Aerodynamic Analysis of Dragonfly Wings Space Distribution On Three-Dimensional During Hovering Flight

Dragonfly has two pairs of wings, which are different from other single-pair-winged insects. The motion law and space distribution of dragonfly's forewing(FW) and hindwing(HW) are different in different flight states. Aerodynamic coupling between FW and HW is the key problem of dragonfly hovering flight. In this paper, we use three-dimensional numerical simulation to investigate the impact of the horizontal spacing and vertical spacing on the vertical force, horizontal force, and efficiency of the hindwing and how these changes affect the leading-edge vortex (LEV) generated by the hindwing surface. It is found that the aerodynamic interference between the forewing and the hindwing is the largest when the motion of the flapping wing reaches the maximum of upstroking and the maximum of downstroking respectively. When the vertical spacing is zero, the total vertical force of the flapping wing increases with the increase of horizontal spacing. And when horizontal spacing is 1.0x rotation axis spacing, the hindwing's lift and thrust decrease with increasing vertical spacing. The interaction between the forewing and hindwing affects the leading-edge vortex formation on the hindwing and results in changes in the aerodynamic force and efficiency of the hindwing. The result of the research shows that when the forewing is higher than the hindwing, the leading-edge vortex of the hindwing is inhibited, but it can promote the generation of the hindwing's leading-edge vortex when the forewing is lower than the hindwing. The study can be helpful for the design of dragonfly-like aircraft.