Aerodynamic and Structural Studies of a Flapping Wing in Forward Flight

Flapping flight is commonly seen in nature at low Reynolds numbers. This work investigates the physical aspects of forward flight for flapping unmanned aerial systems. The kinematics discussed in this paper is based on an anticlockwise figure-8-shaped flapping cycle. The evolution of the complex, unsteady vortical flow system that develops during the flapping motion is presented. Mechanisms for generating the lift and thrust are discussed, with emphasis on the unsteadiness of the flow features during both the downstroke and upstroke phases. A one-way fluid–structure interaction has been investigated, and the relative importance of aerodynamic forces is compared with respect to the inertial forces. The inhomogeneity of the wing in terms of mass distribution is studied, and it is shown that a higher density at the wing root is beneficial in respect to the mechanical power required to achieve the forward flight. Limited benefit is observed when higher material density at the leading edge is adopted.