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Tire aerodynamics has long been viewed as a critical area in the ongoing research on vehicle drag reduction as it is a significant contributor to the overall automotive parasitic drag. Previous wind-tunnel experiments have revealed that the flow over a rotating wheel is a very complex phenomenon. This complexity arises from the tire-ground contact patch, various points of flow separation due to the wheel geometry, and the effects of wheel rotation. These aspects make the numerical simulation of this type of flow rather challenging. Existing literature shows a number of ways, like sliding mesh, by which to simulate the flow over an isolated wheel, but the problem of finding an accurate yet cost-effective solution still remains elusive. The current paper attempts to investigate the different methodologies to emulate the wheel motion. In addition, the paper will address the influence of mesh parameters and solver setting dependency of the solution.

Cost benefit and teraflop restrictions imposed by racing sanctioning bodies make steady-state RANS CFD simulation a widely accepted first approximation tool for aerodynamics evaluations in motorsports, in spite of its limitations. Research involving generic and simplified vehicle bodies has shown that the veracity of aerodynamic CFD predictions strongly depends on the turbulence model being used. Also, the ability of a turbulence model to accurately predict aerodynamic characteristics can be vehicle shape dependent as well. Modifications to the turbulence model coefficients in some of the models have the potential to improve the predictive capability for a particular vehicle shape. This paper presents a systematic study of turbulence modeling effects on the prediction of aerodynamic characteristics of a NASCAR Gen-6 Cup racecar. Steady-state RANS simulations are completed using a commercial CFD package, STAR-CCM+, from CD-Adapco.