Research On Aerodynamic Drag Reduction Of High-speed Train Based On Biomimetic Fishtail Structure Spoiler

Aerodynamic resistance is one of the key aerodynamic indicators that affect the speed of high-speed trains.Good resistance characteristics are an important symbol of energy conservation and environmental protection of trains.As the train speed increases,the ratio of aerodynamic drag to the total train resistance increases.Therefore,research on aerodynamic drag reduction is an important technical means to increase train speed,reduce energy consumption,and improve economic benefits.This paper adopts CFD numerical simulation method and based on dynamic grid technology to study the aerodynamic drag of high-speed trains when the rear spoiler of the bionic fishtail structure of different geometric shapes is installed respectively.The main research results are as follows:(1)The structure and aerodynamic performance of the flow field around the train without a spoiler are studied.The results show that the two vortices at the rear of the train vortex in opposite directions and escape to the rear of the chaser;at the same time,the farther away from the chaser,the strength decreases and the distance between the vortex centers increases,and the vortex frequency of the wake is about 0.2 Hz;The surface pressure of the chaser car is basically symmetrically distributed,and its resistance increases with the increase of the running speed of the train.(2)The structure and aerodynamic performance of the flow field around the train after installing a beluga tail structure spoiler at the tail is studied.The results show that when the positive pressure area on the surface of the chaser is relatively free of spoilers,it is mainly concentrated on the side that is the same as the swing direction of the spoiler,and the aerodynamic drag of the chaser is significantly reduced;When the swing frequency of the spoiler is lower than the vortex frequency and the swing amplitude is 0.3m,the aerodynamic drag reduction rate of the trailing car at the operating speeds of 200km/h,250 km/h and 350 km/h corresponds to 6.24 %,6.33 % and 6.49 % have good drag reduction effect.(3)The structure and aerodynamic performance of the flow field around the train with a dolphin-like fishtail structure spoiler installed at the tail are studied.The results show that the positive pressure area on the chaser surface is not significantly changed when the beluga-like tail structure spoiler is installed,but the strength is slightly greater than the latter;When the swing frequency of the spoiler is close to the vortex frequency and the swing amplitude is 0.3 m,corresponding to the operating speed of the train at 200km/h,250 km/h and 350 km/h,the drag reduction rate of the tail car aerodynamic drag is respectively 7.09 %,7.06 % and 7.08 %,the drag reduction effect is improved to a certain extent compared with the spoiler of the imitation beluga tail structure.(4)The structure and aerodynamic performance of the flow field around the train after the tuna fishtail structure spoiler is installed at the rear are studied.The results show that the strength of the positive pressure area on the surface of the chaser car is reduced compared to when the dolphin-like fishtail structure spoiler is installed,but the effective area is relatively increased;When the swing frequency of the spoiler is close to the vortex frequency and the swing amplitude is 0.3 m,corresponding to the operating speed of the train at 200 km/h,250 km/h and 350 km/h,the drag reduction rate of the tail car aerodynamic drag is respectively 7.09 %,7.06 % and 7.08 %,the drag reduction effect is the best among the three spoilers.(5)The coupling function between the drag reduction rate of the following vehicle and the swing frequency,swing amplitude and vehicle speed of the spoiler is established.