Multi-objective Aerodynamic Optimization Design Of High-speed Train Head

With the rapid development of high-speed railway and the continuous improvement of train speed,the aerodynamics of high-speed train becomes more and more important.The numerical simulation of train aerodynamics with the advantages of low cost,short cycle and high precision is gradually applied to the engineering optimization design.Aerodynamic characteristics such as the aerodynamic resistance of the train are often closely related to the shape of the train.Therefore,the optimal design of the body shape has become the main means to improve its aerodynamic characteristics.In order to improve the aerodynamic characteristics of the train head,in this paper,aerodynamic drag and aerodynamic lift are taken as optimization objectives,and the optimization platform integrated aerodynamics simulation software is used to optimize the geometry of the high-speed train head.Firstly,the aerodynamic characteristics of the basic control lines in the longitudinal and transverse directions of the train are analyzed under different speeds and environments.In the longitudinal direction,the aerodynamic characteristics of three kinds of streamlined head car models are compared and analyzed,and the relationship between the geometric shape of the head car and its aerodynamic characteristics is obtained,as well as the basic law between the aerodynamic characteristics of the train and its running speed.In the transverse direction,the maximum cross section is selected as the calculation sample,and the relevant parameter values describing the dynamic characteristics of the transverse wind of the train under the constant value and crosswind environment are obtained through simulation.After that,four characteristic parameters describing the transverse section of the train are selected as design variables,and three parameters describing the dynamic characteristics of the transverse atmosphere of the train are selected as optimization objectives.In these two crosswind conditions,Isight optimization platform integrated mesh deformation software and aerodynamics simulation software are used for sample generation and automatic calculation,The multi-objective optimization of the transverse section is accomplished by using the response surface methodology,which improves the lateral stability of the train.In the end,Multi-objective aerodynamic optimization is carried out on the threedimensional model of the train.To save computing costs,In order to save the calculation cost,while ensuring the simulation accuracy,the three-dimensional train model in this paper adopts the three-section marshalling model.The eight groups of node positions in the longitudinal,transverse and vertical directions of the head and tail of the train are taken as design variables.Aerodynamic resistance and aerodynamic lift are multiple optimization objectives.The Latin hypercube experimental design method is adopted on the optimization platform and the same optimization design process is used,and the aerodynamic drag and lift characteristics of the model are obtained.The relationship between optimization objective and design variables is obtained by constructing response surface methodology,The multi-objective aerodynamic optimization design of the geometric shape of the train head is accomplished by using multiisland genetic algorithm.The optimization results show that the coupling of the optimization design variables affects the aerodynamic characteristics.And find the optimal solution through Pareto frontier solution set,the optimized geometric shape of the train is obtained.The aerodynamic resistance value was reduced by 13.66%,and the aerodynamic lift value was also effectively reduced from 217.86 N to 1.46 N.