Studies on Substructure FMBEM and Direct Mixed-body FMBEM for Acoustic Performance Prediction of Reactive Mufflers

Due to the advantage of fast computation and drastic memory saving in solving the large-scale problems, the FMBEM has been developed rapidly in recent years. But it is hard to be employed directly to the acoustic computation of mufflers with complex structures (such as mufflers with extended inlet/outlet tubes or perforated tubes). Two approaches for FMBEM (the substructure FMBEM and the direct mixed-body FMBEM) are investigated and applied to predict the acoustic performance of mufflers in the present paper. For the substructure FMBEM, the interior acoustic domain is divided into several subdomains first, and then the FMBEM is applied to each domain. The direct mixed-body FMBEM may deal with the muffler with complex internal geometry without dividing subdomains, which is achieved by summing up all the integral equations in different zones and then adding the hypersingular integral equations at interfaces. The transmission loss of expansion chamber mufflers with extended tubes are predicted by using the two approaches and verified by the experimental data. The computational time is compared, and the computational accuracy and efficiency are discussed for the two approaches.