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This research aims to describe the effect which changing the geometry of confining structures has on transient aerodynamic effects induced by passing high-speed trains. A moving-model high-speed train was fired past walls, partially-enclosed tunnels, and single-track tunnels. A control experiment was carried out in the open air. 3D air velocity components and static pressure were measured inside the structures. The main findings are as follows. The durations and magnitudes of the pressure loads and maximum air velocities were found to be dependent on: the lateral separation of the walls; whether walls on both sides of the tracks are placed symmetrically or asymmetrically; the longitudinal positioning of the sensor in relation to the length of the tunnel; the cross-sectional area of the tunnel; the tunnel’s length in relation to the train’s length; and, finally, the size of an opening in the cross-section of a tunnel in relation to the tunnel’s internal perimeter. Maximum velocities were affected by confinement as a result of changes to: helical vortices in the wake; durations and magnitudes of the pressure fluctuation around the tail; the piston effect in tunnels; the boundary layer shape; and secondary flows induced by pressure gradients in the tunnel cross-section caused by vents. |
