Flags and leaves in the wind
Lionel Schouveiler
IRPHE CNRS & Aix-Marseille University
France
Abstract:
Interactions between a exible structure and a ow can be encountered in many everyday life situations (apping ag, plants in the wind, ...) as well as in industrial applications (paper making or printing industry), in civil engineering (Tacoma bridge) or in biology (snoring, swimming)...
Flutter of a exible plate immersed in a uniform ow is a canonical example of such aeroelastic instability. In this talk I will rst review the previous theoretical approaches of this problem. Then I will present our analytical/experimental works (Fig. that have mainly concerned the nite span e ect. We have also considered the coupled utter modes of an assembly of parallel plates, theoretical results will be compared with experiments performed with 2, 3 and 4 plates.
In the last part I will address another aspect of flexible structure/fluid flow interactions that concerns strategies developed by plants to withstand strong wind. Leaves can for example reconfigure into cones for reducing the area exposed to the wind as observed for some broad-leaved species (as tuliptree or red maple). We have reproduced this behavior in the laboratory and performed a scaling analysis showing that the static equilibrium states of the leaf correspond to balance between leave elasticity
and pressure load.