Taxonomic trees of fluidic oscillators

One of the main advantages of fluidic oscillators is that they do not have moving parts, which brings high reliability whenever being used in real applications. To use these devices in real applications, it is necessary to evaluate their performance, since each application requires a particular injected fluid momentum and frequency. In this paper, the performance of a given fluidic oscillator is evaluated at different Reynolds numbers via a 3D-computational fluid dynamics (CFD) analysis. The net momentum applied to the incoming jet is compared with the dynamic maximum stagnation pressure in the mixing chamber, to the dynamic output mass flow, to the dynamic feedback channels mass flow, to the pressure acting to both feedback channels outlets, and to the mixing chamber inlet jet oscillation angle. A perfect correlation between these parameters is obtained, therefore indicating the oscillation is triggered by the pressure momentum term applied to the jet at the feedback channels outlets. The paper proves that the stagnation pressure fluctuations appearing at the mixing chamber inclined walls are responsible for the pressure momentum term acting at the feedback channels outlets. Until now it was thought that the oscillations were driven by the mass flow flowing along the feedback channels, however in this paper it is proved that the oscillations are pressure driven. The peak to peak stagnation pressure fluctuations increase with increasing Reynolds number, and so does the pressure momentum term acting onto the mixing chamber inlet incoming jet.Original fluidic oscillators design goes back to the 60 s and 70 s. Their outlet frequency ranges from several Hz to KHz and the flow rate is usually of a few dm 3 /min. From their applications in flow control, it is interesting to mention their use in combustion control [3], flow deflection and mixing enhancement [4], flow separation modification in airfoils [5], boundary layer modification on hump diffusers used in turbomachinery [6], flow separation control on compressors stator vanes [7], gas turbine cooling [8], drag reduction on lorries [9], and noise reduction in cavities [10].Despite the existence of particular fluidic oscillator configurations, like the one introduced by Uzol and Camci [11], which was based on two elliptical cross-sections placed transversally and an afterbody located in front of them, or the one proposed by Huang and Chang [12], which was a V-shaped fluidic oscillator, most of the recent studies on oscillators focused on two main, very similar, canonical geometries, which Ostermann et al. [13] called the angled and the curved oscillator geometries. Some very recent studies on the angled geometry are [13][14][15][16][17][18][19][20][21][22][23], while the curved geometry was studied by [4,10,13,[23][24][25][26][27][28][29][30][31][32][33]. Ostermann et al. [13], compared both geometries, concluding that the curved one was energetically the most efficient.One of the first analyses of the internal flow on an angled fluidic oscillator was undertaken by B...

Section: Introductionsupporting

confidence: 80%

Analysis of the Forces Driving the Oscillations in 3D Fluidic Oscillators

Baghaei

Bergadà

2019

“…Typical use of fluidic oscillators [29] is currently found in their increasing heat and/or mass transfer in various chemical and physical processes. The increase is usually the result of destroying the boundary layer, which behaves as an insulating stationary layer at a transfer surface.…”

Section: Very Low Frequency "Flip-flop" Oscillatomentioning

confidence: 99%

“…Oscillator[28,29] with a load-switched bistable diverter and two alternatively rotated vortex chambers, with all components in planar configuration.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Time-Delay Circuits for Fluidic Oscillators and Pulse Shapers

Tesař

2019

Self Cite

Fluidic signals transferred between mutually communicating components of fluidic circuits are nowadays still often in the format of continuously varied value of pressure or flow rate. Especially when transported over longer distances, these simple signals may easily deteriorate due to varying properties they meet in the transmission. An example are friction losses dependent on local temperature. A solution to this signal corruption problem is to encode the signals into flow pulses. Their parameters (such as the number of pulses in a delivered pulse cluster) much less deteriorating during transfer are derived from the time delays generated in delay circuits and oscillators. This paper surveys the basic physical aspects of the fluidic pulse generation and shaping, also presents some examples of circuit design.

“…Characterised by the absence of internal movable components (that could degrade or need maintenance), this rectifier has a virtually unlimited operating life (provided it is built from suitably resistant material). Even the generation of alternating driving flows outside the barrier, as represented in Figure 1 by mechanical components, may be performed by a fluidic oscillator, perhaps one of those presented in reference [7]. There is, however, no particular necessity for this fully fluidic solution involving the oscillator.…”

Section: Handling Dangerous Liquidsmentioning

confidence: 99%

Active Fluidic Turn-Down Rectifier

Tesař

2019

Paper discusses a device belonging into an interesting and yet little-known family of no-moving-part active fluidic rectifiers. The generated steady component of flow and pressure are driven by input alternating flow from an external source. The absence of moving components results in the unique capability of unlimited life and reliability, especially useful for safety devices. In the experiment, the rectifier generated a pressure keeping dangerous liquid in the active zone. When the driving oscillation stops (like, e.g., due to coolant loss), the liquid leaves the zone under gravity, stopping the performed reaction. This safety facility is simple, inexpensive, and extremely reliable.