Prediction of micro-pressure waves generated at the exit of a model train tunnel

Abstract

A micro-pressure wave is discharged from the exit of the train tunnel when a compression wave induced by a high-speed train moves outside the exit of the train tunnel. Micro-pressure waves generate sound noises, making serious environmental problems for local residents. In order to efficiently control the micro-pressure wave discharged from the exit of a train tunnel, numerical simulations investigating the generation and propagation of the micro-pressure wave were carried out. A 2-D axisymmetric model tunnel was simulated at different operating conditions. Different overpressure and pressure gradients across assumed compression waves were investigated and the effect of the length of the tunnel flange was also considered. Micro-pressure waves located in the near field, in the far field and at positions with different angles at a specific radius were studied in detail. In addition, the open-end correction and directivity coefficient affecting the magnitudes of micro-pressure waves at different locations were discussed in-depth as well. Magnitudes of micro-pressure waves induced by different pressure gradients across initial compression waves, magnitudes of micro-pressure waves at locations with different angles at a specific radius and the open-end correction were theoretically calculated and compared with obtained CFD results.