Bioinspired Corrugated Airfoil at Low Reynolds Numbers

Abstract

An experimental study was conducted to investigate the flow behavior around a bioinspired corrugated airfoil compared with a traditional streamlined airfoil and a flat plate at the chord Reynolds number of Re 34; 000 to explore the potential application of such bioinspired corrugated airfoils for micro air vehicle applications. The experiments were conducted in a low-speed wind tunnel. A high-resolution particle image velocimetry system was used to conduct detailed flowfield measurements to quantify the transient behavior of vortex and turbulent flow structures around the studied airfoils. The particle image velocimetry measurement results demonstrated clearly that the corrugated airfoil has better performance over the streamlined airfoil and the flat plate in preventing largescale flow separation and airfoil stall at low Reynolds numbers. It was found that the protruding corners of the corrugated airfoil would act as turbulators to generate unsteady vortex structures to promote the transition of the separated boundary-layer flow from laminar to turbulent. The unsteady vortex structures trapped in the valleys of the corrugated cross section would pump high-speed fluid from outside to near-wall regions to provide sufficient kinetic energy for the boundary layer to overcome adverse pressure gradients, thus discouraging large-scale flow separations and airfoil stall. Aerodynamic force measurements further confirmed the possibility of using such bioinspired corrugated airfoils in micro air vehicle designs to improve their flight agility and maneuverability.