equation for scalar equations like the Laplace problem (cf.<br />
[8]). A preconditioner is called exact, if the preconditioned operator simplifies to the<br />
identity. Unfortunately, this does not hold in the vector case. It is shown in [9] that the<br />
standard Neumann-Neumann preconditioner for the Stokes equations does not possess<br />
this property.<br />
Our aim in this talk is the construction <strong>of</strong> a method, which preserves this property.<br />
Thus, one can expect a very fast convergence for such an algorithm. And indeed, the<br />
numerical results clearly support our approach. In this talk the ideas <strong>of</strong> [4] are extended<br />
Speaker: RAPIN, G. 124 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
F. NATAF, G. RAPIN: Application <strong>of</strong> the Smith Factorization to Domain Decomposition<br />
Methods for the Stokes equations<br />
✬<br />
✫<br />
in several directions. We also give some hints how this approach can be applied to the<br />
Oseen equations. For an application to the compressible Euler equations see [3].<br />
References<br />
[1] Y. Achdou, P. Le Tallec, F. Nataf, and M. Vidrascu. A domain decomposition<br />
preconditioner for an advection-diffusion problem. Comput. Methods Appl. Mech.<br />
Engrg, 184:145–170, 2000.<br />
[2] M. Ainsworth and S. Sherwin. Domain decomposition preconditioners for p and<br />
hp finite element approximations <strong>of</strong> Stokes equations. Comput. Methods Appl.<br />
Mech. Engrg., 175:243–266, 1999.<br />
[3] V. Dolean and F. Nataf. A New Domain Decomposition Method for the Compressible<br />
Euler Equations. M 2 AN, 2005. accepted.<br />
[4] V. Dolean, F. Nataf, and G. Rapin. New constructions <strong>of</strong> domain decomposition<br />
methods for systems <strong>of</strong> PDEs. C.R. Acad. Sci. Paris, Ser I, 340:693–696, 2005.<br />
[5] Ch. Farhat and F.-X. Roux. A Method <strong>of</strong> Finite Element Tearing and Interconnecting<br />
and its Parallel Solution Algorithm. Internat. J. Numer. Methods Engrg.,<br />
32:1205–1227, 1991.<br />
[6] J. Li. A Dual-Primal FETI method for incompressible Stokes equations. Numer.<br />
Math., 102:257–275, 2005.<br />
[7] J. Li and O. Widl<strong>und</strong>. BDDC algorithms for incompressible Stokes equations,<br />
<strong>2006</strong>. submitted.<br />
[8] J. Mandel. Balancing domain decomposition. Comm. on Applied Numerical<br />
Methods, 9:233–241, 1992.<br />
[9] F. Nataf and G. Rapin. Construction <strong>of</strong> a New Domain Decomposition Method<br />
for the Stokes Equations, 2005. Submitted to the Proceedings <strong>of</strong> DD16.<br />
[10] L.F. Pavarino and O.B. Widl<strong>und</strong>. Balancing neumann-neumann methods for incompressible<br />
stokes equations. Comm. Pure Appl. Math., 55:302–335, 2002.<br />
[11] P . Le Tallec and A. Patra. Non-overlapping domain decomposition methods for<br />
adaptive hp approximations <strong>of</strong> the Stokes problem with discontinuous pressure<br />
fields. Comput. Methods Appl. Mech. Engrg., 145:361–379, 1997.<br />
[12] P. Le Tallec, J. Mandel, and M. Vidrascu. A Neumann-Neumann Domain Decomposition<br />
Algorithm for Solving Plate and Shell Problems. SIAM J. Numer.<br />
Anal., 35:836–867, 1998.<br />
[13] A. Toselli and O. Widl<strong>und</strong>. Domain Decomposition Methods - Algorithms and<br />
Theory. Springer, Berlin-Heidelberg, 2005.<br />
Speaker: RAPIN, G. 125 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
N. NEUSS: Numerical approximation <strong>of</strong> bo<strong>und</strong>ary layers for rough bo<strong>und</strong>aries<br />
✬<br />
✫<br />
Numerical approximation <strong>of</strong> bo<strong>und</strong>ary layers<br />
for rough bo<strong>und</strong>aries<br />
N. Neuss<br />
April 5, <strong>2006</strong><br />
In physical problems, interesting phenomena <strong>of</strong>ten occur at bo<strong>und</strong>aries or<br />
interfaces between different media. Often these phenomena are complicated<br />
due to the nature <strong>of</strong> the process or due to the intricate geometry <strong>of</strong> the<br />
interface. Therefore, they are usually described by effective bo<strong>und</strong>ary or<br />
interface laws.<br />
In this talk we will discuss some instructive cases in a quasi-periodic<br />
setting, where the constants in those effective conditions can be calculated<br />
from the microscopic setting.<br />
First, we consider the Poisson problem<br />
−∆u ε = f, x ∈ Ω ε<br />
u ε = 0, x ∈ ∂Ω ε<br />
where Ω ε is a domain with a bo<strong>und</strong>ary ∂Ω ε featuring a micro-structure <strong>of</strong> size<br />
ε. A good approximation to u ε is given by the solution u eff to the problem<br />
−∆u eff = f, x ∈ Ω<br />
u eff = c(x) ∂ueff<br />
∂n<br />
, x ∈ ∂Ω<br />
where Ω is an approximating domain with smooth bo<strong>und</strong>ary ∂Ω and the<br />
function c : ∂Ω → R can be computed solving auxiliary problems taking into<br />
account the fine-scale structure <strong>of</strong> ∂Ω ε , see [?].<br />
Similarly, solving the Navier-Stokes equation in such a domain Ω ε can be<br />
replaced by solving it on Ω with a Navier bo<strong>und</strong>ary condition. Related to this<br />
is the Beavers-Joseph problem, where one can derive an effective interface<br />
law for a rough interface between free flow and porous medium flow, see [?].<br />
Speaker: NEUSS, N. 126 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
N. NEUSS: Numerical approximation <strong>of</strong> bo<strong>und</strong>ary layers for rough bo<strong>und</strong>aries<br />
✬<br />
✫<br />
Finally, the same idea can be used to obtain effective bo<strong>und</strong>ary conditions<br />
for numerical approximations Ωh <strong>of</strong> arbitrary domains Ω. This allows us to<br />
obtain good O(h 2 ) approximation errors although the domain Ωh only needs<br />
to approximate Ω up to order O(h).<br />
References<br />
[1] W. Jäger, A. Mikelić, N. Neuss: Asymptotic Analysis <strong>of</strong> the Laminar<br />
Viscous Flow Over a Porous Bed. SIAM J. Sci. Comp. 22,6, pp. <strong>2006</strong>-<br />
2028 (2001).<br />
[2] N. Neuss, M. Neuss-Radu, A. Mikelić: Effective Laws for the Poisson<br />
Equation on Domains with Curved Oscillating Bo<strong>und</strong>aries. To appear in<br />
Applicable Analysis.<br />
Speaker: NEUSS, N. 127 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
M.A. OLSHANSKII: An Augmented Lagrangian based solver for the low-viscosity<br />
incompressible flows<br />
✬<br />
✫<br />
An Augmented Lagrangian based solver for the low-viscosity<br />
incompressible flows<br />
Maxim A. Olshanskii ∗<br />
We describe an effective solver for the finite element discretization <strong>of</strong> the Oseen problem<br />
−ν∆u + (w · ∇) u + ∇p = f in Ω (1)<br />
div u = 0 in Ω (2)<br />
u = g on ∂Ω (3)<br />
with a known, divergence-free vector function w. Discretization <strong>of</strong> (1)–(3) using LBB-stable<br />
finite elements is based on the following stabilized finite element formulation<br />
L(uh, ph; vh, qh) + �<br />
στ (−ν∆uh + w·∇uh + ∇ph − f, w·∇vh)τ<br />
with<br />
τ∈Th<br />
= (f, vh) ∀ vh ∈ Vh, qh ∈ Qh (4)<br />
L(u, p; v, q) = ν(∇u, ∇v) + ((w · ∇) u, v) − (p, div v) + (q, div u)<br />
and a suitable choice <strong>of</strong> the stabilization parameters στ . With certain assumptions finding FE<br />
solution results in solving the linear system <strong>of</strong> the form<br />
� � � � � �<br />
A BT u f<br />
= . (5)<br />
B O p 0<br />
Linear systems <strong>of</strong> the form (5) are <strong>of</strong>ten referred to as generalized saddle point systems. In<br />
recent years, a great deal <strong>of</strong> effort has been invested in solving systems <strong>of</strong> this form. Most <strong>of</strong><br />
the work has been aimed at developing effective preconditioning techniques; see [1, 3] for an<br />
extensive survey. In spite <strong>of</strong> these efforts, there is still considerable interest in preconditioning<br />
techniques that are truly robust, i.e., techniques which result in convergence rates that are<br />
largely independent <strong>of</strong> problem parameters such as mesh size and viscosity. In this paper we<br />
describe a promising approach based on an augmented Lagrangian formulation [4]:<br />
� A + γB T W −1 B B T<br />
B O<br />
� � u<br />
p<br />
with a positive-definite matrix W and parameter γ > 0. The system (6) has precisely the same<br />
solution as the original one (5). Rather than treating (5), a block-triangular preconditioner is<br />
constructed for solving (6) with a Krylov subspace iterative method.<br />
The success <strong>of</strong> this method crucially depends on the availability <strong>of</strong> a robust multigrid solver<br />
for the (1,1) block (submatrix) in (6); we develop such a method by building on previous work<br />
by Schöberl [5], together with appropriate smoothers for convection-dominated flows. This<br />
multigrid iteration will be used to define a block preconditioner for the outer iteration on the<br />
∗ Department <strong>of</strong> Mechanics and Mathematics, Moscow State M. V. Lomonosov University, Moscow 119899,<br />
Russia (Maxim.Olshanskii@mtu-net.ru). The work was supported in part by the Russian Fo<strong>und</strong>ation for Basic<br />
Research and the Netherlands Organization for Scientific Research grants NWO-RFBR 047.016.008<br />
Speaker: OLSHANSKII, M.A. 128 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
�<br />
=<br />
� f<br />
0<br />
�<br />
(6)<br />
✩<br />
✪
M.A. OLSHANSKII: An Augmented Lagrangian based solver for the low-viscosity<br />
incompressible flows<br />
✬<br />
✫<br />
coupled saddle point system. We will show that this approach is especially appropriate for<br />
discretizations based on discontinuous pressure approximations, but can be used to construct<br />
preconditioners for other discretizations using continuous pressures. As an example <strong>of</strong> finite<br />
element (FE) method with discontinuous pressures we will use the isoP2-P0 pair. In this case,<br />
our numerical experiments demonstrate a robust behavior <strong>of</strong> the solver with respect to h and<br />
ν for some typical wind vector functions w in (1). Further, the isoP2-P1 finite element pair<br />
is used for the continuous pressure-based approximation. For this case numerical experiments<br />
show an h-independent convergence rates with mild dependence on ν, when the viscosity becomes<br />
very small. We note that this approach does not require a sophisticated preconditioner for the<br />
pressure Schur complement <strong>of</strong> (5) or (6).<br />
Some spectral estimates for the preconditioned problem are shown; basic components for<br />
building appropriate multigrid method are discussed. The role <strong>of</strong> parameter γ in (6) is addressed.<br />
We also present a comparison with one <strong>of</strong> the best available preconditioning techniques and<br />
coupled multigrid methods (Vanka multigrid), showing that our method is quite competitive in<br />
terms <strong>of</strong> convergence rates, robustness, and efficiency. Finally we discuss that using SUPG type<br />
stabilization in finite element formulation (4) is vital not only for capturing effects <strong>of</strong> unresolved<br />
subscales in solution to (1)–(3), thus improving accuracy <strong>of</strong> the discrete solution, but also for<br />
developing robust and effective iterative methods.<br />
This presentation is based on the collaborative research with M.Benzi [2].<br />
References<br />
[1] M. Benzi, G. H. Golub and J. Liesen, Numerical solution <strong>of</strong> saddle point problems, Acta<br />
Numerica, 14 (2005), pp. 1–137.<br />
[2] M. Benzi, M.A. Olshanskii, An augmented lagrangian-based approach to the Oseen problem,<br />
(submitted), available at www.mathcs.emory.edu/~molshan<br />
[3] H. C. Elman, D. J. Silvester and A. J. Wathen, Finite Elements and Fast Iterative Solvers:<br />
with Applications in Incompressible Fluid Dynamics, Numerical Mathematics and Scientific<br />
Computation, Oxford University Press, Oxford, UK, 2005.<br />
[4] M. Fortin and R. Glowinski, Augmented Lagrangian Methods: Applications to the Numerical<br />
Solution <strong>of</strong> Bo<strong>und</strong>ary-Value Problems, Studies in Mathematics and its Applications,<br />
Vol. 15, North-Holland, Amsterdam/New York/Oxford, 1983.<br />
[5] J. Schöberl, Multigrid methods for a parameter dependent problem in primal variables,<br />
Numer. Math., 84 (1999), pp. 97–119.<br />
2<br />
Speaker: OLSHANSKII, M.A. 129 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
N. PARUMASUR, J. BANASIAK, J.M. KOZAKIEWICZ: Numerical and Asymptotic<br />
Analysis <strong>of</strong> Singularly Perturbed PDEs <strong>of</strong> Kinetic Theory<br />
✬<br />
✫<br />
Numerical and Asymptotic Analysis <strong>of</strong> Singularly Perturbed PDEs <strong>of</strong><br />
Kinetic Theory<br />
N. Parumasur, J. Banasiak and J.M. Kozakiewicz<br />
University <strong>of</strong> KwaZulu-Natal, Durban, 4041, South Africa parumasurn1@ukzn.ac.za<br />
We consider the numerical solution <strong>of</strong> various equations occurring in kinetic theory. The<br />
numerical algorithm is applied in conjuction with a modified asymptotic procedure. Various<br />
