Flow mechanism study and geometrical parameters analysis of fluidic oscillators based on pressure-sensitive paint measurements and modal analysis

Abstract

The present study optimized some novel uidic oscillator designs, measured their internal-external uid dynamics, and used modal analysis to reveal their underlying oscillation mechanisms. It also investigated the effects of structural parameters on their uid dynamics. The time-resolved internalexternal pressure elds of the oscillators were determined by using pressure-sensitive paint (PSP) measurement. Proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) were used for modal analysis and phase reconstruction. The time-averaged pressure-eld and phasereconstruction results reveal that recirculation bubbles inside the mixing chamber and the feedback ow have underpinned the mechanism of formation of internal and external continuous sweeping ows. The modal analysis results reveal the spatial modal structures and their time evolution, which dominated the internal-external ow pattern. The inlet-wedge width and feedback-channel inlet diameter were found to be the structural parameters affecting feedback ow and recirculation-bubble size, and thereby in uenced ow characteristics such as jet oscillation frequency and divergence angle. Different Coandă surfaces altered the recirculation bubbles and feedback ow of the mainstream, thereby in uencing the formation mechanism of the sweeping jet.