Optimization of Train Nose Shape for Reducing Impulsive Pressure Wave from Tunnel Exit.

Abstract

When a compression wave generated by a train entering a tunnel propagates through the tunnel and arrives at the tunnel exit, an impulsive pressure wave (micro-pressure wave or tunnel sonic boom) is radiated from the tunnel exit. Since the impulsive wave is closely related to the form of the compression wave arriving at the tunnel exit, improvement of the train nose shape is one means of reducing the impulsive wave. In this work, numerical optimization of the train nose shape for reducing the impulsive wave is performed by nonlinear programming combined with numerical simulation. The cross-sectional area distribution of the train nose is determined by the nonlinear programming, while the effect of the train nose shape on the form of the compression wave is estimated by the numerical simulation which solves the unsteady axisymmetric compressible Euler equations by finite volume method, TVD scheme and sliding grid method. The effect of the nose shape obtained by the optimization is confirmed by experiments using models.