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Acoustic Analysis of an Exhaust MANIFOLD by INDIRECT Boundary Element Method

The present work is aimed at the development of a numerical procedure, based on the usage of the Boundary Element Method (BEM) as implemented in the software LMS Virtual.Lab, for the vibro-acoustics analysis of an exhaust manifold. The manifold vibrations are induced by two different ways: engine vibrations (transmitted to the manifold surfaces) and turbulences generated by the air flow in the exhaust system. The indirect BEM (IBEM), with a variational solution algorithm, is adopted to assess the exhaust manifold acoustic radiation. The modal analysis of the acoustic cavity is realized by the Finite Element Method (FEM) and the corresponding eigenfrequencies compared with those obtained by an IBEM forced response analysis and by experimental measurement. Experimental acoustic pressures at the manifold inlet and outlet are measured in anechoic room in order to compare with corresponding numerical predictions and assess the accuracy level obtained.