Validation of a numerical method for extracting liner impedance

Willie, Robert; Michael, G Jones; Sharon, E Tanner; Tony, L Parrott

doi:10.2514/3.13102

Cited by 25 publications

(16 citation statements)

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“…In the objective function method of impedance eduction, the normalized resistance and reactance of the liner are selected such that the objective function F(θ, χ, B R , B I ) is minimized. Note that in our previous works, [13][14][15][16][17] the impedance was educed using data for the upstream source only. This was done because data for the downstream source was not available.…”

Section: The Impedance Eduction Methodsmentioning

confidence: 99%

“…Impedances are educed using the objective function method of impedance eduction. This impedance eduction method has been well documented for an upstream sound source over the last decade [13][14][15][16][17] and has been validated by other impedance eduction methods that employ mode synthesis. 12,18 However, in the current study, modifications are proposed to this methodology that accommodate both upstream and downstream sources.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Wall Boundary Conditions for Impedance Eduction Using a Dual-Source Method

Watson

Jones

2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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The accuracy of the Ingard-Myers boundary condition and a recently proposed modified Ingard-Myers boundary condition is evaluated for use in impedance eduction under the assumption of uniform mean flow. The evaluation is performed at three centerline Mach numbers, using data acquired in a grazing flow impedance tube, using both upstream and downstream propagating sound sources, and on a database of test liners for which the expected behavior of the impedance spectra is known. The test liners are a hard-wall insert consisting of 12.6 mm thick aluminum, a linear liner without a facesheet consisting of a number of small diameter but long cylindrical channels embedded in a ceramic material, and two conventional nonlinear liners consisting of a perforated facesheet bonded to a honeycomb core. The study is restricted to a frequency range for which only plane waves are cut on in the hard-wall sections of the flow impedance tube. The metrics used to evaluate each boundary condition are 1) how well it educes the same impedance for upstream and downstream propagating sources, and 2) how well it predicts the expected behavior of the impedance spectra over the Mach number range. The primary conclusions of the study are that the same impedance is educed for upstream and downstream propagating sources except at the highest Mach number, that an effective impedance based on both the upstream and downstream measurements is more accurate than an impedance based on the upstream or downstream data alone, and that the Ingard-Myers boundary condition with an effective impedance produces results similar to that achieved with the modified Ingard-Myers boundary condition. Subscripts: D,U = a downstream source and an upstream source quantity e, s = an exit plane and a source plane quantity FEM, Meas = a finite element computed and a measured quantity J = lower wall microphone counter (J = 1, 2, 3 . . . nwall)

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Section: The Impedance Eduction Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaluation of Wall Boundary Conditions for Impedance Eduction Using a Dual-Source Method

Watson

Jones

2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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“…(6) and then multiply the resultant equation by (1 + βz −1 )(z 1−σ ) and by the denominator of Eq. (9). Then rearranging and taking the inverse z-transform of the resultant equation we obtain…”

Section: Impedance Conditionmentioning

confidence: 99%

“…Until recently only frequency-domain methods had been developed for the prediction of sound propagation in acoustically treated ducts [7], as well as for the extraction of the impedance property (inverse problem) of the material [9,10]. This is because the development of time-domain impedance conditions had been hindered by the fact that the behavior of the lining material is frequency dependent [5].…”

Section: Introductionmentioning

confidence: 99%

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Time-Domain Numerical Simulation of a Flow-Impedance Tube

Özyörük¹,

Long

Jones

1998

Journal of Computational Physics

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108

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Surface temperature measurement of acoustic liners in the presence of grazing flow and thermal gradient

et al. 2021

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Validation of a numerical method for extracting liner impedance

Cited by 25 publications

References 1 publication

Evaluation of Wall Boundary Conditions for Impedance Eduction Using a Dual-Source Method

Evaluation of Wall Boundary Conditions for Impedance Eduction Using a Dual-Source Method

Time-Domain Numerical Simulation of a Flow-Impedance Tube

Surface temperature measurement of acoustic liners in the presence of grazing flow and thermal gradient

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