Numerical simulations of high speed train impulsive noise using an unsteady deforming mesh algorithm

An impulsive noise produced by a train-tunnel interaction is numerically simulated by using an unsteady deforming mesh algorithm. The applied algorithm for a moving body needs special treatments to satisfy a geometric conservation law (GCL) to preserve a free stream. It is validated in the cases of a 1D moving piston and 2D pulsating and oscillating cylinder problems. The computational results show good agreements with analytic solutions. Finally, the behaviors of the various pressure waves due to the axisymmetric model train passing through a finite tunnel are numerically simulated. The computational results show that the propagation of waves in the tunnel and the pulse-like impulsive wave radiation at the exit of the tunnel depend on various physical and numerical parameters, such as the shape of the train, the train speed, the tunnel length and the resolution of the numerical scheme, and that the emitted impulsive noise decays in proportion to 1/r, not from the exit itself but from a point near the exit, due to the complex wave field.