Transonic Airfoil Drag Reduction Using Suction and Loaded Leading Edge Control

To overcome the huge drag on an airfoil in transonic flow, a hybrid flow control method using suction and loaded leading edge (SLLE) is proposed and its active feedback control effect is studied in the different operation conditions. The loaded leading edge structure can redistribute the pressure as a passive flow control technique, while the suction slot is used to control shock wave's position and flow separation, which can be conducted actively and automatically using feedback control system. Firstly, the investigation is conducted in steady flow, and a significant drag reduction performance is obtained. The highest drag reduction rate of 22.5% can be got when attack angle is 5 degrees, and the increasing of lift-drag ratio can be obtained in each attack angle case. Secondly, a heuristic approach to feedback flow control is conducted in off-design inflow conditions, where a feedback-based SLLE control method is introduced. The results show the SLLE control can achieve a fair drag reduction performance which is over 10%, which indicates to a flow control method with good applicability in changing flow conditions.