Ph.D. Thesis Defense by Barton Smith
Monday, May 10, 1999

(Dr. Ari Glezer, advisor)

"Synthetic Jets and Their Interaction with Adjacent Jets"


A new actuator called a synthetic jet is described, and its use for flow control applications is demonstrated. Synthetic jets have the unique property that they are zero-mass-flux in nature; i.e., they are synthesized from the working fluid of the flow system in which they are deployed.  In current implementations of these devices, a plane turbulent air jet is formed normal to an orifice in a flat plate.  The jet is synthesized by a train of vortices that are formed at the edge of the orifice and are driven by the motion of a diaphragm bounding a sealed cavity under the orifice plate.  These vortices, and thus the characteristic dimension of the jets, scale with the characteristic dimension of the orifices.

 The zero-net-mass nature of a synthetic jet makes them attractive for flow-control applications.  They are able to provide momentum flux, alter pressure distribution, and to introduce arbitrary scales to another flow, without adding mass.  Along with a study of the flow induced by a rectangular synthetic jet in a quiescent medium, the interaction of a synthetic jet with an identical synthetic jet in close proximity, and the interaction of a synthetic jet with a larger continuous jet in close proximity will be discussed.  It is shown that an adjacent pair of rectangular synthetic jets at the same amplitude and frequency can be vectored by altering the relative phase of the driving signals.  It will subsequently be shown that when a synthetic jet is placed in close proximity to a continuos jet of a much larger scale, the synthetic jet entrains fluid from the continuos (primary) jet conduit, which in turn results in the primary jet vectoring toward the synthetic jet.