风沙两相流对铁路路堤响应规律的数值模拟研究

Numerical Simulation of Response Law of Wind-blown Sand Flow around the Railway Embankment

基于FLENT欧拉双流体模型,对路堤周围风沙两相流运动特性进行数值模拟,并将模拟结果与现场实际调查进行比较。结果表明,所用模型能较好地模拟路堤周围风沙两相流的运动特性,数值模拟与现场调查相吻合。数值模拟分析表明:路堤周围气流速度产生分区,分别形成减速区、加速区、高速区、低速区与紊流区;沙粒速度与风速相互影响,形成一种反馈机制;在过渡区内,当风速大于起沙风速时,沙粒速度与风速呈正相关;正交单向来风条件下,揭示了迎风坡积沙量大于背风坡的形成机理;路堤顶面积沙量呈"正态形"分布,中间多,两边少;迎风坡积沙量随着风速增大而减小,背风坡无明显变化;不同地表条件对风沙流密度及结构影响显著,决定着工程防沙措施。

The motion characteristics of wind-blown sand flow around the railway embankment were simulated by the FLENT eulerian two-fluid model,and the simulation results were compared with field surveys.Results show that the model can well simulate the motion characteristics of wind-blown sand flow around the railway embankment,and the numerical simulation is in conformity with field investigations.Numerical simulation analysis shows as follows：Air velocities surrounding the embankment produce partitioned area,i.e.,the deceleration area,acceleration area,high-speed area,low-speed area and turbulent area;sand speeds and wind speeds influence one another,forming a feedback mechanism;in the transition zone,when the wind speed is greater than the initial sand speed,the velocity of sand grain is positively correlated with the wind speed;the formation mechanism that the sand sediment on the windward slope is more than on the leeward slope is revealed under the condition of the single orthogonal wind direction;sand sediment on the top of the embankment is in normal distribution,more in the middle and less on both sides;as the wind speed raizes,windward slope sediment decreases whereas leeward slope sediment has no obvious changes;different ground surface conditions have significant effects on the sand flow density and structure,thus determining the engineering sand prevention measures to be taken.