Large Eddy Simulations of Flow Around Vehicles

PhD student: Sinisa Krajnovic
Supervisor: Lars Davidson
Cooperation: CFD Group, Volvo Cars Corp.
Sponsors: NUTEK
Publications: [2-14], Ensight Story, Designing Aerodynamic Autos , Virvlar ingen har sett förut
Start of project: spring 1998
End of project: autumn 2002

Large Eddy Simulations will be used to predict flow around cars. With LES we expect to be able to predict a number of physical phenomena, such as large-scale structured, unsteadiness etc. LES of the flow around a car will give a deeper understanding of the flow and will help Volvo to optimize the flow around vehicles and thus to design cars and trucks in an aerodynamically better way.
Initially we will work on LES around bluff bodies. The most well-documented test case is a surface-mounted cube where flow visualizations and detailed LDA measurements have been carried out. This flow has also been studied with LES in two workshops, one in Rottach-Egern, Germany and one in Delft, The Netherlands. This flow will be computed both with the computer code CALC-LES used at Chalmers and with the CFX4 code used at Volvo IT. The results obtained with the two methods will be evaluated and one of the codes will be used for the car simulations (see below).
We plan to use two type of subgrid models: the simple Smagorinsky model and a new one-equation model which has been developed at the department. Both type of models are applicable to general three-dimensional flow.
A 64-processor Origin 2000 Silicon Graphics machine will be used. The code has been parallelized by Zacharov [1]. As an example a speed-up of 3.4 (6.2) on 4 (8) processors has been obtained inother projects.


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  1. I. Zacharov, private communication, European Supercomputer Team, Silicon Graphics Inc., Switzerland, 1997.
  2. S. Krajnovic
    Large-Eddy Simulation of the Flow Around a Surface-Mounted Single Cube in a Channel, Master thesis, Rept. 98/7, Thermo and Fluid Dynamics, Chalmers University of Technology, Gothenburg, 1998.
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  3. Krajnovic, S., Müller, D., Davidson, L.
    "Comparison of Two One-Equation Subgrid Models in Recirculating Flows", Direct and Large-Eddy Simulation III, pp. 63-74, Eds: P.V. Voke, N.D. Sandham & L. Kleiser
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  4. Krajnovic, S., Davidson, L.
    Large-Eddy Simulation of the Flow Around a Surface-Mounted Cube Using a Dynamic One-Equation Subgrid Model", The First International Symp. on Turbulence and Shear Flow Phenomena, Santa Barbara, Sept. 12-15, 1999. pp. 741-746, Eds: S. Banerjee & J.K. Eaton, begell house, inc., New York, Wallingford U.K., 1999.
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  5. Krajnovic, S., Davidson, L.
    "Flow Around a Three-Dimensional Bluff Body", 9th International Symposium on Flow Visualisation, Heriot-Watt University, Edinburgh, G.M. Carlomagno and I. Grant (Eds.), 2000.
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  6. S. Krajnovic and L. Davidson
    "Large Eddy Simulation of the Flow Around a Three-Dimensional Bluff Body", AIAA paper 2001--0432, Reno, NV, 2001.
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  7. S. Krajnovic and L. Davidson
    "Large-Eddy Simulation of the Flow Around a Ground Vehicle Body" "SAE Paper 2001-01-0702, Detroit, 2001.
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  8. S. Krajnovic and L. Davidson
    "Large Eddy Simulations of the Flow Around A Simplified Bus", 3rd AFOSR International Conference on DNS and LES, Arlington, Texas, 2001.
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  9. S. Krajnovic and L. Davidson
    "A Mixed One-Equation Subgrid Model for Large-Eddy Simulation", International Journal of Heat and Fluid Flow, Vol. 23, No. 4, pp. 413-425, 2002.
  10. S. Krajnovic and L. Davidson
    "Large Eddy Simulation of the Flow Around a Bluff Body", AIAA Journal, Vol. 40, No. 5, pp. 927--936, 2002.
  11. S. Krajnovic and L. Davidson
    "A test case for large-eddy simulation in vehicle aerodynamics", "Engineering Turbulence Modelling and Experiments 5", pp. 647--656, W. Rodi and N. Fueyo (Eds.), Elsevier, 2002.
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  12. S. Krajnovic and L. Davidson
    "Development of Large Eddy Simulation for Vehicle Aerodynamics", IMECE/ASME HTD-2 TOC, New Orleans, Louisiana, 2002.
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  13. S. Krajnovic and L. Davidson
    Numerical study of the flow around the bus-shaped body, ASME J. Fluid Engng., Vol. 125, pp. 500-509, 2003.
  14. S. Krajnovic and L. Davidson
    "Exploring the Flow Around a Simplified Bus with Large Eddy Simulation and Topological Tools", The Aerodynamics of Heavy Vehicles: Trucks, Buses and Trains, Monterey-Pacific Grove, California, USA, 2002
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Ingalena Ljungström