Wake dynamic characteristics of windproof structures in embankment-bridge sections along a high-speed railway under natural strong crosswinds

A recent trend in railway development around the world is the extension of high-speed railways to areas with harsh climatic environments. The aerodynamic performance of high-speed trains deteriorates when they run through embankment-bridge sections in a windy environment, posing potential safety risks. The present study aims to reveal the evolution mechanism of wake field in the transition section of the windbreak wall and wind barrier under natural strong crosswinds. First, the fluctuating characteristics of natural wind field collected by ultrasonic anemometers during a period of strong wind are captured. Next, the improved delayed detached eddy simulation scheme combined with the shear stress transfer k-w model is used to elucidate the difference of flow field modes on the leeward side of the windproof structure in the transition section under the conditions of constant and fluctuating crosswinds. Finally, the effects of model scale ratio (1:20, 1:10, and 1:1) on wind field simulation results on the leeward side of the windproof structure are revealed. Results show that the incoming flow with time-varying velocity evokes the instability of wake vortices of the windbreak wall in the embankment. The transient evolution results of the vortices obtained by the 1:10 model are in good agreement with those of the 1:1 model, whereas the results obtained by the 1:20 model have a large deviation.