2013 Volume 8 Issue 3 Pages 462-475
A high-speed train entering a tunnel generates a compression wave that propagates through the tunnel toward its exit. When the compression wave reaches the tunnel exit, a pressure pulse causing environmental problems (the micro-pressure wave) is radiated from the exit portal. The micro-pressure wave magnitude is approximately proportional to the maximum pressure gradient of the tunnel compression wave arriving at the exit portal. In a long Shinkansen tunnel with concrete slab tracks, the compression wavefront steepens due to the nonlinear effect during its propagation because all surfaces of the tunnel wall are smooth. Therefore, it is necessary to investigate the compression wave distortion in a tunnel and to clarify the characteristics of the compression wave propagation for estimating and reducing the magnitude of the micro-pressure wave. In this paper, we introduce a new simple equation governing distortion of the tunnel compression wave propagating through a Shinkansen tunnel with concrete slab-tracks. We propose a new simple scheme for numerical calculations. A space evolution type equation with one variable is derived from the three conservation equations (mass, momentum, and energy including the wall friction and heat transfer terms) of the 1D CFD by assuming small disturbances excited by the compression wave. The numerical calculation scheme based on the simple equation reduces the computing time remarkably because its CFL condition is relaxed. The calculation results obtained using the proposed scheme agree well with those by a conventional scheme based on the 1D CFD. The accuracy of the simple equation is verified.
