A Simple Model for Estimation of Sound Absorption of Perforated Liners with Bias Flow
* Presenting author
Perforated liners are commonly used for noise control in ducts and chambers, such as in mufflers, gas turbine combustors, and nacelles of aircraft engines. The mechanism of sound absorption is based on the resonance effect coupled with dissipation of sound at the openings of a perforated plate. In the presence of mean bias flow through the perforations, the dissipation can be induced by means of the vortices, which are formed at the edge of the openings where the flow separates. The existing analytical models for estimation of acoustic performance of liners are often mathematically elaborate and with limited accuracy or range of validity, due to, for example, neglect of the thickness of the plate or potential interaction between the openings at higher porosities. In this work, we consider a model for liners with low Mach number bias flow, which is based on a simple theory of Helmholtz resonators with mean flow. Apart from its simplicity, the model allows the inclusion of finite thickness of the plate, interaction between the openings, and vena contracta factor. The estimated sound absorption is compared with similar solutions and measurement data from literature.