Comparison of aerodynamic performance of trains running on bridges under crosswinds using various motion modes

The high-speed railway bridge, accounting for over 50% of railway lines, plays an important role in high-speed railways. When the train runs at high speed on these bridges, the strong winds will directly pose a risk to the safety of train operation, even causing train overturning accidents. Therefore, it is significantly urgent to accurately simulate the relative motion of the train-bridge system in crosswind environment. An improved delayed detached-eddy simulation study based on the shear stress transfer k-omega (I-ω) turbulence model was used to analyze the aerodynamic characteristics of trains running on bridges under two relative motion modes, i.e., the static synthesis method (SSM) and the dynamic decomposition method (DDM), and the variation rule of train aerodynamic loads. The differences of aerodynamic forces, surface pressure distributions, and flow characteristics around the train body under two motions were discussed. The results show that the applied velocity-inlet boundaries in two relative train-bridge motion modes under crosswinds lead to a large difference in the flow characteristics around bridges. Compared with the SSM, the DDM generates more small-scale vortices in the leeward side of the train, causes more disturbances, and enhances the flow instability. Under the DDM, the side force coefficient and lift force coefficient of the train are decreased by 1.99%, 66.67% (Train on the windward side) and 24.47%, 48.24% (Train on the leeward side), respectively, as compared to the SSM. The achievements obtained in the current study can provide data support for the operation standard of high-speed trains traveling on bridges.