A report presents a study oriented toward optimization of synthetic jet actuators. [A syn- thetic jet actuator is a fluidic control device that partly resembles a loudspeaker. It typically comprises a piezo- electric actuator/ diaphragm situated in a cavity, facing an orifice or nozzle at the opposite end of the cavity.] The instant report describes an experimental synthetic jet actuator equipped for tuning through variation of some of its cavity dimensions and its excitation frequency and for selection of either (1) clamping of the edge of the diaphragm between flat surfaces or (2) pinning of the edge of the diaphragm between steel O rings. The report goes on to discuss the effects of the cavity and nozzle geometry, diaphragm design, excitation frequency, and other design features on the vibrational resonance of the diaphragm, the acoustic resonance of the cavity, the coupling (or lack thereof) of these resonances, and the overall performance as characterized by the displacement at the center of the diaphragm or the speed of the jet at a specified distance from the orifice. Conclusions reached in this study are that (1) the pinning configuration results in better performance than does the clamping configuration and (2) the maximum performance is achieved by matching the resonant frequencies of the diaphragm and the cavity.

This work was done by Fang-Jenq Chen of Langley Research Center.