Active separation control: an overview of Reynolds and Mach numbers effects

Control of vortex shedding on two- and three-dimensional aerofoils

“…Lately, unsteady blowing, zero-net-mass actuators (synthetic jets), piezoelectric flaps, plasma actuators and other unsteady actuators have been shown to achieve similar performance but with far lower mass, momentum and/or energy fluxes than steady blowing or suction [5,6]. For aerofoils and flaps, the lift and lift-to-drag ratio can be substantially increased, but the underlying mechanisms associated with lift enhancement or drag reduction are still debated.…”

“…Reynolds number effects (e.g. [6]) have also been studied. Here the most pressing issue is whether some reports of lift enhancement or drag reduction could be explained by the mechanism of tripping the boundary layer to delay or prevent separation.…”

“…Our scope is restricted to fluid-dynamical and control issues and, for brevity, we must omit many details. Further information is available in several reviews [2][3][4][5][6][7].…”

Effect of Tip Vortices in Low-Reynolds-Number Poststall Flow Control

“…Hence, flow control becomes a key requirement for the vehicle to provide stable performance. Past investigations have employed periodic excitation [21][22][23] to delay airfoil stall. Such excitation is introduced to trigger inherent instabilities in the flow to alter the wake in a favorable manner (i.e., to reattach the flow or delay separation).…”

Lift Enhancement for Low-Aspect-Ratio Wings with Periodic Excitation

“…Seifert et al [11], Greenblatt et al [12], and Amitay and Glezer [13] have studied the use of periodic excitation for delaying airfoil stall. See Seifert et al [14] for a review of active separation control. Circulation control that utilizes the Coanda effect to increase spanwise circulation for lift enhancement have also been examined and is reported with a comprehensive coverage by Joslin and Jones [15].…”