Aerodynamic Simulation Analysis And Optimization Of Electric Vehicle Based On CFD

In the promotion of electric vehicles,people have some doubts about the choice of electric vehicles in the face of its insufficient battery endurance.In this thesis,in order to reduce the aerodynamic drag of the electric vehicle and save the energy to improve the battery life,the aerodynamic simulation analysis and optimization research on a pure electric vehicle body is carried out to optimize the shape of the carbody.This research includes the following main contents.First,the simulation method of the outflow field for the automobile is investigated,the finite element simulation model of the outflow field for carbody is established and numerical simulation is carried out.Through analyzing the flow of the outflow field of the car,the surface pressure of the carbody,and the distribution of the turbulent flow energy near the carbody,the aerodynamic characteristics of the outflow field of the carbody are obtained.Base on which,the influence of carbody shape on the aerodynamic performance of the car,the optimization method of the carbody shape and drag reduction can be investigated.Second,the optimization method of the carbody shape is studied in the thesis.Includding the following.Aiming at the difficulty of parameterization of carbody surface,Free-form Deformation(FFD)technology based on STL format file is realized through algorithm research and programming.The method is used to achieve the parameterization of the carbody.Based on parameterization technology,the optimization model of automobile body aerodynamic modeling is established,which includes the following processes:through selecting the appropriate control points as optimization design variables,sample points are obtained by Latin Hypercube Sampling.Then FFD method is used to parameterize the carbody model of each sample point.CFD simulations are conducted to obtain corresponding responses of each sample point.Based on the sample points and responses,the Kriging surrogate model is built and the accuracy of the model is verified.Last,the genetic algorithm is used to search the global optimal solution of the surrogate model established before.On the basis of the established optimization model of carbody aerodynamic modeling,the optimization is carried out with two targets(C_d and AC_d)of evaluating aerodynamic drag,respectively,without considering the change of carbody frontal projected area caused by deformation and considering the change of it.The relationship between the design variables and the optimization objectives is discussed using the data mining method.In cases study,based on the proposed optimization method of the carbody shape using FFD method,the drag coefficient of the carbody is achieved a maximum 4.15%drag reduction.The maximum optimization rate of aerodynamic drag AC_d reaches 2.9%,indicating the aerodynamic drag decreasing obviously.The results show that the proposed optimization method of the carbody shape in this thesis is feasible and can provide a guide for the future optimization design of the carbody shape.