Acoustic impedance of perforated plates with bias flow

The perforated components are widely used in the intake and exhaust mufflers.Fluid flow has a great influence on the acoustic impedance of perforated components.In order to obtain a precise perforate acoustic impedance model,the present study employs the three-dimensional time-domain Computational Fluid Dynamics (CFD) approach to determine the acoustic impedance of the orifice in the presence of bias flow.The determination method of perforate acoustic impedance is explored and good agreements between the numerical predictions and published measurements of non-dimensional acoustic impedance of orifice are observed.The numerical evaluations are carried out for different bias flow Mach number M_o (0.05-0.20) through the orifice,distribution of the orifices,thickness t (0.8-2 mm) and porosity (4.51%-24.93%) of the perforated plates and their influence on the acoustic impedance of perforate is studied in detail.The acoustic impedance model is obtained by using nonlinear regression analysis of the various results of the parametric studies.As an application,the transmission loss of cross flow perforated tube mufflers is predicted by using Jing & Sun model and the present model.The comparison between measured and predicted values demonstrated that the present model yields high accurate prediction.