Reynolds number dependency on the aerodynamic performance of corrugated wing in unsteady motion*

The dragonfly wing, which has a corrugated structure, may cause higher aerodynamic performance than the flat wing at the low Reynolds number regime (Re \simeq O(10^3)). However, the details are unclear. Not many studies have investigated detailed lift generation process in unsteady motion of the corrugated wing, which is observed in nature. In this study, we concentrate on the translating motion starting impulsively from the rest state in two-dimensional space, which is one of the fundamental modes of unsteady motions.

The direct numerical simulations revealed that the lambda vortex, generated on the upper surface of the wing, is a key for aerodynamic performance. When it is stuck in the V-shaped structure of the corrugated wing, the performance was better.

In the presentation, we report the Reynolds number dependence on this mechanism. Lift enhancement associated with the lambda vortex behavior is more pronounced at the higher Reynolds numbers (1000<Re), whereas the simulations were performed in the range 100<Re<4000.