Numerical Analysis of an Insect Wing in Gliding Flight: Effect of Corrugation on Suction Side

Abstract

We have conducted a numerical study to investigate the relationship between the aerodynamic performance of an insect wing section and the effect of corrugation in gliding flight. In particular, an Airfoil-CR, corresponding to Kesel’s Profile 2 (Kesel, Journal of Experimental Biology, vol. 203, 2000), has been used. This profile represents exactly the cross section of the so-called “Aeshna cyanea”. A smoothed variant of this profile (referred to in the present study as Airfoil-SM) has also been considered. Introducing five different variants of the Airfoil-CR corresponding to different levels of corrugation, namely M1, M2, M3, M4 and M5, an unsteady fluid flow analysis has been carried out in the framework of a Fraction-Step Method (based on a velocity-pressure coupling scheme). Another airfoil M6 has also been considered by taking all the corrugations on the suction side simultaneously while the pressure side remains smooth. Simulations were performed for variety of Reynolds numbers ranging from 150 to 10000, while angle of attack was varied from 0° to 20°. According to the results, the performances (in terms of shear and pressure drags) change as a function of the corrugation and Reynolds number. While the performances of the Airfoil-CR are relatively good at low Reynolds numbers, its behavior changes completely at higher Reynolds number where the best performances are achieved by using the Airfoil-SM. Moreover, steady or oscillatory flow can emerge depending on the considered situations.