| Abstract | Flutter, a self-excited vibration with a sustained amplitude, often leads to structural failure especially in engineered structures such as buildings, plane wings, and bridges. Due to the potential for catastrophic failure with serious consequences, flutter analysis is of primary concern in engineering design. Natural structures such as leaves have the ability to reconfigure themselves in order to reduce the forces experienced by the structure. Analysis of the properties of these natural structures could provide insight into designing artificial structures that exhibit reduced flutter. Here we present preliminary data demonstrating the behavior of leaves in response to fluid forces. Leaves from a tulip poplar (Liriodendron tulipifera) are subjected to laminar and turbulent flow in a wind tunnel in order to observe the reconfiguration of the leaf structure to reduce drag and flutter. Similarly, wild ginger (Asarum canadense) is subjected to flow in a water tank to observe the reconfiguration and to examine of trapped vortices. Preliminary data suggest natural leaves more readily reconfigure into drag reducing and flutter reducing shapes than do morphologically similar artificial leaves constructed from homogeneous materials such as cardboard. Artificial leaves are used to compare biological structures with simple flexible models. Quantitative data on the wake structure within and behind the leaves in water using particle image velocimetry (PIV) will be presented here. |
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