Definition of minimum clearance height of railway bridges in a windblown sand area based on numerical simulation

Railway bridges with lower beam bottom clearances in windblown sand areas tend to accumulate sand particles on the sides of the beams, which seriously impacts railway safety. To investigate the effect of beam clearance height on wind-sand movement near the surface, and to determine the minimum clearance height for railway bridges in such areas, computational fluid dynamics using the Euler-Euler two-phase flow model was employed to simulate the wind-sand flow field beneath bridges with different heights. The results indicated that as clearance height increased, both the high-speed area above the bridge and acceleration area under the bridge increased, while the turbulence area on the leeward side remained unchanged. Furthermore, wind speed on the windward side did not decrease, and no deceleration zone near the surface was observed with increased clearance height. When the bridge height reached 9 m, the wind speed on the windward side no longer decreased. The correlation coefficients of near-surface wind speed under the bridge height of 9 m and above were consistent. As wind speed increased, the fluctuations in wind speed between bridges with different clearance heights became more pronounced, with differing variation trends. On the leeward side, lower clearance heights resulted in greater wind speed fluctuation. With higher wind speeds, the main position of wind speed deceleration moved further from the bridge. Therefore, the clearance height of bridges in the windblown area should be at least 9 m. These results provide a theoretical basis for the survey and design of bridges in the windblown sand areas.