Sophie Ramananarivo (Courant Institute, New York University, USA). Fluid/structure interaction in flapping flight: improving the performance of a wing.

Animal locomotion is an interesting context to study the interaction between a movable/deformable structure and a fluid. Birds and fishes flap their wings (or fins) to impart momentum to the surrounding flow and create a jet that propels them forward. The flow structures generated are very dependent on the characteristics of the wing, such as its geometry and elasticity. By tuning those carefully, propulsive performance can thus be improved.

In the first part, we investigate the influence of flexibility on flight performance. Bird or insect wings are elastic, and thus likely to experiment large bending. Using a simplified mechanical replica of an insect, we show that such passive deformations can considerably improve propulsion when exploited in a constructive way.

We then look at the impact of wing geometry on propulsion and ask the question: what would a fast-flying wing look like? Inspired by the natural mechanism of evolution, we address this search for “good shapes” through a combined experimental and numerical process mimicking natural selection.