The Characteristics of the Spatial and Temporal Distribution of the Initial Compression Wave Induced by a 400 km/h High-Speed Train Entering a Tunnel

The initial compression wave induced by a 400 km/h high-speed train entering a tunnel in two cases (offset running and center running) is investigated by overset mesh technology. The governing equations of the IDDES model for three-dimensional, unsteady, compressible flow are employed. The meshing strategy and numerical algorithm are validated by moving model test data. The spatial and temporal distribution characteristics of the initial compression wave and the one-dimensional planar wave characteristics are analyzed. The results show that the compression waves undergo three stages: from an irregular spherical shape near the train to an oblique shape, and finally to a one-dimensional planar wave. The initial compression wave captured at the measurement points at a distance of 5Di (Di represents the equivalent diameter of the tunnel) from the tunnel portal has been fully characterized by one-dimensional features, which can provide a boundary input for the propagation of the initial compression wave towards the tunnel exit. Compared to the offset running case, the initial compression wave amplitude and pressure gradient amplitude induced by central running are reduced by 3.66% and 6.87%, respectively.