To reveal the aerodynamic characteristics of vehicle in crosswind, the flow direction change according to sine function are achieved by User-Defined Function(UDF), and vehicle aerodynamic characteristics in unsteady crosswind was simulated. The results of calculation show that the unsteady crosswind simulation of vehicle can be realized by UDF which continuously changes the flow direction. In unsteady crosswind, the change of tail flow field structure, the flow separation position of body surface and the speed difference of the upper body and lower body are the main causes for aerodynamic force fluctuations. The aerodynamic characteristics of different car tail shapes can also be explored and it shows that the influence range of different tail shape on roof negative pressure under the crosswind is the main cause for the differences of aerodynamic lift.%为揭示车辆在侧风下的气动特性,通过编写用户自定义函数(UDF)实现来流方向按正弦函数规律变化,模拟了车辆的非稳态侧风工况.计算结果表明:通过UDF连续改变来流方向的方法可实现对车辆非稳态侧风的模拟;非稳态侧风中,尾部流场结构和车身表面气流分离位置的变化,以及车身上、下部的速度差是气动力波动的主要原因.对不同尾部造型车辆的气动特性研究表明,尾部造型对车顶负压区范围的影响是气动升力差异较大的主要原因.
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