Effect of ballast track structures on the crosswind aerodynamics of a high-speed train on a bridge

This study investigates the aerodynamic behavior of a high-speed train during bridge crossings under strong crosswind conditions, with a focus on the influence of different ballast track structures. Three ballast structures were compared: flat track, CRTS (China railway track system) III ballastless track, and ballasted track. Using a combination of wind tunnel experiments and computational fluid dynamics (CFD) simulations, we analyze aerodynamic forces, flow field characteristics, and wind pressure distributions on the trains. The findings reveal that, on windward conditions, the side force coefficient (CFy) of the head train on flat embankments exceeds 130% compared to ballasted and CRTS III tracks, while the CFy of the middle train is only 30% of these values. In leeward conditions, the lift coefficient (CFz) shows significant differences, with flat embankments yielding CFz values of 63% and 69% for the head and middle trains, respectively. Additionally, under crosswinds, notable differences occur at the lower windward side due to flow separation at the bridge's leading edge. CFD analysis indicates that larger-scale gap flow occurs under flat embankments, resulting in more disruptive wake flows compared to other conditions.