汽车风阻系数试验与数值模拟的对比分析

Comparative Analysis of Automobile Drag Coefficient Test and Numerical Simulation

摘要:

汽车风阻系数（C_d）可以通过道路滑行试验、风洞试验和数值模拟获得。其中，滑行试验最接近实际使用工况，但受环境因素影响较大，风阻系数重复性稍差；风洞试验重复性最好；数值模拟具有不确定性，其原因在于湍流模型、网格策略等的选择对结果可能产生直接影响。为此，对15款乘用车滑行试验、风洞试验和数值拟模结果进行分析，结果发现以滑行试验作为对比基准，其结果大多介于风洞试验和数值模拟的0°~5°偏航角之间。此外，通过对以滑行为代表的道路行驶工况、风洞试验与数值模拟的差异点进行讨论，并对某款电动车车型使用3种方法获得的风阻系数进行对比分析，对误差产生原因进行初步解析。

关键词:汽车空气动力学;风阻系数;滑行试验;风洞试验;数值模拟

Abstract:

The coefficient of drag （C_d） can be obtained by road coast down test， wind tunnel test， and numerical simulation. Of the three methods， the coast down test is the closest to the actual use condition of consumers， but it is greatly affected by environmental factors. The C_d has a slightly poor repeatability. The wind tunnel test has the best repeatability. The numerical simulation is uncertain of because the choice of turbulence model and grid strategy may have a direct impact on the results. A comparison of the results of the coast down test， the wind tunnel test， and the numerical simulation of 15 passenger cars indicates that taking the coast down test as the comparison benchmark， most of the results are between 0° and 5° yaw angle of the wind tunnel test and the numerical simulation. By discussing the differences between the road driving conditions represented by the coast down behavior， the wind tunnel test， and the numerical simulation， the C_d obtained by the three methods for an electric vehicle model is compared ，and the causes of errors are preliminarily analyzed.

Key words:vehicle aerodynamics;coefficient of drag;coast down test;wind tunnel test;numerical simulation