Numerical studies on the radiation of train-tunnel impulse waves

Abstract

An impulse wave is always discharged from the exit of a train tunnel when a weak compression wave induced by a moving high-speed train at the tunnel entrance propagates outside of the tunnel exit. An impulse wave is a micro-pressure wave, which leads to environment problems such as noise, vibration and other structural damages in the vicinity of the tunnel exit. Currently, due to the development of the optimization and acceleration systems of the high-speed train, the train speed becomes much higher than before and environmental problems become more serious as well. Therefore, it is significantly important to find effective methods to control and reduce magnitudes of impulse waves discharged from the tunnel exit. In the present study, numerical simulations were carried out to investigate the generation and propagation of impulse waves discharged from the exit of a model tunnel. Weak compression waves with different pressure gradients were assumed at the tunnel entry for investigating the relationship between the compression wave and the impulse wave radiated from the tunnel exit. Several tunnel exit geometries with and without a flange at the exit portal of the tunnel were simulated to check their effects on the radiation of impulse waves. Coefficient of effective radiation solid angle indicating the effects of the surrounding environment near the tunnel exit was discussed in-depth. The comparison was made in terms of the magnitudes of impulse waves and coefficients of effective radiation solid angle at different boundary conditions.