A Wind Tunnel Study of Windbreak Flow Dynamics Using Particle Imaging Velocimetry

Windbreaks play an important role in agriculture through reducing erosion and providing shelter from wind and snow. Additionally, they provide protection for roadways from snow and mitigate dust emissions from un-paved roads. Understanding the motion of air born particles, as well as the behavior of air as it passes over and through these windbreaks can help optimize performance and identify further benefits to plant growth, road protection, and road impact remediation. Here, near windbreak physics are studied using two dimensional particle image velocimetry (PIV). Varying hole geometries are analyzed for a range of overall wind break porosities. In addition to statistics reported in previous work (e.g. mean flow patterns, turbulent fluxes and turbulent kinetic energy), here conditional averages and instantaneous flow realizations are examined. Particular emphasis is placed on the effects of porosity and hole geometry on the quiescent region directly downwind of the windbreak, the reattachment point where wall shear begins to dominate, and the shear layer emanating from top of the wind break. Besides examining average features of these features, unsteady characteristics are also reported. When applicable, comparisons to a recent field study of a vegetative windbreak are made to examine the impact of scale on the reported results.