栅栏对颗粒起动风速影响的实验研究

 气流对栅栏的响应可以定量地用沙粒的起动风速来表征。通过风洞模拟实验研究了栅栏两侧不同距离处沙粒的起动风速及运动特征随疏透度和高度的变化关系。根据颗粒运动的不同典型特征,栅栏附近的水平区域可划分为5个区。栅栏的疏透度是决定其最终防护效果的关键因素,紧密型栅栏,尤其是不透风栅栏,其迎风侧脚容易形成堆积。栅栏疏透度为0.3～0.4时相对起动风速最大,疏透度0.3～0.6时能产生最大的有效防护距离。栅栏越低,产生最佳的防护效果所要求的疏透度就相对越小,反之亦然。疏透度0.3～0.4的栅栏在实际应用中可以起到最佳的防风阻沙效果。

Experimental Investigation into Effects of Porous Fence on Particle Threshold Wind Velocity

The response of porous fence to the near-surface airflow can be characterized quantitatively by sand particle's threshold wind velocity.By using wind tunnel test,we measured the threshold wind velocity at different distances downwind from porous fences and observed the corresponding characteristics of particle movement to assess their shelter effect.We found that the fence's porosity is the key factor that determines the resulting shelter effect.The area near a fence can be typically classified into five regions,each with a different mode of particle movement.Dense fences,and especially solid fences,favor the accumulation of sand upwind of the fences.Fences with porosities of 0.3 to 0.4 produce the maximum threshold wind velocity;those with porosities of 0.3 to 0.6(depending on the fence height) provide the maximum effective shelter distance.The shorter the fence,the lower the required porosity to provide the best shelter effect and vice versa.We confirmed that the fence porosities of 0.3 to 0.4 that have been proposed for practical application in previous research are the most effective for abating wind erosion.