风洞模拟“攀援植物-围栏”复合沙障不同疏透度下的防风效果

Wind tunnel simulation of the wind-breaking effect of“climbing plant-fence”composite sand barriers with different permeabilities

为探索受风蚀影响围封区域的新型治理技术措施,本研究对不同疏透度(β)“攀援植物-围栏”复合沙障的防风作用进行了风洞模拟试验。分别在6、8和10 m·s^(-1)净风条件下对模型A(网围栏,β:96%~98%)与4种复合沙障[模型B(无叶期,β:59%~64%)、模型C(无叶期,β:50%~55%)、模型D(有叶期,β:40%~45%)、模型E(有叶期,β:30%~35%)]进行试验。结果表明:1)不同类型复合沙障流场结构均呈“减-增-减”的变化趋势,障体背风侧存在风影减速区,网围栏前后流场结构一致,不存在减速区。2)不同风速条件下,无叶期复合沙障(模型B、模型C)在10 m·s^(-1)风速下近地表平均防风效能最低,分别为18.55%与18.38%,有叶期复合沙障(模型D、模型E)则在6 m·s^(-1)风速下最低,分别为44.03%与45.42%,有叶期复合沙障防风效应随风速的增大而增强,无叶期复合沙障则相反。3)综合分析表明,当障体疏透度为59%~64%时便可产生防风效果,复合沙障防风效果优于网围栏,障体有叶期防风效果优于无叶期,可测范围内无叶期复合沙障防护距离为0.6H~15H(H表示障体高度,1H=15 cm),有叶期复合沙障防护距离为0H~15H,复合沙障防风效果与疏透度呈反比。因而,“攀援植物-围栏”复合沙障可以提高围封区域的防风效果,降低风力作用下的地表物质流失。

To explore new treatment technology measures for enclosed areas affected by wind erosion,wind tunnel simulation experiments were conducted to determine the wind protection effect of the“climbing plant-fence”composite sand barrier with different porosities(β).Experiments were conducted under 6,8,and 10 m·s^(-1)net wind conditions using model A(fence,β:96%~98%)with four composite sand barriers:Model B(non-leafy stage,β:59%~64%),model C(non-leafy stage,β:50%~55%),model D(leafy stage,β:40%~45%),model E(leafy stage,β:30%~35%).The results show that:1)The flow field structure of composite sand barriers of different types showed a“decrease-increase-decrease”trend,and there was a wind shadow deceleration zone on the leeward side of the barrier.The flow field structure in front and behind the fence was consistent with the no deceleration zones.2)For different wind speeds,the average near-surface wind protection effectiveness of composite sand barriers in the non-leafy stage(models B and C)reached the lowest at a wind speed of10 m·s^(-1),at 18.55%and 18.38%,respectively.The leafy stage composite sand barriers(models D and E)had the lowest effectiveness at a wind speed of 6 m·s^(-1)at 44.03%and 45.42%,respectively.The wind protection effect of composite sand barriers in the leafy stage increased with increasing wind speed.The wind protection effect of composite sand barriers during the non-leafy stage decreased with increasing wind speed.3)The combination showed that wind protection can be achieved when the barrier is 59%to 64%permeable.Composite sand barriers provided better wind protection than did fences.Wind protection at the leafy stage of the barrier was better than that at the non-leafy stage.Within the measurable range,the protective distance was 0.6H~15H(H:height of the sand barrier,1H=15 cm)and 0H~15H for the composite sand barriers in the non-leafy and leafy stages,respectively.The effectiveness of composite sand barriers against wind was inversely proportional to the degree of permeability.Therefore,the“climbing plant-fence”composite sand barrier can improve the protection of the enclosed area and reduce the loss of surface material by wind action.