Numerical simulation of unsteady compressible flows induced by a high-speed train passing through a tunnel

The unsteady flow fields induced by a high-speed train travelling through a tunnel have been numerically simulated. In order to present the relative motion between a train and a tunnel, a modified patched-grid scheme based on the structured grid system has been developed and employed for an axisymmetric unsteady Euler solver using Roe's flux difference splitting method. In this paper, the innovative zonal method, named the hybrid dimension method, is proposed and applied to the train-tunnel interaction problems. The basic idea of this method is to maximize the efficiency of numerical calculations by minimal assumption of spatial dimensions. The numerical results from the modified patched-grid scheme showed good agreement with the inviscid compressible phenomena of the experimental result, i.e. the entry compression wave and the micropressure wave. The hybrid dimension method is successfully applied to the present modified patched-grid method, hardly losing the numerical accuracy. Moreover, the hybrid dimension method is expected to reduce the huge computation time of the train-tunnel interaction problems especially for the cases of long tunnels.