Performance Analysis of Acoustic Liner with Fine-Perforated-Film by Numerical Simulation Using Impulse Response Method

Abstract

With the recent trend toward higher bypass jet engines, the installed area of acoustic liners tends to decrease relative to the engine diameter, and efforts are being made to improve the performance of acoustic liners. The authors have numerically simulated the flow and sound fields of a resonant acoustic liner using the compressible NS equation. However, the relationship between the calculated results and the sound absorption coefficient could not be clarified. In the present study, the impulse response method was used for the numerical analysis, taking advantage of the fact that acoustic phenomena at low sound pressure can be considered as linear. By dividing the impulse response and convolving it separately, it became possible to observe the components of the steady-state sound field separately, and to understand the acoustic phenomena in an easy way. The authors also proposed the use of Fine-Perforated-Film as an acoustic liner with high sound absorption performance under glazing flow. Numerical analysis using the impulse response method also allowed us to infer the mechanism why an acoustic liner with FPF has high sound absorption performance even in the presence of glazing flow.