Experimental and theoretical study of the pressure waves in railway tunnels with long vented tunnel portals

Abstract

The aim of this study is to enhance the knowledge of the generation of pressure waves in railway tunnels and to adopt a method of predicting the influence of vented tunnel portals. Pressure waves in railway tunnels generated by the entry of a train into a tunnel entail many disadvantages and therefore have to be reduced. The experimental study was performed at the Tunnel Simulation Facility Göttingen, a moving-model rig. The influence of the train velocity, size and the head length, as well as the influence of the geometry of the tunnel portal and the number and size of portal vents on the pressure waves were investigated regarding the minimisation of the pressure gradient inside the tunnel. The air outflow through the vents was studied using PIV, especially the amount of air leaving the portal through each vent and the geometry of the stream tube. Furthermore, an acoustical analogy was used to predict the pressure-time history inside a model tunnel equipped with the different types of tunnel portals during the passage of the train. Empirical parameters, which are necessary for the estimation, were assessed both theoretically and experimentally. The given theory was adapted to a realistic train with underbody.