simulate the flow correctly, as shown by the large difference <strong>in</strong> the results. The turbulence <strong>in</strong>tensity was <strong>in</strong>creased to 10%, <strong>and</strong> a much closer agreement with experiment was obta<strong>in</strong>ed. Visualisation of the flow streaml<strong>in</strong>es showed that the separation on the ground upstream of the tra<strong>in</strong> was probably elim<strong>in</strong>ated. Clearly, the turbulence parameters significantly affect the <strong>CFD</strong> modell<strong>in</strong>g of this flow. (The <strong>in</strong>vestigation is still <strong>in</strong> progress, so the results are <strong>in</strong>complete. In particular, the effects of turbulence length scale or ground surface roughness have not been <strong>in</strong>vestigated.) The results suggest that some of the observed variations between different w<strong>in</strong>d tunnel experiments may be due to this effect. The highly turbulent <strong>in</strong>flow of the ABL experiment seems to elim<strong>in</strong>ate the upstream separation. It also makes the flow over the tra<strong>in</strong> less susceptible to Reynolds number effects. Tra<strong>in</strong> on an embankment For a tra<strong>in</strong> on a 4m high embankment, experimental <strong>and</strong> CDF results are shown <strong>in</strong> Figs. 13 <strong>and</strong> 14. The <strong>in</strong>flow turbulence <strong>in</strong>tensity was 3%. The <strong>CFD</strong> <strong>and</strong> experimental results are similar for the roll<strong>in</strong>g moment, but not side force. This appears to contradict the result for the flat ground case above. The flow streaml<strong>in</strong>es around the embankment <strong>and</strong> tra<strong>in</strong> are shown <strong>in</strong> Fig. 15. The flow is attached to the embankment slope <strong>and</strong> separates cleanly at the edge, reattach<strong>in</strong>g upstream of the rail. It is surmised that the well-def<strong>in</strong>ed separation causes the flow to be less sensitive to <strong>in</strong>flow turbulence. Tra<strong>in</strong> motion over the ground It was easy to simulate the effect of the tra<strong>in</strong> mov<strong>in</strong>g over the ground with the <strong>CFD</strong>. Prelim<strong>in</strong>ary runs <strong>in</strong>dicated only a small change from the correspond<strong>in</strong>g steady flow case, but the <strong>in</strong>flow profile was not correctly skewed with height. The prospects for exam<strong>in</strong><strong>in</strong>g the effect of tra<strong>in</strong> motion <strong>and</strong> unsteady cross-w<strong>in</strong>d gusts is encourag<strong>in</strong>g. Conclusions <strong>CFD</strong> has been applied to the case of a tra<strong>in</strong> <strong>in</strong> a turbulent flow. The boundary layer behaviour, particularly on the ground just upstream of the tra<strong>in</strong>, was affected by the <strong>in</strong>flow turbulence <strong>in</strong>tensity <strong>and</strong> scale, which thus had a strong <strong>in</strong>fluence on the forces <strong>and</strong> roll<strong>in</strong>g moment. With appropriate turbulence <strong>in</strong>tensity, the side force coefficient was predicted to good accuracy. Bibliography 1. Ahmed, K., Development of w<strong>in</strong>d tunnel techniques for unsteady tra<strong>in</strong> aerodynamics, MPhil Thesis, QUB Aeronautical Eng<strong>in</strong>eer<strong>in</strong>g, 2003. 2. Baker, C J, Ground vehicles <strong>in</strong> high cross w<strong>in</strong>ds. Part 1: Steady aerodynamic forces. J. Fluids <strong>and</strong> Structures, 1991, 5, 69-90. 3. Baker, C J, Ground vehicles <strong>in</strong> high cross w<strong>in</strong>ds. Part 2: Unsteady aerodynamic forces. J. Fluids <strong>and</strong> Structures, 1991, 5, 91-111. 4. WCRM W<strong>in</strong>d Load<strong>in</strong>g Studies, Atmospheric Boundary Layer Studies. BMT Fluid Mechanics Ltd. Report 43309rep4v3, F<strong>in</strong>al, 16 January 2003. 5. Fann<strong>in</strong>g, C., <strong>CFD</strong> <strong>in</strong>vestigation of aerodynamics of a high speed tra<strong>in</strong>, QUB Aeronautical Eng<strong>in</strong>eer<strong>in</strong>g, MEng project report, May 2003. 6. Chraibi, H., Turbulent flow over a high speed tra<strong>in</strong> on an embankment, QUB Aeronautical Eng<strong>in</strong>eer<strong>in</strong>g, summer project report, Aug. 2003.