mathematical derivations and numerical algorithms are provided for the following singularly<br />
perturbed models <strong>of</strong> kinetic theory<br />
∂tu + Au + Su + 1<br />
Cu = 0 (1)<br />
ε<br />
where u is the particle distribution, ∂t is the time derivative and the operators A , S , and C<br />
describe attenuation, streaming and collisions <strong>of</strong> particles, respectively. We begin by outlining<br />
the features <strong>of</strong> a modified asymptotic method [2, 1] which is quite useful when solving (1).<br />
Let P be a bo<strong>und</strong>ed operator in the Banach space X having zero as its simple isolated<br />
eigenvalue and the corresponding eigenspace V . Then X can be expressed as a direct sum<br />
X = V ⊕ W, where both V and W are invariant subspaces <strong>of</strong> the operator C and C is one-to-one<br />
from W onto itself. Let P be the spectral projection associated with the eigenvalue λ = 0 so<br />
that<br />
V = PX, W = QX,<br />
where Q = I − P is the complementary projection. We use a projection method [2] to write (1)<br />
as a system <strong>of</strong> evolution equations in subspaces V and W . Applying the projections P and Q<br />
on both sides <strong>of</strong> (1), successively, we obtain<br />
with the initial conditions<br />
∂tv = P(A + S)Pv + P(A + S)Qw<br />
ε∂tw = εQ(A + S)Qw + εQ(S + A)Pv + QCQw, (2)<br />
v(0) = o v, w(0) = o w,<br />
where o v = P o u, o w = Q o u. Taking into account that the projected operators PSP, PAQ and<br />
QAP vanish for most types <strong>of</strong> linear equations we obtain the following form <strong>of</strong> (2)<br />
∂tv = PAPv + PSQw<br />
ε∂tw = εQSPv + εQSQw + εQAQw + QCQw (3)<br />
v(0) = o v, w(0) = o w,<br />
Next we apply the modified asymptotic approach to (3). We represent the solution <strong>of</strong> (3) as a<br />
sum <strong>of</strong> the bulk and the initial layer parts:<br />
v(t) = ¯v(t) + ˜v(τ), w(t) = ¯w(t) + ˜w(τ), (4)<br />
where the variable τ in the initial layer part is given by τ = t/ε. The bulk solution will be<br />
considered as a function <strong>of</strong> ρ <strong>of</strong> order zero and the function ¯w (N) will be assumed to be <strong>of</strong> the<br />
form<br />
¯w (N) N�<br />
(t) = ε n Wnρ(t), (5)<br />
Speaker: PARUMASUR, N. 130 <strong>BAIL</strong> <strong>2006</strong><br />
n=0<br />
1<br />
✩<br />
✪
N. PARUMASUR, J. BANASIAK, J.M. KOZAKIEWICZ: Numerical and Asymptotic<br />
Analysis <strong>of</strong> Singularly Perturbed PDEs <strong>of</strong> Kinetic Theory<br />
✬<br />
✫<br />
where the superscript N indicates the order <strong>of</strong> the approximation and W are time-independent<br />
bo<strong>und</strong>ed linear operators from V to W . Substituting this expansion into the first equation in<br />
(3) yields<br />
N�<br />
∂tρ = PAPρ + ε n PSQ(Wnρ). (6)<br />
n=0<br />
Expressing the time derivative ∂tρ in (6) in powers <strong>of</strong> ε and comparing terms <strong>of</strong> the same power<br />
in ε yields at first order<br />
W0 = 0, W1 = −(QCQ) −1 QSP. (7)<br />
The operator W1 can be evaluated since QCQ is invertible on the subspace W. Using (7) in (6)<br />
gives the equation<br />
∂tρ = PAPρ − εPSQ(QCQ) −1 QSPρ. (8)<br />
A similar procedure yields the initial layer terms<br />
and the initial condition for (8)<br />
˜v0(τ) ≡ 0, ˜v1(τ) = PSQ(QCQ) −1 e τQCQ o w,<br />
¯v(0) = o v −εPSQ(QCQ) −1 o w . (9)<br />
We apply the procedure to a wide range <strong>of</strong> problems <strong>of</strong> kinetic theory.<br />
References<br />
[1] J. Banasiak, J. Kozakiewicz, N. Parumasur, Diffusion Approximation <strong>of</strong> Linear Kinetic<br />
Equations with Non-equilibrium Data – Computational Experiments, Transport Theory<br />
Statist. Phys. (accepted).<br />
[2] J. R. Mika, New asymptotic expansion algorithm for singularly perturbed evolution equations,<br />
Math. Methods Appl. Sci. 3 (1981) 172-188.<br />
2<br />
Speaker: PARUMASUR, N. 131 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
B. RASUO: On Bo<strong>und</strong>ary Layer Control in Two-Dimensional Transonic Wind Tunnels<br />
✬<br />
✫<br />
Speaker: RASUO, B. 132 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
B. RASUO: On Bo<strong>und</strong>ary Layer Control in Two-Dimensional Transonic Wind Tunnels<br />
✬<br />
✫<br />
Speaker: RASUO, B. 133 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
H.-G. ROOS: A Comparison <strong>of</strong> Stabilization Methods for Convection-Diffusion-<br />
Reaction Problems on Layer-Adapted Meshes<br />
✬<br />
✫<br />
A Comparison <strong>of</strong> Stabilization Methods for Convection-Diffusion-Reaction<br />
Problems on Layer-Adapted Meshes<br />
Hans-G. Roos, TU Dresden<br />
The use <strong>of</strong> layer adapted meshes allows to prove robust convergence results <strong>of</strong> Galerkin finite element<br />
methods for convection-diffusion-reaction problems. However, the robust solution <strong>of</strong> the generated<br />
discrete problems which are in general nonsymmetric is a nontrivial task.<br />
The situation improves if one uses some stabilization. But the question is: which <strong>of</strong> all the existing<br />
stabilization techniques is optimal?<br />
Speaker: ROOS, H.-G. 134 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
H.-G. ROOS, H. ZARIN: Discontinuous Galerkin stabilization for convectiondiffusion<br />
problems<br />
✬<br />
✫<br />
Discontinuous Galerkin stabilization for convection–diffusion<br />
problems<br />
Hans–Görg Roos<br />
<strong>Institut</strong> <strong>für</strong> <strong>Numerische</strong> Mathematik, Technische Universität Dresden,<br />
Germany<br />
Helena Zarin<br />
Department <strong>of</strong> Mathematics and Informatics, University <strong>of</strong> Novi Sad,<br />
Serbia and Montenegro<br />
Abstract. A convection–diffusion problem with Dirichlet bo<strong>und</strong>ary conditions<br />
posed on a unit square is considered. The problem is discretized using a combination<br />
<strong>of</strong> standard Galerkin FEM and h–version <strong>of</strong> the nonsymmetric discontinuous<br />
Galerkin FEM with interior penalties on a layer–adapted mesh. With<br />
specially chosen penalty parameters for edges from the coarse part <strong>of</strong> the mesh,<br />
we prove uniform convergence (in the perturbation parameter) in an associated<br />
norm. Numerical tests support our theoretical results.<br />
References<br />
[1] Roos, H.–G., Zarin, H., The discontinuous Galerkin method for singularly<br />
perturbed problems. Numerical Mathematics and Advanced Applications<br />
(eds. M. Feistauer et al.), Proceedings <strong>of</strong> the ENUMATH Conference 2003<br />
(Prague, August 18-22, 2003), Springer Verlag, 2004, pp. 736–745<br />
[2] Zarin, H., Roos, H.–G., Interior penalty discontinuous approximations <strong>of</strong><br />
convection–diffusion problems with parabolic layers. <strong>Numerische</strong> Mathematik,<br />
100(4), 2005, pp. 735–759<br />
1<br />
Speaker: ZARIN, H. 135 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
B. SCHEICHL, A. KLUWICK: On Turbulent Marginal Separation: How the Logarithmic<br />
Law <strong>of</strong> the Wall is Superseded by the Half-Power Law<br />
✬<br />
✫<br />
Abstract submitted to the Local Organization Committee <strong>of</strong> the <strong>BAIL</strong> <strong>2006</strong> Conference 1<br />
On Turbulent Marginal Separation: How the Logarithmic Law <strong>of</strong> the Wall is<br />
Superseded by the Half-Power Law ∗<br />
B. Scheichl and A. Kluwick<br />
<strong>Institut</strong>e <strong>of</strong> Fluid Mechanics and Heat Transfer<br />
Vienna University <strong>of</strong> Technology<br />
Resselgasse 3/E322, A-1040 Vienna, Austria<br />
bernhard.scheichl@tuwien.ac.at<br />
1. The Asymptotic Theory <strong>of</strong> Marginally Separating Turbulent Bo<strong>und</strong>ary Layers<br />
A novel rational theory <strong>of</strong> the incompressible nominally steady and two-dimensional turbulent<br />
bo<strong>und</strong>ary layer (TBL) along a smooth and impermeable surface and exposed to an adverse<br />
pressure gradient, which is impressed by the prescribed external potential free-stream flow, has<br />
been developed recently by the authors. This asymptotic flow description exploits the Reynoldsaveraged<br />
Navier–Stokes equations by taking the limit Re→∞ where Re denotes a Reynolds<br />
number formed by using a global length and velocity scale characteristic for the external bulk<br />
flow. In the following all quantities are non-dimensional with that global reference scales.<br />
The so-called classical theory, see for instance [1], is capable <strong>of</strong> describing a strictly attached<br />
TBL only as it employs the assumption <strong>of</strong> an asymptotically small streamwise velocity defect<br />
with respect to the external flow in the fully turbulent main part <strong>of</strong> the TBL. The new theory,<br />
however, is an extension <strong>of</strong> the classical approach ins<strong>of</strong>ar as it is essentially based only on the<br />
hypothesis that the turbulent time-mean motion is governed locally by a single velocity scale. As<br />
an important consequence, by taking a streamwise velocity deficit <strong>of</strong> O(1), which is a necessary<br />
characteristic <strong>of</strong> flows that may even <strong>und</strong>ergo marginal separation, the bo<strong>und</strong>ary layer thickness<br />
ismeasuredbyasmallparameterdenotedby αwhichisseentobeindependent<strong>of</strong> Re as Re→∞.<br />
It then can be shown that in the primary limit α→0, Re −1 = 0 the TBL is represented by a<br />
two-tiered wake-type flow; remarkably, it thus closely resembles a turbulent free shear layer. The<br />
description <strong>of</strong> the outer main layer is addressed in [2]. There it is demonstrated analytically and<br />
numerically by adopting a local viscous/inviscid interaction strategy that in the primary limit<br />
considered marginal separation is associated with the occurrence <strong>of</strong> closed reverse-flow regions<br />
where the surface slip velocity Us, which is a quantity <strong>of</strong> O(1) in general, assumes negative<br />
values along a streamwise distance <strong>of</strong> O(α 3/5 ). Here we add that the overall slip velocity at the<br />
base <strong>of</strong> the whole wake region comprising both layers is written as us = Us + O(α 3/4 ), where<br />
the perturbations reflect the effect <strong>of</strong> the inner wake having a thickness <strong>of</strong> O(α 3/2 ).<br />
2. The Near-Wall Flow Regime for Finite Values <strong>of</strong> Re<br />
It is the main purpose <strong>of</strong> our contribution to rigorously elucidate how high but finite values <strong>of</strong><br />
Re affect the near-wall flow regime in order to provide a rational basis for the calculation <strong>of</strong> the<br />
wall shear stress, in particular immediately up- and downstream <strong>of</strong> separation and reattachment.<br />
We note that the investigation <strong>of</strong> the latter flow situation is not only a challenge to settle an,<br />
for the time being, unsolved problem in turbulent bo<strong>und</strong>ary layer theory, which has attracted<br />
many researchers in the past, but also <strong>of</strong> basic engineering relevance, as none <strong>of</strong> the presently<br />
adopted turbulence models are applicable when the wall shear stress changes sign.<br />
In Figure 1 the resulting four-layer TBL structure is depicted where the case <strong>of</strong> the oncoming<br />
firmly attached flow chosen. We start the analysis by focusing on the viscous wall layer adjacent<br />
∗ This research is granted by the Austrian Science F<strong>und</strong> (FWF) <strong>und</strong>er project no. P 16555-N12.<br />
Speaker: SCHEICHL, B. 136 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
B. SCHEICHL, A. KLUWICK: On Turbulent Marginal Separation: How the Logarithmic<br />
Law <strong>of</strong> the Wall is Superseded by the Half-Power Law<br />
✬<br />
PSfrag replacements<br />
✫<br />
Abstract submitted to the Local Organization Committee <strong>of</strong> the <strong>BAIL</strong> <strong>2006</strong> Conference 2<br />
y<br />
OW<br />
y∼ δ = O(α)<br />
y<br />
u∼us<br />
IW α u∼Us<br />
IL VWL<br />
3/2 u = O(√y) u/uτ ∼ κ−1 lny<br />
u<br />
Figure 1: Asymptotic splitting and streamwise velocity<br />
component u <strong>of</strong> the initially attached turbulent bo<strong>und</strong>ary<br />
layer with thickness δ, which evolves along the surface<br />
given by y = 0. The notations OW, IW, IL, and<br />
VWL mark the outer and the inner wake, the intermediate<br />
and the viscous wall layer, respectively. The<br />
asymptotic relationships are explained in the text.<br />
to the surface where convective terms are negligibly small and Reynolds stresses have the same<br />
magnitude as the molecular shear stress. Let y and τw denote, respectively, the coordinate<br />
perpendicular to the surface and the wall shear stress. As far as low-order results and the<br />
attached case τw > 0 are concerned, the asymptotic description <strong>of</strong> the wall layer turns out to be<br />
