Unsteady Simulation Of A Train Passing By A Tunnel And Two Trains Passing By Each Other

Air pressure pulse from high-speed trains passing each other, compression wave and expan-sion wave for high-speed trains entering a tunnel, as well as the microwave discharged from the tunnel exit are typical unsteady aerodynamic phenomena for the high-speed train system. These particular aerodynamic characteristics make great influence on safe transportation of the rail traffic and comfort level of the passengers.In this paper, the three-dimensional Reynolds average Navier-Stokes equations of viscous compressible fluid are solved, and the two-equation k-ε model is involved for turbulence, and the dynamic mesh technique and the sliding mesh technique are both employed for moving bodies. The trains passing by each other inside a tunnel, as well as the train passing through a tunnel and tunnels are simulated to obtain the changing of the pressure on the tunnel wall and the train surface, the changing of the aerodynamic force of the train and the changing of the microwave. For trains passing through a tunnel and tunnels, we focus on the pressure pulse evolutions at different positions of the trains, the pressure of the train and the tunnel changing with the propagation of the mach wave, the pressure changing with the distance between the tunnels, the amplitude of the pressure changing with the speed of the train, the relationships between the microwave and the speed of the train, the relationship between the microwave and the distance between the tunnels. For trains passing by each other inside a tunnel, we focus on the strong side force and lift force acting on the train, the relationships between the amplitude of the pressure of the train and the tunnel when the trains passing by each other inside a tunnel and the amplitude of the pressure on the train and tunnel when the train passes through a tunnel are also discussed.It is shown that the amplitudes of the pressure changes in the tunnel and on the train surface are both approximately proportional to the square of the train speed, so are the microwave and the drag of the train. There are no big differences between the results of the train passing a tunnel and tunnels, only when the distance between the tunnels is less than100m, the microwave increase as the distance between the tunnels decrease. The results of the trains passing by each other inside a tunnel indicate that the pressure and the aerodynamic drag are complicated due to the propagation of the Mach wave and interaction of the flow induced by the two trains. The side force and the lift force fluctuate rapidly when the two trains pass by each other. The maximum differential pressure of the train and the tunnel are about two times the maximum differential pressure of a train passing through a tunnel.In this paper, the trains passing by each other inside a tunnel and the trains passing through a tunnel are simulated to study the changing history of the pressure, the microwave and the aerody-namic history. It will provide a reference on the safe operation of the high speed train.