Influence of blockage ratio on slipstreams in a high-speed railway tunnel

Abstract

The train-induced airflow in a railway tunnel is of great significance for tunnel ventilation, fire rescue, and ancillary facilities overall. Previous research mainly focused on piston wind in metro tunnels, while the slipstream in high-speed railway tunnels is more drastic and complicated owing to the faster vehicle speed and diverse blockage ratios. In this research, a computational fluid dynamics (CFD) study was carried out to explore the three-dimensional transient airflow induced by a commercial high-speed train circulating through tunnels at 350 km/h under different blockage ratios (β = 0.175, 0.160, 0.140, 0.122, and 0.112). First, the train-tunnel model was established based on the unsteady Reynolds-Averaged Navier–Stokes (URANS) method merged with the sliding mesh technique, altogether validated with experimental evidence. Then, the resultant slipstream and the individual components were investigated, and it was concluded that the longitudinal component was dominant. The variation behaviors of the slipstream and local pressure with the different blockage ratios were comparatively obtained. Finally, the relationships between the slipstream and the spatial distance in longitudinal, lateral, and vertical directions were analyzed. This study provides a guideline for the determination of the tunnel clearance, and wind load evaluation in a high-speed railway tunnel.