Effects of high geotemperature and high altitude on the pressure wave of high-speed trains running in a long tunnel

Considering the high-temperature distribution along a tunnel in a high-altitude area, the effects of high geotemperature and high altitude on the pressure wave of trains running in long tunnels were investigated using a 3D, compressible, unsteady turbulence model. To reduce the simulation cost and reflect the pressure wave characteristics in long tunnels, a representative tunnel length was first determined for simulation. The simulation results indicated that compared to the condition of a normal ambient-temperature tunnel, when trains go through a high geotemperature tunnel, the distribution of the minimum pressure (Pmin) along the tunnel moves to the tunnel entrance. The pressure amplitudes on the tunnel and train decrease integrally, with maximum reductions of 7.9% in the maximum pressure (Pmax) and 44% in Pmin on the tunnel, and 4.6% in Pmax and 12% in Pmin on the train. When trains meet in high geotemperature tunnels, the distributions of Pmax and Pmin along the tunnel change. The pressure amplitudes decrease integrally, with maximum reductions of 13.8% in Pmax and 36.9% in Pmin on the tunnel, and 7.1% in Pmax and 15.6% in Pmin on the train. The pressure difference between the two sides of the train during the intersection decreases by 15.9%. As the altitude rises, when trains cross and meet in tunnels, the waveforms of pressures on the tunnel and train and the pressure difference between the two sides of the train remain unchanged, and the peaks decrease linearly.