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In the present work we investigated experimentally and computationally the unsteady flow around a BMW car model including wheels*. This simulation yields mean flow and turbulence fields, enabling the study aerodynamic coefficients (drag and lift coefficients, three-dimensional/spatial wall-pressure distribution) as well as some unsteady flow phenomena in the car wake (analysis of the vortex shedding frequency). Comparisons with experimental findings are presented. The computational approach used is based on solving the complete transient Reynolds-Averaged Navier-Stokes (TRANS) equations. Special attention is devoted to turbulence modelling and the near-wall treatment of turbulence. The flow calculations were performed using a robust, eddy-viscosity-based ζ - ƒ turbulence model in the framework of the elliptic relaxation concept and in conjunction with the universal wall treatment, combining integration up to the wall and wall functions.

The paper presents the-state-of-the-art numerical simulation of the flow around vehicles by examining a number of various industrial benchmarks. A selection of results, obtained by a finite volume numerical code based on the Reynolds-Averaged Navier Stokes (RANS) approach, illustrates the capability of Computational Fluid Dynamics (CFD) to provide accurate and reliable solutions in the area of external car aerodynamics. Benchmarks presented here are Peugeot 405 model, SAE Notchback Reference Body and VW-CFD model. Due attention was given to the reduction of both numerical as well as turbulence modeling error. This also includes the use of second-order accurate differencing schemes for convection terms and the full Reynolds-stress model to model Reynolds stresses. The computations showed a substantial difference in the flow patterns predicted by the standard k-ε model and by the full Reynolds-stress model.