Comparative Analysis of Automobile Drag Coefficient Test and Numerical Simulation

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