An experimental investigation on the large-scale meandering flow structure causing FIV of high-speed trains running in tunnels

To verify the existence of the large-scale meandering flow structure that causes flow-induced vibration (FIV) of high-speed trains traveling in tunnels, the vertical flow velocities on the sides of the cars of a high-speed train running in a tunnel and in the open air are estimated by a simple method of tuft visualization in running experiments on a real train without conducting large-scale measurements. Tufts are attached to the side windows of the 3rd and the 14th car of the 16-car Shinkansen train, and the mean and peak values of vertical flow velocity fluctuations are estimated from the movement of the tufts. First, the steady flow field around the 16-car train is estimated from the mean values of vertical flow velocity fluctuations. Then, the existence of the large-scale meandering flow structure along the train traveling in the tunnel is identified from the peak values by comparing the results between the numerical simulation of previous research and the running experiments. The results of this study support the validity of the mechanism proposed in the numerical simulation, in which the large-scale meandering flow structure is formed along the train traveling in the tunnel, generating aerodynamic forces acting on the sides of the car.