Abstract: In this paper, the process of aerodynamic optimization for car body is divided into three steps. The first step is the two-dimensional body optimization aiming at global search; the second and third steps are three-dimensional body optimization without wheels and with wheels, respectively, aiming at local approximation and fine-tuning. Finally the corresponding evolution strategies of each step are developed according to the difference between the two- and three-dimensional cases. As the existence of wheels may change the aerodynamic behavior of the car body, so wheels in fixed position is taken as one of the constraint conditions, which may improve the effect of the optimization. Optimization results show that the drag coefficients of the vehicle with wheels are as low as 0.129 in cheese head style and 0.124 in socket head style. The dependability of this method is validated by the scaled model test in wind tunnel.

Key words: fluid mechanics, genetic algorithm, aerodynamic optimization, low drag body, wind tunnel test