Whistling of an orifice in a reverberating duct at low Mach number

Lacombe, Romain; Moussou, Pierre; Aurégan, Yves

doi:10.1121/1.3641427

Cited by 28 publications

(15 citation statements)

References 28 publications

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“…The resonator with the longest neck, shown in Fig. 14 (bottom), gives negative resistance between 1.9 ≤ S L h t ≤ 3, which is consistent the whistling Strouhal number region of an orifice [41][42][43] of approximately 1.3 ≤ S L h t ≤ 2.5. As for the reactance, while Bellucci's and the modified Howe's model underpredict its value compared to our model for S L h t ≤ 2, they overpredict it compared to our model for S L h t > 2.…”

Section: At Low Frequencies (S L Hsupporting

confidence: 60%

The acoustics of short circular holes opening to confined and unconfined spaces

Yang

Morgans

2017

Journal of Sound and Vibration

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The sound generated or absorbed by short circular holes with a mean flow passing through them is relevant in many practical applications. Analytical models for their acoustic response often ignore the fact that such holes open to a confined or finite space either side, or account for this e ect simply by adding an end mass inertial correction. The vortex-sound interaction within a short hole has been recently shown to strongly a ect the acoustic response at low frequencies [D.Yang and A.S.Morgans, J Sound Vib 384 (2016), pp.294 – 311]. The present study considers a semi-analytical model based on the Green’s function method to investigate how the expansion ratios either side of a short hole a ect the vortex-sound interaction within it. After accounting for expansions to confined spaces using a cylinder Green’s function method, the model is substantially simplified by applying a half-space Green’s function for expansions to large spaces. The e ect of both the up- and downstream expansion ratio on the acoustics of the hole is investigated. These hole models are then incorporated into a Helmholtz resonator model, allowing a systematic investigation into the e ect of neck-to-cavity expansion ratio and neck length. Both of these are found to a ect the resonator damping

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Section: At Low Frequencies (S L Hsupporting

confidence: 60%

The acoustics of short circular holes opening to confined and unconfined spaces

Yang

Morgans

2017

Journal of Sound and Vibration

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“…5. This is because a longer hole is more likely, than a shorter hole, to generate acoustics, this being consistent with results from [12,13,17,21,22].…”

Section: The Effect Of the Vortex Sheet Shapesupporting

confidence: 86%

On the sensitivity of the acoustics of short circular holes to inlet edge geometries

Yang

Inigo

Johnson

et al. 2018

2018 AIAA/CEAS Aeroacoustics Conference

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Short circular holes with a low Mach number mean bias flow passing through them can absorb or generate acoustics. A recent semi-analytical model (Yang & Morgans, Journal of Sound and Vibration, 384 (2016) pp. 294-311 & 393 (2017) pp. 41-61) based on the Green's function method has been shown to be able to capture both the acoustic absorption and generation. The model indicates the importance of accurately capturing the path of the shed vorticity from the hole inlet edge. In the present work, the effect of this vorticity path on the hole acoustics is first studied systematically using the semi-analytical model. As the vorticity path is sensitive to the sharpness of the hole inlet edge, CFD tools are then used to obtain the vortex sheet shape after slightly changing the hole inlet edge shape. The acoustic responses of these modified holes are obtained using the semi-analytical model. A slightly chamfered edge case and a small ellipse edge case are considered to show that a very small change to the shape of the hole inlet edge can give a significant difference in the hole acoustic response.

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“…al. [13] investigated the whistling frequency from a sharp edged orifice at very low Mach number of around 0.02. They also found the acoustic velocity during whistling and showed its dependence on Strouhal number and acoustic reflection within the pipe.…”

Section: Introductionmentioning

confidence: 99%

Transonic Resonance Tones in Orifice and Pipe Jets

Jothi

Srinivasan

2013

International Journal of Aeroacoustics

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This paper investigates the flow resonance while the jet is issued out from a nozzle at transonic Mach numbers. In present study the jets emerging out from orifice and pipe nozzles are considered. The jet flow diameter of orifice and pipes is 10 mm, and the length of the pipe is varied in the range of 1 ≤ L/D ≤ 6. The pressure ratio of the jet flow is varied in the range of subsonic to supersonic Mach numbers; however the study predominantly concentrates on transonic regimes. Results indicate that distinct transonic resonance tones occur in the range of transonic Mach numbers (0.95 to 1.01). Unlike screech that occurs during the presence of shock cells, the transonic frequencies slightly increase with Mach number. Moreover numerous multiple non-harmonic frequency tones are observed during this transonic resonance thus indicating the non-linearity in the flow resonance. In case of pipe nozzles, the transonic tones tend to diminish with increase in pipe length and cease to exist beyond a certain length.

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Whistling of an orifice in a reverberating duct at low Mach number

Cited by 28 publications

References 28 publications

The acoustics of short circular holes opening to confined and unconfined spaces

The acoustics of short circular holes opening to confined and unconfined spaces

On the sensitivity of the acoustics of short circular holes to inlet edge geometries

Transonic Resonance Tones in Orifice and Pipe Jets

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