车轮辐板形状对汽车气动阻力影响分析

Effect of the Shape of Wheel Spokes on Vehicle Aerodynamic Performance

汽车旋转的车轮所产生的复杂分离流对整车外部流场有重要影响,是整车气动阻力主要来源之一。应用计算流体力学对包含轮胎的整车进行仿真分析,并通过风洞试验验证了方法的可靠性。重点讨论了车轮边界条件的设置对计算结果的影响,并对同一型号的车轮,通过改变辐板的开孔个数和开孔面积分析对整车气动阻力系数的影响。结果表明,对车轮的模拟,采用旋转壁面模型比采用多参考坐标系(MRF)更为合理;当辐板开孔数不变时,随着开孔面积的增大,前、后车轮阻力系数都随之增大,整车阻力系数先增大后减小;当单个孔面积不变时,随着开孔数目的增多,后轮阻力系数随之增大,前轮、整车阻力系数先增大后减小。结果为汽车车轮的设计提供一定参考。

The complex separated flow induced by wheel and wheel cavity has a great impact on the exterior flow field,and also is one of the major causes of aerodynamic drag. In the present paper,the exterior flow field of a whole car model including wheel is simulated using the computational fluid dynamics method. The related experiments were carried out in HD-2 wind tunnel to validate the reliability of the simulation method. In order to get the accurate flow around rotating wheel and wheel cavity,two different boundary conditions of wheel are compared with those in literature. Then,the influence of the number and size of holes in wheel spoke on the aerodynamic drag coefficient was investigated using the same type wheel. The results show that the rotating wall boundary condition is more reasonable than the MRF; the wheel＇s drag coefficient increases with the hole open size when the hole number is a constant,while the whole car＇s drag coefficient is first increased and then decreased; when the single-hole size is fixed but the opening number is increased,the rear wheel＇s drag coefficient increases,while the front wheel＇s and the vehicle＇s drag coefficients are increased first and then decreased. This work can provide a reference for wheel design in the future.