Aerodynamic and dynamic characteristics of an aeroelastic tree model with a range of crown porosity

Many major cities worldwide have recently initiated tree-planting programs to improve the resilience of urban environment based on several environmental and social benefits of trees. However, wind loads are known to have a significant impact on trees, and presently, little is known about tree aerodynamics. A wind tunnel test at BLWTL of Western University was carried out to investigate the aerodynamic loads and response of a tree using an aeroelastic model with a range of crown porosity. These loads reflect the level of alteration imparted to the momentum of the flow by the presence of trees. This study estimates the changes in the aerodynamic behavior of a tree all around the year, due to seasonal change of leaves by considering different crown porosities. The drag force on the tree was found to vary quadratically with the wind speed, consistent with the literature for stiff trees. Moreover, the results show that for an aerodynamic porosity greater than 0.6, the drag coefficient decreases drastically for all the wind speeds considered in the study.