两车间距对超车过程轿车气动特性的影响

Effect of spaces between cars on aerodynamic characteristics of cars in overtaking process

利用计算流体力学方法对超车过程中两种间距工况下的超车车辆和被超车辆周围非定常流场进行数值模拟,超车车辆和被超车辆均为简化直背式模型,得到超车车辆和被超车辆受到的侧向力、侧倾力矩和横摆力矩在超车过程中的变化情况,并根据超车过程中两种间距情况下速度场和压强场的分布情况,分析流场特性对气动力特性的影响.计算结果表明:被超车辆受到的侧向力、侧倾力矩和横摆力矩在两种间距下的变化趋势基本相同,但它们各自变化趋势有所不同;超车车辆受到的侧向力、侧倾力矩和横摆力矩在两种间距下的变化趋势有着明显差别.

Numerical simulation of unsteady flow fields around overtaking and overtaken cars by two different overtaking spaces between cars were conducted with computational fluid dynamics（CFD） method. Spalart-Allmaras turbulence model, QUICK discrete scheme, SIMPLEC pressure and velocity coupling arithmetic and unstructured tetrahedral mesh and dynamic mesh technology were adopted. Both car models were simplified fastback reduced scale car models. The side forces, rolling moments and yawing moments of the cars during the overtaking process were calculated. The influences of the flow field on the aerodynamic forces were analyzed according to the distribution of velocity and pressure fields. The results show that the variation tendencies of the side force, rolling moment and yawing moment of the overtaken car by two different spaces are the same. But the variation tendencies of these forces are different from each other; The variation tendencies of the side force, rolling moment and yawing moment of the overtaking cars by two spaces are different apparently.