A Study On Aerodynamic Influence Of High-speed Trains Passing Tunnels

With the increasing of train speed, the aerodynamic problems of the high-speed train are becoming more and more important. When the train at a higher speed entry into a tunnel will cause obvious pressure fluctuation in tunnel and micro-pressure wave radiated from the exit of the tunnel, which will influence passengers'comfort and environment around a tunnel. Therefore, lucubration of tunnel aerodynamic effect's mechanism and corresponding alleviation measure is very necessary.In this paper, the aerodynamic effects of high-speed train passing in tunnels are investigated in numerical calculation method of hydromechanics associating of field measurement data. Based on 3D time Reynolds average Navier-Storkes equations of viscous compressible fluid, and on k-εtwo equations turbulent model, the aerodynamic effects of high-speed train in tunnels were investigated by means of the technology of moving grids in computational fluid dynamics method. And its main works include:1. The flow field including a train running into a tunnel and two trains passing each other in tunnel is analyzed in the round. By observing the intuitionistic graphic display which reflecting the current situation, we obtained the pressure distributions and changes on tunnel walls and train surfaces. The tunnel transient pressure and the tunnel entry pressure waves and the train crossing pressure wave in tunnel have been studied in-depth. Our results indicate that, as a train running into a tunnel, the flow near tunnel entrance has a remarkable three-dimensional characteristic. The pressure throughout the same tunnel cross section is obviously different. The results also show that the tunnel entry pressure waves are propagating in a tunnel with the speed close to sound.as two trains passing through a tunnel concurrencely, the pressure at the mid of tunnel is combined with the two train's tunnel entry pressure waves. The train crossing pressure wave in tunnel is combined with the two train's tunnel entry pressure waves and the pressure wave by trains passing each other.2. By means of carring on the integral to the pressure field of the train surface, we obtained the aerodynamic forces and moments of train in tunnel.The changes of train's aerodynamic forces and moments as a train running in a tunnel and two train passes through each other in tunnel are studied in-depth. The results show that the train's aerodynamic forces and moments in tunnel are much more than that in the open. The train's aerodynamic forces and moments continuously take place the changes when a train enters a tunnel and two trains passes through each other in tunnel.Thus, it will induce some directly threat to the train's driving safety and stationarity.3. According to the actual situation of railway tunnel construction in China, the influence of the tunnel structure on the train aerodynamic force and the pressure in tunnel were analyzed, such as the blocking ratio, the shape of tunnel cross section, the entrance structure and the horizontal channel. The results show that block ratios between maximum values of pressure in tunnel or aerodynamica drag is the linear function relations. The influence of the shape of tunnel cross section on the tunnel entry pressure waves is very tiny, but on the flow field near tunnel entrance and on the aerodynamic force of train is important. Building the entrance structure can reduce the aerodynamic problems effectively. Connecting many tunnels with the horizontal channel can reduce the pressure in tunnel effectively.