Mitigating Mechanism Of Aerodynamic Effects Of Pressure Relief Structure For High-speed Train In Tunnel

High-speed railway develops so fast in recent years that it attracts much attention of the world. However, aerodynamic problems in tunnel are highlighted increasingly because of many mountains in China. The pressure relief structure has been paid more attention by its outstanding performance on decompression, ventilation and rapid relief and so on. Therefore, it is necessary to further study the distribution regularities of pressure relief structure and the influence rule of tunnel aerodynamic effect by structural parameters, which provides theoretical basis and engineering reference for high-speed railway tunnel construction.Based on the basic theory of tunnel aerodynamics and analytical method of CFD, this thesis considers the tunnel air flow as turbulent flow with three dimensional viscous, compressible, unsteady and non-isentropic. In addition, according to the characteristics of tunnel aerodynamic effect and the different boundary conditions of pressure relief structure, pressure relief wall and pressure relief channel of pressure relief structure are firstly divided into two parts in this thesis. By numerical simulation, a detailed analysis about the formation process and propagation mode of compression wave and expansion wave and two wave form characteristics and pressure contour map at different time are given out. At the same time, the credibility of the numerical method is tested by using the site test result of Eryan Tunnel. The aerodynamic effect of the high-speed train passed through a tunnel with pressure relief structure is analyzed. And the change of pressure peak inside the tunnel with and without pressure relief structure is compared, which contributes to the study of mechanism of pressure relief structure in relieving tunnel aerodynamic effects. This thesis analyzes the influence of alleviation effect of pressure relief structure on tunnel aerodynamic effect by different structure parameters, such as length, aperture ratio, shape, gradient and so on. In the comparative analysis of the results, secondary compression wave and transverse wind are firstly considered into influence factors. In addition, according to analysis results, pressure relief structure parameters are optimized and puts forward the basic schemes in the selection of pressure relief structure construction.After the selection of optimal parameters, this thesis synthesize compared the alleviating effect of two pressure relief structures in tunnel pressure peak, pressure gradient peak, peak lower rate and transverse wind. At last, the combination of two pressure relief structures is optimized and the basic distribution of appropriate pressure relief structure for alleviating the aerodynamic effect of pressure relief structure on tunnel is given out.