Numerical Simulation Of External Flow Field Around Low Resistance Car And The Error Analysis

With the development of China’s economy, people’s requirement for cars is increasing.Although our country is a big producer and consumer country of cars, it lacks developmentability of new cars. Auto style is an important factor for car development. Excellent autostyles not only have to meet the aesthetic standard, but also have outstanding aerodynamicperformances.The main research methods of external flow field include wind tunnel test method andnumerical simulation method. Compared with expensive tunnel test, the numerical simulationmethod has obvious advantages in product development cycle, cost and applicable scope.Subject to the development of the theory of turbulence and computer performance, numericalsimulation method needs to be used with wind tunnel test together.This paper uses a Japanese low resistance car model as the research object to simulatethe external flow field by SC/Tetra software. With Cd&Cl, the distribution of the surface andthe surface streamline as evaluation indexes to compare the results of the numericalsimulation and the wind tunnel test, the paper analyzes the main error sources of the externalflow field simulation, and the effect of the grid discrete, wall function and turbulence modelon calculation accuracy. The paper aims to apply some references to improving the caroutflow field simulation accuracy.The results show the following three findings. For different turbulence models, the y+value, the total thickness and the aspect ratio of the meshes in the boundary layers, should becontrolled in a corresponding range for higher computational accuracy. The computationalerrors will be reduced with the refinement of meshes in turbulent area. And the SST turbulence model with the LRN Adaptive Wall Function can obtain more accurate results thanthe Standard turbulence model.