Influence of Polymeric Sand Porous Material on the Aerodynamic Effect when a High-Speed Train is Entering into a Tunnel

In order to effectively reduce the compression wave in tunnel and the micro pressure wave at the exit of tunnel, improve the comfort of passengers, this study put forward laying polymeric sand porous material in tunnel by using the sound absorption properties of porous media, and give the numerical simulation calculation method of the aerodynamic effect of three-dimensional compressible, viscous and unsteady flow field when a high-speed train entering into a tunnel, furthermore, the influence of sound absorption board on the aerodynamic effect in tunnel was studied. Theoretical analysis and numerical results show the compression wave in tunnel and the micro pressure wave at the exit of tunnel can be decreased significantly when pasting porous materials in tunnel. The reason is mainly due to there are lots of micro-pores in the material and it could absorb the energy from compression wave, then the peak value of it and pressure gradient are decreased. Secondly, the method of laying polymeric sand sound absorption material has influence on the change of the pressure in the tunnel and the micro pressure wave at the exit of tunnel. When the length and height of sound absorption materials are same, calculation results show that the best pressure reduction effect is achieved when laying the material at the entrance of tunnel. However, when laying the material at different circumferential positions of tunnel, the pressure reduction effect at haunch is better than vault and spandrel. Based on that, considering the pressure noise reduction problem, material cost and height of construction in practical engineering, when laying the material at haunch, the relationship between the reduction effect of pressure gradient and the length of laying is summarized with 3 different speeds, which have certain reference value for the design of the method of laying sound absorption material in tunnel.