Aerodynamic performance and flow mechanism of multi-flapping wings with different spatial arrangements

In nature, the phenomenon of cluster movements of fish, birds, and insects is universal, which constantly inspires people to explore its advantages. In this study, the aerodynamic performance of three three-dimensional flapping wings under different spatial arrangements was numerically investigated at a low Reynolds number and the interactions among the individuals and the associated underlying fluid mechanisms were explored. In addition, the effects of the number of individuals on the aerodynamic performance of the group as well as the individual were also considered based on the spatial arrangement when the three-wing group produces the maximum thrust. The results show that the spatial arrangement between flapping wings has an important impact on the aerodynamic performance of the whole group and individuals. At a specific spacing (in-line tandem arrangement), the overall thrust of the group can be increased by about 40%, while the overall lift has little change. It is also found that the overall lift of the group decreases with the increase in the number of individuals in the group, and the thrust remains unchanged. The detailed analysis of the wake flow reveals that the downwash of the vortex wake plays a dominant role in the aerodynamic interference.