Wind tunnel observation on the effect of a porous wind fence on shelter of saltating sand particles

Abstract

A porous wind fence is an artificial barrier widely employed to abate wind erosion. This study investigated the shelter effect of a porous wind fence on saltating sand in a simulated atmospheric boundary layer (ABL). A wind fence with a porosity ε = 38.5% was installed on a flat bed of sand collected from a beach (diameter, d = 200–300 μm). A high-speed digital camera was used to capture consecutive images of saltating sand particles around the fence at a frame rate of 4000 frames per second (fps). In addition, the particle tracking velocimetry (PTV) method was employed to extract the instantaneous velocity fields of saltating sand particles. From these data, the mean velocity and volume concentration of saltating sand, mass flux, and kinetic energy were evaluated. As a result, the mean velocities decrease dramatically on the leeward side of the fence, and a high-velocity region exists in the shear layer above the fence. The sand mass flux distributions with height around the fence are represented by an exponential function. Both the particle concentration and mass flux decay largely in the leeward region. The present experimental results can provide useful information to understand sand transport through a porous fence and allow the creation of a new control measure of wind erosion of sand particles.