Aerodynamic Characteristics and Flow Structure of Hawkmoth-Like Wing with LE Vein

Aerodynamic force and flow vector-fields were measured using a 3-DOF robotic model mounted with a flexible wing with leading-edge veins to study aerodynamic characteristics in a hawkmoth hovering motion consisting of translational, rotational, and deviational motions. The flapping motion was asymmetric between downstroke and upstroke, causing the different aerodynamic performance. In particular, the wing experienced advanced rotation before the end of the downstroke, augmenting lift. This lift increase was caused by the encounter of vortices generated during the downstroke, inducing the rapid flow toward the wing surface. In addition, the amount of lift generated in the upstroke was similar to in the downstroke, whereas the drag amount was not. During the upstroke, the wing motion had a higher rotation amplitude, leading to low angles of attack in flapping. The wing with the low angles of attack flapped down like a bird, enhancing the lift and hindering the drag. These results demonstrate that the hawkmoth motion obstructed the LEV dispersal by taking the wing-wake interaction effect and appropriately using rotational and deviational motions, achieving high aerodynamic performance in an asymmetrical motion. They also suggest that the hawkmoth flight is still an important model for developing flapping-wing micro aerial vehicles.