Structural Dynamics of Leaves and Stems
Flexible plants, fungi, and sessile animals are thought to reconfigure in the wind and water to reduce the drag forces that act upon them. In strong winds, for example, leaves roll up into cone shapes that reduce flutter and drag when compared to paper cut-outs with similar shape and flexibility. Simple mathematical models of a flexible beam immersed in a two-dimensional flow will also exhibit this behavior. What is less understood is how the mechanical properties of a two-dimensional leaf in a three-dimensional flow will passively allow roll up and reduce drag. In this project, we use computational fluid dynamics and flow visualization to determine how leaves roll up into drag reducing shapes during storms. In addition to gaining insight into mechanical adaptation in the natural world, this project might also inspire innovation in the engineering of structures and underwater vehicles.
A related project is to understand how plants deal with gusting wind forces, and what causes catastrophic failure (i.e. uprooting or snapping). Some ways that plants might deal with resonance is by increasing structural damping, ‘distorting’ resonance with nonlinearities, and transfering bending energy into twisting energy.
APS DFD Movie of Broad Leaf Reconfiguration