Boundary layer effects on sound in a circular duct

Nagel, Robert T.; Brand, R. S.

doi:10.1016/0022-460x(82)90467-9

Cited by 12 publications

(9 citation statements)

References 11 publications

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“…Variations in flow speed can be expected to change the received sound level (due to altered propagation up and downstream [28], and across the pipe diameter [29,30]). Measurements in a flow of clean air revealed an apparent insertion loss of less than 1 dB due to air flow over a velocity range 0-47 m/s.…”

Section: Acoustic Instrumentationmentioning

confidence: 99%

Measured dependence of the attenuation of audio-frequency sound on concentration in flowing particulate suspensions

Moss

Attenborough

Woodhead

1999

Proceedings of the Institution of Mechanical Engineers, Part E:

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The relationship between the attenuation of sound at frequencies between 500 and 3500 Hz and the concentration of flowing suspensions of various powdered solids has been explored. The suspensions were conveyed in a pipeline of 53 mm diameter and the particle concentration was varied up to a maximum of 2.8 kg/kg. Three materials were tested: flour (mean radius, 27 mm), olivine sand (mean radius, 278 mm) and barytes. The feasibility of measuring the acoustic attenuation of particulate suspensions at audio-frequencies and relating the measured attenuation to concentration has been demonstrated. Although the audio-frequency attenuation is smaller at a given concentration than at ultrasonic frequencies, audio-frequency measurements are less susceptible to inhomogeneity of flow and to in-pipe turbulence than ultrasonic measurements.

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Section: Acoustic Instrumentationmentioning

confidence: 99%

Measured dependence of the attenuation of audio-frequency sound on concentration in flowing particulate suspensions

Moss

Attenborough

Woodhead

1999

Proceedings of the Institution of Mechanical Engineers, Part E:

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“…Mungur & Plumblee 1969), which neglects temperature variation and viscous and thermal dissipation (Eversman 1971;Mariano 1971;Goldstein & Rice 1973;Jones 1977;Nagel & Brand 1982;Campos & Serrão 1998;Vilenski & Rienstra 2007). These dissipative terms were included by Nayfeh (1973) when considering viscous flow over a permeable boundary, although gradients of the mean flow at the wall were assumed to be O(1), and so this analysis is not applicable to thin boundary layers.…”

Section: Introductionmentioning

confidence: 99%

Acoustic implications of a thin viscous boundary layer over a compliant surface or permeable liner

BRAMBLEY

2011

J. Fluid Mech.

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This paper considers the implications of a high-Reynolds-number thin parallel boundary layer on fluid-solid interaction. Two types of boundaries are considered: a compliant boundary which is flexible but impermeable, such as an elastic sheet or elastic solid, and a permeable boundary which is rigidly fixed, such as a perforated rigid sheet. The fluid flow consists of a steady flow along the boundary and a small time-dependent perturbation, with the boundary reacting to the perturbation. The fluid displacement due to the perturbation is assumed to be much smaller than the boundary-layer thickness. The analysis is equally valid for compressible and incompressible fluids. Numerical examples are given for compressible flow along a cylindrical duct, for both permeable and compliant cylinder walls. The difference between compliant and permeable walls is shown to be dramatic in some cases. High-and low-frequency asymptotics are derived, and shown to compare well to the numerics. When used with a mass-spring-damper boundary, this model is shown to lead to similar, but not identical, temporal instability with unbounded growth rate to that seen for slipping flow using the Myers boundary condition. It is therefore suggested that a regularization of the Myers boundary condition removing the unbounded growth rate may lead to, or at least inform, a regularization of the model presented here.

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“…Several authors [1][2][3][4][5][6][7][8] have addressed the problem of propagation in lined flow ducts for adiabatic, inviscid sound propagation. In these cases, they have assumed continuity of displacement at the wall since it seems to be the more appropriate.…”

Section: Introductionmentioning

confidence: 99%

Influence of grazing flow and dissipation effects on the acoustic boundary conditions at a lined wall

Aurégan

Starobinski

Pagneux

2001

The Journal of the Acoustical Society of America

114

112

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The problem of sound propagation near a lined wall taking into account mean shear flow effects and viscous and thermal dissipation is investigated. The method of composite expansion is used to separate the inviscid part, in the core of the flow, from the boundary layer part, near the wall. Two diffusion equations for the shear stress and the heat flux are obtained in the boundary layer. The matching of the solutions of these equations with the inviscid part leads to a modified specific acoustic admittance in the core flow. Depending on the ratio of the acoustic and stationary boundary layer thicknesses, the kinematic wall condition changes gradually from continuity of normal acoustic displacement to continuity of normal acoustic mass velocity. This wall condition can be applied in dissipative silencers and in aircraft engine-duct systems.

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Boundary layer effects on sound in a circular duct

Cited by 12 publications

References 11 publications

Measured dependence of the attenuation of audio-frequency sound on concentration in flowing particulate suspensions

Measured dependence of the attenuation of audio-frequency sound on concentration in flowing particulate suspensions

Acoustic implications of a thin viscous boundary layer over a compliant surface or permeable liner

Influence of grazing flow and dissipation effects on the acoustic boundary conditions at a lined wall

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