Unsteady phenomena in the edge tone

Paál, György; Vaik, István

doi:10.1016/j.ijheatfluidflow.2007.04.011

Cited by 20 publications

(22 citation statements)

References 14 publications

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“…Also a criterion for the value of the time step was determined in order to keep the numerical error at the constant value of the reference state also in the case of simulations at higher Reynolds numbers. These are all discussed in more detail in a former paper of the authors [21].…”

Section: Frequency and Phase Characteristics Of The Edge Tonementioning

confidence: 95%

Frequency and Phase Characteristics of the Edge Tone, Part I

Vaik

Varga²,

Paál³

2014

Period. Polytech. Mech. Eng.

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This paper is the first half of a two-part publication. In these papers the well-known low Mach number edge tone configuration is investigated which is one of the canonical selfsustained flow configurations leading to simple aeroacoustic flow phenomena. The configuration consist of a planar free jet that impinges on a wedge shaped object. Under certain circumstances the jet starts to oscillate more or less periodically thereby creating an oscillating force on the wedge that acts as a dipole sound source. This first part contains a detailed literature overview and the qualitative discussion of the authors' results of a detailed parametric study. The formulae in the literature describing the dependence of the frequency on exit velocity and nozzle-wedge distance show a broad scatter, although similar in form. In this paper a systematic and thorough study is made by experimental and numerical means and remarkable agreement is found.

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Section: Frequency and Phase Characteristics Of The Edge Tonementioning

confidence: 95%

Frequency and Phase Characteristics of the Edge Tone, Part I

Vaik

Varga²,

Paál³

2014

Period. Polytech. Mech. Eng.

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“…the valve disc) or reaching open cavities like T-junctions Paál et al (2006) or wedge-like obstacles Paál and Vaik (2007) might result in periodic vortex shedding, with welldefined frequencies that might excite the whole system. Note that such 'microscopic' flow properties are unlikely to result in instabilities per se.…”

Section: Vortex Sheddingmentioning

confidence: 99%

Dynamic behaviour of direct spring loaded pressure relief valves connected to inlet piping: IV review and recommendations

Hős

Champneys

Paul

et al. 2017

Journal of Loss Prevention in the Process Industries

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. AbstractRecent progress by a number of different groups and authors is reviewed on the stability properties of direct-spring pressure relief valves connected to pressure vessels with or without piping systems. Various different notions of stability and mechanisms for instability are revealed both in the case of gas and liquid service. It is stressed that it is not the valve itself that is stable or unstable, rather the harmful vibrations arise through interactions between the valve and its surroundings -the inlet piping, the reservoir, and any outlet piping. A distinction is drawn between underlying instability mechanisms and how these may be triggered during transient operations. The purpose of the work is to provide a coherent simplified account that will be of practical use for proposing new operational guidelines and mitigation strategies. Among these various mechanisms, oscillatory instability due to the interaction with a quarter-wave acoustic mode in the inlet piping is argued to be the most important to mitigate.

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“…Given the right conditions, edgetone flows can cause acoustic tones. For brevity, the feedback mechanism of the edgetone can be assumed to the same as that of the impingement tone (details on the exact mechanism can be found in reference [62]) but the edgetone oscillates in a flapping manner -much like a flag in the wind -about the apex of the wedge. As the jet velocity or the nozzle to wedge distance changes the frequency of the tone changes gradually until the oscillation abruptly changes modes in a discrete fashion.…”

Section: Edgetone Noisementioning

confidence: 99%

“…While this formula presents the general trend of edge tones, some other sources in the literature present additional constants applied to u j and/or h in order for the formulation to more closely match experiment. The value of q is not well accepted and has been the subject of a long debate ( [62,66]). The exact value appears to vary with experiment specifics (such as wedge angle or jet velocity profile).…”

Section: Edgetone Noisementioning

confidence: 99%

“…In formula 3.7 the exit velocity profile, shape of the nozzle, wedge tip radius and transverse position of the wedge are not considered. Reference [62] explains that while these will affect the flow, they are secondary factors which have a much smaller effect than the variables in formula 3.7. To further elaborate on this, reference [67] finds that the wedge angle has little impact under 40 • and reference [63] experiences tones for all wedge angles investigated (10 • , 20 • , 60 • and 180 • ).…”

Section: Edgetone Noisementioning

confidence: 99%

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A Theoretical and Experimental Investigation on Ejector Acoustics and Ejector Silencer Design

Desmarais¹

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Ejectors are common devices used across many industries, however, they are often plagued by the presence of low frequency pressure pulsations causing both broadband and tonal noise. This thesis presents a theoretical and experimental investigation into the acoustics of an ejector-silencer combination with the emphasis placed on silencer design. More specifically, the noise generated by the jet, the diffuser and natural modes is explained and estimated. The noise generation mechanisms of impingement tones and edgetones are presented but accurate predictions are found to be hard to make. An outline of the experimental facility is followed by the mechanical, acoustical and aerodynamic design details of the approximately 70:1 ejector scale model. A detailed analysis on the primary nozzle control and calibration is presented before beginning an aerodynamic and acoustic characterization of both the ejector and the wind tunnel facility. From experimentation, it is found that the placement of a perforated cone in front of the solid cone is beneficial in reducing the noise generated without overly affecting the entrainment ratio. Other configurations tested tend not to be as acoustically effective or to decrease the entrainment ratio below an acceptable level. Experiments prove that the low frequency noise generated by the ejector is mainly caused by natural mode excitation.iv

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Unsteady phenomena in the edge tone

Cited by 20 publications

References 14 publications

Frequency and Phase Characteristics of the Edge Tone, Part I

Frequency and Phase Characteristics of the Edge Tone, Part I

Dynamic behaviour of direct spring loaded pressure relief valves connected to inlet piping: IV review and recommendations

A Theoretical and Experimental Investigation on Ejector Acoustics and Ejector Silencer Design

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