On acoustics and flow behaviour of the perforated mufflers

Recent advances in modeling and accurate performance prediction have led to the development of simulation methods for practical muffler components in commercial design. Muffler designers need simple, fast and accurate modeling tools, especially in the preliminary design evaluation stages. Perforated pipes are used as primary elements in mufflers which are expected to have a high-level attenuation for a given volume. Perforated pipe elements are used with other elements as a series or parallel connection. In a wide band commercial combined muffler, perforated pipes can take a place to generate cross flow, grazing flow and dissipation surface. Although in narrow band mufflers they are used as a resonator. Perforation created by drilling holes on pipes is commonly used application for mufflers. Especially their resistance and resonance effects are utilized to reduce low frequency noise. On the other hand, these perforated structures are most important source of backpressure, which limits muffler design due to resistance against flow. In this study, flow and acoustic properties of perforated mufflers are investigated and compared. Study is carried by using analytical, numerical and experimental methods.