Comparison of the effect of flow direction on liner impedance using different measurement methods

Bodén, Hans; Cordioli, Júlio A.; Spillere, Andre; Serrano, Pablo G.

doi:10.2514/6.2017-3184

Cited by 13 publications

(16 citation statements)

References 36 publications

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“…Experiments showed that, in presence of a flow, the educed impedance depends on the direction of the sound wave relative to the mean flow direction [2,8,9]; this result goes against the definition of locally-reacting liner. This finding was attributed to the use of the Ingard-Myers boundary condition [10] in the impedance eduction techniques.…”

Section: Introductionmentioning

confidence: 91%

Lattice-Boltzmann Very Large Eddy Simulation of a Multi-Orifice Acoustic Liner with Turbulent Grazing Flow

Avallone

Manjunath

Ragni

et al. 2019

25th AIAA/CEAS Aeroacoustics Conference

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A lattice-Boltzmann Very Large Eddy simulation of a multi-orifice acoustic liner, grazed by a turbulent flow at Mach number equal to 0.3 and a planar acoustic wave with amplitude equal to 130 dB and frequency equal to 1800 Hz, is carried out. The geometry of the liner replicates the experiments carried out in the Grazing Flow Impedance Tube (GFIT) facility at NASA Langley. It is found that the impedance, obtained from numerical simulations using the Dean's method, is a function of the orifice location. This is attributed to two phenomena: the interaction between the wake behind the upstream orifices and the downstream ones; and the interaction between the flow fields in the cavity induced by the ejected vortices. Results show that, for the investigated configuration, two vortical structures are generated in the orifice: one, formed along the downstream inner wall of the orifice, weakly penetrates into the cavity; the second, formed at the bottom downstream corner of the orifice, is ejected into the cavity up to three orifice diameters. The direction along which the latter is ejected varies with the orifice location. The ejected vortices are characterized by an annular vortex and a trailing vortex similarly to what found for synthetic jets. In the cavity, large scale vortical structures are found. On the face sheet, it is found that the turbulent wakes behind the upstream orifices increases the vertical velocity component within the orifices. These findings suggest that local measurement techniques, such as the Dean's method, might be affected by the sampling location in realistic configurations.

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Section: Introductionmentioning

confidence: 91%

Lattice-Boltzmann Very Large Eddy Simulation of a Multi-Orifice Acoustic Liner with Turbulent Grazing Flow

Avallone

Manjunath

Ragni

et al. 2019

25th AIAA/CEAS Aeroacoustics Conference

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“…While intrinsic by definition, the educed impedance of locally reacting materials has recently been shown to depend on the direction of the incident waves relative to the mean flow [23][24][25][26], i.e., upstream or downstream sources. This observed behavior has led to questions about the assumptions underlying the current eduction methods [27][28][29]: is the impedance definition insufficient, and should its modeling be augmented to take into account source direction?…”

Section: Introductionmentioning

confidence: 99%

Wavenumber-Based Impedance Eduction with a Shear Grazing Flow

Roncen¹,

Piot²,

Méry³

et al. 2020

AIAA Journal

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While intrinsic by definition, the impedance measured by impedance eduction has been shown to depend on the direction of the incident waves relative to the mean flow. The purpose of the present work is to evaluate whether part of the observed differences could stem from a biased wavenumber definition made during the impedance eduction process.Comparisons are made between the results of impedance eductions with uniform flow and the Ingard-Myers boundary condition, with the 1D linearized Euler equations and with the 2D linearized Euler equations, i.e., in the cross section. Both numerical synthetic data and experimental data are used for the eduction of two sample liners, with bulk Mach numbers ranging from 0 to 0.3, and at frequencies ranging from 400 to 3000 Hz.Results show that for a rectangular cross-section duct, the knowledge of the 2D flow profile in the cross section is valuable for impedance eduction. Using only 1D flow profiles bias the educed impedance estimation.

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“…However, some recent applications 7-9 have indicated a possible dependence of the educed impedance on the direction of incident waves relative to the mean flow. This unexpected behavior for locally reacting liners has led to the proposal of alternative boundary conditions and to the questioning of the hypotheses underlying the classical impedance eduction methods (see for instance Zhou and Bodén, 10 Spillere et al, 11 Bodén et al 12 ). The purpose of the current study is to investigate the effects of flow profile and axial wavenumber uncertainties on impedance eduction methods based on the Pridmore-Brown and convected Helmholtz equations for upstream and downstream sources.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Axial Wave Number and Mean Flow Uncertainty on Acoustic Liner Impedance Eduction

Nark

Jones

Piot³

2018

2018 AIAA/CEAS Aeroacoustics Conference

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Comparison of the effect of flow direction on liner impedance using different measurement methods

Cited by 13 publications

References 36 publications

Lattice-Boltzmann Very Large Eddy Simulation of a Multi-Orifice Acoustic Liner with Turbulent Grazing Flow

Lattice-Boltzmann Very Large Eddy Simulation of a Multi-Orifice Acoustic Liner with Turbulent Grazing Flow

Wavenumber-Based Impedance Eduction with a Shear Grazing Flow

Assessment of Axial Wave Number and Mean Flow Uncertainty on Acoustic Liner Impedance Eduction

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