Acoustic Impedance of Small Orifices

Sivian, L. J.

doi:10.1121/1.1915795

Cited by 156 publications

(48 citation statements)

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“…Early work by Sivian (1935) to examine small-orifice impedance was expanded by Ingard & Labate (1950) who observed that the size of the orifice could significantly change the sound-induced flow inside the orifice due to viscosity, possibly generating an oscillatory turbulent jet, and displaying a nonlinear impedance. Rogers & Hersh (1975) and Hersh & Rogers (1976) used a single orifice mounted within a water tunnel to visualize the oscillatory flow to develop a semi-empirical impedance model that accounted for high-amplitude conditions.…”

Section: Literature Reviewmentioning

confidence: 98%

Numerical investigation of a honeycomb liner grazed by laminar and turbulent boundary layers

Zhang

Bodony

2016

J. Fluid Mech.

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Direct numerical simulations are used to study the interaction of a cavity-backed circular orifice with grazing laminar and turbulent boundary layers and incident sound waves. The flow conditions and geometry are representative of single degree-of-freedom acoustic liners applied in the inlet and exhaust ducts of aircraft engines and are the same as those from experiments conducted at NASA Langley. The simulations identify the fluid mechanics of how the sound field and state of the grazing boundary layer impact the in-orifice flow and suggest a simple flow analogy that enables scaling estimates. From the scaling estimates the simulations are then used to develop reduced-order models for the in-orifice flow and a time-domain impedance model is constructed. The liner is found to increase drag at all conditions studied by an amount that increases with the incident sound pressure amplitude.

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Section: Literature Reviewmentioning

confidence: 98%

Numerical investigation of a honeycomb liner grazed by laminar and turbulent boundary layers

Zhang

Bodony

2016

J. Fluid Mech.

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“…here is a large number of papers on the effect of high level acoustic excitation on the acoustic properties of perforates and orifice plates [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . Orifice plates and perforates appear in many technical applications where they are exposed to a combination of high acoustic excitation levels and either grazing or bias flow or a combination.…”

Section: Introductionmentioning

confidence: 99%

Acoustic properties of perforates under high level multi-tone excitation

Bodén

2013

19th AIAA/CEAS Aeroacoustics Conference

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This paper discusses the effect of high level multi-tone acoustic excitation on the acoustic properties of perforates. It is based on a large experimental study of the nonlinear properties of these types of samples without mean grazing or bias flow. Compared to previously published results the present investigation concentrates on the effect of multiple harmonics. It is known from previous studies that high level acoustic excitation at one frequency will change the acoustic impedance of perforates at other frequencies, thereby changing the boundary condition seen by the acoustic waves. This effect could be used to change the impedance boundary conditions and for instance increase the absorption. It could obviously also pose a problem for the correct modelling of sound transmission through ducts lined with such impedance surfaces. Experimental results are compared to a quasi-stationary model. The effect of the combination of frequency components and phase in the excitation signal is studied.

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“…The nonlinear effect of high level acoustic excitation has for instance been studied in Ref. [1][2][3][4][5][6][7][8][9][10]. It is well known from this literature that perforates can become non-linear at fairly low acoustic excitation levels.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of an In-Duct Orifice with Bias Flow under Medium and High Level Acoustic Excitation

Zhou

Bodén

2014

International Journal of Spray and Combustion Dynamics

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This paper experimentally investigates the acoustic properties of an orifice with bias flow under medium and high sound level excitation. Orifices with two different edge configurations were tested. The study includes a wide range of bias flow velocities, various acoustic excitation levels and different frequencies. The nonlinear acoustic scattering matrix was identified by a finely controled two-source method. Aeroacoustic modal analysis was introduced based on eigenvaluedecomposition. Acoustic properties, such as impedance, nonlinear scattering matrix and the eigenvalues were compared and discussed. Experimental results also show that bias flow makes the acoustic properties more complex compared to the no bias flow case, especially when the velocity ratio between acoustic particle velocity and mean flow velocity is near unity.

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Acoustic Impedance of Small Orifices

Cited by 156 publications

References 0 publications

Numerical investigation of a honeycomb liner grazed by laminar and turbulent boundary layers

Numerical investigation of a honeycomb liner grazed by laminar and turbulent boundary layers

Acoustic properties of perforates under high level multi-tone excitation

Experimental Investigation of an In-Duct Orifice with Bias Flow under Medium and High Level Acoustic Excitation

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