Aerodynamic and flow behaviors of Ahmed model mounted with wheel under crosswinds using the orthogonal test design

Increasing wheel spoke coverage area can reduce vehicle aerodynamic drag but may be detrimental to vehicle crosswind stability. This study aims to reveal the influence of the spoke openings, the yaw angles, and the vehicle speed on the aerodynamic performance of the vehicle under crosswind. The simulation model is first valeted using the wind tunnel. After that, three different wheels spoke openings (opening area ratio is 1:2:3) were selected to mount on the Ahmed model, and the effects results were obtained using an orthogonal test design. The results indicated that increasing spoke openings and yaw angles increased aerodynamic drag. Especially in the test of increasing the yaw angle, the drag coefficients of the car model and the front and rear wheels increased by 47.69%, 68.58%, and 79.89%, respectively. The lateral stability of the car model and its components was not obviously affected by the spoke openings. Increasing the yaw angle substantially increased the coefficients of lateral force and roll moment and generated stronger positive pressure on the windward side of the car body. In comparison, the leeward side exhibited more significant negative pressure and pressure fluctuation. Furthermore, the vortex volume and wake development length of the front wheels exceeded those of the rear wheels in the studied tests. Increasing the spoke openings and yaw angle intensified the vortex influence width in the wheel region and vortex strength at the model tail. Under crosswind conditions, the strength of the leeward side spiral shedding vortex intensified, and the velocity field revealed the wake impact ranges in the vertical and longitudinal directions expanded.