Interaction of gusts and forest edges - An experimental wind-tunnel study

Abstract

Observations in nature suggest a particularly high risk of wind-induced forest damage near stand edges. Unsteady processes caused by strong gusts from the atmospheric boundary layer are likely to play a major role. To gain more insight into the corresponding flow behaviour, wind-tunnel experiments were made with artificially generated 3D wind gusts, produced by short inductions of pressurized air, combined with time-resolved particle-image velocimetry measurements. In the near-edge region of the laboratory forest, the developing gust-induced disturbance at canopy, the top shows a wave-like shape in the measurement planes. The highest values of downward momentum flux above the canopy were measured 1.5 to 4 tree heights behind the leading edge. This was found to be caused by an edge-induced primary vortex, which formed behind the edge and directed high momentum fluid from the overflowing gust into the canopy. © 2013 © Institute of Chartered Foresters, 2013. All rights reserved.