Numerical Study on Aerodynamic Efficiency of Varying Axial Flapping Kinematics

Abstract

An ornithopter is a flying vehicle which flaps its wings imitating the flapping nature of newlinebirds and insects. In the present study, an innovative concept of umbrella jellyfish hybrid newlineprototype flapping wing model is analysed in two dimension to study the effects on newlineaerodynamic efficiency generated by placing additional flappers in axial direction. The newlineflapping mechanism is confined with the leading edge of the primary and axial flappers newlinehinged around a central hub. The size of the axial flappers is varied from its axis of newlinesymmetry in lateral direction. The analysis is performed in ANSYS -FLUENT® to study newlineabout the effect of placing axial flappers that maximizes the lift/drag ratio for significant newlinelift conditions. The chord length of the primary flappers is fixed at 10cm and axial flappers newlineat 5cm as the model needs to be constrained according to DARPA regulations. The flapping newlinekinematics are chosen as inward, outward and symmetricity based on the feasibility of newlineflapping in axial direction to produce airflow for generating lift in vertical direction. The newlineamplitude of the flappers also set at 30º to restrict its comparison with other kinematics newlinemodels. The flow structures developed by the interactions of vortices of flapping wings newlineinfluence the aerodynamic characteristics of the model. The velocity and vorticity newlinemagnitude of the flappers are illustrated which are useful to understand the mechanism of newlineaxial flappers in providing better lift/drag ratio. The additional flappers underneath the newlineprimary flapper model under inwards kinematics was better than primary flapper alone newlinemodel which significantly increased the aerodynamic performance by 18%.