fully analogous to that in the classical theory. That is, sufficiently far from the positions where<br />
τw vanishes the streamwise velocity component u is expanded in the usual manner according to<br />
u/uτ ∼ u + 0 (y+ )+··· , sgn(τw)uτ =|τw| 1/2 = (|∂u/∂y|y=0/Re) 1/2 , y + = y|uτ|Re = O(1). (1)<br />
Most important, the hypothesis stated above is seen to require the celebrated logarithmic<br />
match with the fully turbulent flow regime on top <strong>of</strong> the viscous wall layer,<br />
u + 0 ∼ A± −1 lny + + B±, A± > 0, y + →∞. (2)<br />
Here the subscripts + and−denote the cases τw > 0 and τw < 0, respectively. Therefore, A+<br />
equals the v. Kármán constant, and the values <strong>of</strong> B± shall refer to a perfectly smooth surface.<br />
Note that for separated flows (τw < 0) an asymptotic behavior akin to (2) was already proposed<br />
in [3] on semi-empirical gro<strong>und</strong>s. Moreover, the velocity components u in the wall layer and the<br />
intermediate layer <strong>of</strong> thickness τw, see Figure 1, match provided that the skin friction law<br />
uτ/us∼ A±ɛ+O(ɛ 2 ), ɛ = 1/ln|u 3 τRe|→0, Re→∞, (3)<br />
holds. This relationship between uτ and the aforementioned slip velocity us represents a generalization<br />
<strong>of</strong> the well-known classical result which, in principle, is included in (3).<br />
Let η = y/u 2 τ = O(1) be the coordinate characteristic for the intermediate layer. The match<br />
<strong>of</strong> u with the inner wake reveals a half-power law, u/uτ = O( √ η) for η→∞. Such a behavior<br />
is believed to hold also on top <strong>of</strong> the viscous wall layer <strong>of</strong> a separating TBL. On the other<br />
hand, the viscous wall and the intermediate layer collapse and, in turn, (3) ceases to be valid<br />
when us/uτ = O(1), that is, for us = O(Re −1/3 ). As a highlight <strong>of</strong> the asymptotic analysis, it is<br />
pointed out how that merge <strong>of</strong> the near-wall layers generates a new strongly viscosity-affected<br />
flow regime near the locations where τw = 0. There (1) is replaced by the appropriate expansion<br />
u/up∼ u × 0 (p× ,y × )+··· , p × = (up/uτ) 3 , up = (px/Re) 1/3 , y × = yupRe = O(1). (4)<br />
Herein the local value px = O(1) <strong>of</strong> the leading-order streamwise pressure gradient enters the<br />
velocity scale up. Finally, then the generalized logarithmic law (2) is gradually transformed into<br />
References<br />
u × 0 ∼ C(p× ) � y × + D(p × ), C(p × ) > 0, D(p × )∼us/up = O(1), y × →∞. (5)<br />
[1] G.L. Mellor, “The Large Reynolds Number, Asymptotic Theory <strong>of</strong> Turbulent Bo<strong>und</strong>ary Layers” J. Engn<br />
Sci., 10, 851–873 (1972).<br />
[2] B. Scheichl and A. Kluwick, “Turbulent Marginal Separation and the Turbulent Goldstein Problem”, AIAA<br />
paper 2005-4936 (2005), also AIAA J. (submitted in extended form).<br />
[3] R.L.Simpson, “AModelfortheBackflowMeanVelocityPr<strong>of</strong>ile”, TechnicalNote, AIAA J., 21(1), 142–143<br />
(1983).<br />
Speaker: SCHEICHL, B. 137 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
O. SHISHKINA, C. WAGNER: Bo<strong>und</strong>ary and Interior Layers in Turbulent Thermal<br />
Convection<br />
✬<br />
✫<br />
Bo<strong>und</strong>ary and Interior Layers in Turbulent Thermal Convection ∗<br />
1. Introduction<br />
O. Shishkina & C. Wagner<br />
DLR - <strong>Institut</strong>e for Aerodynamics and Flow Technology,<br />
Bunsenstrasse 10, 37073 Göttingen, Germany<br />
Olga.Shishkina@dlr.de, Claus.Wagner@dlr.de<br />
Numerous scientifical problems and industrial applications require solutions <strong>of</strong> the Rayleigh-<br />
Bénard problem, i.e. turbulent convection <strong>of</strong> fluids heated from below and cooled from above,<br />
with the Rayleigh number (Ra) from 10 5 up to 10 20 . For a review on this classical problem and<br />
for the references to earlier literature we refer to the paper Ahlers, Grossmann and Lohse [1].<br />
Since the diffusion coefficient in the Navier-Stokes equation, which is inversely proportional to<br />
the square root <strong>of</strong> Ra, is very small, the solution - both the temperature and the velocity fields -<br />
have very thin bo<strong>und</strong>ary layers near the horizontal walls. For moderate Rayleigh numbers (from<br />
10 5 up to 10 8 ) interior layers, i.e. thermal plumes, are also observed. The bo<strong>und</strong>ary layers, the<br />
thermal plumes and the turbulent backgro<strong>und</strong> are indicated, respectively, by high, moderate and<br />
small values <strong>of</strong> the temperature gradient norm and, hence, by large, moderate and small values<br />
<strong>of</strong> the thermal dissipation rate. By means <strong>of</strong> direct numerical simulations (DNS) we invesigate<br />
bo<strong>und</strong>ary and interior layers which take place in turbulent Rayleigh-Bénard convection.<br />
2. Governing equations and the numerical method<br />
The governing dimensionless equations for the Rayleigh-Bénard problem in Boussinesq approximation<br />
can be written in cylindrical coordinates (z, r, ϕ) as follows<br />
ut + u · ∇u + ∇p = Γ −3/2 Ra −1/2 P r 1/2 ∇ 2 u + T z, (1)<br />
Tt + u · ∇T = Γ −3/2 Ra −1/2 P r −1/2 ∇ 2 T, (2)<br />
∇ · u = 0, (3)<br />
where u is the velocity vector, T the temperature, ut and Tt their time derivatives, p the<br />
pressure. Here Ra = αgH 3 ∆T/(κν) denotes the Rayleigh number, P r = ν/κ the Prandtl<br />
number, Γ = D/H the aspect ratio with H the height and D the diameter <strong>of</strong> the cylindrical<br />
container. Further, α is the thermal expansion coefficient, g the gravitational acceleration, ∆T<br />
the temperature difference between the bottom and the top plates, ν the kinematic viscosity and<br />
κ the thermal diffusivity. The dimensionless temperature varies between +0.5 at the bottom<br />
plate to −0.5 at the top plate. An adiabatic lateral wall is prescribed by ∂T/∂r = 0. Finally, on<br />
the solid walls the velocity field vanishes according to the impermeability and no-slip conditions.<br />
To investigate turbulent Rayleigh-Bénard convection in cylindrical containers <strong>of</strong> the aspect<br />
ratios Γ = 10 and Γ = 5 for Ra from 10 5 to 10 7 and P r = 0.7 we conducted DNS. The simulations<br />
were performed with the fourth order accurate finite volume method developed for solving (1)<br />
– (3) in cylindrical coordinates on staggered non-equidistant grids. For the numerical method<br />
used in the DNS we refer to [2].<br />
∗ The work is supported by Deutsche Forschungsgemeinschaft (DFG) <strong>und</strong>er the contract WA 1510-1<br />
Speaker: SHISHKINA, O. 138 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
O. SHISHKINA, C. WAGNER: Bo<strong>und</strong>ary and Interior Layers in Turbulent Thermal<br />
Convection<br />
✬<br />
✫<br />
Ra = 10 5 Ra = 10 6 Ra = 10 7<br />
Figure 1: Snapshots <strong>of</strong> the temperature, −0.37 ≤ T ≤ 0.37, for Γ = 10 and z = H/(2Nu).<br />
Colour scale spreads from blue (negative values) through white (zero) to red (positive values).<br />
3. Mesh generation<br />
In [3] it was proven that the ratio <strong>of</strong> the area averaged (over the top or the bottom plates) to<br />
the volume averaged thermal dissipation rate ɛθ = Γ −3/2 Ra −1/2 P r −1/2 (∇T ) 2 is greater than<br />
or equal to the Nusselt number (Nu = Γ1/2Ra1/2P r1/2 〈uzT 〉 t,S − Γ−1 � �<br />
∂T<br />
∂z ≥ 1) for all Ra,<br />
t,S<br />
P r and Γ. It means that the largest values <strong>of</strong> ɛθ take place in the bo<strong>und</strong>ary layers near the<br />
horizontal walls. To resolve these bo<strong>und</strong>ary layers special meshes are required.<br />
The grid equidistribution ansatz (see for example [4]) enables to detect the bo<strong>und</strong>ary layers<br />
and construct appropriate meshes for their resolution. In our solution-adapted mesh generation<br />
algorithm we used grid equidistribution <strong>of</strong> the arc-length <strong>of</strong> the mean temperature pr<strong>of</strong>iles<br />
computed on equidistant meshes. The algorithm produces meshes that lead to principally more<br />
accurate solutions in comparison with the equidistant meshes.<br />
4. Numerical experiments<br />
Using the solution-adapted meshes with 110, 192 and 512 nodes in z-, r- and ϕ-directions,<br />
respectively, we conducted the DNS <strong>of</strong> three-dimensional Rayleigh–Bénard convection in wide<br />
cylindrical containers <strong>of</strong> the aspect ratios Γ = 10 and Γ = 5 and for moderate Rayleigh numbers<br />
from 10 5 to 10 7 . The snapshots <strong>of</strong> the temperature field on the borders between the lower<br />
thermal bo<strong>und</strong>ary layers and the bulk are presented in Fig. 1 as they were obtained in the DNS<br />
for Γ = 10. The coherent flow patterns reveal the horizontal extension <strong>of</strong> hot and cold plumes.<br />
Analysing spatial distribution <strong>of</strong> ɛθ for different Ra we conclude that the role <strong>of</strong> the thermal<br />
plumes in thermal convection decreases with growing Ra. Some other physical results obtained<br />
in the DNS <strong>of</strong> turbulent Rayleigh–Bénard convection in wide containers are discussed in [3].<br />
References<br />
[1] G. Ahlers, S. Grossmann & D. Lohse, “Hochpräzision im Kochtopf: Neues zur turbulenten<br />
Wärmekonvektion”, Physik Journal, 1, 31–37 (2001).<br />
[2] O. Shishkina & C. Wagner, “A fourth order accurate finite volume scheme for numerical<br />
simulations <strong>of</strong> turbulent Rayleigh-Bénard convection”, C. R. Mecanique, 333, 17–28 (2005).<br />
[3] O. Shishkina & C. Wagner, “Analysis <strong>of</strong> thermal dissipation rates in turbulent Rayleigh-<br />
Bènard convection”, J. Fluid Mech., 546, 51–60 (<strong>2006</strong>).<br />
[4] N. Kopteva & M. Stynes, “A robust adaptive method for a quasilinear one-dimensional<br />
convection-diffusion problem”, SIAM J. Numer. Anal., 39, 1446–1467 (2001).<br />
Speaker: SHISHKINA, O. 139 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
M. STYNES, L. TOBISKA: Using rectangular Qp elements in the SDFEM for a<br />
convection-diusion problem with a bo<strong>und</strong>ary layer<br />
✬<br />
✫<br />
Using rectangular Qp elements in the SDFEM for a convection-diffusion<br />
problem with a bo<strong>und</strong>ary layer<br />
Martin Stynes 1 and Lutz Tobiska 2<br />
1 National University <strong>of</strong> Ireland, Cork, Ireland.<br />
m.stynes@ucc.ie<br />
2 Otto-von-Guericke Universität Magdeburg, Postfach 4120, D-39016 Magdeburg, Germany<br />
tobiska@mathematik.uni-magdeburg.de<br />
We consider the convection-diffusion problem<br />
−ε∆u + b · ∇u + cu = f on Ω = (0,1) 2 , u = 0 on ∂Ω,<br />
where the parameter ε lies in the interval (0,1], the function b(x,y) = (b1(x,y),b2(x,y)) with<br />
b1(x,y) > β1 > 0 and b2(x,y) > β2 > 0, c(x,y) ≥ 0 on ¯ Ω, and c(x,y) − (div b(x,y))/2 ≥ c0 > 0<br />
on ¯ Ω. We assume that the functions b, c, and f are sufficiently smooth. Layer-adapted meshes<br />
are usually used for solving the singularly perturbed bo<strong>und</strong>ary value problem since its solution<br />
typically has bo<strong>und</strong>ary layers at the sides x = 1 and y = 1 <strong>of</strong> Ω.<br />
The convergence properties <strong>of</strong> the streamline diffusion finite element method (SDFEM; the<br />
method is also known as SUPG) on a rectangular Shishkin mesh are analyzed. The trial functions<br />
in the SDFEM are piecewise polynomials that lie in the space Qp, i.e., are tensor products<br />
<strong>of</strong> polynomials <strong>of</strong> degree p in one variable, where p > 1. In [1, 2], for sufficiently small ε<br />
(ε ≤ N −1/2 ln 2 N), the error bo<strong>und</strong><br />
�u I − u N �SD ≤ C N −2 ln 2 N<br />
has been proven in the case p = 1, where u I is the nodal interpolant <strong>of</strong> the solution u, u N is<br />
the SDFEM solution, and � · �SD is the streamline-diffusion norm. This error bo<strong>und</strong> is based on<br />
anisotropic interpolation estimates, superconvergence <strong>of</strong> the piecewise linear nodal interpolation,<br />
and a detailed study <strong>of</strong> the behaviour <strong>of</strong> the solution in the different parts <strong>of</strong> the domain.<br />
The main objective is to extent the error analysis to the case p > 1 by using a nonstandard<br />
interpolation. A detailed study <strong>of</strong> the approximation and superconvergence properties leads to<br />
the estimate<br />
�u I − u N �SD ≤ C N −(p+1/2) , p > 1.<br />
Comparisons are made between this result and the corresponding result for the case p = 1, which<br />
turns out to be exceptional [3]. Moreover, we discuss the possibilities to derive similar estimates<br />
for �u − Pu N �SD and �u − u N �d,SD, where Pu N denote a suitable postprocessed numerical<br />
solution and � · �d,SD a discrete version <strong>of</strong> the streamline-diffusion norm, respectively.<br />
References<br />
[1] M. Stynes and L. Tobiska, “Analysis <strong>of</strong> the streamine-diffusion finite element method for<br />
a convection-diffusion problem with exponential layers”, East-West J. Numer. Math., 9,<br />
59–76 (2001).<br />
[2] M. Stynes and L. Tobiska, “The SDFEM for a convection-diffusion problem with a bo<strong>und</strong>ary<br />
