Application of the Boundary Element Method to Predicting Acoustic Performance of Expansion Chamber Mufflers With Mean Flow

Abstract

A boundary element method (BEM) is applied to predicting the acoustic performance of expansion chamber mufflers with mean flow. The formulation of the boundary element method is derived for three-dimensional and axisymmetric expansion chambers incorporating only the convective effect of mean flow, by means of which the four-pole parameters including high order mode effects can be easily obtained at any frequency; therefore the acoustic performance such as transmission loss can be predicted. A substructure boundary element method is presented for long or complex shape mufflers. Predicted values of transmission loss of expansion chambers without and with mean flow are compared with those reported in the literature and they agree very well.