Abstract：Finite element method is applied to calculate the cross-sectional modes of perforated tube silencer, the corresponding finite element formulation is derived and the computational code is written. For the radial modal frequencies of circular concentric configuration, the finite element predictions agree well with the analytical results, which illustrated that the finite element method can predict cross-sectional modes of perforated tube silencer accurately. The finite element method is then used to investigate the effects of the hole diameter, porosity and the perforated tube offset on the cross-sectional modes and acoustic attenuation characteristics of the straight-through perforated tube silencer. The results showed that smaller hole diameter or higher porosity lead to higher frequencies for (0, 1) mode when the porosity is lower than 40%, and then better acoustic attenuation in the middle frequency range; while the hole diameter and porosity have negligible effect on the (0, 1) modal frequencies when the porosity is higher than 40%. For the non-coaxial silencers, the plane wave cut-off frequency is the second modal frequency. The effect of perforated tube offset on the second mode frequency is not remarkable for the fixed hole diameter and porosity.
2012, Vol. 31 
