Validation of a Time &amp; Frequency Domain Grazing Flow Acoustic Liner Model

Burak, Markus Olander; Billson, Mattias; Eriksson, Lars‐Erik; Baralon, Stephane

doi:10.2514/6.2008-2929

Cited by 19 publications

(27 citation statements)

References 11 publications

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“…(10) for the Myers impedance boundary condition and Eq. (27) for the modified impedance boundary condition. For a locally reacting impedance, Eq.…”

Section: Surface Wavesmentioning

confidence: 99%

“…In such situations, it is unclear how well the analytic and numerical solutions should be expected to match, since the analytic solution is only approximate. Similarly, validating numerical simulations against experimental results, as performed by Richter [19] using the NASA Grazing Incidence Tube experimental results [25], has the disadvantage that the mode excited, the definition of the liner impedance and the measured results are all subject to experimental error, and that moreover the results appear sensitive to other factors such as the tube's downstream exit impedance, 3D effects, and viscous and boundary layer effects [26][27][28]. Simple test cases therefore allow an exact comparison between the numerical simulation and an analytic solution, one of the simplest of which is that of an oblique plane wave reflecting from an impedance surface [29]; a number of common validations for 2D and 3D time-dependent numerical acoustics simulations with flow are described by Richter [19, chapter 7.1], and similar validations are also used in 2D and 3D frequency-domain simulations [e.g.…”

Section: Introductionmentioning

confidence: 99%

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Reflection of an acoustic line source by an impedance surface with uniform flow

Gabard

2014

Journal of Sound and Vibration

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An exact analytic solution is derived for the 2D acoustic pressure field generated by a time-harmonic line mass source located above an impedance surface with uniform grazing flow. Closed-form asymptotic solutions in the far-field are also provided. The analysis is valid for both locally-reacting and nonlocally-reacting impedances, as is demonstrated by analysing a nonlocally reacting effective impedance representing the presence of a thin boundary layer over the surface. The analytic solution may be written in a form suggesting a generalization of the method of images to account for the impedance surface. The line source is found to excite surface waves on the impedance surface, some of which may be leaky waves which contradict the assumption of decay away from the surface predicted in previous analyses of surface waves with flow. The surface waves may be treated either (correctly) as unstable waves or (artificially) as stable waves, enabling comparison with previous numerical or mathematical studies which make either of these assumptions.The computer code for evaluating the analytic solution and far-field asymptotics is provided in the supplementary material. It is hoped this work will provide a useful benchmark solution for validating 2D numerical acoustic codes.

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“…(10) for the Myers impedance boundary condition and Eq. (27) for the modified impedance boundary condition. For a locally reacting impedance, Eq.…”

Section: Surface Wavesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reflection of an acoustic line source by an impedance surface with uniform flow

Gabard

2014

Journal of Sound and Vibration

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“…However, for specific liners and under particular flow conditions, some experiments have shown that a convective hydrodynamic instability may grow on the liner and is likely to lead to sound amplification [1,2,3,4,5,6]. Evidence of such instabilities have been shown as well numerically [7,8].…”

Section: Introductionmentioning

confidence: 99%

Global linear stability analysis of flow in a lined duct

Pascal

Piot

Casalis

2017

Journal of Sound and Vibration

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Eigenmodes of the linearised Euler equations are computed in order to study lined flow duct global stability. A simplified configuration is considered and the governing equations are discretised by means of the discontinuous Galerkin method. A biorthogonal technique is used to decompose the global eigenfunctions into local eigenmodes. The system dynamics switches from noise amplifier to resonator as the length of the liner is increased. The global mode in the liner region is shown to be mainly composed of a hydrodynamic unstable wave and a left-running acoustic mode.

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“…13,14 On the contrary, if the boundary-layer is fully resolved, these numerical treatments are unnecessary since the base-flow is zero at the wall. For instance, Richter et al 2 have performed computations on a base-flow obtained by RANS simulation while Burak et al 15 have integrated time domain impedance condition in a Navier-Stokes code.…”

Section: Fully Resolved Boundary-layer or Uniform Flow Assumptionmentioning

confidence: 99%

A New Implementation of the Extended Helmholtz Resonator Acoustic Liner Impedance Model in Time Domain CAA

2016

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. The application of wall acoustic lining is a major factor in the reduction of aircraft engine noise. The extended Helmholtz Resonator (EHR) impedance model is widely used since it is representative of the behavior of realistic liners over a wide range of frequencies. Its application in time domain CAA methods by means of z-transform has been the subject of several papers. In contrast to standard liner modeling in time domain CAA, which consists in imposing a boundary condition modeling both the cavities and the perforated sheet of the liner, an alternative approach involves adding the cavities to the computational domain and imposing a condition between these cavities and the duct domain to model the resistive sheet. However, the original method may not be used for broadband acoustics since it implements an impedance condition with frequency independent resistance. This paper describes an extension of this method to implement the EHR impedance model in a time domain CAA method.

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Validation of a Time & Frequency Domain Grazing Flow Acoustic Liner Model

Cited by 19 publications

References 11 publications

Reflection of an acoustic line source by an impedance surface with uniform flow

Reflection of an acoustic line source by an impedance surface with uniform flow

Global linear stability analysis of flow in a lined duct

A New Implementation of the Extended Helmholtz Resonator Acoustic Liner Impedance Model in Time Domain CAA

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