Impact of Rim Orientation on Road Vehicles Aerodynamics Simulations

Aerodynamic CFD simulations in the automotive industry, which are based on the steady-state RANS (Reynolds-averaged Navier-Stokes) approach typically utilize approximate numerical methods to account for rotating wheels. In these methods, the computational mesh representing the rim geometry remains stationary, and the influence of the wheel rotation on the air flow is modelled. As the rims are considered only in one fixed rotational position (chosen arbitrarily in most cases), the effects of the rim orientation on the aerodynamic simulation results are disregarded and remain unquantified.
This paper presents a numerical sensitivity study to examine the impact of the rim orientation position on the aerodynamic parameters of a detailed production vehicle. The simulations are based on the steady-state RANS approach. These investigations are carried out for three rim geometries, and for simulation cases with stationary and rotating wheels for comparison, where the Moving Wall (MW) and the Moving Reference Frame (MRF) methods [1, 2], as well as combinations of the two approaches are used to model the wheel rotation.
For the test vehicle, alterations in the flow field, and subsequently an influence on the development of the aerodynamic vehicle drag could be detected, which results in a significant effect on the integral vehicle drag. These results demonstrate that the rim orientation position is an important parameter for vehicle aerodynamics simulation.