Insect flight in the unsteady wakes of flowers – how unsteady environments impact maneuverability and leading-edge vortex stability

Flying insects use unsteady aerodynamic mechanisms to achieve stable hovering flight. When maneuvering, they must manipulate these aerodynamics, yet the surrounding airflow is typically unsteady. How do animals control their movement in unsteady environments so they can maintain aerodynamic structures, like the bound leading-edge vortices (LEVs) that assist lift in insect wings? Hawkmoths, Manduca sexta, hover while feeding from flowers and can actively track flower motion up to 14 Hz during flight. Using a 3D-printed robotic flower in a wind tunnel, we study how the unsteady flower wake affects the animals’ ability to control maneuvers and aerodynamics. Moths in still and unsteady air exhibit near perfect tracking at low frequencies, but flower wake tracking shows larger overshoot at mid-range. Smoke visualization of the flower wake shows that the dominant vortex shedding matches the frequency band of increased overshoot. However, the LEV remains bound throughout the wingstroke. This suggests that maneuverability and LEV stability are not equally impacted by unsteady flow. Moths may encode coherent structures in airflow to sense and control aerodynamics during maneuvers. Future work will quantify the interaction between unsteady flow and the bound LEV with 3D tomographic PIV.