Finite element analysis of transversal modes and acoustic attenuation characteristics of perforated tube silencers

Finite element method (FEM) is employed to determine the transversal modes of perforated tube silencers, and the corresponding computational code is written. In order to validate the present method and computational code, the transversal modal cut-on frequencies (called as modal frequencies hereafter) of circular coaxial straight-through perforated tube silencer are evaluated analytically and compared with the finite element results, and good agreements between them are observed. The FEM is then used to investigate the effects of perforated tube offset, number of perforated tubes, hole diameter and porosity on the transversal modes and acoustic attenuation characteristics of circular and oval perforated tube silencers. The numerical results demonstrated that the plane wave cut-off frequencies of the coaxial silencers are higher than those of the non-coaxial silencers in general.?Smaller hole diameter or higher porosity leads to higher plane wave cut-off frequency and better acoustic attenuation in the middle frequency range, while the hole diameter and porosity have negligible effect on the plane wave cut-off frequency when the porosity is higher than 40%.