The effects of span-wise and chord-wise flexibility on the aerodynamic performance of micro flapping-wing

The flexibility of flapping-wing strongly affects the aerodynamic performance of Flapping-wing Micro Air Vehicle (FMAV), and the deformations in span-wise and chord-wise directions are coupled together in flight. In this study, the flexible deformation is formulated in span-wise and chord-wise separately in order to analyze its effects on aerodynamic behavior. The preconditioned Navier-Stokes equations based on chimera grid are used in the computational fluid dynamics method to study the aerodynamic effects caused by flexible deformation, and the simulation results are compared with experimental test to illustrate the capability of above method. Based on our results, it is clearly showed that the span-wise flexible deformation should be limited in a small range to achieve higher aerodynamic performance and the chord-wise deformation could enhance the aerodynamic performance. The results also suggest that FMAV designers should design the flapping-wing with high stiffness leading edge to limit the span-wise deformation, and more flexible chord ribs to keep chord-wise deformation in suitable range.