Research On Aerodynamic Characteristics Of High-speed Trains Passing Through Tunnels

With the development of high-speed railways,the design speed of modern high-speed trains has reached Mach 0.3,and the test speed has reached Mach 0.5.This makes the research on aerodynamics of high-speed trains more and more important.The compression wave and expansion wave generated when the train passes through the tunnel at a high speed will produce very intense pressure fluctuations in the tunnel and cause the phenomenon of micro pressure waves at the exits on both sides of the tunnel.This will have a certain impact on the stability and safety of train operation,the comfort of passengers while riding,and the environment around the tunnel.At the same time,the drastic pressure changes in the tunnel will also have higher requirements for the rigidity and strength of the train.Therefore,it is necessary to conduct a detailed analysis of the train passing through the tunnel,carefully study the pressure characteristics of the flow field in the tunnel when the train passes through the tunnel,the pressure change on the surface of the train,and the aerodynamic force on the car body.In this paper,the three-dimensional transient,viscous compressible Reynolds timeaverage equation and the k-ε STANDARD two-equation turbulence model are used to describe the air flow caused by the train passing through the tunnel.Two common working conditions of single train passing through the tunnel and constant speed meeting of two trains in the tunnel are selected.The main work of this paper includes:(1)The CRH3 EMU model is simplified as a train model;the tunnel model refers to the design drawing of the Beijing-Shanghai high-speed railway tunnel,and the simplified train,tunnel and external flow field models are combined to form the numerical simulation calculation model of this article.(2)Numerical simulation calculation of the process of train running at 350km/h tunnel,study the pressure characteristics of the flow field in the tunnel and the time-varying law of the train surface pressure;and set up monitoring points in the tunnel to study the pressure wave in the tunnel.Spread the situation.(3)Numerical simulation calculation of the process of two trains meeting in the tunnel at a constant speed of 350km/h to study the pressure characteristics of the flow field in the tunnel and the time-varying law of the surface pressure of the train;The internal pressure change characteristics are compared and analyzed.Through the analysis of the simulation calculation results of the two working conditions,the following conclusions are drawn: when the train passes through the tunnel,the complex changes in pressure are caused by the propagation and reflection of compression waves and expansion waves.Complicated pressure fluctuations will have a non-negligible impact on the normal operation of vehicles.Therefore,at the beginning of the design of highspeed trains,the study of aerodynamic problems has become more important.Through the numerical analysis of the two mechanical behaviors of the train running in the tunnel and the constant speed intersection in the tunnel,the following conclusions are drawn:the magnitude of the pressure change on the surface of the train during the meeting in the tunnel is about 2 times that of a single train passing through the tunnel.-3 times;when the train meets in the tunnel,the pressure difference in the tunnel at the same time can reach 9000 Pa,and in the case of a single train passing through the tunnel,the difference is about 7000Pa;when the train is about to enter the tunnel At this time,the train head will generate a compression wave with a propagation speed close to the speed of sound.For the pressure of the flow field in the tunnel,the influence of the pressure around the train body is much greater than the compression wave.