Numerical investigation on two-orifice synthetic jet actuators of varying orifice spacing and diameter

Flow control is an important issue in the performance of aircrafts and many fluid mechanical devices. In recent years, synthetic jet actuators have shown good promise in delivering active flow control. Unsteady three dimensional incompressible laminar numerical studies were performed on single and two-orifice synthetic jet actuators in order to investigate the benefits of dual circular orifice synthetic jets over a single one for higher circulation production. The flow features of synthetic jets and the circulation of the vortex rings from one orifice and two-orifice actuators are examined and compared in this paper. Two dominant parameters in two-orifice actuators are the orifice diameter and spacing between them. The effects of these parameters on the vortex rings produced were investigated in detail. It was found that the generation of two distinct and non-interacting vortex rings has direct dependency on the spacing between the orifices. It is important that the vortex rings do not interact with each other to prevent any circulation cancellation, and in this regard, the present study suggests that a minimum spacing related to the diameter of the orifice (Do) and the dimensionless stroke length (L) is required (~1.5 L*Do). The present study also demonstrates that it is possible to increase circulation by more than 160 percent with a fixed input energy as a result of having two orifices with smaller diameters but higher dimensionless stroke lengths using two-orifice actuators.