Effects of Wing Vein Flexibility on the Aerodynamic Characteristics of Dragonfly-Like Wings in Forward Flight

Abstract

The passive deformation of the flexible wing plays a crucial role in enabling insects to generate high lift and efficient flight. This study aims to investigate the impact of wing vein flexibility distributions on the aerodynamic characteristics of an imitation dragonfly wing during flapping forward flight. The structural deformation and the flow field characteristics of the flapping wing model under different degrees of freedom are studied for three cases: uniform flexibility, nonuniform flexibility, and rigidity. The nonuniform flexible distribution is modeled by command flow, and the bidirectional fluid–structure coupling technology is used to model the interaction between structure and fluid. The results indicate that the nonuniform flexible distribution can significantly improve the peak thrust coefficients and time-averaged thrust coefficients in the flapping condition, as well as the thrust duration in the flapping-torsion condition. In the former condition, the flexible wing primarily exhibits spreading deformation. In the latter condition, it involves both spreading and chordal bending deformation. Based on the vortex theory, it is observed that the flexible wing generates stronger and wider vortices compared with the rigid wing, forming a vortex ring that contributes to the wing’s high lift. Consequently, the flexible wing exhibits superior aerodynamic performance. The numerical examples suggest that the nonuniform flexible distribution is optimal for the imitation dragonfly wing.