Numerical Simulation And Analysis Of Turbulent Characteristics Near Wake Area Of Vacuum Tube EMU

As a sign of the development of railway transportation,the speed increase of railway trains has always been the goal,but the increase in speed inevitably brings many neglected problems at low speeds,such as aerodynamic resistance and aerodynamic noise,which affect the speed increase of trains.Therefore,the emergence of vacuum tube high-speed trains has become a solution to increase speed.Based on the research and analysis of domestic and foreign scholars on the aerodynamic drag and turbulence characteristics of the following trains under open-line conditions,this article mainly discusses two important aspects of the aerodynamic drag and turbulence characteristics of the wake area of high-speed trains in vacuum ducts under different conditions.In this paper,the standard k-ε turbulence model is used to simulate the high-speed train in the vacuum pipe,and the aerodynamic characteristics of EMU under different operating speed,vacuum degree and characteristic length are analyzed.The results show that when the characteristic length and blocking ratio of the high-speed train are constant,the ratio of the differential pressure resistance to the aerodynamic resistance remains basically the same;when the train speed is fixed,the aerodynamic resistance increases with the increase of the pressure in the pipeline,and the aerodynamic resistance is consistent with the pipeline The internal pressure is approximately linear;when the pipeline pressure is fixed,the aerodynamic resistance increases with the increase of the train speed,which is approximately a square relationship with the speed.The improved delayed separation eddy simulation(IDDES)is used for simulation calculation to analyze the turbulence characteristics of the high-speed train near the wake region.According to the Q criterion,it can be captured that a pair of reverse spiral vortices alternately fall off from the rear of the train near the nose of the train.The results show that there are strong vortices in the wake area near the rear of the train,concentrated at the lower end of the nose near the ground,and It continuously falls off from the tail end,presents a symmetrical distribution in the process of propagation downstream,and develops laterally to both sides.Among them,the vortex structure far away from the chaser is gradually increasing,but from the perspective of speed,the strength of the vortex is gradually decreasing.