Numerical and experimental investigation of bionic airfoils with leading-edge tubercles at a low-Re in considering stall delay

The hydrodynamic characteristics and suction side flow behaviour of bionic airfoils are investigated numerically and experimentally at a low Reynolds number (Re). Hydrodynamic coefficient curves indicate that the hydrodynamic performance of the bionic airfoils is sensitive to the amplitude but not to the wavelength. When the amplitude is large enough, the bionic airfoils do not stall. As determined from numerical results and dye visualization, the bionic airfoils exhibit a double periodic flow pattern in the wingspan direction, and the trough-1 cross-section exhibits prominent separation at the leading edge, while the inflow flow attaches to the airfoil surface until the trailing-edge at the trough-2 cross-section. Because the vortex pairs formed by each group of adjacent tubercles interact with each other, the effective angle of attack (AOA) at the trough-2 cross-section is decreased, delaying the stall. In the post-stall region, the lift coefficient (CL) of each bionic airfoil is larger than that of the reference airfoil. The vortex pairs generated by the tubercles are completely mixed downstream, bringing more energy from the far wall to the near wall. The flow separation is delayed on both sides, and the effective AOA is decreased.