Abstract:
Airfoil slotted is a passive flow control technology that can effectively inhibit flow separation on the airfoil suction surface, and it has been widely studied by researchers domestically and abroad. In this study, slots on the airfoil NACA 4421 are investigated with numerical simulations. The selection of the slot location on the airfoil is first analyzed, and the influence of the geometry change of the slot on the stall characteristics of the airfoil is discussed. Seven slot configurations are designed, and the geometric relations among them are given. The flow control effects of slots with curve lines, polylines and straight lines, on the airfoil stall are compared. It is found that the curve-line slot can significantly improve the maximum lift coefficient and the stall angle of attack of the airfoil. The "double peak" phenomenon of the lift coefficient distribution of the curve-line slot airfoil is analyzed, and the design of a new deflector slot is proposed. This new slot configuration is based on the Coanda effect, and can improve the stall characteristics of the baseline airfoil comprehensively, with the stall angle of attack delayed by 14° and the maximum lift coefficient increased by 122% to 2.785. The deflector slot presented in this study provides a novel idea and reference for the design of high-lift devices.