Effect of synthetic jets spacing on flow separation over swept, flapped airfoils

Abstract

An experimental study was performed on flow field interactions and aerodynamic performance enhancement due to the activation of an array of synthetic jet actuators on a swept, flapped, modified NACA 0012 airfoil model at two angles of attack (0° and 5°) and two control surface deflection angles (20° and 30°) at a chord-based Reynolds number of 720,000 and sweep angle of 20°. The focus was on understanding the mechanisms for separation reduction and lift enhancement due to the application of the flow control. Activating all the jets resulted in up to ∼13% increase in the sectional lift, which was measured via an array of surface-mounted pressure ports. Stereoscopic particle image velocimetry revealed the presence of trains of pinched, skewed vortical rings that were created by the synthetic jets and that caused flow reattachment over the control surface. The characteristics of the train of these vortical rings varied with the spacing between active jets, where smaller spacing resulted in the largest modification to the flow field. The proposed mechanisms for separation reduction in a swept cross flow via pinched vortex rings are discussed, revealing further potential for how to leverage synthetic jets for separation postponement and lift enhancement over control surfaces.