Meeting Abstract
Natural environments create unsteady airflow when wind interacts with flowers, trees, and other obstacles. Most small flying animals rely on coherent, but unsteady structures to maintain lift like the ubiquitous leading edge vortex (LEV). Many insects flap at Reynolds numbers where the LEV can burst while remaining attached to the wing, but this has not yet been observed on a freely behaving animal. Hawk moths hover feed at flowers and must interact with environmental disturbances including the flower wake. Using a robotic flower our previous work showed that maneuverability suffers most at the vortex shedding frequencies in the flower wake. Since flight dynamics are altered but overall hovering persists, is the structure of the LEV disrupted by interaction with shed vortices? We examined the structure and persistence of the LEV using smoke visualization over the wings and thorax of hawk moths in the roboflower wake. Although LEV bursting is expected at the Reynolds number relevant for hawk moth flight, the LEV in the flower wake remains bound throughout the wingstroke with no apparent bursting. The LEV also maintains the same qualitative structure seen in steady air. We continue to probe the limits of LEV structure and stability with a systematic exploration of vortex shedding in cylinder wakes.
