Wing Flexabilty impacts LEV Bursting location on hawkmoth wings

Flapping flight involves a variety of phenomena that allow centimeter scale aviation. These phenomena act on both the flapping wing and environment in complex ways. In the hawkmoth (Manduca sexta) vortices develop along the leading edge of the wing which allows for an increase in lift; however, as this leading-edge vortex (LEV) gets further from the root, the LEV can destabilize, losing its quasi-stable circulation and becoming disordered in a process known as bursting. Here we show how aging effects the flexibility, and shape of hawkmoth wings, impacting flow dynamics and leading to an earlier bursting of LEVs along the span. By measuring the flexural stiffness (EI) and digitally capturing the deformation of a mounted hawkmoth wing, we show how aging decreases wing flexibility and causes irregular shape change. Additionally, by comparing smoke visualization of mounted wings, we find that aging effects shifts the transition point of bursting along the spanwise direction by about 10%. Further experiments utilizing rigid 3D printed wings quantify the impact of shape on force production and circulation along the wings. Our results show how aging acts as an aerodynamic inhibitor in the stability of leading-edge vortices, and suggest that changes in flexibility and shape due to aging may be a key factor in LEV stability.