fluid_mechanics

712 Appendix A ■ Computational Fluid Dynamics and FlowLab
A.8 FlowLab
of the convergence criterion, whether the time step is adequate for the time scale of the problem, and
comparison of CFD solutions to existing data, at least for baseline cases. Even when using a commercial
CFD code that has been validated on many problems in the past, the CFD practitioner still
needs to verify the results through such measures as grid-dependence testing.
A.7.4 Summary
In CFD, there are many different numerical schemes, grid techniques, etc. They all have their
advantages and disadvantages. A great deal of care must be used in obtaining approximate numerical
solutions to the governing equations of fluid motion. The process is not as simple as the
often-heard “just let the computer do it.” Remember that CFD is a tool and as such needs to be
used appropriately to produce meaningful results. The general field of computational fluid dynamics,
in which computers and numerical analysis are combined to solve fluid flow problems, represents
an extremely important subject area in advanced fluid mechanics. Considerable progress
has been made in the past relatively few years, but much remains to be done. The reader is encouraged
to consult some of the available literature.
The authors of this textbook are working in collaboration with Fluent, Inc., the largest provider
of commercial CFD software (www.fluent.com), to offer students the opportunity to use a new
CFD tool called FlowLab. FlowLab is designed to be a virtual fluids laboratory to help enhance
the educational experience in fluids courses. It uses computational fluid dynamics to help the student
grasp various concepts in fluid dynamics and introduces the student to the use of CFD in
solving fluid flow problems. Go to the book’s website at www.wiley.com/college/munson to
access FlowLab resources for this textbook.
The motivation behind incorporating FlowLab with a fundamental fluid mechanics textbook is
twofold: (1) expose the student to computational fluid dynamics and (2) offer a mechanism for students
to conduct experiments in fluid dynamics, numerically in this case. This educational software
allows students to reinforce basic concepts covered in class, conduct parametric studies to gain a better
understanding of the interaction between geometry, fluid properties, and flow conditions, and provides
the student a visualization tool for various flow phenomena.
One of the strengths of FlowLab is the ease-of-use. The CFD simulations are based on previously
developed templates which allow the user to start using CFD to solve flow problems without
requiring an extensive background in the subject. FlowLab provides the student the opportunity
to focus on the results of the simulation rather than the development of the simulation. Typical
results showing the developing velocity profile in the entrance region of a pipe are shown in the
solution window of Fig. A.9.
Axial Velocity
Axial Velocity (m/s)
0.0442
0.0395
0.0347
0.03
0.0253
0.0205
0.0158
Legend
inlet
x = 0.5d
x = 1d
x = 5d
x = 10d
x = 25d
outlet
0.0111
0.00631
0.00157
0
Position (n)
0.1
F I G U R E A.2 Entrance
flow in a pipe. Velocity profiles as a
function of radial position for various
locations along the pipe length.