Aerodynamic Forces of Exposed and Enclosed Rotating Wheels as an Example of the Synergy in the Development of Racing and Passenger Cars

The aim of this report is to present the results obtained from the wind tunnel tests performed in the BMW wind tunnel regarding the pressure distribution on a rotating wheel. The acquired data is used to examine its flow topology for the “open” and “enclosed” cases and determine the wheel drag, lift and side forces by integrating the pressure distribution on its surface.

The investigation concerned such measurements on a half scale model wheel. Its pressure distribution was identified with and without the presence of a racecar body. The wheel was also mounted on a half scale passenger car body and pressure measurements were taken with and without a wheel spoiler. After the pressure distributions were known for all configurations, the aerodynamic forces generated were determined. The influence of boundary layer thickness on them was also investigated.

A better understanding of the forces the model wheel is subjected to is gained. These forces are resolved for parts of the wheel to make precise statements about the influences the various tested configurations have on the flow field. This analysis method confirmed the existence of known vortex structures. Furthermore, testing with and without boundary layer suction proved to be crucial in revealing new flow structures that normally would not have been visible just from the pressure distribution.