Study on the Influence of Blocking Ratio on Slipstream in Tunnel

Abstract

When a train moves through air, it generates a turbulent flow around it called a slipstream. The slipstream is associated with high air velocities and rapidly-changing pressure fields. The air velocity, pressure variation and direction of the flow inside tunnels are different than the slipstream in open air. These differences depend on the size of the tunnel and length of the tunnel and the shape and speed and length of the train. In the present paper, the effect of tunnel length on the velocity flow and pressure inside is investigated. The investigation uses computational fluid dynamics techniques (CFD), in which a model of the CRH380A train is used. Two tunnel lengths are also investigated; one is 200m called case 1 and the other is 400m called case 2.The sliding mesh technique is employed to simulate the movement of the train in the tunnel. The simulation uses unsteady RANS and applies the Shear Stress Transport (SST) turbulence model. The effect of tunnel length on both pressure and velocity fields is discussed.