Aerodynamic mechanisms behind enhanced gliding efficiency of slotted wingtips

The remarkable flight capabilities of birds are made possible by the aerodynamic contributions of their diverse wing structures. However, the mechanisms that enable slotted wingtips to achieve high aerodynamic performance remain unclear. Focusing on slotted wingtip configurations, which are frequently observed in gliding and flapping birds, this study numerically investigated their aerodynamic advantages and underlying mechanisms using computational fluid dynamics. Based on prior experimental models, we performed a two-step optimization combining two-dimensional global and three-dimensional local searches to identify high-performance configurations. The resulting slotted-tip device improved the lift-to-drag ratio compared with both the base wing and the single-tip device. Through an isolated vortex analysis using Lamb–Oseen models, we revealed that the slotted structure helps reduce the aerodynamic influence of the wingtip vortices. This is achieved not only by shifting the vortex positions away from the wing but also by reducing the net circulation through vortex splitting. Despite the geometric simplifications made, our results are consistent with prior experimental measurements and provide insights into the functional advantages of the slotted wing morphology. The findings contribute to a deeper understanding of avian flight and offer valuable design cues for bioinspired aerial robots.