3D ultrasonic anemometer array reveals jet flow structures at the entrance of high-speed railway tunnel

Abstract

High-speed trains (HSTs), traveling at speeds of up to 300 km/h, are subjected to safety risks in crosswind conditions, particularly when they enter or exit tunnels due to transient aerodynamic effects. The study employs a three-dimensional (3D) ultrasonic anemometer array positioned at the tunnel entrance to investigate the jet flow structure and its 3D characteristics that are induced by HSTs as they enter tunnels. The main results are as follows: The jet flow speed reaches approximately 3%–7% of the train's operational speed, with a maximum length of around 0.48 L. When the train speed is increased from 300 km/h to 400 km/h, the effect of its slipstream on the surrounding wind speed increases by 33% upon entering the tunnel, while in the jet flow section, the wind speeds from both sources are comparable. Through field measurement and numerical simulation, this study provides better understanding of the characteristics of the 3D jet flow structure generated from HSTs entering tunnels, thus offering more insight in developing means for reducing jet flows.