Study On Aerodynamic Effect Of High-speed Train Passing The Short Tunnel And Tunnel Group

In today’s world, the high-speed railways are developing rapidly. 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 enters into a tunnel will cause a dramatic change of the air pressure around the tunnel which is constrained by the tunnel wall. Pressure fluctuation is caused and micro-pressure were radiated from the exit of the tunnel, which will influence passengers’comfort and environment around the tunnel. There is a large number of tunnels under construction and pre-built, which the short tunnel and tunnel group occupy a considerable proportion. Therefore, it is very urgent to make a through study of the aerodynamic problems caused by the high-speed train enter a short tunnel and tunnel group.Based on the three-dimensional unsteady N-S equation of compressible viscous fluid and the two-equation k-s turbulent model, the moving mesh method was used to study for the aerodynamic problems caused by a high-speed train passing through the short tunnel group. Stress distributions of the train surface and the middle cross-section of the tunnel and the micro-pressure wave in different entry speeds and tunnel spacing are analyzed for studying the aerodynamic characteristic.The results show that front of the head facing the air suffering the maximum positive pressure and the tail suffering the maximum negative pressure when the train is passing a tunnel. With the increasing of the entry speed, the surface pressure also increases exponentially, and the amplitude is equal to the square of the speed. The pressure distribution in the tunnel and cross section is very inhomogeneous, where changes fiercely near the train and hardly changes far from the train. The amplitude of the micro-pressure wave is roughly inversely proportion to the distance from the tunnel exit and which is proportional to square to the train speed.Compared with the condition of train passing through single tunnel, the pressure amplitude of the head and tail of the train is equal when the train passing a tunnel group. As the increasing of the tunnel spacing, the micro-pressure wave amplitude gradually reduces and the change rate decreases. The amplitude of the micro-pressure wave is similar as the single tunnel when the tunnel spacing reaches100m.In this paper, the aerodynamic problem caused by high-speed train passing the short tunnel and tunnel group is numerical simulated. Stress distributions of the train surface and the middle cross-section of the tunnel in different entry speeds and tunnel spacing are analyzed for studying the aerodynamic characteristic. The study results have important practical value and reference significance for safety guidance of high-speed train and environment and research for the future related problems.