Suppression of flow separation in the slat cut-out region of a high-lift wing with active flow control

Flow separation caused by the integration of the leading edge slat cut-out, to accommodate an ultra-high bypass ratio engine, leads to a reduction in maximum lift coefficient and an increase in drag. A novel active flow control method is used to control separation over a multi-element high-lift airfoil. Scale-resolving computational fluid dynamics (CFD) analysis is performed along with an experimental test program. The novel active flow control technique consists of a large number of pulsed jet actuators which are added near the leading edge to suppress the flow separation. Then, a hybrid large-eddy simulation and stress-blended eddy simulation (LES-SBES) CFD methodology is used to analyze flow physics and small-scale wind tunnel tests are performed for the flow with/without control. Flow physics and flow separation associated with the control are presented and analyzed in detail. By visualizing the streamlines on the airfoil’s surface via numerical and experimental methods, severe flow separation is observed for the baseline case without flow control when the angle of attack is larger than 10 degrees. The maximum lift coefficient is increased by ∼ 11% (∼ 18% for the simulation result), and the stall angle is delayed by around 4° via imposing the jet flow control with a pulsing frequency of F+ = 0.56 and a duty circle of 25%.