A numerical analysis of dynamic flight stability of hawkmoth hovering

A numerical analysis of dynamic flight stability of a hovering hawkmoth is presented. A computational fluid dynamic (CFD) method is used to simulate the unsteady flow about a realistic hawkmoth model and to compute the aerodynamic derivatives of the aerodynamic forces and pitching moment in response with a series of small disturbances. With these parameters, the techniques of eigenvalue and eigenvector analysis is employed to investigate dynamic flight stability of the hawkmoth hovering. In the longitudinal disturbance motion, three natural modes are identified of a stable oscillatory mode, a stable fast subsidence mode and a stable slow subsidence mode, which indicate that the hawkmoth hovering flight is stable. In short, a hovering hawkmoth, if the body motion is dynamically stable and hence the disturbance dies out fast, might not need to make any adjustment with wing motions and could return to the equilibrium state 'automatically'.