layer: Optimal error analysis and enhancement <strong>of</strong> accurary”, SIAM J. Numer. Anal., 41,<br />
1620–1642 (2003).<br />
[3] L. Tobiska, “Analysis <strong>of</strong> a new stabilized higher order finite element method for advectiondiffusion<br />
equations”, Tech. Rep. 05-36, Department <strong>of</strong> Mathematics, Otto-von-Guericke<br />
University (2005).<br />
Speaker: TOBISKA, L. 140 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
P. SVÁ ˘CEK: Numerical Approximation <strong>of</strong> Flow Induced Airfoil Vibrations<br />
✬<br />
✫<br />
Numerical Approximation <strong>of</strong> Flow<br />
Induced Airfoil Vibrations<br />
Petr Sváček<br />
Department <strong>of</strong> Technical Mathematics, Karlovo náměstí 13,<br />
121 35 Praha 2, CTU, Faculty <strong>of</strong> Mechanical Engineering.<br />
The strong interaction between the aerodynamic field and the aero-elastic field<br />
plays an important role in the design <strong>of</strong> aerospace vehicles. The fluid-structure<br />
interaction is usually a complex nonlinear problem. The aero-elastic stability<br />
<strong>of</strong> aerospace vehicles has a great impact on their design. In this paper we are<br />
interested in the interaction <strong>of</strong> two dimensional incompressible viscous laminar<br />
flow and a solid airfoil. The airfoil can rotate and oscillate in vertical direction.<br />
The numerical simulation <strong>of</strong> such a problem is very challenging topic - it<br />
consists <strong>of</strong> discretization and stabilization <strong>of</strong> the Navier-Stokes equations for a<br />
high Reynolds number. Also the nonlinear discrete problem has to be treated<br />
carefully. Moreover, the computational domain is time dependent and one has<br />
to recompute it for each time step together with the used grid. In order to take<br />
the grid motion into account the Arbitrary Lagrangian-Eulerian formulation <strong>of</strong><br />
the Navier-Stokes equation is used.<br />
The most difficult part <strong>of</strong> the fluid-structure interaction is a fluid flow simulation.<br />
We consider viscous laminar incompressible two dimensional flow which is fully<br />
time dependent<br />
D A u<br />
Dt − ν△u + ((u − wg) · ∇) u + ∇p = 0, in Ωt,<br />
∇ · u = 0, in Ωt<br />
equipped with appropriate bo<strong>und</strong>ary conditions.<br />
The above problem is discretized by the finite element method(FEM). Nevertheless,<br />
the Galerkin FEM leads to unphysical solutions if the grid is not fine<br />
enough in regions <strong>of</strong> strong gradients (e.g. bo<strong>und</strong>ary layer). In order to obtain<br />
physically admissible correct solutions it is necessary to apply suitable mesh<br />
refinement combined with a stabilization technique giving stable and accurate<br />
schemes. In our paper we present a special version <strong>of</strong> the GLS stabilization<br />
method for Navier-Stokes equations, see [1], [2].<br />
Further, the computation <strong>of</strong> the force acting on the airfoil requires correct evaluation<br />
<strong>of</strong> bo<strong>und</strong>ary integral <strong>of</strong> the stress tensor. A straightforward evaluation<br />
<strong>of</strong> the stress tensor integral may lead to inaccurate results. This obstacle is<br />
avoided with the aid <strong>of</strong> a weak formulation <strong>of</strong> the force acting on the pr<strong>of</strong>ile.<br />
Speaker: SVÁ ˘CEK, P. 141 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
P. SVÁ ˘CEK: Numerical Approximation <strong>of</strong> Flow Induced Airfoil Vibrations<br />
✬<br />
✫<br />
The fluid forces acting on the pr<strong>of</strong>ile causes its motion or deformation, which<br />
depends on the airfoil properties. We simulate the situation, when the airfoil is<br />
a solid body with two degrees <strong>of</strong> freedom. Its motion is obtained as the solution<br />
<strong>of</strong> two ordinary differential equations coupled with the Navier-Stokes system.<br />
We discuss the GLS stabilization <strong>of</strong> the FEM, evaluation <strong>of</strong> forces acting on<br />
the pr<strong>of</strong>ile, time discretization and the solution <strong>of</strong> the discrete problem. The<br />
obtained results are compared with available data.<br />
References<br />
[1] Sváček, P., Feistauer, M. Application <strong>of</strong> a stabilized FEM to problems<br />
<strong>of</strong> aeroelasticity. In: Feistauer, M., Dolejˇsí, V., K., N. (Eds.),Numerical<br />
Mathematics and Advanced Applications, ENUMATH2003. Springer, Heidelberg,<br />
pp. 796–805, 2004<br />
[2] Sváček, P. , Feistauer, M., Horáček, J., Numerical simulation <strong>of</strong> flow<br />
induced airfoil vibrations with large amplitudes. Journal <strong>of</strong> Fluids and<br />
Structures(submitted), 2004.<br />
Speaker: SVÁ ˘CEK, P. 142 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
N.V. TARASOVA: Full asymptotic analysis <strong>of</strong> the Navier-Stokes equations in the<br />
problems <strong>of</strong> gas flows over bodies with large Reynolds number<br />
✬<br />
✫<br />
Full asymptotic analysis <strong>of</strong> the Navier-Stokes equations<br />
in the problems <strong>of</strong> gas flows over bodies<br />
with large Reynolds number<br />
N.V.Tarasova<br />
Baltic State Technical University<br />
1, 1st Krasnoarmeiskaya ul., 190005 St Petersburg, Russia<br />
E-mail: natali_t3@pr<strong>of</strong>essor.ru, tsrknv@bstu.spb.su<br />
Investigation <strong>of</strong> the gas flows over bodies with large Reynolds number in most cases can be<br />
significantly simplified when the flow area is divided into two parts: the external inviscid one<br />
and the narrow area near the body surface well-known as viscous bo<strong>und</strong>ary layer. As this takes<br />
place the Navier-Stokes equations describing such flows are splitted into the Eulier equations for<br />
the external flow area and the Prandtl bo<strong>und</strong>ary layer equations. Such splitting <strong>of</strong> the problem<br />
is obtained on the base <strong>of</strong> the matched asymptotic expansion method proposed by Van Dike for<br />
hypersonic flow [1]. All gas parameters are written in the form <strong>of</strong> power series in the standard<br />
small parameter ε = 1/ √ Re∞ (Re∞ is the Reynolds number in the free stream flow) and the<br />
system <strong>of</strong> the Navier-Stokes equations reduces to the sequences <strong>of</strong> partial differential equation<br />
systems in the external flow area and internal flow area. As a result, in a first approximation we<br />
derive the Euler equations (in external flow area) and the Prandtl bo<strong>und</strong>ary layer equations.<br />
Traditionally the model <strong>of</strong> incompressible gas flow is used both in the external flow area<br />
and inside the bo<strong>und</strong>ary layer if the Mach number in the free stream M∞ is less than 0.3 and<br />
the characteristic temperature drop is small enough, otherwise the model for compressible gas<br />
flow is used. At the same time in practice in many problems <strong>of</strong> gas flows over bodies, such as<br />
calculation <strong>of</strong> induced convection in heat exchanges, we have hyposonic gas flows in which the<br />
gas temperature across the bo<strong>und</strong>ary layer on the body surface can be changed significantly that<br />
leads to considerable changes <strong>of</strong> the gas density. As a result, the gas flow outside the bo<strong>und</strong>ary<br />
layer can be considered as incompressible but inside the layer as essentially compressible one.<br />
In the described case the researchers usually use the common model <strong>of</strong> the compressible gas<br />
both inside the bo<strong>und</strong>ary layer and in the external inviscid flow area. However, such approach<br />
implies the necessity to solve the compressible Euler equations in the external area that leads to<br />
significant computational difficulties if the Mach number in the free stream flow is small enough<br />
(in the case <strong>of</strong> hyposonic flows).<br />
The main aim <strong>of</strong> this paper is to carry out the strict asymptotic analysis based on the method<br />
<strong>of</strong> matched asymptotic expansions <strong>of</strong> the complete system <strong>of</strong> the Navier-Stokes equations in all<br />
possible situations:<br />
1) flows with the Mach number greater than 0.3 and the large temperature drop across the<br />
bo<strong>und</strong>ary layer,<br />
2) flows with the Mach number greater than 0.3 and the small temperature drop across the<br />
bo<strong>und</strong>ary layer,<br />
3) flows with the Mach number less than 0.3 and the large temperature drop across the<br />
bo<strong>und</strong>ary layer,<br />
4) flows with the Mach number less than 0.3 and the small temperature drop across the<br />
bo<strong>und</strong>ary layer,<br />
and as a result to suggest the setting <strong>of</strong> the problem for the Euler equations and the bo<strong>und</strong>ary<br />
layer equations including the procedure <strong>of</strong> sewing together the appropriate gas parameters.<br />
Cases 1) and 4) are seen to give us the well-known models for the compressible and incompressible<br />
gas flow in both areas respectively. Because <strong>of</strong> this, they have not been the major subject<br />
<strong>of</strong> investigation in the present study. At the same time cases 2) and 3) give us some intermediate<br />
situations which are <strong>of</strong> great interest. This problem is not trivial for example for case 3) because<br />
Speaker: TARASOVA, N.V. 143 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
✩<br />
✪
N.V. TARASOVA: Full asymptotic analysis <strong>of</strong> the Navier-Stokes equations in the<br />
problems <strong>of</strong> gas flows over bodies with large Reynolds number<br />
✬<br />
✫<br />
the application <strong>of</strong> the Euler equations for incompressible flow outside the bo<strong>und</strong>ary layer and the<br />
classical equations <strong>of</strong> the compressible bo<strong>und</strong>ary layer near the body surface makes impossible<br />
the agreement between both equation systems.<br />
To consider the proposed problems from common positions another special dimensionless<br />
variables for gas parameters in the Navier-Stokes equations are introduced. These new variables<br />
are varied inside the studied flow area usually from 0 to 1 (in other words, they can vary to the<br />
value <strong>of</strong> the order <strong>of</strong> unit). The main idea to use such special dimensionless variables is that in<br />
this case all governing parameters that can be both small and not small are indicated explicitly<br />
as the coefficients in the equation system. Among these parameters are M 2 ∞ and ∆T/T0 (∆T is<br />
the temperature drop and T0 is the characteristic value <strong>of</strong> the temperature in the area).<br />
It should be noticed that in the hyposonic flows the gravity force can affect significantly the<br />
gas flow (in studies <strong>of</strong> free and induced convection). In term <strong>of</strong> asymptotic analysis it means<br />
that it is necessary to take account <strong>of</strong> one more parameter, for example 1/Fr (Fr is the Frud<br />
number) that can be both small and not small.<br />
The full asymptotic analysis is carried out for all mentioned situations on the base <strong>of</strong><br />
comparison <strong>of</strong> all parameters mentioned above (M 2 ∞, ∆T/T0, 1/Fr) with the standard small<br />
parameter ε in order <strong>of</strong> magnitude. As a result, the model for gas flow in both areas is formulated<br />
and an attempt to construct the procedure <strong>of</strong> the agreement <strong>of</strong> the solutions in both areas is<br />
made. It should be stressed that the equation systems derived <strong>und</strong>er the assumptions 1) - 4)<br />
differ from each other.<br />
This model constructed for the cases 2) and 3) possibly can occupy the intermediate place<br />
between two classical approaches when a gas is considered as incompressible or compressible one<br />
over the whole flow field.<br />
The equations describing hyposonic flows (M → 0) with the arbitrary values <strong>of</strong> the Reynolds<br />
number (Re), ∆T/T0 and 1/Fr were derived in [2] from the Navier-Stokes equations on the base<br />
<strong>of</strong> the asymptotic analysis with the Mach number (M) as a small parameter. In this work an<br />
attempt to compare the model constructed for cases 2) and 3) with the results obtained in [2]<br />
when considered flow with the large Reynolds number was made.<br />
References<br />
1. M. Van Dyke. 1962 In: Hypersonic Flow Research (Ed. F.R.Riddell). Academic Press.<br />
2. A.I. Zhmakin, Yu.N. Makarov. 1985 Numerical modelling <strong>of</strong> hyposonic flows <strong>of</strong> viscous gas,<br />
Dokl. AN SSSR, Mekh. Zh. i Gaza 280 (4), 827–830. [in Russian]<br />
Speaker: TARASOVA, N.V. 144 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
✪
C.H. TAI, C.-Y. CHAO, J.-C. LEONG, Q.-S. HONG: Effects <strong>of</strong> golf ball dimple<br />
configuration on aerodynamics, trajectory, and acoustics<br />
