On the Modeling of a Rectangular Synthetic Jet

The flow field of a rectangular synthetic jet is studied in this paper. It is known that synthetic jets exhibit similarities to continuous turbulent jets in that the far field velocity profile of synthetic jets displays self-similar behavior as well. In this paper we systematically model the a rectangular synthetic jet by applying the argument that synthetic jets can be described by the same equations used to describe continuous laminar jets, with the replacement of the kinematic viscosity of laminar flow, with the virtual kinematic viscosity obtained from the experiments on a synthetic jet. The virtual kinematic viscosity is obtained through experimental measurements of the time average velocity profiles using hot wire anemometry. The virtual kinematic viscosity of the synthetic jet under study was found to exceed that of a turbulent jet of equivalent momentum. The inherent periodic excitation of the synthetic is attributed to the increased virtual kinematic viscosity, which results in the faster spreading and increased entrainment observed in experiments. It is observed that the variation in the centerline velocity and jet width with axial distance, for various actuator stroke lengths collapse onto single curves when scaled appropriately.