Influence of orifice aspect ratio on synthetic jet trajectory in crossflow*

The periodic ingestion and ejection of fluid through an orifice yield vortex rings forming an unsteady jet. The ability to impart momentum with a zero net mass flux makes synthetic jet actuators coveted components in flow control applications, most of which include interaction of the jet with an incoming boundary layer. Knowledge of the trajectory of the jet becomes important under such circumstances as it allows targeted use of the actuator. Trajectory of the synthetic jet relies on critical parameters such as the Strouhal number, the velocity ratio and the orifice geometry. In this investigation, a synthetic jet is issued from rectangular orifices with aspect ratio 3, 6 and 12, for different operating frequencies and blowing ratios. We will attempt to establish the scaling characteristics of the jet trajectory that accounts for aspect ratio, momentum ratio and Strouhal number of the jet.