Sound Transmission through Perforated Absorbing Mufflers with Flow

Absorption materials are frequently used in modern mufflers, which often are constructed with muffler chambers separated by perforated elements. The present study considers acoustic characteristics of perforated dissipative mufflers in the presence of uniform or non-uniform mean flow, which strongly affects the acoustic characteristics of the muffler. The flow dynamics can be predicted with Computational Fluid Dynamics (CFD) simulation. An automated process for using an open source Computational Fluid Dynamics solver to compute the flow field is presented. The CFD results are then used in an acoustic Finite Element (FE) model to predict the acoustic performance of the perforated absorbing muffler. Validation case studies demonstrating the process to obtain accurate muffler predictions by chaining a CFD prediction to an acoustic FE prediction are presented. The model predictions are compared with some experimental results demonstrating the accuracy of the prediction for a muffler with non-zero mean flow, perforated elements and porous materials.