The performance of active flow control on a NACA 64_3-618 laminar airfoil at post-stall angles of attack is evaluated using discrete, wall-normal pulsed jets. Actuation is implemented near the leading edge of the airfoil. The effect of actuation duty cycle and blowing ratio on lift coefficient are studied for an actuation period equal to the convective period of the flow. Lift coefficient shows a large dependence on both blowing ratio and duty cycle for α ≥ α_(stall), and improvements increase as the duty cycle is reduced for a given blowing ratio. Phase-locked particle image velocimetry shows the development of two vortices associated with the onset and termination of actuation. For low duty cycle forcing, the early interaction of the two vortices cause a roll up of the separated shear layer, and increased mixing and momentum entrainment in the boundary layer. Data taken at a higher Reynolds number (128,000 vs. 64,000) suggest that the same mechanisms for control exist.
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