Relationship between vortex dynamics in lift enhancement mechanism of corrugated wing

For flying insects, the flow behaviour around a wing is important for lift generation. In particular, the dragonfly wing, which has a corrugated structure, may produce higher aerodynamic performance than a flat wing in the low Reynolds number regime (Re simeq O(10^3); based on a chord length).

Aerodynamic performance of a corrugated wing may be closely related to the vortex motion generated due to the wing structure. We focus on the translational motion starting impulsively from the resting state in two-dimensional space. Flow analysis suggested that the eruption of a vortex with the opposite sign to the leading-edge vortex, called lambda vortex, discourages the aerodynamic performance [1,2]. Thus, the breakdown of lambda vortex looks a key of good aerodynamic performance. However, the analysis remains qualitative and quantitative validations are required.



In this presentation, we performed the quantitative analysis by focusing on a spatiotemporal distribution of vorticity above the wing. In particular, the quantities representing lambda vortex eruption were identified. We discuss the relationship between the quantities and the observed vortex dynamics as well as the lift coefficient [3].