Fluid Structure Interaction Of Unsteady Aerodynamics Of Membrane Flapping Wing At Low Reynolds Number

Wing flexibility controls the aerodynamic-force generation of flapping-wing flyers. Asthe wing flaps through the air, it is subjected to both aerodynamic force acting on thesurface of the wing and inertial force due to the acceleration or deceleration of the wing’smass. The interaction between these inertial–elastic and aerodynamic forces resulted inwing deformation, which can influence the structure of flow field around the wing.Therefore, both values and distribution of pressure on the surface would change, fliers likeinsects can easily achieve maneuverability and attitude control.To study the effects of skin flexibility and wing deformation on the aerodynamicperformance of a flapping wing, Peters et al.’s inflow theory and finite element analyseswere taken,besides, program adequate for solving fluid structure interaction of flexiblemembrane flapping wing were built and validated based onMatlab. Based on the theory andprogram, this study compare instantaneous and time-average aerodynamic performancebetween rigid and flexible dragonfly wing model in forward flight, effects of materialproperties and motion model on the aerodynamic performance of a model wing, andperformance of two different wing model with different veins.Main results for this study are as follows:1. The dynamic deformation of flexible wings can produce the unsteady aerodynamiceffect significantly, especially influence peak values of lift coefficient and thrust coefficientin downstroke. The trailing edge near wing’s tip has larger deformation and mainlyproduces more thrust, however, deformation of wing’s root is smaller and mainly producelift force. Compared with the rigid flapping wing, flexibility could improve the lift andthrust coefficient and is beneficial.2. Compared with membrane, material of the leading edge and battens have greaterinfluence on the wing’s aerodynamic performance. Dynamic de formation is mainly due toleading edge, battens and veins, which have larger stiffness. Aerodynamic performance issensitive to their thickness. Three different kind of materials (aluminium alloy, titaniumalloy, carbon fiber) contribute to thrust force, the wing with titanium alloy behaves best,and the wing with aluminium alloy take second place.3. Flapping plane angle could improve thrust, lift and lift-drag ration within certainrealms and flapping frequency can also enhance thrust but affect little to lift. Time-averaged lift and trust coefficient decrease with the increase of the forward speed. There is significantdifference in the aerodynamic performance of two different wing model, which confirmflexibility and dynamic deformation of the viscoelastic wing are important to membraneflapping wing again, simultaneously, the results may provide some reference and guidancefor design of complex structure and model materials of membrane flapping MAVs.