Investigation on the Formation Mechanism of Stall Cells on the NACA 0012 Tubercle Wing at Low Reynolds Number

The tubercles on the leading edge of a wing draw inspiration from the flippers of humpback whales. These tubercles play a crucial role in delaying flow separation at high angles of attack of the wings, unlike wings with smooth leading edges, which tend to experience earlier flow separation. However, wings featuring tubercles do experience intermittent flow separation along their span, commonly referred to as "stall cells." This study aims to investigate the formation and evolution mechanisms of these stall cells across various tubercle profiles on the NACA 0012 wing, tested at a chord-based (c) Reynolds number (Re) of 20,000. Four distinct tubercle wing configurations are analysed numerically, with amplitudes of 0.05c and 0.15c, and wavelengths of 0.15c and 0.45c. The simulation results were thoroughly examined, focusing on skin friction lines on the wing surface, vorticity contours, and streamlines at various time intervals. The findings indicate that the placement of the stall cells along the span of the wing varies depending on the configuration of the tubercles. Furthermore, the formation mechanism of the stall cells is similar to the biased wake mechanism observed in the wake of flow around cylinders arranged side by side. Further complexities of the related fluid dynamics will be discussed during the presentation.