BEHAVIOR OF A WEAK SHOCK-WAVE PROPAGATING THROUGH A GAS WITH DENSITY GRADIENT IN A DUCT

When a high-speed train such as the Shinkansen enters a long tunnel, a pressure wave is generated at the nose of the train causing a sonic boom at the tunnel exit. This noise, which can be very disturbing to nearby residents, is strongly dependent on the speed of the train. Hence, a bottleneck has developed in the quest for increased rail capacity through the use of even faster trains. In order to reduce sonic boom, the authors have proposed passing the pressure or weak shock wave through a density gradient field perpendicular to the axis of a tunnel and located at its exit. In this report, the behavior of a weak shock wave passing through such density gradient fields is examined by means of both computer simulation and experiment.