Aerodynamic characterization of an isolated rotating wheel in ground contact using dual-balance measurements

In this study, the aerodynamic characteristics of a full-scale, isolated passenger car wheel equipped with three rim configurations—a five-spoke rim, an aerodynamic rim, and a closed rim—were experimentally investigated in a wind tunnel. A dual-balance system was developed to measure the drag, lift, and side force of the wheel. The wake flow behind the wheel was assessed using a 14-hole pressure probe. The numerical simulation was employed to assist in analyzing the aerodynamic flow phenomena underlying the observed forces. The results indicated that the drag coefficients for the aerodynamic and closed rim configurations decreased by approximately 10% as the Reynolds number increased from 7.8 ×105 to 1.56 ×106, whereas the coefficient for the five-spoke rim setup remained nearly constant. Additionally, drag measurements obtained using the dual-balance system were approximately 8% lower than those recorded with a single-balance setup. Furthermore, the difference in drag between different rim configurations significantly increased with increasing wheel yaw angles. Notably, the closed rim design exhibited 15.2% less drag than the five-spoke rim at a 0∘ yaw angle and 48.2% less drag at a 20∘ yaw angle.