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Advances in External-Aero Simulation of Ground Vehicles Using the Steady RANS Equations
ISSN: 0148-7191, e-ISSN: 2688-3627
Published March 06, 2000 by SAE International in United States
Annotation ability available
Event: SAE 2000 World Congress
Numerical prediction of the aerodynamics around cars has long been one of the rudimentary needs in automotive engineering. Despite all of the recent developments in Computational Fluid Dynamics (CFD) and its constituent technologies, however, it’s still not an easy task to accurately predict the flows around and the aerodynamic forces and moments acting on ground vehicles. The complex configurations and flow physics involved in ground-vehicle aerodynamics require, among other things, sophisticated geometry modeling and meshing tools, advanced turbulence models and an efficient solution algorithm.
This paper discusses various aspects of applying modern Computational Fluid Dynamics (CFD) to the prediction of aerodynamic flows around ground vehicles. The discussion will be in the framework of an unstructured mesh finite-volume method applied to the steady-flow Reynolds-averaged Navier-Stokes (RANS) equations, which has been established as a standard CFD approach for external aerodynamics applications. The main issues in this paper include mesh, numerics, and turbulence modeling. The issue of mesh will be discussed with the primary focus on unstructured meshes that allow the use of cells of arbitrary topology, including hexahedra, tetrahedral, pyramids, prisms, and any combination of these. Special emphasis will be placed on viscous-hybrid meshes, which combine prism layers in near-wall regions (for better resolution of strong gradients in wall boundary layers) and a tetrahedral mesh in the far field. Solution adaptive mesh refinement will be discussed in view of its ability to resolve economically a wide range of length scales in the flow. We’ll discuss the impact of various turbulence models on the prediction of the aerodynamics of ground vehicles. We’ll also consider the great challenges posed by the salient features of the subject flow, including strong streamline curvature, crossflow, various types of flow separation on the body, and the ensuing shear layers and vortices. A second-moment turbulence closure, employing Reynolds-stress transport equations, is proposed as a viable turbulence model that can accurately model the salient features of the flow around ground vehicles. The issue of near-wall treatment will be addressed with an emphasis on the use of wall functions. This paper describes all of these issues in detail and it showcases simulations for a selected number of vehicle shapes and related configurations.
CitationMakowski, F. and Kim, S., "Advances in External-Aero Simulation of Ground Vehicles Using the Steady RANS Equations," SAE Technical Paper 2000-01-0484, 2000, https://doi.org/10.4271/2000-01-0484.
- Han, T. Computational Analysis of Three-Dimensional Turbulent Flow Around a Bluff Body in Ground Proximity AIAA J. 27 9 1213 1219 1988
- Yamada, A. Ito, S. Computational Analysis of Flow Around a Simplified Vehicle-Like Body SAE 930293 March 1993
- Hucho, W. Sovran, G. Aerodynamics of Road Vehicles Annual Review of Fluid Mechanics 25 485 537 1993
- Mathur, S.R. Murthy, J.Y. A Pressure-Based Method for Unstructured Meshes Numerical Heat Transfer 31 195 215 1997
- Kim, S.-E., Mathur, S.R., Murthy, J.Y., Choudhury, D., A Reynolds-Averaged Navier-Stokes Solver Using Unstructured Mesh-Based Finite-Volume Scheme AIAA-Paper 98-0231 1998
- Batchelor, G. K., An Introduction to Fluid Dynamics Cambridge University Press 1967
- Issa, R. I. Rise of Total Pressure in Frictional Flow AIAA Jour. 33 4 May 1994
- Gibson, M.M. Launder, B.E. Ground Effects on Pressure Fluctuations in the Atmospheric Boundary layer J. Fluid Mechanics 86 491 511 1978
- Speziale, C.G. Sarkar, S. Gatski, T.B. Modeling of Pressure-Strain Correlation of Turbulence: An Invariant Dynamical Systems Approach J. Fluid Mech. 227 245 272
- Baskaran, V., Smits, A. J. Joubert, P. N. A Turbulent Flow over a Curved Hill – Part 1. Growth of an Internal Boundary Layer J. Fluid Mechanics 182 47 83 1987
- Kim, S.E. Choudhury, D. A Near-Wall Treatment Using Wall Functions Sensitized to Pressure Gradient, ASME FED-Vol. 217 Symposium on Separated and Complex Flows Otugen M.V. 1995
- Ahmed, S. R., Ramm, G. Faltin, G. Some Salient Features of the Time-averaged Ground Vehicle Wake SAE Technical Paper Series, No. 840300, International Congress & Exposition, Detroit, Michigan February 27 March 2 1984