✬<br />
✫<br />
International Conference: <strong>BAIL</strong> <strong>2006</strong><br />
Bo<strong>und</strong>ary and Interior Layers<br />
- Computational & Asymptotic Methods -<br />
Effects <strong>of</strong> golf ball dimple configuration on aerodynamics, trajectory, and acoustics<br />
*Chang-Hsien Tai + Chih-Yeh Chao ++ Jik-Chang Leong + Qing-Shan Hong +<br />
*Corresponding author<br />
Department <strong>of</strong> Vehicle engineering, National Pingtung University <strong>of</strong> Science and Technology +<br />
Department <strong>of</strong> Mechanical engineering, National Pingtung University <strong>of</strong> Science and Technology ++<br />
1, Hseuh Fu Road, Neipu Hsiang, Pingtung Taiwan, R.O.C.<br />
Fax: 886-8-7740398 E-mail: chtai@mail.npust.edu.tw<br />
Abstract<br />
In many reports about golf ball, including the<br />
history <strong>of</strong> its development, have introduced the<br />
standards on golf ball specification. However,<br />
there is not a single well-documented solid<br />
requirement fo<strong>und</strong> for the design <strong>of</strong> golf ball<br />
surface. Not only have a lot <strong>of</strong> reports discussed<br />
the material and structure <strong>of</strong> a golf ball, but also<br />
most <strong>of</strong> the golf ball manufacturers improve their<br />
products by modifying the number <strong>of</strong> layers<br />
beneath the golf ball surface and their materials.<br />
Even so, there are relatively very few papers<br />
focused on the influence <strong>of</strong> different concave<br />
surface configurations on the aerodynamic<br />
characteristics <strong>of</strong> the golf ball. Furthermore, the<br />
noise a golf ball generates in a tournament is very<br />
likely to affect the emotion and hence the<br />
performance <strong>of</strong> the golf ball player. For these<br />
reasons, this study investigates the performance <strong>of</strong><br />
a golf ball based on the CFD method with the<br />
validation using a wind tunnel.<br />
In 1938, Goldstein [1] had proposed an<br />
important parameter – the spin ratio. In<br />
corporation with different Reynolds numbers, this<br />
parameter makes the study <strong>of</strong> life and drag effects<br />
feasible for whirling smooth bodies. In his book,<br />
Jorgensen [2] especially emphasized that the main<br />
objective <strong>of</strong> concaved surfaces on a golf ball is to<br />
generate small scale turbulence. When flying, this<br />
turbulence postpones air separation, reduces the<br />
low pressure region trailing the golf ball, and<br />
eventually lowers the air drag. Warring [3] used<br />
numerical approach to perform a series <strong>of</strong> studies<br />
related to golf ball using Excel spreadsheets. The<br />
goal <strong>of</strong> his paper was to provide guidance for golf<br />
ball players and manufacturers so that their golf<br />
ball was capable <strong>of</strong> flying for a longer distance. In<br />
the study <strong>of</strong> acoustics, Singer, et al. [4] calculated<br />
the noise level from a source using a hybrid grid<br />
system with the help <strong>of</strong> Lighthill’s acoustics<br />
analytic approach. On the other hand, Montavon,<br />
et al. [5] combined CFD method and<br />
Computational Aeroacoustics Approach (CAA) to<br />
simulate noise generation from a cylinder. Using<br />
CFX-5 with LES (Large Eddy Simulation) as their<br />
turbulence model and Ffowcs-Williams Hawkings<br />
formulation, they had successfully shown that their<br />
predicted so<strong>und</strong> levels agreed very well with<br />
theoretical ones for Reynolds numbers about 1.4×<br />
10 5 .<br />
Figure 1 shows the flow field aro<strong>und</strong> a typical<br />
golf ball (Case 1). In Case 2, additional dimples<br />
are added onto the golf ball considered in Case 1.<br />
The orientation <strong>of</strong> these additional dimples is<br />
depicted in Figure 3. It is fo<strong>und</strong>, based on Figure 2,<br />
that the flow field associated to Case 2 is no longer<br />
symmetrical because <strong>of</strong> the presence <strong>of</strong> the<br />
additional dimples. Figure 3 demonstrates the<br />
distribution <strong>of</strong> lift and drag coefficients <strong>of</strong> Cases 1<br />
and 2. Clearly, the addition <strong>of</strong> small dimples<br />
increases the drag. This implies that the golf ball in<br />
Case 2 suffers more serious drag effect at low<br />
trajectory speeds. The lift the golf ball in Case 2<br />
experiences at moderate Reynolds numbers<br />
increases so greatly that it becomes greater than<br />
that for Case 1. The life force in overall is<br />
therefore greater for Case 2 than Case 1. Although<br />
the drag imposed on the golf ball is always smaller<br />
for Case 1 than for Case 2, the drag in Case 1 is<br />
only about 38.5% less than that in Case 2.<br />
However, the lift in Case 2 is 103% greater than<br />
that in Case 1. This somewhat indicates the lift<br />
effect is 2.68 times <strong>of</strong> the drag effect. The overall<br />
performance <strong>of</strong> the golf ball for Case 2 is much<br />
greater than that for Case 1. Therefore, the former<br />
golf ball is capable <strong>of</strong> traveling further, as shown<br />
in Figure 4.<br />
Speaker: HONG, Q.-S. 145 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
C.H. TAI, C.-Y. CHAO, J.-C. LEONG, Q.-S. HONG: Effects <strong>of</strong> golf ball dimple<br />
configuration on aerodynamics, trajectory, and acoustics<br />
✬<br />
✫<br />
This thesis used structured and non-structured<br />
grids to come out with the most appropriate grid<br />
systems for the current golf balls simulations. Then,<br />
numerical simulations were carried out to estimate<br />
the aerodynamics parameters and noise levels for<br />
various kinds <strong>of</strong> golf balls having different dimple<br />
configurations. With the obtained aerodynamics<br />
parameters, the flying distance and trajectory for a<br />
golf ball were determined and visualized. The<br />
results showed that structured grids produced more<br />
accurate results. In terms <strong>of</strong> dimple layout, the lift<br />
coefficient <strong>of</strong> the golf ball increased if small<br />
dimples were added between the original large<br />
dimples. When launched at small angles, golf balls<br />
with deep dimples were fo<strong>und</strong> to have greater lift<br />
effect than drag effect. Therefore, the golf balls<br />
would fly further until a critical depth <strong>of</strong> 0.25 mm.<br />
As far as noise generation was concerned, deep<br />
dimples produced lower noise levels.<br />
Keywords: golf ball, CFD, dimple, flying<br />
trajectory, noise<br />
Fig.1 The velocity vector contour on rotation <strong>of</strong><br />
Case1(Re=1×10 5 )<br />
Fig.2 The velocity vector contour <strong>of</strong><br />
Case2(Re=1×10 5 )<br />
International Conference: <strong>BAIL</strong> <strong>2006</strong><br />
Bo<strong>und</strong>ary and Interior Layers<br />
- Computational & Asymptotic Methods -<br />
Drag coefficient<br />
Fig.3 Life, Drag coefficient <strong>of</strong> Case1 and Case2<br />
Height (m)<br />
0.7<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
10 3 0<br />
250<br />
200<br />
150<br />
100<br />
50<br />
0<br />
Case1-Drag coefficient<br />
Case2-Drag coefficient<br />
Case1-Lift coefficient<br />
Case2-Lift coefficient<br />
10 4<br />
Reynolds number<br />
Case1 = 215.2m<br />
Case2 = 262.1m<br />
50 100 150 200 250<br />
Distance (m)<br />
Fig.4 Flying trajectory <strong>of</strong> Case1 and Case2<br />
Reference<br />
[1] Goldstein, S., “Modern Developments in Fluid<br />
Dynamics,” Vols. I and II. Oxford: Clarendon<br />
Press, 1938.<br />
[2] Jorgensen, T. P., “The Physics <strong>of</strong> Golf, 2nd<br />
edition,” New York: Springer-Verlag, pp. 71-72,<br />
1999.<br />
[3] Warring, K. E., “The Aerodynamics <strong>of</strong> Golf Ball<br />
Flight,” St. Mary’s College <strong>of</strong> Maryland, pp. 1-37,<br />
2003.<br />
[4] Singer, B. A., Lockard, D. P. and Lilley, G. M.,<br />
“Hybrid Acoustic Predictions,” Computers and<br />
Mathematics with Application 46, pp. 647-669,<br />
2003.<br />
[5] Montavon, C., Jones, I. P., Szepessy, S.,<br />
Henriksson, R., el-Hachemi, Z., Dequand, S.,<br />
Piccirillo, M., Tournour, M. and Tremblay, F.,<br />
“Noise propagation from a cylinder in a cross<br />
flow: comparison <strong>of</strong> SPL from measurements and<br />
from a CAA method based on a generalized<br />
acoustic analogy,” IMA Conference on<br />
Computational Aeroacoustics, pp. 1-14, 2002.<br />
Speaker: HONG, Q.-S. 146 <strong>BAIL</strong> <strong>2006</strong><br />
10 5<br />
0.16<br />
0.14<br />
0.12<br />
0.1<br />
0.08<br />
0.06<br />
0.04<br />
0.02<br />
Lift coefficient<br />
✩<br />
✪
H. TIAN: Uniformly Convergent Numerical Methods for Singularly Perturbed Delay<br />
Differential Equations<br />
✬<br />
Uniformly Convergent Numerical Methods for Singularly Perturbed Delay<br />
Differential Equations ∗<br />
1 Introduction<br />
Hongjiong Tian<br />
Department <strong>of</strong> Mathematics, Shanghai Normal University,<br />
100 Guilin Road, Shanghai 200234, P. R. China<br />
hjtian@shnu.edu.cn<br />
Singularly perturbed problems form a special class <strong>of</strong> problems containing a small parameter<br />
which may tend to zero. Singularly perturbed delay differential equations (DDEs) has arose in<br />
many fields, such as in the study <strong>of</strong> an “optically bistable device” [1] and in a variety <strong>of</strong> models<br />
for physiological processes or diseases [2]. Such problems include a subclass <strong>of</strong> what we frequently<br />
thought <strong>of</strong> as “stiff” equations. We will concentrate on uniformly convergent numerical methods<br />
for linear and nonlinear singularly perturbed delay differential equations with a fixed lag.<br />
2 Uniformly convergent schemes<br />
Linear problems<br />
Consider linear singularly perturbed delay differential equations<br />
Ly(t) ≡ εy ′ (t) + a(t)y(t) = b(t)y(t − 1) + g(t), 0 ≤ t ≤ T,<br />
y(t) = φ(t), −1 ≤ t ≤ 0,<br />
where ε > 0 is a small parameter, a(t) ≥ α > 0, b(t), φ(t) and g(t) are smooth functions. We<br />
concentrate on the following difference schemes<br />
and<br />
L h yi ≡ εσi(ρ)D+yi + a(ti)yi+1 = b(ti)yi−m + g(ti), i ≥ 0,<br />
y−j = φ(t−j), j = 0, 1, 2, . . . , m,<br />
L h yi ≡ εσi(ρ)D+yi + a(ti+1)yi+1 = b(ti+1)yi+1−m + g(ti+1), i ≥ 0,<br />
y−j = φ(t−j), j = 0, 1, 2, . . . , m,<br />
where the step length h satisfies the constraint 1 = mh with a positive integer m, ti = ih, ρ = h<br />
ε<br />
and<br />
σi(ρ) =<br />
�<br />
ρa(0)<br />
1−exp(−ρa(0))<br />
ρa(j)<br />
1−exp(−ρa(j))<br />
Nonlinear problems<br />
Consider nonlinear problems <strong>of</strong> the form<br />
exp(−ρa(0)), i = 0, 1, · · · , m − 1,<br />
exp(−ρa(j)), i = jm, jm + 1, · · · , (j + 1)m − 1, j = 1, 2, · · · .<br />
εy ′ (t) = f(t, y(t), y(t − 1)), 0 ≤ t ≤ T,<br />
y(t) = φ(t), −1 ≤ t ≤ 0,<br />
∗ The work <strong>of</strong> this author is supported in part by E-<strong>Institut</strong>es <strong>of</strong> Shanghai Municipal Education Commission<br />
(No. E03004), Shanghai Municipal Science and Technology Commission (No.03QA14036), Science and Technology<br />
Fo<strong>und</strong>ation <strong>of</strong> Shanghai Higher Education (No.03DZ21), and The Special F<strong>und</strong>s for Major Specialties <strong>of</strong> Shanghai<br />
Education Committee.<br />
✫<br />
1<br />
Speaker: TIAN, H. 147 <strong>BAIL</strong> <strong>2006</strong><br />
(1)<br />
(2)<br />
(3)<br />
(4)<br />
(5)<br />
✩<br />
✪
H. TIAN: Uniformly Convergent Numerical Methods for Singularly Perturbed Delay<br />
Differential Equations<br />
✬<br />
✫<br />
where we assume that −fy(t, y, z) ≥ α > 0 for all t ≥ 0 and all real y, z. We now linearize (5)<br />
and introduce the Newton sequence {ys(t)} ∞<br />
s=0 for the initial guess y0(t) satisfying the initial<br />
condition y0(t) = φ(t), t ∈ [−1, 0]. This is done by defining ys+1(t), for all s ≥ 0, to be the<br />
solution <strong>of</strong> the linear problem<br />
�Lsys+1(t) ≡ ε dys+1(t)<br />
dt − fy(t, ys(t), ys(t − 1))ys+1(t)<br />
−fz(t, ys(t), ys(t − 1))ys+1(t − 1)<br />
= f(t, ys(t), ys(t − 1)) − fy(t, ys(t), ys(t − 1))ys(t)<br />
−fz(t, ys(t), ys(t − 1))ys(t − 1), t > 0,<br />
ys+1(t) = φ(t), −1 ≤ t ≤ 0.<br />
We may show that not only the convergence <strong>of</strong> this sequence is quadratic, but also its proportionality<br />
constant is independent <strong>of</strong> s and ε. If the initial guess y0(t) is sufficiently close to y(t),<br />
converges to y(t).<br />
then the Newton sequence {ys(t)} ∞<br />
s=0<br />
3 Numerical experiments<br />
Consider<br />
We take initial guess as<br />
y0(t) =<br />
�<br />
εy ′ (t) = −y(t) + y 2 (t − 1), t ≥ 0,<br />
y(t) = 2, t ∈ [−1, 0].<br />
t<br />
− 4 − 2e ε , t ∈ [0, 1),<br />
16 − (8 + 16 t−1<br />
t−1<br />
t−1<br />
−2<br />
ε )e− ε − 4e ε , t ∈ [1, 2).<br />
The true solution and the numerical solution using the optimal scheme after two iterations are<br />
plotted in Figure 1. This figure indicates that the uniformly convergent scheme works well also<br />
for nonlinear problem.<br />
References<br />
y<br />
