Experimental study of flow field airfoil with synthetic jets for flow separation control

The flow over a wing or a deployed flap of a wing should remain attached to the surface; otherwise its aerodynamic performance will decrease drastically. Flow separation control aims at affecting the flow by actively delaying flow separation and thus improving the aerodynamic performance of the wing. In the present study synthetic jet actuators (SJA’s) have been applied for flow separation control in the case of a 2D wing with a chord of 165 mm and a span of 455 mm with a NACA0018 airfoil section. The SJA’s employed feature a piezo-electric disk inside a cavity and an exit slot of a span of 30 mm and a width of 0.25 mm. First the performance of a stand-alone SJA has been investigated in order to replicate the promising results found by the University of Florida for the present SJA design. Subsequently, a configuration with ten of these SJA’s integrated in the 2D NACA0018 wing has been considered. The jet from the SJA’s is directed tangentially to the surface of the airfoil. During the in-stroke of the actuator, air from the surroundings is ingested through the slot into the cavity, while during the out-stroke air is blown through the slot out of the cavity. The maximum peak velocity generated for a range of actuation frequencies of the integrated synthetic jets, have been measured, using a hot-wire anemometry (HWA) setup, first in quiescent air. These HWA results for the velocity field induced by the SJA’s have been compared with analytical results for a wall jet. In the next step the aerodynamic performance of the wing with ten SJA’s has been investigated inside a wind-tunnel at a free-stream velocity of 25 m/s, corresponding to a Reynolds number of 273,000. These measurements of the lift have been performed for a range of actuation frequencies and ratios of jet velocity and free-stream velocity. Finally, HWA measurements have been performed for a number of chord-wise positions, for a number of angles of attack, at a free-stream velocity of 25 m/s.