Experimental Investigation into Effects of Porous Fence on Particle Threshold Wind Velocity
栅栏对颗粒起动风速影响的实验研究

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.