Numerical simulation of wind sand flow fields and deposition-erosion characteristics in the bridge-road transition section under different wind angles

Railways in desert suffer from windblown sand hazards, in which the problems at bridge-road transitions are usually more serious. However, the evolution of wind-sand flow fields and the associated deposition-erosion patterns around bridge-road transitions under different wind directions remain limited. In this study, numerical simulations are employed to study the influence of wind angle on the flow field structure, wind profiles, horizontal wind speed distribution, and sand deposition-erosion behavior around the bridge-road transition. The results indicate that as the wind angle increases, the leeward vortex recirculation zone expands, the peak of the vertical wind speed profile increases, and the horizontal wind speed decreases. With respect to deposition-erosion patterns, the sand deposition length on the windward sides of both the bridge pier and the bridge-road transition decreases with increasing wind angle. In contrast, the deposition length on the leeward side increases. Specifically, when the wind angle increases from 60° to 90°, the windward deposition length at the bridge-road transition decreases from 1.99H to 1.49H (H, the clear height of bridge), while the leeward deposition expands from 0.70H to 13.28H. In addition, the bridge-road transition section serves as a channel for sand transport, promoting the migration of sand toward the subgrade. A smaller wind angle enhances the lateral guidance effect on the wind-sand flow, resulting in a greater sand deposition length on the leeward side of the subgrade. Therefore, the prevention and control of sand hazards in the bridge-road transition section should not be neglected. It is necessary to regularly remove accumulated sand to prevent its spread from the transition section to the subgrade, which could threaten traffic safety.