Study and Evaluation of the Effects of Bionic Groove Structures Applied to Wheel Spokes on the Aerodynamics of a Car Model

Decreasing the wheel aerodynamic drag is one of the important measures for lowering vehicle drag and improving fuel efficiency. The innovation of this study is designing the bionic non-smooth groove structure on the spoke surface as a drag reduction method and introducing the energy gradient function K value to characterize the aerodynamic drag. Wheels with and without grooved spoke structures were mounted on the Ahmed body, and the flow characteristics around the wheel region and car model were numerically investigated. A comparison between the numerical and experimental pressure distribution results was used to verify the accuracy of the numerical method. The numerical results demonstrated that the spoke designed with groove structures could reduce the aerodynamic drag of the car model and the wheels. Among the three groove structures studied, Case 1 (the forward groove structure) exhibited the greatest impact on drag decrease, with a reduction in the vehicle drag coefficient by 2.85%, the front wheels drag coefficient by 8.37%, and the rear wheels drag coefficient by 7.93%. The Q criterion was used to analyze the vortex flow around the wheels, and this analysis revealed that the designed groove structures reduced vortex generation, resulting in delayed flow separation and weakened energy dissipation, which decreased aerodynamic drag. Finally, the calculated K values suggested that the designed groove structures improved flow stability around the wheels, and the vehicle drag coefficient was positively correlated with K in the unstable-flow regions of the front and rear wheels.