1371 / 2019-08-09 20:42:39

青藏铁路错那湖段防护体系的风沙两相流数值模拟

10、干旱区环境与风沙科学 > 专题6：风沙灾害与治沙工程

摘要：【背景】错那湖段是青藏铁路沿线风沙灾害最严重的区域之一，风沙活动严重威胁着铁路的运行安全。【方法】为科学评价并系统优化当前沙害防护体系，对其进行数值模拟实验。使用Fluent欧拉双方程模型求解防护体系内流场分布，结合可视化分析总结挡沙墙周围风沙两相流运动规律。【结果】结果表明：1) 数值模拟与风洞模拟结果具有流动相似性，数值模拟相较风洞试验能获得更准确且分辨率更高的数据。2）气流与挡沙墙上部接触时发生转捩，能量在挡沙墙处大量损耗。当前防护体系内，铁路路基与挡沙墙间平均动能损耗达到64.31 %，有效防护距离超过74.37 %。3) 挡沙墙周围沙相粒子受涡旋作用，产生局部富集效应，从挡沙墙后1~3 H范围内开始沉积。随着沙相物质不断沉积，起始沉积位置前移，流动低速区不断扩大，防护效果不断减弱，第二道挡沙墙下部逐渐被掩埋。4)根据气流结构特征进行流场功能区划分，防护体系内沙相物质在耗散减速区、涡旋沉降区发生减速、沉降以此实现沙害的防治。为进一步提高挡沙墙防护效益，可适当加大挡沙墙底部空隙及上部能量损耗。【结论】在没有沙相物质沉积时，当前防护体系能发挥较好防护效益，然而随着沙相物质逐渐沉积，防护效益会不断减弱。在今后强风地区防护体系建设时，可结合风沙两相流输运特性，合理改进防护措施结构，设置合理的防护措施间距。本研究可为青藏铁路沙害防护体系建设提供理论依据和科学支撑。

关键词：青藏铁路，挡沙墙，风沙两相流，数值模拟，可视化分析



Abstract: [Background] The Qinghai-Tibet railway (QTR) has been under constant threat from aeolian sand since its opening, and the Cuona lake section is one of the worst areas along the railway line, wind-sand disaster seriously threatening the safety of railway operation. [Methods] To evaluate and optimize the current protective system scientifically, the wind-sand two-phase flow is simulated using the Eulerian model of Fluent software. It is clear the two-phase flow rules around sand fences combined with visual analysis and the theory of multiphase flow. [Results] The results indicate that: 1) Numerical simulation and wind tunnel experiment with similarity flow, and numerical simulation has higher measurement resolution can provide more accurate results. 2) Flow transition when contact with the upper part of the sand-blocking fences, when passing through the sand-blocking fences a large amount of energy was lost. In the present protective system, the average energy loss between railway subgrade and the sand-blocking fences is 64.31%, and the effective protection distance is over 74.37%.3) The sand particles are locally enriched by the vortex, and start to deposit from within 1~3H of the sand retaining wall. With the continuous deposition of sand particles, the initial deposition position is moving forward, and the protective effect is continuously weakened. The low-speed flow area expands continuously with the second sand block fence buried by sand. 4) According to the flow structure characteristics flow field, functional areas are divided into five parts. Sand particles will settle in the dissipation deceleration area and vortex settlement area, to achieve the protective effect. [Conclusion] In the absence of sand material deposition, the current protective system can play a better protective effect. However, with the deposition of sand material, the protective effect is gradually weakened. When construction protection system in the future, the structure of fences can be reasonably improved and reasonable spacing of fences can be set according to the dynamic characteristics of wind-sand two-phase flow. This paper provides relevant theoretical basis and scientific support for the construction of the protective system in the strong wind area in the future.

Keywords: Qinghai-Tibet railway; sand-blocking fences; wind-sand two-phase flow; numerical simulation; visualization analysis