Numerical Study of the Influence of Rim Design on the Aerodynamics of an Isolated Wheel

Wheel and tire contribute up to 25% of the total aerodynamic drag of passenger cars. Under the same tire mounted on the wheel, the rim holes induce air flow and result in complex flow separation in a highly unsteady regime. To have a clearer understanding of the flow mechanisms and assign sensitivity of rim parameters. The effect of rim spoke design parameters on the aerodynamics of an isolated wheel had been investigated with unsteady CFD simulation. Four design variables, the angle A, radius R1, and R2, and chord length L, which characterized the rim spoke are proposed, and the Latin hypercube sampling is used to conduct the design of the experiment (DOE). Based on the simulation results of different rim designs, the Kriging model and adaptive simulated annealing algorithm are selected to obtain the optimum parameters. The results show that the aerodynamic characteristics are very sensitive to the selected four design variables, the optimized rim changes the flow state, and the drag coefficient of the Ahmed body mounted with the optimized wheel decreased by 4.7%.