Mode-matching techniques for sound propagation in lined ducts withflow

Description/Abstract

This paper discusses the use of mode-matching techniques to model sound propagation in lined ducts with flow. With no flow mode-matching methods are relatively well established and the continuity of acoustic pressure and axial velocity is generally applied. But with a base flow the behaviour of the solution at the transition between, say, a hard wall and a lined wall is not well understood. For this reason different assumptions can be made on the behaviour of the acoustic field and these lead to different models. This paper presents a comparison of different models and illustrates that significant differences can be observed. A modified mode-matching scheme based on conservation of mass and momentum is proposed. The conservation of sound power is investigated for different matching conditions. Finally, the link between the solutions obtained with mode-matching methods and finite element methods is discussed, and the present analysis can shed some light on the underlying assumptions used in finite element models