Novel Operating Mode of a Fluidic Oscillator

Nicholls, Chris; Tang, Brian M. T.; Turner, James; Bacic, Marko

doi:10.1115/1.4053554

Cited by 6 publications

(3 citation statements)

References 29 publications

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“…5. The unexcited curve is typical of a sonic oscillator and in agreement with previous studies [22,30,33]. The effect of excitation is to lower the oscillation frequency for all but the lowest flow rates.…”

Section: Device Characterisationsupporting

confidence: 91%

“…The outlet ball valves are partially closed to supply a small back pressure, which serves to increase the oscillation magnitude, which is otherwise intermittent. As explained in Nicholls et al [30], the back pressure has the effect of reducing the jet attachment strength in the quasi-steady portion of the oscillation period where the jet is stably attached to one of the walls. This is because the adverse pressure gradient experienced by the diffusing flow increases the likelihood of separation and has a destabilising effect on attachment.…”

Section: Methodsmentioning

confidence: 99%

“…This makes it easier for the oscillation mechanism (the flow through the control port tube) to switch the jet. In this paper, the device operates in the traditional, flow-rate dependent mode characterised by Spyropoulos [22], rather than the back-pressure driven mode described by Nicholls et al [30].…”

Section: Methodsmentioning

confidence: 99%

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Fluidic Oscillator with Active Phase Control

Nicholls

Bacic

2023

AIAA Journal

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This paper demonstrates the closed-loop control of the frequency and phase of a fluidic oscillator using acoustic excitation. It is shown experimentally that the use of acoustic excitation modifies the passive feedback mechanism and slows down the jet switching process. Closed-loop control is employed to vary the oscillation frequency at a fixed flow rate and track a sinusoidal reference target without phase error, using measurements from a pitot probe in the device. The controller is demonstrated to be effective at rejecting disturbances, which is illustrated with both time and frequency domain data. The controller’s ability to track step changes to the reference signal phase is tested, and the closed-loop bandwidth is shown to be around 20% of the oscillation frequency, in close agreement with the theoretical prediction.

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Section: Device Characterisationsupporting

confidence: 91%

Section: Methodsmentioning

confidence: 99%

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Fluidic Oscillator with Active Phase Control

Nicholls

Bacic

2023

AIAA Journal

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An analytical model of the dynamics of reattaching jets

Nicholls,

Tang,

Turner

et al. 2023

Physics of Fluids

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A jet that emerges from a nozzle and attaches to an inclined, setback wall is studied. The reattaching jet is the canonical element of most fluidic devices, and the aim of this paper is to improve the understanding of its dynamics. An analytical model is developed that describes the dynamic behavior of the jet position in response to acoustic excitation. A novel, unsteady jet curvature equation is derived from first principles, which forms the basis of the model. The Görtler velocity profile for a plane, turbulent jet is assumed, and an alternative approach to determining its virtual origin is used. A novel approach to modeling the momentum balance at the jet reattachment point is demonstrated to predict the observed behavior in response to acoustic excitation. The resulting model is linearized at a series of operating points informed by data from the literature at a range of flow rates, wall setback distances, and gas types. A Monte Carlo analysis is conducted to quantify the model sensitivity to parameter uncertainty. The bandwidth of the jet response to acoustic excitation is demonstrated to depend linearly on jet velocity.

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An Investigation of a Newly Developed Bistable Load-Type Supersonic Fluidic Oscillator for Generating Large-Amplitude Pressure Pulsations

Ryzer²,

Rankin

2023

Journal of Fluids Engineering

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Unique aspects in the development of bi-stable load-type fluidic oscillators that satisfy the requirement of producing large-amplitude pressure fluctuations during the charging of vessels for potential implementation in industrial processes such as the superplastic forming process are addressed in this paper. A Pseudo-3D computational fluid dynamic model is shown to be capable of accurately predicting the experimental values of the dimensionless frequencies and pressure fluctuation amplitudes as well as the experimental Schlieren images of the flow field obtained over a wide range of operating conditions. The Pseudo-3D model is also used to provide details of the fluid motion in the oscillator which could not be measured experimentally when investigating the operation of the device. The flow switching mechanism is identified as a consequence of a reduction of the flow deflection angle due to the increase of the downstream pressure load by the charging of feedback tanks. Some examples of the usefulness of the model as a cost-effective industrial design tool are also demonstrated. The effects of changing the number and size of the feedback tank volumes on the device frequency and amplitude of the oscillation are clearly shown using dimensionless variables.

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Novel Operating Mode of a Fluidic Oscillator

Cited by 6 publications

References 29 publications

Fluidic Oscillator with Active Phase Control

Fluidic Oscillator with Active Phase Control

An analytical model of the dynamics of reattaching jets

An Investigation of a Newly Developed Bistable Load-Type Supersonic Fluidic Oscillator for Generating Large-Amplitude Pressure Pulsations

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