Fluidic oscillators for flow control

Peszyński

Smyk

2016

Abstract. Paper discusses a new configuration of fluidic oscillators, a subject of recent Patent application. There is some similarity with the standard Warren oscillator with its bistable jet-deflection diverter and two feedbacks -which is not suitable for situations demanding very low oscillation frequency. For these conditions the new design replaces jet-deflection switching in the diverter by load-switching effects, with the gradually increased loading by spin-up of fluid in the vortex chambers. The spin-up time also provides the needed time delays. Behaviour is characterised by the oscillation frequency increasing with increasing fluid flow rate -for which was derived a surprisingly simple theoretical solution.

Section: Introductionmentioning

confidence: 92%

“…(3) and the half-period eq. (4) are divided, their ratio was found to be an integer constant (5) -with the exception of the deviation at small flow rates, already discussed as insignificant because of the too low values of Reynolds number. By substitution of eq.…”

Section: Characteristic Time -And a Simple Theory Of Oscillator Functmentioning

confidence: 99%

Fluidic low-frequency oscillator consisting of load-switched diverter and a pair of vortex chambers

Peszyński

Smyk

2016

“…It could be first described in open literature ref. [7] later, after the war in 1919. Prior to this publication, however, two British electrical engineers, Prof. Eccless (Fig.…”

Section: Electronic Circuits With Anti-parallel Mutually Blocked Valvesmentioning

confidence: 99%

“…This seemed quite logical because the microbubbles, due to their small size and dominance of relatively strong surface tension forces, posses very high natural frequency of surface oscillation, of the order of kilohertz [3]. It was believed that the small size of the microbubbles is the result of pulsation-promoted fragmentation of initially larger [6,7]. The main component is a bistable diverter amplifier.…”

Section: Introductionmentioning

confidence: 99%

Stochastic regimes in very-low-frequency fluidic oscillator

2016

Abstract. Paper discusses interesting unexpected stochastic regimes discovered in a fluidic oscillator designed for operation at very low oscillation frequencies -without the inconvenience of the long feedback loops needed in standard low-frequency oscillator designs. The new oscillator contains a pair of bistable turn-down active valves operating in anti-parallel -essentially analogous to Abraham & Bloch electric "multibrateur" invented in 1919. Three different self-excited oscillation regimes were found. In the order of increasing supplied flow rate, these regimes are characterised by: (A) generation of stochastic-duration multi-pulse packs, (B) generation of individual pulses with a degree of periodicity, and (C) regime with randomly appearing flow pulses separated by intervals of the order of seconds.

“…The large difference between the weak control flow and strong output means the devices posses an amplification property. The basic jet-deflection mechanism has been developed into a wide spectrum of various designs [1]. Often used is the Coanda effect of jet attachment to an adjacent wall.…”

Section: Introductionmentioning

confidence: 99%

Induced fluid rotation and bistable fluidic turn-down valves (a survey)

2015

Abstract. Paper surveys engineering applications of an unusual fluidic principle -momentum transfer through a relatively small communicating window into a vortex chamber, where the initially stationary fluid is put into rotation. The transfer is often by shear stress acting in the window plane, but may be enhanced and perhaps even dominated by fluid flow crossing the boundary. The case of zero-time-mean fluid transport through the window has found use in experimental fluid mechanics: non-invasive measurement of wall shear stress on objects by evaluating the induced rotation in the vortex chamber. The case with the non-zero flow through the interface became the starting point in development of fluidic valves combining two otherwise mutually incompatible properties: bistability and flow turning down.