Aerodynamic flow control over an unconventional airfoil using synthetic jet actuators

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Aerodynamic flow control over an unconventional airfoil using synthetic jet actuators

Amitay, M. / Smith, D.R. / Kibens, V. / Parekh, D.E. / Glezer, A.

Control of flow separation on an unconventional symmetric airfoil using synthetic (zero net mass flux) jet actuators is investigated in a series of wind tunnel tests. The symmetric airfoil comprises the aft portion of a NACA four-digit series airfoil and a leading edge section that is one-half of a round cylinder The experiments are conducted over a range of Reynolds numbers between 3.1 x 10⁵ and 7.25 x 10⁵. In this range, the flow separates near the leading edge at angles of attack exceeding 5 deg. When synthetic jet control is applied near the leading edge, upstream of the separation point, the separated flow reattaches completely for angles of attack up to 17.5 deg and partially for higher angles of attack. The effect of the actuation frequency, actuator location, and momentum coefficient is investigated for different angles of attack. The momentum coefficient required to reattach the separated flow decreases as the actuators are placed closer to the separation point. In some cases, reattachment is also achieved when the actuators are placed downstream of the stagnation point on the pressure side of the airfoil. Control effectiveness is distinctly different for low and high actuation frequencies and is influenced by the disparity of the characteristic timescale of the actuation.