Study of three dimensional flow structures based on orifice geometry of a synthetic jet in a crossflow

Abstract

The use of synthetic jets for flow control has been the focus of many different studies over several decades. As more studies have been conducted on synthetic jets, more challenges are identified and the system continues to progress towards a level of technology readiness. One finding is that the effectiveness of synthetic jets is reduced in the presence of a spanwise flow compared to those in a 2-D crossflow. The present study investigates the effects of orifice geometry on a synthetic jet in a laminar unswept crossflow to increase its effectiveness in 3-D flowfields. Three orifice geometries (rectangular, trapezoidal, and triangular), having the sameexit area and the same aspect ratio of 19, were tested in a low speed wind tunnel. The velocity and vorticity fields downstream of the synthetic jet’s orifice were investigated using phase-averaged and time-averaged Stereo Particle Image Velocimetry. All three orifices produced unsteady vortical structures near the orifice that broke down into a quasi-steady pair of streamwise counter-rotating vortices. In case of the rectangular orifice, both the vortices had equal strength and existed till the end of the downstream interrogation region.