Experimental study of wind load on tree using scaled fractal tree model

Abstract

Green urbanism has stimulated more research on the aerodynamics of tree in recent years. The insight gained in studying wind load on trees would mitigate risk of tree falling and enable sustainable landscape planning. However, deciphering the effect of wind on trees is a daunting task because trees come in various species, shapes and sizes. In this study, we aim at conducting wind tunnel tests on various species of trees, including measuring the respective drag coefficient and turbulent flow field using a force balance and particle image velocimetry system. The wind tunnel experiment is conducted using scaled down fractal tree model at 10 and 15 m/s. The 3D-printed tree model is grown based on the data collected on the species-specific tree parameters, such as the height, trunk diameters, crown box dimensions, etc. In this paper, the wind tunnel result of Yellow Flame (Peltophorum pterocarpum) is presented. Results show that the drag coefficient for this inflexible tree model is not sensitive to wind speed. The Reynolds shear stress and turbulence kinetic energy are observed to be the largest at the top and bottom of the crown where the velocity gradients are the highest.

Scanning Doppler lidar measurements of drag force on a solitary tree

“…Solitary trees are very efficient in reducing the mean wind speed. Experimental observations of this capability have been performed by both wind tunnel studies on young trees (Lee, Lee & Lee 2014;Manickathan et al 2018) and tree-shaped structures (Gromke & Ruck 2008;Bai, Meneveau & Katz 2012;Chan et al 2020), as well as in full-scale experimental studies (Dellwik et al 2019). Due to this characteristic, trees act as obstacles † Email address for correspondence: nang@dtu.dk to the wind in the surface layer of the atmospheric boundary layer.…”