18<br />
16<br />
14<br />
12<br />
10<br />
8<br />
6<br />
4<br />
Numerical and analytic solutions:ε y’(t)=−y(t)+y 2 (t−1),ε=10 −2<br />
Numerical solution<br />
True solution<br />
2<br />
0 0.2 0.4 0.6 0.8 1<br />
t<br />
1.2 1.4 1.6 1.8 2<br />
Figure 1: Comparison between numerical and analytical solutions.<br />
[1] M. W. Derstine, H. M. Gibbs, F. A. Hopf, D. L. Kaplan, Bifurcation gap in a hybrid optical<br />
system, Phys. Rev., A, 26(1982)3720–3722.<br />
[2] M. C. Mackey, L. Glass, Oscillation and chaos in physiological control systems, Science,<br />
197(1977)287–289.<br />
Speaker: TIAN, H. 148 <strong>BAIL</strong> <strong>2006</strong><br />
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A.I. TOLSTYKH, M.V. LIPAVSKII, E.N. CHIGEREV: Highly accurate 9th-order<br />
schemes and their applications to DNS <strong>of</strong> thin shear layer instability<br />
✬<br />
✫<br />
Highly accurate 9th-order schemes and their applications to<br />
DNS <strong>of</strong> thin shear layer instability<br />
A.I.Tolstykh , M.V.Lipavskii, E.N.Chigerev<br />
Computing Center <strong>of</strong> Russian Academy <strong>of</strong> Sciences, Vavilova str.40, 119991 Moscow GSP-1,<br />
Russia e-mail tol@ccas.ru<br />
ABSTRACT<br />
The principle <strong>of</strong> constructing arbitrary-order approximations and schemes is outlined. Its<br />
essence is forming linear combinations <strong>of</strong> basis operators from certain types <strong>of</strong> one-parametric<br />
operators families by fixing distinct values <strong>of</strong> the parameter. The details <strong>of</strong> the procedure first<br />
proposed in [1] can be fo<strong>und</strong> in [2],[3] where the linear combinations were referred to as multioperators.<br />
The multioperators were designed for parallel machines providing approximation<br />
orders which are linear functions <strong>of</strong> numbers <strong>of</strong> processors involved in calculations.<br />
In the present talk, extremely accurate ninth-order multioperators-based schemes for fluid<br />
dynamics equations are presented, the basis operators being Compact Upwind Differencing<br />
(CUD) ones from [4]. The schemes preserve upwinding and conservation properties <strong>of</strong> CUD<br />
schemes; they are characterized by very small phase & amplitude errors for physically relevant<br />
wave numbers supported by grids and damping spurious oscillations. They are capable to<br />
resolve properly small scale phenomena using reasonable meshes and allow to perform highaccuracy<br />
unsteady calculations for large time intervals. Their properties make them very useful,<br />
in particular, for thin layers, DNS and LES computations.<br />
Illustrative examples followed by direct numerical simulations <strong>of</strong> thin incompressible 2D shear<br />
layers instability are presented. The Navier-Stokes calculations were carried out for various high<br />
Reynolds number flows with complete resolution <strong>of</strong> turbulent scales as well as for zero molecular<br />
viscosity. In the latter case, ninth-order dissipative mechanism was responsible for generating<br />
small-scale vorticity. The results obtained for large time intervals show the full history <strong>of</strong> the<br />
flow development with rolling-up,pairing,generation and decaying <strong>of</strong> turbulence.The resulting<br />
energy and enstrophy spectra are discussed.<br />
References<br />
[1] A. I. Tolstykh, Multioperator high-order compact upwind methods for CFD parallel calculations,<br />
in Parallel Computational Fluid Dynamics, Elsevier, Amsterdam, 1998, pp. 383-390.<br />
[2] A. I. Tolstykh, On ultioperators principle for constructing arbitrary-order difference<br />
schemes, Applied Numerical Mathematics 46 (2003),pp.411-423<br />
[3] A. I. Tolstykh, Centered prescribed-order approximations with structured grids and resulting<br />
finite-volume schemes, Applied Numerical Mathematics, 49(2004),pp.431-440.<br />
[4] A. I. Tolstykh, High accuracy non-centered compact difference schemes for fluid dynamics<br />
applications, World Scientific, Singapore, 1994.<br />
Speaker: TOLSTYKH, A.I. 149 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
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ABOUTUNSTEADYBOUNDARYLAYERONADIHEDRALANGLE<br />
beingatrest.Letdenotethelinearangle<strong>of</strong>?.Itisassumed,thattheanglemovesin bythesuddenmotion<strong>of</strong>thedihedralangle?withtheconstantvelocityUintheuid Keldysh<strong>Institut</strong>e<strong>of</strong>AppliedMathematics,Miusskajasq.4,Moscow125047,Russia Theunsteadyow<strong>of</strong>theviscousincompressibleuidisconsidered.Thisowiscaused vasiliev@keldysh.ru M.M.Vasiliev<br />
investigatedrstbyStokes[2].Steadybo<strong>und</strong>arylayerontherightdihedralanglewas consideredbyLoytsjansky[3]. theangle?.Since?isinniteinthedirection<strong>of</strong>axis0zandtheowiscausedonlyby thedirection<strong>of</strong>theedge(0z)andonlyonevelocitycomponent<strong>of</strong>uidwinthisdirection isdierentfromzero.Suchowsarecalledbylayered[1].<br />
coordinatez.Accordingtomadeassumptions,themotionequationsreducet<strong>of</strong>ollowing thewallmotion,weshallassumethatallhydrodynamicfunctionsareindependentfrom Letusintroducethecylindricalcoordinates(r;#;z).Weconnectthiscoordinateswith Theunsteadylayeredowcausedbythesuddenmotion<strong>of</strong>aninniteatplateis<br />
wheretisthetime-coordinate,s=r=p,{kinematicviscouscoecient. intersectionthewingandthefuselage<strong>of</strong>anaircraftatenoughdistancesfromtheleading andthetrailingedges<strong>of</strong>thewing. oneequation:<br />
Inthisworkthepowergeometrymethods[4]areusedforobtaining<strong>of</strong>self-similar Theconsideredowsimulatesroughlyabo<strong>und</strong>arylayerintheneighborhood<strong>of</strong>the @w @t? @2w @s2+1s@w @s+1s2@2w @#2!=0: (1)<br />
solutions<strong>of</strong>bo<strong>und</strong>ary-valueproblems.Thesemethodshavesimplealgorithms.They wereappliedsuccesifullebothtolinearandnonlinearproblemsinworks[5]{[9]and<br />
wasobtainedintheform wherew=U(1;2).Solution<strong>of</strong>theequation(2)bycorrespondingbo<strong>und</strong>aryconditions others. Fortheself-similarvariables1=s=pt;2=#theequation(1)is<br />
where==andfunction1isdeterminedasaresult<strong>of</strong>thesolution<strong>of</strong>thebo<strong>und</strong>aryvalueproblemfortheequation 12@2 @12+11+1212@1+@2 w=U1(1)cos(#); @22=0: (3) (2)<br />
Theanalyticalsolution<strong>of</strong>theconsideredprobleminCartesiancoordinates(x;y;z)was obtainedonlyincase==2.Thissolutionis where 12100+11+121210?21=0; w=Uerferf; (5) (4)<br />
=x 2pt;=y 2pt;erf'=2 p' Z0e?l2dl:<br />
M. VASILIEV: About unsteady Bo<strong>und</strong>ary Layer on a dihedral angle<br />
✬<br />
✫<br />
Speaker: VASIELIEV, M. 150 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
!+1. Trans.Cambr.Phil..IX,8.1851. Itischeckedthatasymptotics<strong>of</strong>thesolutions(3)and(5)coinsidebothbyr!0and<br />
Moscow,1998(Russian).=ElsevierScience,Amsterdam,2000. [1]Schlichting,H.,Grenzschicht-Theorie.VerlagG.Braun.Karlsruhe.1951. [2]Stokes,G.G.,Ontheeect<strong>of</strong>internalfriction<strong>of</strong>uidonthemotion<strong>of</strong>pendumlums. [3]Loytsjansky,L.G.,LaminarBo<strong>und</strong>aryLayer.Fizmatgiz,Moscow,1962(Russian). [4]Bruno,A.D.,Powergeometryinalgebraicanddierentialequations.Fizmatlit, References<br />
bypowergeometry.Proc.<strong>of</strong>theInternationalConferenceonBo<strong>und</strong>aryandInterior Layers(<strong>BAIL</strong>2002),Perth,WesternAustralia,2002,pp.251-256. <strong>of</strong>theInternationalConferenceonBo<strong>und</strong>aryandInteriorLayers(<strong>BAIL</strong>2002),Perth, WesternAustralia,2002,pp.251-256. [5]Bruno,A.D.,Algorithmicanalysis<strong>of</strong>singularperturbationsandbo<strong>und</strong>arylayers [6]Vasiliev,M.M.,Asymptotics<strong>of</strong>someviscous,heatconductinggasows//Proc.<br />
Toulouse,France,2004,9pp. 2003,pp.93-101. //Proc.<strong>of</strong>theInternationalConferenceonBo<strong>und</strong>aryandInteriorLayers(<strong>BAIL</strong>2004), equationsbymethods<strong>of</strong>powergeometry//Proc<strong>of</strong>ISAAC-2001,WorldScientic,Singapore, [8]Bruno,A.D.,Shadrina,T.V.,Theaxiallysymmetricbo<strong>und</strong>arylayeronaneedle [9]Vasiliev,M.M.,Ontheself-similarsolution<strong>of</strong>somemagnetohydrodynamicproblems [7]Vasiliev,M.M.,Abouttheobtainingself-similarsolutions<strong>of</strong>theNavier-Stokes<br />
Toulouse,France,2004,6pp. //Proc.<strong>of</strong>theInternationalConferenceonBo<strong>und</strong>aryandInteriorLayers(<strong>BAIL</strong>2004),<br />
M. VASILIEV: About unsteady Bo<strong>und</strong>ary Layer on a dihedral angle<br />
✬<br />
✫<br />
Speaker: VASIELIEV, M. 151 <strong>BAIL</strong> <strong>2006</strong><br />
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A.E.P. VELDMANN: High-order symmetry-preserving discretization on strongly<br />
stretched grids<br />
✬<br />
✫<br />
High-order symmetry-preserving discretization on strongly stretched grids<br />
Arthur E.P. Veldman<br />
<strong>Institut</strong>e <strong>of</strong> Mathematics and Computing Science, University <strong>of</strong> Groningen<br />
P.O. Box 800, 9700 AV, Groningen, The Netherlands<br />
Many physical phenomena feature thin bo<strong>und</strong>ary layers, in which the solution varies much more<br />
rapidly than elsewhere in the domain <strong>of</strong> interest. A ‘natural’ approach is to adapt a computational grid<br />
to the variations <strong>of</strong> the solution. In this way one obtains grids with a large diversity in mesh size. Also<br />
the size <strong>of</strong> adjacent mesh cells can be quite different, i.e. the grid shows strong stretching.<br />
‘Traditional’ discretization methods (based on Lagrangian interpolation) focus on minimizing local<br />
truncation error, but experience has shown that these methods prefer low grid stretching rates (e.g. [2]<br />
and the refernces therein). The problems arise because this approach does not take into account the<br />
properties <strong>of</strong> the discrete system matrices that arise after discretization. An alternative approach is to<br />
develop discretization schemes with the properties <strong>of</strong> the system matrix in mind - a general name for<br />
this philosophy is mimetic discretization. Here certain properties <strong>of</strong> the analytic operator are mimiced<br />
in their discrete counterpart.<br />
At RuG we have chosen to retain the symmetry properties <strong>of</strong> the operator, in our application a<br />
combination <strong>of</strong> convection and diffusion. In particular, we discretize convection such that the discrete<br />
version remains skew-symmetric. An almost immediate consequence is that the system matrix remains<br />
diffusively stable (hence never can become singular) on any grid. In formula: Let the system <strong>und</strong>er study<br />
be given by<br />
dφ<br />
+ Lφ = 0,<br />
dt<br />
then the evolution <strong>of</strong> the kinetic energy � φ �H= φ∗Hφ, where H represents the local mesh size, is given<br />
by<br />
d<br />
dt � φ �= −φ∗ ((HL) ∗ + HL)φ.<br />
With skew-symmetric convection, the symmetric part (HL) ∗ + (HL) <strong>of</strong> the system matrix comes only<br />
from diffusion, and the above assertion follows.<br />
Another consequence is that the convective discretization does not produce unphysical numerical diffusion,<br />
which unavoidably will interfere with the physical diffusion. This strategy has been applied e.g.<br />
in direct numerical simulation <strong>of</strong> turbulent flow, where the small-scale balance between convection and<br />
diffusion is quite delicate [3].<br />
In the presentation we would like to illustrate the performance <strong>of</strong> various symmetry-preserving finitevolume<br />
methods: second- and fourth-order central schemes (that we apply in DNS), but also higher-order<br />
upwind schemes. It is less known that on contracting and expanding grids the traditional upwind method<br />
produces negative diffusion [4]; a symmetry-preserving upwind version (a suitable combination <strong>of</strong> skewsymmetric<br />
odd derivatives and symmetric even derivatives) will repair this.<br />
For instance, the fourth-order symmetry-preserving discretization <strong>of</strong> a first-order derivative ∂φ/∂x<br />
becomes<br />
∂φ<br />
∂x ≈ −φi+2 + 8φi+1 − 8φi−1 + φi−2<br />
.<br />
−xi+2 + 8xi+1 − 8xi−1 + xi−2<br />
After muliplication with the denominator (as is usual in a finite-volume setting), the convective contribution<br />
to the coefficient matrix is clearly seen to become skew symmetric.<br />
As a main example we consider a one-dimensional convection-diffusion equation on the unit interval at<br />
a diffusion coefficient k = 0.001. Our ‘favorite’ grid is the Shishkin grid, consisting <strong>of</strong> piecewise-uniform<br />
grid regions with an abrupt (very large) change in mesh size (e.g. [1]). Figure 1 shows a comparison between<br />
the individual solutions <strong>of</strong> second- and fourth-order traditional methods and symmetry-preserving<br />
methods on an abrupt Shishkin grid and on a (smoothly stretched) exponential grid. Both grids contain<br />
Speaker: VELDMANN, A.E.P. 152 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
