兰新铁路戈壁地区路基周围风沙流运动特征数值分析

Numerical Analysis on the Features of Sand Flow Movement around the Embankment of Lan-Xin Railway in Gobi Region

运用FLUENT软件,进行兰新铁路戈壁地区路基周围风沙流场数值分析。结果表明,在路基周围风沙流场中,迎风侧坡脚、路基表面附近和背风侧坡脚出现气流运动的相对低速区,迎风侧路肩上方出现气流运动的相对高速区;在相对高速区产生风蚀沙害;在相对低速区产生积沙,且迎风侧坡脚的积沙多于背风侧坡脚。设置不同高度挡沙墙的路基周围风沙流场数值分析表明,流场中的最大风速区由迎风侧路肩上方前移至挡沙墙的上方,减弱了风沙流对迎风侧路肩的风蚀,且积沙大部分落在挡沙墙的前面,跃过挡沙墙的沙粒在挡沙墙和路基之间相对低速旋流的作用下继续跌落。因此挡沙墙的合理高度应满足:气流中大部分沙粒被挡沙墙拦截,在迎风侧路肩处不出现相对高速区,以避免迎风侧路肩产生强烈风蚀,且相对高低速区界线平稳穿过路基表面。

FLUNENT software was used to simulate and analyze the sand flow field near the embankment of Lan-Xin Railway in gobi region. The results demonstrate that relatively low-speed areas occur at the slope foot of the windward side,near the embankment surface and at the slope foot of the leeward side,while relatively high-speed areas occur at the shoulder of windward side in the sand flow field around the embankment.Wind erosion occurs at the relatively high-speed area while,sand accretion happens at the relatively low-speed area and the sand accretion at the slope foot of the windward side is more serious than that on the leeward side.The numerical analyses of sand flow surrounding embankment with anti-sand walls of different height illustrate that the maximum wind regions shift from the shoulder of the windward side to the above of anti-sand walls.Meanwhile,the wind erosion at the shoulder of windward side is weakened.Most sand accretes in front of the anti-sand walls and sand crossing the walls falls down under the impact of the relatively low speed vortex areas between the anti-sand walls and embankment.The reasonable height of the antisand wall should meet the following requirements： firstly,most sand in the air flow should be blocked by the anti-sand wall.Secondly,no relatively high-speed area occurs at the shoulder of the windward side so as to avoid the strong wind erosion there.Thirdly,the boundary line of the high and low speed areas gets across the embankment surface steadily.