On the use of synthetic jet actuator arrays for active flow separation control

Present study highlights the flow control effectiveness of newly designed synthetic-jet-actuator (SJA) arrays placed at 23% and 43% of the chord from the leading edge of a low-speed wing model. First, the characteristics of a single SJA were investigated under the quiescent-flow condition. It was found that the jet velocity attains a peak between 400. Hz and 500. Hz, which corresponds to the SJA's Helmholtz resonance frequency. The SJA arrays were then implemented on the wing model and investigated under the cross-flow condition. Both force balance and hot-wire measurements showed that the SJA arrays are able to effectively delay the flow separation and hence improve the aerodynamic performance of the wing model. The highest improvement in the lift coefficient is 27.4% and the average reduction in the drag coefficient is 19.6%. It was also found that the front (upstream) SJA array is more effective than its rear (downstream) counterpart. Tomographic-PIV measurements were also performed to unravel the three-dimensional flow details over the suction surface of the wing model with and without the SJA actuation. The time-averaged results showed that the introduction of synthetic jets substantially changes the flow structures of the separated shear layer, brings the outer high-momentum flow into the near-wall region, and delays the flow separation. In the end, the power consumption of a single SJA array was measured and found to be less than 5. W.