Numerical Analysis of Underbody Diffusers with Different Angles and Channels 2019-01-0668

The underbody diffusers are used widely in race cars to improve the flow field structure at the bottom of the car and provide enough downforce. In recent years, passenger cars have begun to use bottom diffuser to improve aerodynamic characteristics, so as to reduce drag and increase downforce. In this paper, the aerodynamic characteristics of the bus with different underbody diffuser angles and channel numbers are studied by numerical simulation analysis. Firstly, the aerodynamics of the bus under different diffuser inlet and outlet angles are studied, and then an optimal inlet and outlet angle is determined based on the simulation results. Then, using this angle as a constant, the 2, 3, and 4 channel numbers were chosen as the diffuser channel variables to study the influence of the multiple-channel diffusers on the aerodynamic drag of the vehicle. The results of the study show that reasonable diffuser inlet and outlet angles can improve the bottom pressure distribution and wake structure of the bus, resulting in a maximum increase in downforce of 38.2%. In addition, under a certain diffuser angle, the effect of number of diffuser channels on lift and drag is small.