Simulation of swaying tree in wind field considering coupling effect

A finite element model of swaying tree was established to explore the kinetic mechanism of swaying tree in wind field. The fluctuate drag and lift forces of tree branches in wind due to vortex shedding were estimated using the vortex induced vibration theory of circular cylinder. An arbitrary Lagrange-Eulerian (ALE) based fluid-structure interaction method was used to calculate the wind force exerted on a leaf under various wind speeds and leaf angles. A simplified fluid-structure method based on the experimental data of circular cylinder in flow field was proposed to estimate the variation of wind load on the tree branches due to large deformation. Simulation showed that the investigated nodes are all moving in a looping manner, and the trajectories under two different wind fields are very similar. The branches are shaking in high frequencies due to the vortex shedding on branches, but the amplitudes are very small. Different branches interact with each other, and can change the motion trajectories of the investigated points.