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A.E.P. VELDMANN: High-order symmetry-preserving discretization on strongly<br />
stretched grids<br />
✬<br />
✫<br />
28 grid points, with half <strong>of</strong> the grid points located in [1 − 10k, 1]). On both grids the ‘traditional’<br />
fourth-order method suffers from an almost singular system matrix.<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
error=3.5e−02<br />
2nd Lagrange<br />
−0.2<br />
0 0.2 0.4 0.6 0.8 1<br />
50<br />
0<br />
−50<br />
−100<br />
error=7.4e+01<br />
4th Lag (+ exact bc)<br />
−150<br />
0 0.2 0.4 0.6 0.8 1<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
error=7.0e−04<br />
2nd symm−pres<br />
−0.2<br />
0 0.2 0.4 0.6 0.8 1<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
4th symm−pres (+ 2nd bc)<br />
error=2.2e−04<br />
−0.2<br />
0 0.2 0.4 0.6 0.8 1<br />
1.4<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
error=3.7e−03<br />
2nd Lagrange<br />
0<br />
0 0.2 0.4 0.6 0.8 1<br />
200<br />
0<br />
−200<br />
−400<br />
−600<br />
error=4.6e+02<br />
4th Lag (+ exact bc)<br />
−800<br />
0 0.2 0.4 0.6 0.8 1<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
error=2.5e−04<br />
2nd symm−pres<br />
−0.2<br />
0 0.2 0.4 0.6 0.8 1<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
4th symm−pres (+ 2nd bc)<br />
error=1.6e−05<br />
−0.2<br />
0 0.2 0.4 0.6 0.8 1<br />
Figure 1: Discrete solutions for k = 0.001 at an abrupt grid (left) and an exponential grid (right). The ’traditional’<br />
discretization, especially the fourth-order version, has problems with the stretching <strong>of</strong> the grid.<br />
Figure 2 shows a grid-refinement study <strong>of</strong> the second- and fourth-order traditional and symmetrypreserving<br />
methods on both typs <strong>of</strong> grids (abrupt and exponential). The much more regular and forgiving<br />
character <strong>of</strong> the symmetry-preserving discretization is evident.<br />
global error<br />
10 0<br />
10 −5<br />
Abrupt: d=10k<br />
10 −2<br />
mean mesh size<br />
10 −1<br />
10 0<br />
10 −5<br />
Exponential: d=10k<br />
2L<br />
2SP<br />
4L<br />
4SP<br />
10 −2<br />
mean mesh size<br />
Figure 2: The global error as a function <strong>of</strong> the mean mesh size. Half <strong>of</strong> the grid points is located in the bo<strong>und</strong>ary<br />
layer <strong>of</strong> thickness d. Four methods are shown: 2L (second-order Lagrangian), 2S (second-order symmetrypreserving),<br />
4L (fourth-order Lagrangian with exact bo<strong>und</strong>ary conditions) and 4S (fourth-order symmetry-preserving<br />
with second-order bo<strong>und</strong>ary treatment).<br />
References<br />
[1] P.A. Farrell, J.J.H. Miller, E. O’Riordan and G. I. Shishkin: A uniformly convergent finite difference<br />
scheme for a singularly perturbed semilinear equation. SIAM J. Num. Anal. 33 (1996) 1135–1149.<br />
[2] A.E.P. Veldman and K. Rinzema: Playing with nonuniform grids. J. Eng. Math. 26 (1992) 119–130.<br />
[3] R.W.C.P. Verstappen and A.E.P. Veldman: Symmetry-preserving discretisation <strong>of</strong> turbulent flow. J.<br />
Comput. Phys. 187 (2003) 343–368.<br />
[4] G. Golub, D. Silvester and A. Wathen: Diagonal dominance and positive definiteness <strong>of</strong> upwind approximations<br />
for advection diffusion problems. In: D.F. Griffiths and G.A. Watson (eds.) Numerical<br />
Analysis: A R. Mitchell 75th Birthday Volume, World Scientific, Singapore (1996) 125–132.<br />
Speaker: VELDMANN, A.E.P. 153 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
10 −1<br />
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Z.-H. YANG, Y.-Z. LI, Y. ZHU: Application <strong>of</strong> Bifurcation Method to Computing<br />
Numerical Solutions <strong>of</strong> Lane-Emden Equation<br />
✬<br />
✫<br />
Application <strong>of</strong> Bifurcation Method to Computing Numerical<br />
Solutions <strong>of</strong> Lane-Emden Equation ∗<br />
Zhong-hua Yang, Ye-zhong Li, Ying Zhu<br />
Department <strong>of</strong> Mathematics,Shanghai Normal University<br />
Shanghai,200234,China<br />
Abstract<br />
In this paper, the Lane-Emden equations <strong>of</strong> index p<br />
� ∆u + u p = 0, (x, y) ∈ Ω<br />
u|∂Ω = 0, (x, y) ∈ ∂Ω<br />
where Ω is a bo<strong>und</strong>ed open domain in R2 , p > 0, are concerned. Equation (0.1) describes the<br />
behavior <strong>of</strong> the density <strong>of</strong> a gas sphere in hydrostatic equilibrium in appropriate units. The<br />
index p, which is called the polytropic index in astrophysics, is larger than 1<br />
2 . It means that no<br />
polytropic stellar system can be homogeneous in galactic dynamics([3],[7]).Using the Liapunov-<br />
Schmidt method and symmetry-breaking bifurcation theory, we compute and visualize multiple<br />
solutions <strong>of</strong> Lane-Emden equation on a bo<strong>und</strong>ed domain <strong>of</strong> R2 with a homogeneous Dirichlet<br />
bo<strong>und</strong>ary condition, which plays an important role in stellar structure and evolution theory.<br />
The domains we consider here include the unit square and the square cut by small square.<br />
The critical point theory was applied to prove the existence and multiplicity <strong>of</strong> solutions<br />
<strong>und</strong>er various assumptions([2], [8]). But what distribution and structure they have and how to<br />
compute them have attracted the attention <strong>of</strong> many mathematicians, physicists and engineers.<br />
Due to the multiplicity, degeneracy and instability <strong>of</strong> the critical points with higher Morse index,<br />
the computation <strong>of</strong> multiple solutions encounters essential difficulties and is truly challenging.<br />
Since 90’s <strong>of</strong> last century, numerical works to compute numerical solutions <strong>of</strong> (0.1) appeared<br />
in the literature. The mountain-pass algorithm, the scaling iterative algorithm ,the monotone<br />
iteration, the direct iteration algorithm and the research extension method([4],[5],[6]) are used<br />
to compute the solutions <strong>of</strong> (0.1). But in these algorithms “ good guess <strong>of</strong> solution” <strong>of</strong> (0.1),<br />
which is a difficult task, is needed. Therefore only few solutions <strong>of</strong> (0.1) are computed yet.<br />
In this paper, we try to use the bifurcation method to overcome this difficulty. Our main<br />
idea is to embed (0.1) into nonlinear elliptic BVP with parameter λ <strong>of</strong> the form<br />
�<br />
F (u, λ) = ∆u + λu + up = 0, (x, y) ∈ Ω,<br />
(0.2)<br />
u|∂Ω = 0, (x, y) ∈ ∂Ω.<br />
According to the bifurcation theory (0.2) has nontrivial solution branches which bifurcate from<br />
its bifurcation points, so we can compute the solutions <strong>of</strong> (0.1) by using continuation method([1])<br />
along these nontrivial solution branches <strong>of</strong> (0.2) until λ = 0. Many new solutions <strong>of</strong> (0.1) with<br />
different symmetry are computed by the bifurcation method.<br />
∗ Supported by Shanghai Development Fo<strong>und</strong>ation for Science and Technology (No.03QA14036), Science<br />
Fo<strong>und</strong>ation <strong>of</strong> Shanghai Municipal Education Commission(05DZ07), Shanghai Leading Academic Discipline<br />
Project(T0401).<br />
Speaker: YANG, Z.-H. 154 <strong>BAIL</strong> <strong>2006</strong><br />
1<br />
(0.1)<br />
✩<br />
✪
Z.-H. YANG, Y.-Z. LI, Y. ZHU: Application <strong>of</strong> Bifurcation Method to Computing<br />
Numerical Solutions <strong>of</strong> Lane-Emden Equation<br />
✬<br />
✫<br />
On the other hand, Lyapunov-Schmidt reduction is used to get the bifurcation equation <strong>of</strong><br />
(0.2), from which we can easily obtain the initial guesses for computing directly the different<br />
solutions <strong>of</strong> (0.1) with different symmetry. Therefore the bifurcation method also <strong>of</strong>fers a more<br />
effective way to computing the multiple solutions <strong>of</strong> Lane-Emden equation and other nonlinear<br />
elliptic bo<strong>und</strong>ary value problem.<br />
References<br />
[1] E.L.,Allogower, K.Georg, Numerical continuation Methods, An Introduction, Springer Series<br />
in Computational Mathematics(Springer, Berlin), 1990.<br />
[2] A.Ambrosetti, P.H. Rabinowitz, Dual variational mehtods in critical point theory and application,<br />
J.Funct. Anal., Vol.14(1973), 327-381.<br />
[3] S.Chandrasekhar, An Introduction to the stellar structure, Dover Publication, Inc., NY,<br />
1967.<br />
[4] Chuanmiao Chen, Ziqing Xie, Structure <strong>of</strong> multiple solutions for nonlinear differential equations.<br />
Science in China Ser.A Mathematics Vol.47 Supp.(2004), 172-180.<br />
[5] Goong Chen,Jianxin Zhou, Wei-ming Ni, Algorithms and visualization for solutions <strong>of</strong> nonlinear<br />
elliptic equations.International Journal <strong>of</strong> Bifurcation and Chaos,Vol.10,No.7(2000)<br />
1565-1612.<br />
[6] Y. Li, J.X. Zhou, A minimax method for finding multiple critial points and its applications<br />
to semilinear PDEs, SIAM J.Sci. Comput., Vol.23(2002), 840-865.<br />
[7] R. Kippenhaln, A. Weigert, Stellar Structure and Evolution, Springer-Verlag, New York,<br />
Berlin, 1990.<br />
[8] P.H. Rabinowitz, Minimax Methods in Critical Point Theory with Applications to Differential<br />
Equations, CBMS Regional Conf. Series in Math.65, Amer.Math.Soc., Providence,<br />
1986.<br />
Speaker: YANG, Z.-H. 155 <strong>BAIL</strong> <strong>2006</strong><br />
2<br />
✩<br />
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Q. YE: Numerical simulation <strong>of</strong> turbulent bo<strong>und</strong>ary for stagnation-flow in the spraypainting<br />
process<br />
✬<br />
✫<br />
Numerical simulation <strong>of</strong> turbulent bo<strong>und</strong>ary for stagnation-flow<br />
in the spray-painting process<br />
Q. Ye<br />
<strong>Institut</strong> <strong>für</strong> Industrielle Fertigung <strong>und</strong> Fabrikbetrieb Universität Stuttgart<br />
Nobelstr. 12, 70569 Stuttgart, Germany<br />
(Abstract for submission to the <strong>BAIL</strong> <strong>2006</strong>)<br />
In order to optimise the painting process, which amounts to a high percentage <strong>of</strong> fixed and<br />
flexible costs in automotive production, numerical simulations <strong>of</strong> spray painting for the<br />
automotive industry, especially using high-speed rotary bell and electrostatically supported<br />
methods, have been performed [1]. Previous numerical studies were mainly concerned with<br />
the calculation <strong>of</strong> the two-phase turbulent flow <strong>of</strong> the spray jet, the modelling <strong>of</strong> the<br />
electrostatic field including space charge and the prediction <strong>of</strong> the film thickness distribution<br />
on the coated work piece. Less attention was paid to the near-wall turbulent flow in the<br />
painting process, which is, however, quite important for particle deposition.<br />
The current numerical investigation is aimed at the turbulent bo<strong>und</strong>ary <strong>of</strong> the stagnationairflow.<br />
A CFD code (Fluent) based on Reynolds-averaged Navier-Stokes equations (RANS)<br />
has to be used because <strong>of</strong> the complicated turbulent flow in the spray-painting process (Fig. 1).<br />
A two-dimensional turbulent channel flow first is calculated using different turbulent models<br />
with near-wall functions. The simulated results are compared with the DNS data [2] (Fig.2),<br />
in order to obtain a suitable model for the investigation <strong>of</strong> the real near-wall flow. The<br />
complicated three-dimensional turbulent flow is then calculated using a real geometry <strong>of</strong> the<br />
atomizer, high-speed rotary bell, and simple target geometry, e.g., a flat plate. The influences<br />
<strong>of</strong> the near-wall mesh resolution and the near-wall functions on the velocity distributions (Fig.<br />
3) and the turbulent magnitudes close to the target are analysed. The computational results<br />
provide useful information for the further study <strong>of</strong> the particle deposition in spray-painting<br />
processes.<br />
up<br />
down<br />
Figure 1: Contours <strong>of</strong> the air velocity magnitude (m/s)<br />
Speaker: YE, Q. 156 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
Q. YE: Numerical simulation <strong>of</strong> turbulent bo<strong>und</strong>ary for stagnation-flow in the spraypainting<br />
process<br />
✬<br />
✫<br />
normalized k<br />
velocity(m/s)<br />
k-yplus<br />
5<br />
4.5<br />
4<br />
3.5<br />
3<br />
2.5<br />
2<br />
1.5<br />
1<br />
0.5<br />
0<br />
1.00E-03 1.00E-02 1.00E-01 1.00E+00<br />
yplus<br />
1.00E+01 1.00E+02 1.00E+03<br />
3.5<br />
3<br />
2.5<br />
2<br />
1.5<br />
1<br />
0.5<br />
velocity magnitude<br />
0<br />
-0.5 -0.3 -0.1 0.1 0.3 0.5<br />
z(m)<br />
standard-wall<br />
DNS<br />
enhanced-wall<br />
Reynolds-stress<br />
k-omega<br />
Figure 2: Comparison <strong>of</strong> non-dimensional turbulent kinetic energy in the fully<br />
developed turbulent channel flow between different turbulent models<br />
enhanced -w all<br />
non-equilibrium<br />
