Direct numerical simulation of three dimensional honeycomb liner with circular apertures

Acoustic liners play an important role in aircraft gas turbine engine noise reduction by converting acoustic fluctuations into nonradiating vortical disturbances through small openings, or apertures. In the recent years, numerical investigations of acoustic liners have become a popular tool to analyze their characteristics. Although most of the previous efforts focused on 2D simulations to uncover many of the working mechanisms of acoustic liners, a better understanding requires 3D simulations. Hence, in this paper, a 3D model of a honeycomb liner with circular apertures is used. The configuration of this model is based on one of the designs investigated at the NASA Langley Research Center. The goal of the simulations is to analyze the flow characteristics of normal incident sound interacting with the liner aperture. A series of simulations were performed by varying the intensity and frequency of the incident sound. Through the numerical simulation data, a detailed flow visualization and acoustic energy dissipation quantification at different sound pressure levels and frequencies are presented. Impedance values were predicted using the traditional two microphone method. Reasonable agreement between the experimental measurements and numerical predictions of the normalized impedance are found. Finally, a time domain analysis of the data is also presented.