The Influence of Rotating Wheels on Vehicle Aerodynamics - Numerical and Experimental Investigations

Investigations of the aerodynamic influence of rotating wheels on a simplified vehicle model as well as on a series production car are presented. For this research CFD simulations are used together with wind tunnel measurements like LDV and aerodynamic forces. Several wheel rim geometries are examined in stationary and in rotating condition. A good agreement could be achieved between CFD simulations and wind tunnel measurements.

Based on the CFD analysis the major aerodynamic mechanisms at rotating wheels are characterized. The flow topology around the wheels in a wheel arch is revealed. It is shown, that the reduction of drag and lift caused by the wheel rotation on the isolated wheel and the wheel in the wheel arch are based on different effects of the airflow. Though the forces decrease at the front wheel due to the wheel rotation locally, the major change in drag and lift happens directly on the automotive body itself. This increase of aerodynamic efficiency of the automotive body caused by the wheel rotation is attributed to a changed interaction between the wakes of the rear wheels and the car's rear end. These results emphasize that wheel rotation is essential for aerodynamic shape optimization of production cars.