Numerical Simulation of the Airflow across Trees of a Windbreak

i Abstract In the present study, the effect of the trees in windbreaks on the leeward airflow is investigated, for the first time, employing numerical models. Different arrangements of windbreaks have been considered: (i) a single row of cypress trees, (ii) two rows of cypress trees and (iii) two rows of cypress trees with a low hedge that represent shrubs in the first row. The RANS equations have been solved using a mesh of 12.5∙10 nodes. The canopy of the trees and the hedge are modeled as porous regions. The resistance of the porous region is correlated with the optical density of trees. The wind velocity reduction is examined with regard to the different trees arrangements, canopy density and approaching wind velocity. It is shown that the second row of trees has a significant effect on the lee of the windbreak, however the hedge has only a limited effect that is significant near the ground only. The effect on the lateral flow behind the trees is limited to less than two tree-heights. A wind reduction as much as 40% and 55% is found at a half tree height and a distance of three tree-heights, for the one row and two rows of cypress trees, respectively. The numerical model can be further employed for studying additional details of the flow field including mass and heat transfer effects or different tree types.