Multi-objective Aerodynamic Optimization Design for Head Shape of High-Speed Trains

To improve the aerodynamic performance of high-speed trains running in open air, an optimization design method of the head shape of high-speed trains was proposed. Taking the aerodynamic drag force of the head car and the aerodynamic lift force of the tail car as the optimization objectives, the automatic multi-objective optimization design of the head shape of high-speed trains was carried out. Based on a new type high-speed train, the parametric model of the high-speed train including bogie zones was established. Seven design variables were extracted, which control the nose height, the top height of the opening and closing mechanism of lids, the cab window height, the lateral width of the maximum horizontal contour line, the concave-convex degree of the central auxiliary control line of the streamlined head, and the lateral width and partition angle of the bogie zone, respectively. The aerodynamic models of high-speed trains were then established based on the theory of computational fluid dynamics (CFD). With the models, the aerodynamic forces acting on the trains were calculated. The design variables were automatically updated through the multi-objective genetic algorithm to achieve the automatic optimization design of the head shape of high-speed trains. In addition, the correlations between the optimization objectives and the design variables were analyzed. The results show that the cab window height and the lateral width of the bogie zone have the most influences on the drag force of the head car, while the nose height and the concave-convex degree of the central auxiliary control line have the most influences on the lift force of the tail car. After optimization, 6 Pareto-optimal head shapes are obtained. For these 6 Pareto-optimal head shapes, when compared with the head shape before optimization, the drag force of the head car is reduced by up to 3.15%, and the lift force of the tail car is reduced by up to 17.05%.