Near-Field Measurements and Cavity Design for Synthetic Jets

Abstract

Synthetic jet literally means a jet which has been synthesized from the ambient fluid and results because of oscillation of a diaphragm in a cavity. One of the important aspects that have not received much attention in the literature is cavity design which strongly affects the ensuing jet flow. In this paper, we experimentally study the effects of cavity depth, orifice diameter, and excitation frequency, on the exit velocity for an axisymmetric synthetic jet. Velocity measurements in the near field and flow visualization results are presented. The exit velocity indicates a lower and an upper bound on frequency for the formation of a jet and shows resonance at two frequencies. We discuss approaches to manipulate these frequencies from the point of view of cavity design and optimization.