Figure 3: Comparison <strong>of</strong> velocity magnitudes along the painting target at a distance <strong>of</strong><br />
0.1 mm to the wall for two different near-wall functions<br />
[1] Q. Ye, J. Domnick, A. Scheibe, K. Pulli: Numerical Simulation <strong>of</strong> the Electrostatic Spraypainting<br />
Process in the Automotive Industry. High-Performance Computing in Science<br />
and Engineering’04, Springer-Verlag Berlin, Heidelberg, , 2004, pp. 261-275.<br />
[2] J. Kim, P. Moin, R. Moser: Turbulence statistics in fully developed channel flow at low<br />
Reynolds number. J. Fluid Mech. 177, pp.133-166. 1987.<br />
Speaker: YE, Q. 157 <strong>BAIL</strong> <strong>2006</strong><br />
✩<br />
✪
Participants
<strong>BAIL</strong> <strong>2006</strong><br />
Mr. Alizard Frédéric SINUMEF ENSAM Paris Paris FRANCE<br />
Mr. Alrutz Thomas DLR - <strong>Institut</strong>e <strong>of</strong> Aerodynamics and Flow Technology Goettingen Germany<br />
Mr. Apel Thomas Universität der B<strong>und</strong>eswehr München <strong>Institut</strong> f. Mathematik <strong>und</strong> BauinformatikNeubiberg Germany<br />
Mr. Bause Markus Universitaet Erlangen-Nuernberg <strong>Institut</strong> fuer Angewandte Mathematik Erlangen Germany<br />
Mr Boguslawski Poznan University <strong>of</strong> Technology Poland<br />
Mr. Buschmann Matthias H. ILK Dresden / TU Dresden Luft-<strong>und</strong> Kältetechnik /Strömungsmechanik Dresden Germany<br />
Mr. Clavero Carmelo UNIVERSIDAD DE ZARAGOZA CENTRO POLITÉCNICO SUPERIOR ZARAGOZA SPAIN<br />
Mr. Das Debopam Departmnet <strong>of</strong> Aerospace Engg Indian <strong>Institut</strong>e <strong>of</strong> Technology Kanpur Kanpur India<br />
Mr Dillmann Andreas DLR - <strong>Institut</strong>e <strong>of</strong> Aerodynamics and Flow Technology Goettingen Germany<br />
Mr. Donkor Jackson CAPSTONE MINISTRIES TRANS-AFRICAN COLLEGE ACCRA GHANA<br />
Mr. Eisfeld Bernhard DLR Braunschweig Inst. f. Aerodynamik u. Strömungstechnik Braunschweig Germany<br />
Mr. Firooz Abdolhamid University <strong>of</strong> Sistan & Baloochestan Mechanical Engineering Department Zahedan Iran<br />
Mr. Fynn Richard LUGANSK STATE MEDICAL UNIVERSITY LUGANSK UKRAINE<br />
Mr. Gaponov Serguei INSTITUTE OF THEORETICAL AND APPLIED MECHANICS Novosibirsk Russia<br />
Mr Georgoulis Emanuil University <strong>of</strong> Leicester United Kingdom<br />
Mr Gersten Klaus Ruhr-Universitaet Bochum Bochum Germany<br />
Mr. Gracia Jose Luis UNIVERSIDAD DE ZARAGOZA ESCUELA POLITÉCNICA DE TERUEL TERUEL SPAIN<br />
Ms. Hammouch zakia LAMFA UMR CNRS 6140 Faculté de Mathématiques et d'Info, UPJV Amiens France<br />
Mr. Hamouda Makram Faculty <strong>of</strong> Science <strong>of</strong> Bizerte Jarzouna Tunisia<br />
Mr. Hartmann Ralf German Aerospace Center (DLR) Inst. <strong>of</strong> Aerodynamics & Flow Technology Braunschweig Germany<br />
Mr. Hegarty Alan Dept <strong>of</strong> Mathematics and Statistics University <strong>of</strong> Limerick Limerick Ireland<br />
Mr Heinemann Hans-J. DLR - <strong>Institut</strong>e <strong>of</strong> Aerodynamics and Flow Technology Goettingen Germany<br />
Mr. Hemker Pieter W CWI CWI Amsterdam Netherlands<br />
Mr. Herwig Heinz Hamburg University <strong>of</strong> Technology Therm<strong>of</strong>luiddynamics Hamburg Germany<br />
Mr. Heuveline Vincent Universität Karlsruhe (TH) <strong>Institut</strong> <strong>für</strong> Angewandte Mathematik II Karlsruhe Germany<br />
Mr. Hölling Marc Hamburg Univesity <strong>of</strong> Technology Therm<strong>of</strong>luiddynamics Hamburg Germany<br />
Mr. Houston Paul University <strong>of</strong> Nottingham School <strong>of</strong> Mathematical Sciences Nottingham England<br />
Mr. Huerre Patrick Ecole Polytechnique Laboratoire d'Hydrodynamique (LadHyX) Palaiseau France<br />
Mr Il'in A.M. State University Chelyabinsk Russia<br />
Mr Jang Jiin-Yuh Department <strong>of</strong> Mechanical Engineering Air Force Inst. <strong>of</strong> Technology Kaohsiung Taiwan<br />
Mr. Kachuma Dick Computing Laboratory Oxford University Oxford United Kingdom<br />
Mr. Knobloch Petr Charles University Faculty <strong>of</strong> Mathematics and Physics Praha 8 Czech Republic<br />
Mr. Knopp Tobias DLR (German Aerospace Center) Aerodynamics and Flow Technology Goettingen Germany<br />
Mr. Kroll Norbert DLR Inst. f. Aerodynamik u. Strömungstechnik Braunschweig Germany<br />
Mr. Linss Torsten Technische Universität Dresden <strong>Institut</strong> <strong>für</strong> <strong>Numerische</strong> Mathematik Dresden Germany<br />
Mr. Liseykin Vladimir <strong>Institut</strong>e <strong>of</strong> Computational Technologies Novosibirsk Russia<br />
Mr Leong Jik-Chang National Pingtung University Pingtung Taiwan<br />
Mr. Lube Gert University <strong>of</strong> Goettingen <strong>Institut</strong> for Numerical and Applied Mathe Goettingen Germany<br />
Mr. Luedeke Heinrich DLR Aerodynamics and Flow Technology Braunschweig germany<br />
Mr. Mackenzie John Department <strong>of</strong> Mathematics University <strong>of</strong> strathclyde Glasgow U.K<br />
Mr. Mansour kamyar Department <strong>of</strong> Aerospace Engineering Amirkabir University <strong>of</strong> technology Tehran, 15875-4413 Iran<br />
161 <strong>BAIL</strong> <strong>2006</strong>
Mrs.Maragatha Meenakshi Ponnusamy P. Maragatha Meenakshi Government <strong>of</strong> Tamilnadu, India FIP Teacher Fellow, St.Josephs college Tiruchirappalli, Tamil Nadu, India<br />
Mr. Matthies Gunar Ruhr-Universität Bochum Fakultät <strong>für</strong> Mathematik Bochum Deutschland<br />
Mr. maubach joseph technical university <strong>of</strong> Eindhoven faculty <strong>of</strong> mathematics and computer scie Eindhoven netherlands<br />
Mr Mauss J. IMFT Toulouse France<br />
Mr. Mierka Otto Fachbereich Mathematik, LSIII Universität Dortm<strong>und</strong> Dortm<strong>und</strong> Germany<br />
Mr. Miller John Royal College <strong>of</strong> Surgeons in Ireland INCA Dublin 2 Ireland<br />
Mr. Morinishi Koji Dept. Mechanical & System Engineering Kyoto Institue <strong>of</strong> Technology Kyoto Japan<br />
Mrs Nastase Adriana RWTH Aachen Aaachen Germany<br />
Mr. Neuss Nicolas University Kiel Scientific computing Kiel Germany<br />
Mr. Olshanskii Maxim Moscow M.V.Lomonosov State University Dept. Mech. & Math. Moscow Russia<br />
Mr. O'Riordan Eugene Dublin City University Dublin Ireland<br />
Mr. Parumasur Nabendra University KwaZulu-Natal Durban South Africa<br />
Mrs Perotto Simona Politecnico di Milano Milano Italy<br />
Mr. Rapin Gerd University Goettingen NAM Goettingen Germany<br />
Mr. Rasuo Bosko University <strong>of</strong> Belgrade/Faculty <strong>of</strong> Mechan Aeronautical Department Belgrade, 35 Serbia + Montenegro<br />
Mr. Roos Hans-G. TU Dresden Dresden Germany<br />
Mr Saiful-Islam Wan Salim KUiTTHO Batu Pahat Malaysia<br />
Mr. Scheichl Bernhard F. Vienna University <strong>of</strong> Technology Inst. <strong>of</strong> Fluid Mechanics & Heat Transfer Vienna Austria<br />
Mr. Schneider Rene TU-Chemnitz, Fakultät <strong>für</strong> Mathematik Chemnitz Germany<br />
Mr. Sengupta Tapan Dept. <strong>of</strong> Aerospace Engineering Indian <strong>Institut</strong>e <strong>of</strong> Technology Kanpur KANPUR India<br />
Mr. Shishkin Grigory Russian Academy <strong>of</strong> Sciences, Ural Branch <strong>Institut</strong>e <strong>of</strong> Mathematics and Mechanics Ekaterinburg Russia<br />
Mrs.Shishkina Lidia Russian Academy <strong>of</strong> Sciences, Ural Branch <strong>Institut</strong>e <strong>of</strong> Mathematics and Mechanics Ekaterinburg Russia<br />
MrsShishkina Olga DLR Aerodynamics and Flow Technology Goettingen Germany<br />
Ms. Stanculescu Iuliana University <strong>of</strong> Pittsburgh Pittsburgh USA<br />
Mr. Steinrück Herbert Vienna University <strong>of</strong> Technology Fluid Mechanics and Heat Transfer Vienna Austria<br />
Ms. Stephens Meghan Maths Dept National University <strong>of</strong> Ireland, Galway Galway Ireland<br />
Mr. Stynes Martin Department <strong>of</strong> Mathematics National University <strong>of</strong> Ireland Cork Ireland<br />
Mr. Svacek Petr CTU in Prague, Faculty <strong>of</strong> Mech. Eng. Department <strong>of</strong> Technical Mathematics Praha 2 Czech Republic<br />
Mrs.Tarasova Natalia Baltic State Technical University St Petersburg Russia<br />
Mr. Tian Hongjiong Department <strong>of</strong> Mathematics Shanghai Normal University Shanghai P. R. China<br />
Mr. Tobiska Lutz Otto-von-Guericke University Department <strong>of</strong> Mathematics Magdeburg Germany<br />
Mr Tolstykh A.I. Comp. Center <strong>of</strong> Russian Acad. <strong>of</strong> Science Moscow Russia<br />
Mrs.Tselishcheva Irina Russian Academy <strong>of</strong> Sciences, Ural Branch <strong>Institut</strong>e <strong>of</strong> Mathematics and Mechanics Ekaterinburg Russia<br />
Mrs.Valarmathi Sigamani Church <strong>of</strong> South India Bishop Heber College Tiruchirappalli India<br />
Mr. Vasanta Ram Venkatesa Iyengar Ruhr University Bochum <strong>Institut</strong> fuer Thermo- <strong>und</strong> Fluiddynamik Bochum Germany<br />
Mr Vasliiev M.M. Keldysh Inst. <strong>of</strong> Appl. Math. Moscow Russia<br />
Mr. Veldman Arthur University <strong>of</strong> Groningen Mathematics and Computing Science Groningen The Netherlands<br />
Mr. Wall Wolfgang A. TU München Chair for Computational Mechanics Garching Germany<br />
Mr. Wang Hong Department <strong>of</strong> Mathematics University <strong>of</strong> South Carolina Columbia USA<br />
Mr. Yang Zhong-hua Shanghai Normal Univ. Shanghai P.R.China<br />
Mrs.Ye Qiaoyan Fraunh<strong>of</strong>er <strong>Institut</strong> IPA Stuttgart Germany<br />
Mr. Zadorin Alexander Russian Academy <strong>of</strong> Sciences <strong>Institut</strong>e <strong>of</strong> Mathematics SB RAS Omsk Russia<br />
Mrs.Zarin Helena Faculty <strong>of</strong> Science and Mathematics Dept. <strong>of</strong> Mathematics and Informatics Novi Sad Serbia<br />
162 <strong>BAIL</strong> <strong>2006</strong>
Mr. Zegeling Paul Dep. <strong>of</strong> Math. Utrecht Universitz Utrecht Netherlands<br />
Mr. Georgoulis Emanuil University <strong>of</strong> Leicester U.K.<br />
Mr. Boguslawski Leon Poznan University <strong>of</strong> Technology Poland<br />
163 <strong>BAIL</strong> <strong>2006</strong>
Authors<br />
Alizard, F., 67<br />
Alrutz, Th, 69<br />
Anthonissen, M., 57<br />
Apel, Th., 71<br />
Banasiak, J., 130<br />
Bause, M., 72<br />
Bleier, N., 37<br />
Boguslawski, L., 73<br />
Branley, D., 44<br />
Buschmann, M.H., 32<br />
Cangiani, A., 75<br />
Chao, C.-Y., 145<br />
Chigerev, E.N., 149<br />
Chou, Y.-C., 106<br />
Clavero, C., 77<br />
Cousteix, J., 113<br />
Das, D., 35<br />
Dunne, R.K., 14<br />
Eisfeld, B., 79<br />
Firooz, A., 81<br />
Gad-el-Hak, M., 32<br />
Gadami, M., 81<br />
Gaponov, S.A., 85<br />
Georgoulis, E.H., 75<br />
Gersten, Kl., 3<br />
Gracia, J.L., 77<br />
Gravemeier, V., 8<br />
Hölling, M., 91<br />
Hammouch, Z., 87<br />
Hamouda, M., 88<br />
Hartmann, R., 22<br />
Hegarty, A.F., 44, 56<br />
Hemavathi, S., 53<br />
Herwig, H., 91<br />
Heuveline, V., 24<br />
Hong, Q.-S., 145<br />
Houston, P., 4<br />
Huerre, P., 5<br />
Hussong, J., 37<br />
Il’in, A.M., 93<br />
Islam, W.S., 96<br />
Jang, J.-Y., 106<br />
Jensen, M., 75<br />
Jimack, P., 28<br />
Kachuma, D., 98<br />
Kameswara Rao, A., 39<br />
Kaushik, A., 100<br />
Kluwick, A., 136<br />
Knobloch, P., 102<br />
Knopp, T., 69, 104<br />
Kozakiewicz, J.M., 130<br />
Kuzmin, D., 118<br />
Lüdeke, H., 111<br />
Lenz, S., 8<br />
Lesshafft, L., 5<br />
Leu, J.-S., 106<br />
Li, S., 59<br />
Li, Y.-Z., 154<br />
Likhanova, Y.V., 108<br />
Linß, T., 47<br />
Lipavskii, M.V., 149<br />
Lisbona, F., 77<br />
Liseykin, V.D., 108<br />
Lube, G., 109
Mackenzie, J.A., 25<br />
Madden, N., 47<br />
Mansour, K., 113<br />
Matthies, G., 71, 115<br />
Maubach, J., 57, 58<br />
Mauss, J., 116<br />
Mierka, O., 118<br />
Morinishi, K., 120<br />
Nastase, A., 122<br />
Nataf, F., 124<br />
Nayak, A., 35<br />
Neuss, N., 126<br />
Nicola, A., 25<br />
O’Riordan, E., 14<br />
Olshanskii, M.A., 128<br />
Parumasur, N., 130<br />
Patrakhin, D.V., 108<br />
Perotta, S., 27<br />
Petrov, G.V., 85<br />
Purtill, H., 44<br />
Raghavan, V.R., 96<br />
Ram, V.V., 37<br />
Rapin, G., 124<br />
Rasuo, B., 132<br />
Robinet, J.-Ch., 67<br />
Roos, H.-G., 134, 135<br />
Sagaut, P., 5<br />
Savić, L., 41<br />
Scheichl, B., 136<br />
Schneider, R., 28<br />
Sedykh, I., 57<br />
Sengupta, T.K., 39<br />
Sharma, K.K., 100<br />
Shishkin, G.I., 16, 44, 48, 49, 51, 56, 59<br />
Shishkina, L.P., 49, 59<br />
Shishkina, O., 138<br />
Sikwila, S., 56<br />
Smorodsky, B.V., 85<br />
Sobey, I., 98<br />
Stanculescu, I., 18<br />
Steinrück, H., 41<br />
Stynes, M., 6<br />
Stynes, M., 140<br />
Svá˘cek, P., 141<br />
Tai, C.H., 145<br />
Tarasova, N.V., 143<br />
Temam, R., 88<br />
Terracol, M., 5<br />
Tian, H., 147<br />
Tobiska, L., 117, 140<br />
Tolstykh, A.I., 149<br />
Tselishcheva, I.V., 51<br />
Turner, M.M., 14<br />
Valarmathi, S., 53<br />
Vaseva, I.A., 108<br />
Vasieliev, M., 150<br />
Veldmann, A.E.P., 152<br />
Wagner, C., 138<br />
Wall, W.A., 8<br />
Wang, H., 19<br />
Yang, Z.-H., 154<br />
Ye, Q., 156<br />
Zadorin, A.I., 61<br />
Zarin, H., 135<br />
Zegeling, P., 63<br />
Zhu, Y., 154