Wing–wing coupling enhances the aerodynamic performance of dragonflies during forward flight

Dragonflies have garnered significant attention due to their ability to perform various complex flight maneuvers. As a dipteran insect, the wing–wing coupling between forewing and hindwing (FW and HW) in dragonflies plays a crucial role in aerodynamic performance. In this study, a numerical simulation model is developed to elucidate the impact mechanism of wing–wing coupling in dragonflies during forward flight. The results reveal that the wing–wing coupling mainly enhances the aerodynamic force for hindwing, thereby improving the aerodynamic performance of dragonflies. There is a synergy between flapping deviation angle and phase angle. Dragonflies with negative flapping deviation angle and a suitable phase angle about 45° can generate high horizontal force and propulsive efficiency significantly while maintaining the vertical force. The effect of wing–wing coupling is related to the wing spacing of dragonflies, and proves to be advantageous at small dimensionless wing spacing (less than 2.5). These findings deepen our understanding of the exceptional flight capabilities of dragonflies and provide valuable insights for the design of tandem flapping wings.