Abstract
This research deals with the oscillation mechanism of a flip-flop jet nozzle with a connecting tube, based on the measurements of pressures and velocities in the connecting tube and inside the nozzle. The measurements are carried out varying: 1) the inside diameter d of the connecting tube; 2) the length L of the connecting tube and 3) the jet velocity VPN from a primary-nozzle exit. We assume that the jet switches when a time integral reaches a certain value. At first, as the time integral, we introduce the accumulated flow work of pressure, namely, the time integral of mass flux through a connecting tube into the jet-reattaching wall from the opposite jet-un-reattaching wall. Under the assumption, the trace of pressure difference between both the ends of the connecting tube is simply modeled on the basis of measurements, and the flow velocity in the connecting tube is computed as incompressible flow. Second, in order to discuss the physics of the accumulated flow work further, we conduct another experiment in single-port control where the inflow from the control port on the jet-reattaching wall is forcibly controlled and the other control port on the opposite jet-un-reattaching wall is sealed, instead of the experiment in regular jet’s oscillation using the ordinary nozzle with two control ports in connection. As a result, it is found that the accumulated flow work is adequate to determine the dominant jet- oscillation frequency. In the experiment in single-port control, the accumulated flow work of the inflow until the jet’s switching well agrees with that in regular jet’s oscillation using the ordinary nozzle.
Highlights
IntroductionThe fluidics, or the elements in fluid logic, is applications of the Coanda effect where a jet reattaches to a solid side wall, and has been researched since the 1960s [1]-[5]
In order to discuss the physics of the accumulated flow work further, we conduct another experiment in single-port control where the inflow from the control port on the jet-reattaching wall is forcibly controlled and the other control port on the opposite jet-un-reattaching wall is sealed, instead of the experiment in regular jet’s oscillation using the ordinary nozzle with two control ports in connection
In order to discuss the physics of the accumulated flow work further, we conduct another experiment in single-port control where the inflow from one control port on the jet-reattaching wall is forcibly controlled by a blower-and-value system and the other control port on the opposite jet-un-reattaching wall is sealed by a plug, as opposed to the experiment in regular oscillation using the ordinary FFJN with two control ports in connection
Summary
The fluidics, or the elements in fluid logic, is applications of the Coanda effect where a jet reattaches to a solid side wall, and has been researched since the 1960s [1]-[5]. The FFJN retains useful features as well as other flow-induced-vibration devices: namely, 1) low production cost and high reliability due to non-mechanically-moving parts; 2) usability due to a linear frequency response in proportion to flow rate; and 3) robustness against fluid density, temperature, pressure and composition. Owing to the above features, the FFJN is applicable for such products as flow meters, fuel injectors, micro mixers and various control devices to disturb the shear layer or to enhance heat transfer, for singlephase flows and for multi-phase flows. The FFJN is often called a “fluidic oscillator” or “oscillatory-jet-type flowmeter” in different applications
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