Numerical simulation study of a tree windbreak

In this study, computational fluid dynamics (CFD) was utilised to investigate the flow characteristics around tree windbreaks. The efficiency of windbreaks depends on many factors which can be investigated in field experiments, though this is limited due to several reasons such as unstable weather conditions, few measuring points, etc. Fortunately, the investigation is possible via computer simulations. The simulation technique allows the trees to be modelled as a porous media where the aerodynamic properties of the trees are utilised in the model. The trees employed are Black pine trees (Pinus thunbergii) with a drag coefficient value of 0.55. The simulation provides analysis of the effect of gaps between trees, rows of trees, and tree arrangements in reducing wind velocity. The simulations revealed that 0.5 m gap between trees was more effective in reducing wind velocity than 0.75 and 1.0 m. The percentage reduction in velocity at the middle of the tree section for 0.5, 0.75 and 1.0 m gap distance was found to be 71, 65 and 56%, respectively. Two-rows of alternating trees were also found to be more effective than one-row and two-rows of trees. The reduction at the middle of the tree region for one-row and two-rows of trees and two-rows arranged alternately was 71, 88 and 91%, respectively. Results revealed that the percentage reduction in wind velocity measured at distance 15H, where H is the tree height, for one-row, two-rows of trees and two-rows arranged alternately was approximately 20, 30 and 50%, respectively.