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.
In: J. Math. Industry, Springer, p. 15, 8, (1), ISSN 2190-5983,
DOI: 10.1186/s13362-018-0057-0,
[Online-Edition: https://doi.org/10.1186/s13362-018-0057-0],
[Article]

Official URL: https://doi.org/10.1186/s13362-018-0057-0

Abstract

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.

Item Type:

Article

Erschienen:

2018

Creators:

Schmidt, Kersten and Semin, Adrien and Thöns-Zueva, Anastasia and Bake, Friedrich

Title:

On impedance conditions for circular multiperforated acoustic liners

Language:

English

Abstract:

Journal or Publication Title:

J. Math. Industry

Volume:

Number:

Publisher:

Springer

Divisions:

04 Department of Mathematics
04 Department of Mathematics > Numerical Analysis and Scientific Computing

Date Deposited:

25 Dec 2018 15:50

DOI:

10.1186/s13362-018-0057-0

Official URL:

https://doi.org/10.1186/s13362-018-0057-0

Alternative Abstract:

Alternative abstract

Language

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.

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