A Numerical Simulation Study Of Aerodynamic Characteristics Of High-speed Trains Passing Through Tunnel With Speed 300 Km/h

As the speed of the train continues to increase,the aerodynamic problems of the train gradually become apparent.The flow field characteristics and aerodynamics around the train during high-speed operation have become a huge problem in the development and operation of high-speed trains.When the train enters the tunnel at high speed,the air in the tunnel is rapidly compressed,generating pressure waves,and the pressure waves propagate back and forth in the tunnel,forming complex fluid fluctuations,and causing a series of aerodynamic problems.when the train meets,a complex fluid field will be generated around the two trains,and the smooth impact on the train will also cause hidden dangers.In this paper,a certain type of standard EMU in China is used as the research object,and the characteristics of turbulent outflow field and aerodynamic characteristics of trains passing through tunnels are studied by 3D numerical simulation methods.Based on the pressure correction solution algorithm,the RANS turbulence simulation method is used to solve the three-dimensional,unsteady,compressible and turbulent flow of external air when the train passes through the tunnel at high speed,and the overlapping grid technology is used to realize the relative motion process between the train and the tunnel.Firstly,the characteristics of the outflow field of the bicycle passing through the tunnel are analyzed,showing that after the train enters the tunnel,the pressure characteristics of the body of the head car curve are positive and negative pressure fluctuations,the pressure fluctuation of the longitudinal center section of the train is the largest,and the pressure fluctuation of the remote tunnel side is the smallest.Along the length of the train,the thick Ness of the train speed boundary layer gradually increases,and the vortex on both sides of the train gradually increases from small to small along the direction of the head car to the tail train.At the same horizontal position,with the increase of height,the vortex strength decreases,the size of the vortex structure increases,and the vortex shedding phenomenon becomes more obvious.Secondly,the aerodynamic characteristics of the train passing through the tunnel were analyzed,and when the train entered the tunnel and the expansion wave generated by the tail car entering the tunnel reached the head car,the vehicle resistance reached a maximum of70.15 k N.In typical moments,straight bodies experience the largest proportion of resistance and windshields suffer the least proportion of resistance.Finally,the aerodynamic characteristics of the train during the rendezvous in the train tunnel were analyzed,and at the same horizontal position,with the increase of train height,the train body pressure began to decrease,the train body isobaric line gradually became thinner,and the train body pressure change rate gradually decreased.The velocity of the fluid flow around the train gradually decreases,the intensity of the fluid flow gradually decreases,and the range of wake fluctuations gradually decreases.