Flow around a simplified bus is analyzed using large-eddy simulation. At the Reynolds number of based on the model height and the incoming velocity, the flow produces features and aerodynamic forces relevant for the higher (interesting in engineering) Reynolds number. A detailed survey of both instantaneous and time-averaged flows is made and a comparison with previous knowledge on similar flows is presented. Besides the coherent structures observed in experimental and previous numerical studies, new smaller-scale structures were registered here. The mechanisms of formation of flow structures are explained and the difference between instantaneous and time-averaged flow features found in the experimental observations is confirmed. Aerodynamic forces are computed and their time history is used to reveal the characteristic frequencies of the flow motion around the body. A comparison is made of pressure and velocity results with experimental data and shows fairly good agreement.
Issue Section:
Technical Papers
Keywords:
external flows,
flow simulation,
aerodynamics,
drag,
road vehicles,
computational fluid dynamics
Topics:
Flow (Dynamics),
Vortices,
Separation (Technology),
Simulation,
Wakes,
Bubbles,
Aerodynamics
1.
Hucho, W-H., 1998, Aerodynamics of Road Vehicles, 4th Ed., Society of Automotive Engineers, Warrendale, PA.
2.
Bearman, P. W., Davis, J. P., and Harvey, J. K., 1983, “Measurement of the Structure of Road Vehicle Wakes,” International Journal of Vehicle Design (Technological Advances in Vehicle Design Series, SP3, Impact of Aerodynamics on Vehicle Design), pp. 493–499.
3.
Ahmed, S. R., Ramm, G., and Faltin, G., 1984, “Some Salient Features of the Time Averaged Ground Vehicle Wake,” SAE Paper No. 840300.
4.
Barlow, J., Guterres, R., Ranzenbach, R., and Williams, J., 1999, “Wake Structures of Rectangular Bodies With Radiused Edges Near a Plane Surface,” SAE Paper No. 1999-01-0648.
5.
Duell, E. G., and George, A. R., 1999, “Experimental Study of a Ground Vehicle Body Unsteady Near Wake,” SAE Paper No. 1999-01-0812.
6.
Ahmed
, S. R.
, 1981
, “Wake Structures of Typical Automobile Shapes
,” ASME J. Fluids Eng.
, 103
, pp. 162
–169
.7.
Bearman, P. W., De Beer, D., Hamidy, E., and Harvey, J. K., 1989, “The Effect of a Moving Floor on Wind-Tunnel Simulation of Road Vehicles,” SAE Paper No. 880245.
8.
Han
, T.
, 1989
, “Computational Analysis of Three-Dimensional Turbulent Flow Around a Bluff Body in Ground Proximity
,” AIAA J.
, 27
(9
), pp. 1213
–1219
.9.
Duell, E. G., 1994, “Experimental Investigation of Unsteady Near Wakes of Ground Vehicle Bodies,” Ph.D. thesis, Cornell University, Ithaca, NY.
10.
Barlow, J. B., Guterres, R., and Ranzenbach, R., 1999, “Rectangular Bodies With Radiused Edges in Ground Effect,” AIAA Paper No. 99-3153.
11.
Bearman
, P. W.
, 1997
, “Near Wake Flows Behind Two- and Three-Dimensional Bluff Bodies
,” J. Wind. Eng. Ind. Aerodyn.
, 69–71
, pp. 33
–54
.12.
Kataoka, T., China, H., Nakagawa, K., Yanagimoto, K., and Yoshida, M., 1991, “Numerical Simulation of Road Vehicle Aerodynamics and Effect of Aerodynamic Devices,” SAE Paper No. 910597.
13.
Hashiguchi, M., Kawaguchi, K., Yamasake, R., and Kuwahara, K., 1989, “Computational Study of the Wake Structure of a Simplified Ground-Vehicle Shape With Base Slant,” SAE Paper No. 890597.
14.
Aoki, K., Ohbayashi, T., Zhu, M., and Miyata, H., 1993, “Finite-Volume Simulation of 3D Vortical Flow-Fields About Road Vehicles With Various After-Body Configuration,” SAE Paper No. 931896.
15.
Sohankar
, A.
, Davidson
, L.
, and Norberg
, C.
, 2000
, “Large Eddy Simulation of Flow Past a Square Cylinder: Comparison of Different Subgrid Scale Models
,” ASME J. Fluids Eng.
, 122
(1
), pp. 39
–47
.16.
Sohankar
, A.
, Davidson
, L.
, and Norberg
, C.
, 2000
, erratum, ASME J. Fluids Eng.
