Abstract: The application of computational fluid dynamics (CFD) technology in the numerical simulation of external flow for car overcomes the limitations of wind tunnel test, but there are some problems such as non-standard simulation method, low accuracy, and unclear evaluation index and dimension. Focusing on the whole process of the simulation, in this paper, the external flow simulation analysis was carried out on the concept a surface (CAS) of a car. Firstly, the CAS was geometrically cleaned by pre-treatment technology to build the simulation model of CAS. Then, the CFD numerical simulation technology of the external flow was carried out based on the finite element software STAR-CCM+. Finally, the 3D velocity field, pressure field and flow diagram of CAS were obtained, so as to realize the calculation and analysis of the flow field distribution around the body, the main separation area and the air resistance coefficient. The simulation analysis and evaluation methods provided references for the early stage of vehicle development.

Key words: External flow; Aerodynamic drag coefficient; Computational fluid dynamics (CFD)

摘要： 计算流体动力学（CFD）技术应用到汽车外流场数值模拟计算中，克服了风洞试验的 局限性，但存在着模拟方法不规范、精度较低、评价指标与维度也不明确等问题。文章面向 车身外流场数值模拟的全环节，针对某车型汽车初步造型面（CAS）外流场模拟技术进行了 梳理与分析，首先通过前处理软件对外 CAS 进行几何清理，搭建外 CAS 仿真模型，然后基 于有限元软件 STAR-CCM+进行汽车外流场 CFD 数值模拟技术，最后根据有限元仿真分析方 法，得出汽车外 CAS 三维速度场、压力场和流线图，从而实现对车身周围流场分布、主要分 离区域及空气阻力系数的计算与分析。文中的模拟分析与评价方法对整车开发前期提供了一 定的参考作用、指导意义及价值。

关键词: 外流场；空气阻力系数；计算流体动力学（CFD）