Comparative Analysis of Vortex Dynamics in Orifice-Driven and Deformable Surface Synthetic Jets

This study presents a detailed experimental comparison between two synthetic jet (SJ) actuation mechanisms: the conventional cavity-based synthetic jet (SJ) and a novel deformable dynamic surface synthetic jet (DDS-SJ). While the traditional SJ operates via periodic diaphragm motion driving fluid through a fixed orifice, the DDS-SJ leverages oscillatory deformation of a compliant membrane to induce jet formation without a rigid cavity structure. Phase-resolved particle image velocimetry (PIV) measurements were conducted to characterize the velocity and vorticity fields across a range of orifice/membrane diameters and actuation frequencies. The results reveal fundamentally different jet formation dynamics: the SJ produces distinct vortex rings whose evolution and interactions depend strongly on orifice diameter, transitioning from isolated to merged structures as the diameter increases. In contrast, the DDS-SJ generates a continuous, columnar jet with no observable vortex ring roll-up, resulting in highly directional, low-diffusion flows. Stroke length and peak velocity metrics further highlight divergent scaling trends between the two actuators. While SJ performance peaked at intermediate diameters, DDS-SJ performance improved monotonically with diameter. These findings demonstrate the distinct fluid dynamic behaviors and application potentials of orifice- and membrane driven synthetic jets. The DDS-SJ, in particular, offers a promising pathway for compact, energy-efficient, and morphing-capable flow control systems.