Elastohydrodynamics and optimal flight of seeds

Par Andreas Carlson, Associate Professor, Department of Mathematics, University of Oslo

Mardi 29 Mai, 14h, Salle des séminaires (215), 2ème étage, Bâtiment A4N

Abstract :

In this talk I will present some of our recent work on;

i) Elastohydrodynamics of deforming blisters
The dynamics of an elastic surface near a solid substrate manifest itself in microelectronics engineering processes, synthetic lipid membrane systems, as well as in a myriad of biological processes ie. adhesion of epithelial cell sheets, membrane blebbing. We develop a thin-film model to study this class of phenomena, were we couple membrane bending, the viscous flow and a stochastic fluctuations. I will show some elastic analogues to classical capillary flows i.e. cusp formation and drop spreading (Tanners law) together with some of our recent activities.

ii) Curving to Fly: Synthetic adaptation unveils optimal flight performance of whirling fruits
Fruits have elongated sepals, a leaf like structure as part of its flower, that are essential for wind dispersal of seeds, as they act as wings and enable them to fly. Whirling fruits generate an auto-gyrating motion from their sepals, which curve upwards and outwards, creating a lift force that counteracts gravitational force. The link of the fruit’s sepal shape to flight performance, however, is as yet unknown. By combining hydrodynamic theory and experiments involving synthetic, double winged fruits we show that to produce a maximal flight time there is an optimal curvature for the desiccated sepals. A similar sepal curvature is found for a wide range of whirling fruits collected in the wild, highlighting that wing curvature can aid as an efficient mechanism for wind dispersal of seeds.

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