Examination of a Variable Diameter Synthetic Jet

Abstract

Synthetic jet actuators are used to produce net axial momentum flow without net mass flux. Through strategic application, such devices can be used for flow control, propulsive thrust, and cooling. A novel application uses a variablediameter orifice to constrict the exiting flow, and the motion can be synchronized with the pulse of the jet. This device is examined using phaselocked particle image velocimetry (PIV), permitting investigation of the flow fields and momentum flow. When compared to fixeddiameter synthetic jets, the variablediameter actuator produces a larger vortex ring that lingers nearer the aperture. In addition, the experiments show increased momentum when the aperture is contracted in phase with the pulsing jet, with peak levels more than twice that of a constantdiameter jet.