The Numerical Study On The Aerodynamic Performance Of The Dragonfly Flexible And Corrugated Forewing

The development of flapping wing micro air vehicle(FMAV)is inspired by the wide use of the FMAV in the military and civil fields.With the development of microelectronics,materials science and bionics,the design and manufacture of FMAV have been rapidly developed.FMAV is completely different from the traditional flying mode,which causes the development of FMAV to encounter the difficulty.Dragonflies are capable of carrying out dramatic flight manoeuvres through the effect of its multiple factors such as the morphology,structure and material of its wings,they are natural biological models for the design and manufacture of FMAV.However,it is difficult to study by experiment because of low Reynolds number during flight,flexible flight mode and small size of the dragonfly wings,the numerical simulation method is used to calculate the aerodynamic performance of dragonfly forewing in gliding and flapping flight.To reveal the effect of aerodynamic loading on the dragonfly forewings during gliding flight,five different positions of the cross-sections were selected and the corresponding two-dimensional pleated airfoils were established.The numerical simulation of Fluid-Structure Interaction(FSI)of two-dimensional pleated airfoils in gliding flight based on Computational Fluid Dynamics(CFD)/Computational Structural Mechanics(CSD)coupling method,the results show that the flexible deformation and stress of the pleated airfoils are small,and near the dragonfly body pleated airfoils are higher than near the wing tip pleated airfoils,corrugations change the stress distribution of the forewings and make it more reasonable.To explore the aerodynamic influence of the corrugations and flexibility on dragonfly forewings,the CFD and CSD models of three-dimensional corrugated dragonfly forewing were established by software CATIA based on the current research.This research is to use numerical simulations to explore corrugations and flexibility effect on aerodynamic performance of the dragonfly forewings in gliding and flapping flight,including numerical simulation of FSI of three-dimensional corrugated dragonfly forewing in gliding flight based on CFD/CSD coupling method,the results show that the vortex is filled in the upper and lower surface of the corrugations,and the vortex in the lower surface is rotated counterclockwise,which reduces the frictional resistance of the dragonfly forewings.Corrugations improve the aerodynamic performance of dragonfly forewings during gliding and flapping flight because of the leading edge vortex.The flexible and corrugated forewings is subjected to aerodynamic load,which only produces bending deformation without torsion deformation in gliding flight,and the aerodynamic response time is short.Compared with the rigid and corrugated forewings,the aerodynamic performance of the flexible forewings is better at large angle of attack,this result can be a potential inspiration to the flexible airfoil design of FMAV,in this respect,nature provides a perfect design of wings that are suitable for FMAV.