Optimal Wings for Flying Fruits

If you were to design wings for flying fruit, how best to optimize the wing shape? If you don’t already know the answer to that, you might begin your knowledge adventure by reading this study:

Curving to Fly: Synthetic Adaptation Unveils Optimal Flight Performance of Whirling Fruits,” Jean Rabault, Richard A. Fauli, and Andreas Carlson, Physical Review Letters, vol. S122, no. 024501, 2019. The authors, at the University of Oslo, Norway, report:

“Appendages of seeds, fruits, and other diaspores (dispersal units) are essential for their wind dispersal, as they act as wings and enable them to fly. Whirling fruits generate an autogyrating motion from their sepals, a leaflike structure, 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. We develop a theoretical model and perform experiments for double-winged biomimetic 3D-printed fruits, where we assume that the plant has a limited amount of energy that it can convert into a mass to build sepals and, additionally, allow them to curve. Both hydrodynamic theory and experiments involving synthetic, doublewinged fruits show that to produce a maximal flight time there is an optimal fold angle for the desiccated sepals. A similar sepal fold angle 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 and may improve the fitness of their producers in the context of an ecological strategy.”