A new segmentation approach for sound propagation in non-uniform lined ducts with mean flow

An analytical model is presented to study sound attenuation in a non-uniform lined duct with mean flow in this paper. This work is an extension of segmentation approach with emphasis on the physical and mathematical descriptions of locally or non-locally reacting liners in flow ducts. Various numerical results show that the model not only gives the same prediction as the existing models for both continuously and abruptly varying cross-sectional area ducts without flow, but also provides a convenient tool for the optimization of sound attenuation in a non-uniform flow duct at the preliminary design stage of acoustic treatments. As one of the objectives of the present model, attention is also paid to how to improve the sound attenuation in a varying flow environment by the change of the wall impedance using bias flow. In particular, a better physical understanding to the interaction mechanism of different liner combinations may be expected with the help of the proposed model.