Numerical Study On Aerodynamic Characteristics Of Three Dimensional Double Flapping Wings

FMAV (Flapping Micro Aerial Vehicle), a new kind of aircraft which imitates flapping wings of birds or insects, is different from fixed-wing and rotor-wing aircraft, with those advantages of stronger concealed and lower energy consumption. The aerodynamic characteristics of the flapping wing are the key to the stable flight and flight control of the flapping wing aircraft, the study of flapping wing shows that compared to the general single-wing layout,the use of the dragonfly fore and hind the two pairs of wings of the double wings layout has a better stability and handling, and the double wings flapping of the dragonfly achieves different flight modes mainly through varying the flapping frequency, phase and other flapping parameters, as well as flapping wing distance and other geometric parameters of the common adjustment and coupling.Therefore, it is very important to analyze the influence of various flapping and geometric parameters on the aerodynamic characteristics of the flapping wing.In this paper, in order to cover the shortage in the study of the aerodynamic characteristics of the double wings, the computational fluid dynamics method is used to calculate the three-dimensional flow of the flying dragonfly, and study the three-dimensional flow characteristics of the flapping and the aerodynamic characteristics of the flapping wing under the coupling of different flappings and geometric parameters.Firstly, the calculation model of the three-dimensional which is about single-wing and double-wings dragonfly forward fight and hovering process is established,the wing motion program is coded according to the actual flapping law of the dragonfly. Secondly, the influence of different flapping frequencies on the aerodynamic of single wing is analyzed,the results show that the effect of flapping frequency on the forward flight process is more significant than that of the hovering process. Finally, for the double wings in the forward flight and hovering process, flapping frequency, fore and back wing flapping phase difference, fore and back wing spacing of a variety of parameters combined flapping wing of the instantaneous and average aerodynamic and wing surface pressure, the corresponding flow field structure changes are analyzed,and the interaction characteristics of the wing between the parameters are also analyzed,the results show that the lifting force of the double wings in phase flapping is larger than that of the reverse flapping,the frequency of the flapping is the direct and effective way to improve the lifting force and thrust in forward flight. The effect of aerodynamic interactions on the back wing is greater than that of the fore wing.The studies of this paper reveal the variation law of aerodynamic characteristics and the corresponding flow coupling and aerodynamic jamming mechanism under the coupling of the double wings with multiple parameters in different flight postures are studied,the related results can provide an important theoretical basis for designing the FMAV.