S1-4.4 Jan. 5 A new insect flight model is just around the bend MOUNTCASTLE, A.M.*; DANIEL, T.L.; Univ. of Washington, Seattle; Univ. of Washington, Seattle firstname.lastname@example.org
Models of insect flight commonly assume wings behave as rigid airfoils. Many insect wings are flexible, however, with dynamic bending occurring as a consequence of flapping flight. In moths, wing deformations are most prominent at stroke reversals, and their kinematics may have significant aerodynamic consequences that are not considered in previous flight models. The ventral wing stroke reversal of the hawkmoth Manduca sexta is accompanied by a transient chordwise wave passing from leading to trailing edge. Such waves have not been explored as a potential source of aerodynamic force in insect flight. Here we document the wing wave propagation at stroke reversal of Manduca during free-flight hovering and estimate the impulse of the wave using blade element theory. We used high speed digital videography to quantify three-dimensional wing kinematics from hawkmoths hovering in free flight. Wing deformation was measured at each time step relative to a two-dimensional plane best fit to the wing surface, representing a rigid wing model. We then employed a blade element analysis by dividing the wing into a series of longitudinal strips extending from the leading to trailing edge, fitting each strip with a model of a harmonically oscillating two-dimensional plate, and calculating the induced force on each strip. Forces were summed over all strips of the wing surface. Our results suggest that rapidly propagating waves of deformation can contribute aerodynamic forces significant to flight, on the order of the impulse of the animalís weight.