Study of unsteady aerodynamic performance of a high-speed train entering a double-track tunnel under crosswind conditions

Significant variation exists in the aerodynamic performances of high-speed trains (HSTs) traveling in different infrastructure scenarios. When high-speed trains travel from one infrastructure scenario to another, the aerodynamic loads acting on the trains change significantly. To investigate the safety as a HST enters a tunnel under crosswind conditions, the unsteady aerodynamic performance of the HST and the flow structures around the train were numerically studied. The results demonstrated that the flow field and the pressure field were symmetrically distributed under conditions with no crosswind, while the distribution of the flow field and the pressure field were clearly asymmetric when crosswinds were present at the tunnel entrance. Furthermore, the flow structures near the train and the pressure distributed on the train surfaces outside the tunnel were most severely affected by the presence of crosswinds. Vortex structures appeared on the windward side surface of the train inside the tunnel and on the leeward side surface of the train outside the tunnel during the entrance of the train into the tunnel. Due to the sudden changes in the flow and the pressure as the train entered the tunnel, the aerodynamic loads changed drastically, and the variations of each vehicle were different, resulting in complex dynamic responses, including lateral vibrations and pitching movement. In particular, the aerodynamic performance of the rear vehicle was the worst as the train entered the tunnel when no crosswind conditions existed, while the head vehicle was the most negatively affected for safe operation of the HST when strong crosswinds were present at the tunnel entrance.