Abstract Bird wings contain several feather groups, some of which contribute to their aerodynamic performance during flight. One of these groups is the emarginated primary feathers, which exhibit slots, bending, and twisting in flight. Slotted wingtips vary in morphology across the avian clade, raising questions about the relationship between their form and function, particularly with regard to their aerodynamic role. This study expands the current understanding of the functional morphology of slotted wingtips by systematically studying slots, bending, and twist using various engineered wingtip configurations: one that captures the slotting only, another that has both slotting and bending, and a third that combines slots, bending, and twist. Force, moment, and PIV data acquired during wind tunnel testing reveal that the bioinspired wingtips have both global and local aerodynamic effects. The wingtips’ global aerodynamic effect is to delay spanwise stall propagation, thereby altering the lift distribution over the wing. Local aerodynamic effects include the reduction of aerodynamic load over the wingtips as well as changes to the separated shear layer location and the breakdown of tip vorticity. The results show that while global aerodynamic effects are universal across all configurations, local effects are sensitive to wingtip design. Nonetheless, both the global and local effects enable structural resilience and effective roll and yaw control authority. These results demonstrate that the emarginated primary feathers may have multiple aerodynamic functions, offering new insights into their role in bird flight and showcasing their potential as flow- and flight-control devices for engineered aerial vehicles.
Wiswell et al. (Tue,) studied this question.