0.9 Cs vs yaw angle Side force coefficient (Cs) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 10 20 30 40 50 60 70 80 90 100 Yaw angle (deg) QUB 1/50 scale (M-III) MIRA 1/5 scale (APT) Cranfield 1/50 (APT) Turbulence simulation AEA 1/50 (AEA) Turbulence simulation Fig. 1. Coefficient of side force vs. yaw angle: APT (various) <strong>and</strong> Mark 3 coach (QUB) Fig 2. Class 87 locomotive <strong>and</strong> Mark 3 coaches: prototype for w<strong>in</strong>d tunnel model
- Page 1 and 2:
Integrating CFD and Experiment in A
- Page 3 and 4:
Experimentalist’s requirements fo
- Page 5 and 6:
persistent discrepancy may be due t
- Page 7 and 8:
numbers significantly lower than th
- Page 9 and 10:
Heat flux measurements. Over the pa
- Page 11 and 12:
The measurements are made on select
- Page 13 and 14:
advantage that the signal is emitte
- Page 15 and 16:
12. Mébarki, Y. and Mérienne, M.
- Page 17 and 18:
castellated nozzles entrained more
- Page 19 and 20:
Axisymmetric Regular Convergent Div
- Page 21 and 22: Figure 5: Typical instantaneous PIV
- Page 23 and 24: Figure 8: Streamwise Velocity Profi
- Page 25 and 26: 1.25 CFD (SKW PRESTO) Experimental
- Page 27 and 28: 5 Conclusions In this paper we have
- Page 29 and 30: 2 which include boundary layer and
- Page 31 and 32: 4 not received much attention in th
- Page 33 and 34: 6 Although a great deal of effort h
- Page 35 and 36: 8 Computational simulations can con
- Page 37 and 38: 10 separation location over rounded
- Page 39 and 40: 12 3.7 Vortex / flexible wing inter
- Page 41 and 42: 14 [8] Mitchell, A.M. and Molton, P
- Page 43 and 44: 16 [31] Gursul, I., Proposed Mechan
- Page 45 and 46: 18 Figure 3: Spectrum of unsteady f
- Page 47 and 48: 20 Figure 7: Flow visualisation of
- Page 49 and 50: Figure 11: Upper surface pressure d
- Page 51 and 52: While the information presented in
- Page 53 and 54: Figure 3 : DFR against Flap angle f
- Page 55 and 56: Figure 7 shows a series of plots of
- Page 57 and 58: Figure 9 : Contours of Mach number,
- Page 59 and 60: ¥:97§Y©R¥e©H !V( H ¨9#f§e!"
- Page 61 and 62: é¡êŒëWì¤í?î(ïeð±ñWòL
- Page 63 and 64: Ó3×ÓnØ*Ù(Ú*Û+Ü ÝÞ#ß)ÝG
- Page 65 and 66: 6‹wB6h67 C,7D4 ')(r,+.st/9:!/L£8
- Page 67 and 68: ACBDsEutCIvwlxV^ c Q!Lkd_Q_SFM PQ_^
- Page 69 and 70: ǹºF»¼@½:¾¿_À!Á »_ÂÃk
- Page 71: yaw angle. Also, extreme value coef
- Page 75 and 76: Fig. 5. Grid block structure around
- Page 77 and 78: Cs comparison at V=0.6 m/s Fig. 10.
- Page 79 and 80: Investigation of Flow Turning in a
- Page 81 and 82: duct as it approaches the blocker c
- Page 83 and 84: Figure 1. Natural Blockage Thrust R
- Page 85 and 86: Figure 7. Post-Exit rake Total Span
- Page 87 and 88: Figure 11. Comparison of Static Pre
- Page 89 and 90: 2.2 Data Aquired The Embedded Laser
- Page 91 and 92: First, plots of the turbulent Reyno
- Page 93 and 94: Particles seeding tube 3 m 1 m mode
- Page 95 and 96: 000000000 MEASUREM ENT S MEASUREM E
- Page 97 and 98: Figure 5: Influence of the pseudo t
- Page 99 and 100: Figure 7: Turbulent Reynolds' numbe
- Page 101 and 102: Figure 9: Turbulent Reynolds' numbe
- Page 103 and 104: Figure 11: Vortex Shedding cycle fo
- Page 105 and 106: Figure 13: Comparison with experime