Passive Pitching of a Flapping Wing in Turning Flight.

Insect wings are flexible structures that passively deform under the action of inertial and aerodynamic forces in flight. Previous studies have focused on the aerodynamic and energetic merits of these deformations. Here, the effect of torsional wing flexibility on maneuverability is investigated by modeling the dynamics of the wing pitch motion when body yaw rotation is imposed. Analyses were carried out for different nondimensional stiffness levels, characterized by Cauchy number and body-to-wing velocity ratios Ω/ω. In addition, the impacts of inertial effects were evaluated via changing mass ratio. It was demonstrated that body rotations change the balance between the aerodynamic and elastic torque exerted about the wings' pitching axes. This results in passive variations in the wing pitch angles that are bilaterally asymmetric and increase linearly with the ratio of the body rotational velocity to the wing flapping velocity Ω̄. The passive changes in the bilateral pitch angles induce a torque about the body's yaw rotation, which curtails rotational damping effects due to the flapping motion of the wings, known as flapping counter-torque. The results reveal that torsionally flexible wing designs could enhance maneuverability by mitigating the need for active wing kinematic modulations during aerial maneuvers. [ABSTRACT FROM AUTHOR]