基于整车风洞试验的MIRA车型数值计算

Aerodynamic calculation of MIRA model correlated with wind tunnel test

为了明确稳态数值计算对于整车气动力,特别是车身表面压力的预测能力,首先以全尺寸MIRA车型整车风洞试验数据为基准,进行网格方案研究并得出结论、车身面网格为10mm、5层边界层网格且第1层网格无量纲高度Y+=30可以满足网格无关性要求。然后,基于该网格方案进行数值计算后得到:无偏航工况下,阻力系数CD与试验值误差为0.34%,升力系数CL误差为1.06%;3°~20°偏航工况下,CD和侧向力系数CS误差分别不超过5%和9%,表明气动力计算准确性较高;车身表面254个测压点中,压力系数CP预测误差大于50%的测点个数基本不超过20%,其中误差较大的测点主要位于车身底部以及背风侧等流动较为复杂的区域。

The prediction capability of steady numerical simulation on aerodynamic forces and surface pressure of generic vehicles was clarified.First,a detailed study on mesh scheme for MIRA reference car model was carried out with baseline data derived from full-scale wind tunnel test.Results show that the gridindependent strategy requires 10 mm for car surface mesh,Y+=30 for the first layer grid and 5 layers around the car.Based on this mesh scheme,aerodynamic force calculation of MIRA model could yield satisfactory predictions,that at 0°yaw,the error of drag coefficient CDfrom test data was 0.34%,error of lift coefficient CL1.06%,and at 3°~20°yaw conditions,error of CDand side force coefficient CSwere respectively no more than 5%and 9%,which indicate the reliability of aerodynamic forces computation for simplified cars like MIRA model.For surface pressure,of all 254 pressure taps all over the car,error of CP over 50%are less than 20%,while surface pressure was poorly calculated mostly where flow is so complicated that separation or reattachment tends to happen,such as the underbody and the leeward side..