Numerical Analysis of Slipstream Caused by Interface Between Train and Acoustic Screen

초록

The slipstream phenomena caused by interface between train and acoustic screen are numerically investigated. One of Korean existing train, “Mugungwha”, which has a sharp-edge nose is used as model. The analyzed train length is one and half unit of train and the gap between the train and surface is 17% of train height (H). The distance between the center of train and the acoustic screen is 1.41H and the height of screen is assumed to be the same as train height. Uniform flow is given in the inlet and 18H length is set up to investigate the wake flow after train. Zero-gradient boundary condition is given at the outlet. Surface is assumed to be zero. The symmetry condition is used in the center of train. Overall flow is considered to be steady state. The Re number is 10,000. RANS calculations are performed with non-orthogonal, collocated, cell-centered finite-volume approach implemented in the code STREAM. 17 multi-blocks are generated to solve the slipstream effects. Launder & Sharma low Re EVM is employed to account for turbulent flow. To provide adequate resolutions of the viscous sub-layer and buffer layer adjacent to a solid surface, the minimum grid spacing in the near-wall region is maintained at of body length, which corresponds to a wall coordinate of order of 0.1. Total grid points are about 1.6 million. The flow separation is occurred at the train nose and reattached on the top and two sides of train. The two vortexes are generated after train body. These vortexes hit and push the acoustic screen.