Numerical analysis of the effect of ground clearance on a simplified car model

Lots of researches were focus on aerodynamic characters of the head, top and tail of vehicle in the past, but researches on bottom of vehicle were quite rare. This has been changed in these days. Optimization of aerodynamics via shape of vehicle was limited by modern automotive styling. So the focus has been moved to bottom of vehicle. In current work, the aerodynamic influence of ground clearance on the bottom was simulated using the commercial CFD code STAR-CD. To compare with the results of wind tunnel, the SAE model that has been used in wind tunnel was selected as the model of simulation. The ground clearances were 200,150,100, and 50 millimeter with the diffuser angle was fixed at 12 degree. The mesh is hybrid to make meshing easy and results precise. The distribution of the pressure and velocity was obtained. The simulation results were compared with those obtained from wind tunnel experiment. It was found that the lift firstly decrease with the ground clearance decreasing from 200 to 150, then increase from 100 to 50. The drag decreased with the ground clearance decreasing from 200 to 50 millimeter.