1th International Symposium on Flow Visualization

The fluidic oscillator is a device that generates an oscillating jet when supplied with fluid at pressure. The oscillator has no moving parts – the creation of the unsteady jet is based solely on fluid-dynamic interactions. Fluidic oscillators can operate at frequencies ranging up to 20 kHz, and are useful for flow control applications. The fluidic oscillator evaluated in the current study is comprised of two fluid jets that interact in an internal mixing chamber, producing the oscillating jet at the exit. The mixing characteristics and internal fluid dynamics of this fluidic oscillator are not yet fully understood. Therefore, advanced optical measurement techniques are employed in the current work to study the physics of the fluidic oscillations. Both porous pressure-sensitive paint (PSP) and dye-colored water flow are used to visualize the internal fluid dynamics of the oscillator. Porous PSP formulations have been shown to have frequency responses on the order of 100 kHz, more than adequate for visualizing the fluidic oscillations. In these tests, one of the internal jets of the fluidic oscillator is supplied with oxygen, and the other with nitrogen, to provide high-contrast PSP data. Phase-averaged PSP data animations provide unique insight into the flow physics of the jet interactions that generate the fluidic oscillations. Results indicate that two counter-rotating vortices within the mixing chamber drive the oscillations in a unique manner that has not been previously observed. Furthermore, an intriguing mode-hopping behavior was observed at extremely low flow rates.