Publiée le 07/04/11 à 11h45

Licence Creative Commons CC-By-NC

One of the major hypotheses underlying many aerodynamic theories states that the flow near the wings can be sufficiently well described within the two-dimensional approximation. This viewpoint is classical and very appealing since it greatly simplifies the modelling. The two-dimensional approximation is well justified for propellers, but experiments with insects showed new and important three-dimensional effects. Obviously, they are also relevant to insect-like flying robots.
The three-dimensional character of the flow strongly influences the dynamics of the vortex shedding. Even though the wings operate at large angles of attack, the leading-edge vortices persist over the upper surfaces and increase the lift. This feature makes a striking contrast to the periodic vortex shedding that occurs in the two-dimensional motion. This ‘stable’ behaviour of the leading-edge vortices is accompanied by a strong flow in the spanwise direction. In the present work we explore this flow using numerical simulations and propose a very simple, but elucidating, potential flow model.