Abstract: When a train transits through a double-track tunnel at high speed, the geometric space between the train and the tunnel is asymmetrical, the air flows asymmetrically on both sides of the train, and the pressure environment inside the tunnel is complex. These factors result in different degrees of variation in pressure on both sides of the train, which are induced by the train body and tail vortex. To examine the pressure fluctuations at the train surface and the aerodynamic interrelationships and vibration spectral characteristics of the train body, a 1:1 aerodynamic simulation model of a high-speed train with eight coaches traveling at 400 km/h is established using a threedimensional, unsteady compressible flow NS equation and the IDDES turbulence model. The overlapping grid technology is used to simulate the relative motion between the train and the tunnel. The results indicate the following. (1) The train traveling inside the tunnel undergoes large-scale changes in pressure differential and lateral force amplitude on both sides of the carriage under the action of the pressure waves in the tunnel, and the degree of change increases from the head to the rear of the train. (2) There is a pair of reverse vortices in the wake area of the train when it is traveling inside the tunnel. (3) The main frequency of vortex shedding of the train tail in an open-track section is 2.002 Hz, whereas it is 3.003 Hz when the train is traveling inside the tunnel. (4) When the train is traveling on in open-track section or tunnel, the vibration frequency of the train body caused by aerodynamic lateral force and its yaw moment is 2.002 Hz.

Key words: high-speed train at 400 km/h, double-track tunnel, surface pressure fluctuations of train body, aerodynamic lateral force of train, yaw moment, wake flow, vortex shedding frequency, lateral vibration