Study of the Effect of Grazing flow on the Performance of Microperforated and Perforated Panels

摘要

Microperforated Panels (MPP) and Perforated Panels (PP) can be used as an alternative to fibrous materials in flow duct lining applications as they can reduce weight and do not suffer from the hazards associated with fibrous materials. When modeling MPPs and PPs with Finite Element Methods (FEM), it is not practical to model explicitly the holes as their diameter can be as small as sub-millimeter. In this paper, MPPs and PPs are modeled as an equivalent fluid, having the acoustical properties predicted by using the Johnson-Champoux-Allard (JCA) model. The effect of grazing flow was modeled by adding a grazing flow correction term to the transfer impedance of MPPs and PPs based on empirical formulae given by Guo et al. and by Rao and Munjal, respectively. A formulation is discussed to convert the transfer impedance to a complex density and complex bulk modulus, which in turn are required to model MPPs and PPs in the FEM. The duct lining Transmission Loss was obtained using the commercial FEM code Abaqus. Transmission Loss results are presented to show the effects of mean flow and grazing flow on MPP and PP performance.