Vortical Structure and Aerodynamics of Hawkmoth Hovering

Abstract

A multi-block-and overset grid-based computational fluid dynamic (CFD) study is conducted for the unsteady flows about a realistic body-wing model and the force-generation in the flapping flight of hawkmoth hovering. Computations are performed with the geometric-and-kinematic model constructed based on the experimental data of a real hawkmoth. The computed results demonstrate the presence of interaction among the leading-edge vortex (LEV), the trailing-edge vortex (TEV) and the wing tip vortex (TV), and hence quantify the roles of the vortices in aerodynamic force-generation. Moreover, both inertial and aerodynamic torques and powers are evaluated for the flight maneuver and the cost in hovering flight. Our results indicate that relative roles played by the inertial and aerodynamic torques in the translational phase of the wing motion show distinguishable discrepancy compared with those in the rotational phase of the wing motion; and the aerodynamic power shows much higher magnitude rather than the inertial one, very likely owing to the unsteady mechanisms.