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On impedance conditions for circular multiperforated acoustic liners

Schmidt, Kersten and Semin, Adrien and Thöns-Zueva, Anastasia and Bake, Friedrich (2018) On impedance conditions for circular multiperforated acoustic liners. Journal of Mathematics in Industry, 8 (1), p. 15. Springer. DOI: 10.1186/s13362-018-0057-0 ISSN 2190-5983

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Background: The acoustic damping in gas turbines and aero-engines relies to a great extent on acoustic liners that consists of a cavity and a perforated face sheet. The prediction of the impedance of the liners by direct numerical simulation is nowadays not feasible due to the hundreds to thousands repetitions of tiny holes. We introduce a procedure to numerically obtain the Rayleigh conductivity for acoustic liners for viscous gases at rest, and with it define the acoustic impedance of the perforated sheet. Results: The proposed method decouples the effects that are dominant on different scales: (a) viscous and incompressible flow at the scale of one hole, (b) inviscid and incompressible flow at the scale of the hole pattern, and (c) inviscid and compressible flow at the scale of the wave-length. With the method of matched asymptotic expansions we couple the different scales and eventually obtain effective impedance conditions on the macroscopic scale. For this the effective Rayleigh conductivity results by numerical solution of an instationary Stokes problem in frequency domain around one hole with prescribed pressure at infinite distance to the aperture. It depends on hole shape, frequency, mean density and viscosity divided by the area of the periodicity cell. This enables us to estimate dissipation losses and transmission properties, that we compare with acoustic measurements in a duct acoustic test rig with a circular cross-section by the German Aerospace Center in Berlin. Conclusions: A precise and reasonable definition of an effective Rayleigh conductivity at the scale of one hole is proposed and impedance conditions for the macroscopic pressure or velocity are derived in a systematic procedure. The comparison with experiments show that the derived impedance conditions give a good prediction of the dissipation losses.

Item URL in elib:https://elib.dlr.de/125905/
Document Type:Article
Title:On impedance conditions for circular multiperforated acoustic liners
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Schmidt, KerstenTechnische Universität Darmstadthttps://orcid.org/0000-0001-7729-6960
Semin, AdrienTechnische Universität DarmstadtUNSPECIFIED
Thöns-Zueva, AnastasiaTechnische Universität BerlinUNSPECIFIED
Bake, FriedrichFriedrich.Bake (at) dlr.dehttps://orcid.org/0000-0002-3235-428X
Date:18 December 2018
Journal or Publication Title:Journal of Mathematics in Industry
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:No
DOI :10.1186/s13362-018-0057-0
Page Range:p. 15
Keywords:Acoustic liner; Perforated plates; Multiscale analysis; Rayleigh conductivity; Impedance conditions
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:propulsion systems
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Combustion Chamber Technologies, L - Turbine Technologies
Location: Berlin-Charlottenburg
Institutes and Institutions:Institute of Propulsion Technology > Engine Acoustic
Deposited By: Bake, Dr.-Ing. Friedrich
Deposited On:15 Jan 2019 11:05
Last Modified:15 Jan 2019 11:05

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