Sound Propagation in Varying Cross Section Ducts Lined with Non-uniform Impedance by Multimode Propagation Method

Bi, Wenping; Pagneux, Vincent; Lafarge, Denis

doi:10.2514/6.2005-3066

Cited by 3 publications

(2 citation statements)

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“…The process of transverse decomposition and axial reformulation was then applied to solve the wave propagation in rigid bends. 16,17 This process was also applied in uniform ducts lining nonuniform impedance, 14 uniform bends lining uniform impedance, 18 and varying cross-section ducts lining nonuniform impedance, 19 and was extended to include mean flow in ducts. 20 The objective of Refs.…”

Section: Mpm and Mode Scatteringmentioning

confidence: 99%

“…21, this method was improved by introducing another matrix variable, with which the decomposition coefficients can be solved by marching algorithm in axial direction. This significantly improves the practical implementation of this method for the problem needed large transverse decomposition ͑e.g., in aeroengine intakes 19 ͒. This method was also improved by efficient transverse decomposition.…”

Section: Mpm and Mode Scatteringmentioning

confidence: 99%

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Characteristics of penalty mode scattering by rigid splices in lined ducts

Pagneux

Lafarge

et al. 2007

The Journal of the Acoustical Society of America

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In lined ducts, incident modes are scattered by axially and circumferentially nonuniform impedance. Experiments and numerical calculations have proved that this mode scattering can reduce the liner performance in some cases. This paper is devoted to the characterization of the penalty mode scattering excited by hard-walled splices which often exist in lined ducts. It is shown that, in the range of small splice angles, the transmission loss may decrease sharply with increasing splice angle when one mode, which is near cut-off or has high azimuthal order, is incident. When the incident sound field is composed of several acoustical modes, the phase interferences of incident modes are important for the penalty mode scattering. The effects of other parameters, e.g., liner length, mode quasiresonance on the penalty mode scattering are also presented.

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