A sub-structuring approach, along with a unit cell treatment, is proposed to model expansion chamber silencers with internal partitions and micro-perforated panels (MPPs) in the absence of internal flow. The side-branch of the silencer is treated as a combination of unit cells connected in series. It is shown that, by connecting multiple unit cells with varying parameters, the noise attenuation bandwidth can be enlarged. With MPPs, the hybrid noise attenuation mechanism of the silencer is revealed. Depending on the size of the perforation hole, noise attenuation can be dominated by dissipative, reactive, or combined effects together. For a broadband sound absorption, the hole size, together with the perforation ratio and other parameters, can be optimized to strike a balance between the dissipative and reactive effect, for ultimately achieving the desired noise attenuation performance within a prescribed frequency region. The modular nature of the proposed formulation allows doing this in a flexible, accurate, and cost effective manner. The accuracy of the proposed approach is validated through comparisons with finite element method and experiments.
As is known to all, there always exists the numerical dispersive effects of the standard finite element (FE) for the wave propagation problems and the corresponding FE solutions are usually unreliable in relatively high frequency range. In this work, a coupled “FE-Meshfree” element based on triangular mesh is introduced to reduce the dispersion effects for wave propagation problems. In this coupled element, the standard FE nodal shape functions are combined with the meshfree nodal shape functions to give a new hybrid nodal shape functions. As a result, both the individual advantages of the FE technique and the meshfree technique are strengthened by the present hybrid method. Through the dispersion analysis for the wave propagation problems, it is found that this coupled “FE-Meshfree” element could significantly reduce the numerical dispersive effects and it also have a higher tolerance to the mesh distortion than the other existing elements, hence the present method is quite promising to handle the general wave propagation problems in practical engineering application.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.