Abstract
In this paper, the potential of a novel active flow control strategy by means of a modulated pulse jet vortex generator to enhance high-lift performance is demonstrated on a two-dimensional supercritical National Aeronautics and Space Administration (NASA) SC(2)-0714 airfoil with a single slotted trailing-edge flap at a high deflection angle. Fast-switching solenoid valves and compressed air were used as actuators to excite the flow. The vortex generator slot pairs were incorporated into the shoulder of the trailing-edge flap, where the flow separation occurs due to the high flow deflection and severe adverse pressure gradient. In these experiments, in addition to the simple square-wave excitation signal, a burst-modulated excitation signal as a novel pulse jet sequence was implemented to produce the unsteady blowing. The burst-modulation signal was used for the first time for a fast-switching solenoid valve actuator. The experiments were performed at a freestream velocity of 25 m/s with a corresponding Reynolds number of about 1×106 for a range of angles of attack from 0° to 20° at flap deflection angles from 0° to 35°. The results indicated that the ejection from vortex generator slot pairs was able to prevent flow separation completely in most conditions. These measurements revealed that the burst-modulated excitation was accompanied by more aerodynamic improvements and less air consumption relative to the simple pulsed jet excitation. In the best flow control mode, the results showed about a 12.6% increase in the lift coefficient and a 19.8% decrease in the drag coefficient.
Published Version
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