Development of high-power, compact synthetic jet actuators for flow separation control

This work presents the development of high-power, compact synthetic jet actuators (SJA) for flow separation control. The developed actuator is compact enough to fit in the interior of a NACA0015 profiled wing with a chord of 0.375 in. Test bench experiments showed that the multi-piston actuator array was capable of producing exit velocities of up to 90 m/s for an actuator frequency of 130 Hz. The actuator was placed in a NACA 0015 wing and tested in a wind tunnel. An experimental investigation into the effects of a synthetic jet actuator on the performance of the wing is described. Emphasis is placed on the capabilities of the actuator to control the separation of the flow over the wing at high angles of attack. The investigation included the use of force balance measurements, on-surface flow visualization with oil and tufts, off-surface flow visualizations with smoke, surface pressure distribution measurements and wake surveys. In addition to flow separation control data, results corresponding to hot wire measurements at the exit of the slot, are also presented and are used for the characterization of the flowfield generated by the synthetic jet actuators. Most of the tests were performed at a freestream velocity of 35 m/s, corresponding to a Reynolds number of 8.96 × 105. The angle of attack was varied from −2.0 to 29 degrees.; For the tests presented here, at angles of attack lower than 10 degrees the actuator tends to increase the lift curve slope as the actuation frequency is increased. At higher angles of attack, the SJA extends the range of angle of attack for which the wing may be operated without stalling. The use of the actuator causes an 80% increase in the value of maximum lift coefficient, and the angle at which stall occurs is increased from 12 to 18 degrees (for the Reynolds number range of the test). The drag on the wing is decreased as a consequence of SJA actuation. This was verified with the force balance measurements and by analysis of the wake surveys. For angles of attack larger than 18 degrees, once massive stall has occurred over the wing, the operation of the SJA still provides a small amount of lift augmentation. At angles of attack larger than 25 degrees, a large frequency of actuation is required to produce any noticeable effects.