Meeting Abstract
Birds, insects, and many other animals have developed mechanisms to maintain hovering flight to feed from flowers across varied biological length scales and environments. Although recent studies have examined flight performance in unsteady wind, few examine these flight mechanisms during a prescribed task. Understanding how flying insects feed from flowers in nature requires coupled analysis of the effects of unsteady flows in the wake of an object and flight maneuverability. We investigate the dynamics of insect maneuverability in an unsteady wake by having Manduca sexta, known to hover while feeding, track a 3D-printed robotic flower in a wind tunnel and compare to results from previous experiments in a still air flight chamber. Overall, moths tracking laterally in the flower wake with a freestream velocity of 0.7 m/s perform worse, and do so at earlier frequencies, than moths tracking in still air suggesting that they track in a narrower frequency band in an unsteady flow environment. Smoke visualization of the flower wake shows vortex shedding at approximately 3-4 Hz with a localized region of unsteady flow dominating the hovering location of the moths. Aerodynamic interactions between the moth and the flower wake may require the animal to make more small corrections to maintain a stable feeding position, thus using more mechanical power than tracking in still air. It is also possible that the flower wake affects the stability of the leading-edge vortex bound to the wing, leading to changes in flight stability since the LEV is responsible for generating most of the lift during the wingstroke. In general, flying in unsteady wind seems to decrease maneuverability; the hawkmoths track effectively in a smaller frequency range and use more mechanical power when their tracking performance is worse.
