Aerodynamic efficiency of axial flapping kinematics.

In the present study, an innovative concept of axial flapping wing model is analysed to study and improve the aerodynamic efficiency for vertical takeoff microaerial vehicle. The flapping kinematics are inspired by merging aquatic jellyfish locomotion, and umbrella's in and out mechanisms with the flappers hinged around a central hub. Also, additional flappers are placed beneath the primary flappers at varied distances. The analysis is performed using FLUENT to study the effect of placing axial flappers that maximize the lift/drag ratio. The chord length of the primary flappers is fixed at 10 cm, and axial flappers at 5 cm as the model needs to be constrained according to DARPA regulations of 15cm. The flapping kinematics are chosen as inward, outward, and symmetrical based on the feasibility of flapping in the axial direction to produce the airflow for generating lift in the vertical direction. The amplitude of the flappers is set at 30° to have a comparative study of other kinematics. The flow structures developed by the interactions of vortices of flapping wings influence the aerodynamic characteristics of the model. The velocity and vorticity magnitude of the flappers are studied and analysed in detail to understand the mechanism of axial flappers in providing better lift/drag ratio. The effect of adding additional flappers underneath the primary flapper model under inwards kinematics was better than primary flapper (Model 0) which significantly increased the aerodynamic performance of axial flapper's inter-distance variations at 5 cm by 18.3% (Model 1), at 10 cm by 15.2% (Model 2) and at 15 cm by 10.5% (Model 3). The outward and symmetric kinematics models exhibit a decrease in aerodynamic efficiency compared to inward kinematic models. [ABSTRACT FROM AUTHOR]