It has been shown previously that incompressible computational fluid dynamics (CFD) models can be solved in the time domain to calculate the transfer impedances of microperforated panels. However, these models require relatively lengthy run times, do not allow for thermal losses due to irreversible heat transfer to the panels, and rely on the assumption that the solid parts of the panels are rigid. In the present work, compressible, thermo-acoustic models, solved in the frequency domain, have been used to compute thermal losses in addition to viscous losses; these calculations enable the visualization and spatial localization of both loss mechanisms. Thermal losses prove to be relatively small compared to viscous losses in typical geometries, but they become progressively more important as the frequency increases. Additionally, the fully-coupled fluid-structure interaction (FSI) problem has been solved to determine the range of parameters within which the transfer impedance of a rigid microperforated panel can be added in parallel to the impedance of a limp panel ( ) to account for panel flexibility. In particular it will be shown under what conditions the relative motion between the fluid velocity through the perforations and the velocity of the panel, including its phase, must be explicitly considered.
microperforated panels, thermal dissipation, viscous dissipation, flexibility
Acoustics and Noise Control
Date of this Version