Investigation of Tyre Pattern Effect on the Aerodynamics of a Passenger Vehicle

The wheels of a passenger vehicle are one of the major contributors to the total aerodynamic drag, making their aerodynamic performance a considerable factor for the overall energy efficiency of the vehicle. Previous studies have shown that the complex flow field created by the wheels is sensitive to small geometrical variations of the tyre and that features such as shoulder profile and tread pattern can have a significant impact on drag and lift. In this study, the DrivAer model is used to evaluate the flow fields and aerodynamics of four tyre tread patterns with two rim designs. Full-scale wind tunnel tests were conducted where forces, surface pressures and flow fields were measured. Numerical simulations were also performed to aid the analysis. Using a slick tyre as the reference, it was found that rain grooves typically reduced the drag, whereas the effect of lateral grooves was dependent on the rim configuration. For the lift forces, the largest lift variations were obtained for the front lift which, in general, was reduced by rain grooves and increased by lateral grooves, most notably for the closed rim. The importance of considering the parasitic lift force acting on the wheel drive units when comparing experiments and simulations was demonstrated.