Delay of airfoil stall via bio-inspired herringbone groove array

Taking the NACA0012 airfoil as the research object, the bio-inspired herringbone groove array, a new passive control method, is applied to relieve the flow separation under the large angle-of-attack conditions, and its effectiveness and mechanism in delaying airfoil stall are investigated by numerical simulations. The herringbone groove array is placed on the airfoil’s upper surface near the trailing edge, and the effects of groove depth and yaw angle on the control effect are investigated. The results demonstrate that different designs of herringbone groove array can effectively broaden the stable operating range of the airfoil, and the application of herringbone groove array with a depth of only 0.001 35 times the chord length and a yaw angle of 45° can result in a 28.57% increase in the stable operating range. The flow details indicate that a pair of induced vortices with the same strength and opposite direction are formed near the converging line under the combined action of the accumulation effect of small-scale vortices in the grooves and the spanwise migration flow above the grooves. The induced vortices increase the mixing between the main flow and the boundary layer, allowing the boundary layer to gain sufficient energy to withstand the adverse pressure gradient at high angles of attack, effectively delaying airfoil stall.