Numerical Flow Simulation for a Generic Vehicle Body on Wheels with Variable Underbody Diffuser

Being a continuous subject of research, the authors present in this paper new aspects and results concerning the relevance of diffusers in vehicle aerodynamics. In the first stage of investigation, a generic car model with wheels was considered, starting from the Ahmed body, and the effect of adding wheels to the body was studied. Latter, the influence of diffuser length and angle, within ranges relevant to hatchback passenger cars, on drag and lift was studied for the Ahmed body with wheels. The results show that the addition of wheels and wheelhouses results in increasing of drag and lift due to the vortices which originate from the wheels. Concerning the underbody diffuser, the results show that both drag and lift of the bluff bodies with wheels are reduced with increasing diffuser length for moderate values of angle, up to six degrees for the cases studied.