Vortex evolution mechanism of dual-diaphragm three-cavity synthetic jet actuator

The near-field jet development characteristics of a dual-diaphragm three-cavity synthetic jet actuator were systematically investigated from the perspectives of vortex evolution and energy transfer using Particle Image Velocimetry (PIV). Based on the flow field evolution laws, it was divided into three characteristic zones: formation zone, development zone and merging zone. The evolution laws and mutual influence mechanisms of velocity field, vorticity field, kinetic energy, jet width, mass flow rate and momentum flux in each zone were elaborated in detail. The results indicate that vortex merging and “axis switching” in the merging zone substantially promote jet entrainment and mixing, and lead to a secondary increase in momentum flux. The spanwise time-averaged velocity transitions from a triplepeak profile to a typical single-peak distribution, and the width of the flow-stabilization zone increases by approximately 60%. With increasing operating voltage, the jet width decreases, indicating that it serves as an effective control parameter for jet focusing. Furthermore, the periodic kinetic energy in the near-field exceeds the turbulent kinetic energy by over an order of magnitude, indicating that the large-scale coherent vortical structures play the dominant role in mixing enhancement. The mass flow rate of the near-field exhibits an upward trend, reflecting sustained entrainment capability throughout the jet development. These research results have potential applications in efficient flow control, mixing enhancement and thermal management.