, 122
(3
), p. 643
643
.17.
Krajnovic´
, S.
, and Davidson
, L.
, 2002
, “Large Eddy Simulation of the Flow Around a Bluff Body
,” AIAA J.
, 40
(5
), pp. 927
–936
.18.
Ghosal
, S.
, 1999
, “Mathematical and Physical Constraint on Large-Eddy Simulations of Turbulence
,” AIAA J.
, 37
(2
), pp. 425
–433
.19.
Ghosal
, S.
, and Moin
, P.
, 1995
, “The Basic Equations for the Large Eddy Simulation of Turbulent Flows in Complex Geometry
,” J. Comput. Phys.
, 118
(1
), pp. 24
–37
.20.
Meneveau
, C.
, and Katz
, J.
, 2000
, “Scale-Invariance and Turbulence Models for Large-Eddy Simulation
,” Annu. Rev. Fluid Mech.
, 32
, pp. 1
–32
.21.
Smagorinsky
, J.
, 1963
, “General Circulation Experiments With the Primitive Equations
,” Mon. Weather Rev.
, 91
(3
), pp. 99
–165
.22.
Pope, S. B., 2000, Turbulent Flows, 1st Ed., Cambridge University Press, Cambridge, UK.
23.
Davidson, L., and Farhanieh, B., 1995, “CALC-BFC: A Finite-Volume Code Employing Collocated Variable Arrangement and Cartesian Velocity Components for Computation of Fluid Flow and Heat Transfer in Complex Three-Dimensional Geometries,” Report 95/11, Department of Thermo and Fluid Dynamics, Chalmers University of Technology, Gothenburg.
24.
Nilsson, H., and Davidson, L., 1998, “CALC-PVM: A Parallel SIMPLEC Multiblock Solver for Turbulent Flow in Complex Domains.” Internal Report 98/12, Department of Thermo and Fluid Dynamics, Chalmers University of Technology, Gothenburg.
25.
Sohankar, A., 1998, “Numerical Investigation of Vortex Shedding Around Square Cylinders at Low Reynolds Number,” Ph.D. thesis, Department of Thermo and Fluid Dynamics, Chalmers University of Technology, Gothenburg.
26.
Cooper, K. R., 1985, “The Effect of Front-Edge Rounding and Rear Edge Shaping on the Aerodynamic Drag of Bluff Vehicles in Ground Proximity,” SAE Paper No. 850288.
27.
Hucho, W. H., Janssen, L. J., and Emmelmann, H. J., 1976, “The Optimization of Body Details–A Method for Reducing the Aerodynamic Drag of Road Vehicles,” SAE Paper No. 760185.
28.
Krajnovic´, S., and Davidson, L., 2002, “A Test Case for Large-Eddy Simulation in Vehicle Aerodynamics,” Proceedings of the 5th International Symposium on Engineering Turbulence Modelling and Measurements, W. Rodi and N. Fueyo, eds., Mallorca, Spain, Elsevier, New York, pp. 647–656.
29.
Chong
, M. S.
, Perry
, A. E.
, and Cantwell
, B. J.
, 1990
, “A General Classification of Three-Dimensional Flow Fields
,” Phys. Fluids
, 5
(2
), pp. 765
–777
.30.
Sujudi, D., and Haimes, R., 1995, “Identification of Swirling Flow in 3-D Vector Fields,” AIAA Paper No. AIAA 95-1715.
31.
Baker
, C. J.
, 2001
, “Flow and Dispersion in Ground Vehicle Wakes
,” J. Fluids Struct.
, 15
(7
), pp. 1031
–1060
.32.
Chandrsuda
, C.
, and Bradshaw
, P.
, 1981
, “Turbulence Structures of Reattaching Mixing Layer
,” J. Fluid Mech.
, 110
, pp. 171
–194
.33.
Krajnovic´, S., 2002, “Large Eddy Simulations for Computing the Flow Around Vehicles,” Ph.D. thesis, Department of Thermo and Fluid Dynamics, Chalmers University of Technology, Gothenburg.
34.
Rodi
, W.
, Ferziger
, J. H.
, Breuer
, M.
, and Pourquie´
, M.
, 1997
, “Status of Large-Eddy Simulations: Results of a Workshop
,” ASME J. Fluids Eng.
, 119
, pp. 248
–262
.35.
Jeong
, J.
, and Hussain
, F.
, 1995
, “On the Identification of a Vortex
,” J. Fluid Mech.
, 285
, pp. 69
–94
.Copyright © 2003
by ASME
You do not currently have access to this content.
