Using CFD flow fields to inform acoustic finite element models of complex mufflers with thermal and flow effects

Many actual muffler systems with complex geometry have large temperature variations and large variations in the flow field under normal operating conditions. Often perforated regions and other complex design elements complicate the flow patterns. The temperature and flow strongly affects the acoustic performance and these parameters must be addressed in acoustic models to accurately predict the performance of complex muffler designs. The temperature variation and the time-average flow patterns can be predicted with computational fluid dynamics (CFD) simulations. This paper describes an automated process for using an open source computational fluid dynamics (CFD) solver to compute the temperature variations and flow field. These results are then used in an acoustic finite element (FE) model to predict the acoustic performance of the muffler. A validation case study demonstrating the process to obtain accurate muffler predictions by chaining a CDF prediction to an acoustic FE prediction is presented. The model predictions are compared with some simple experimental results demonstrating the accuracy for a muffler with nonzero mean flow and perforated elements.