Numerical transmission loss calculations for perforated dissipative mufflers containing heterogeneous material and mean flow

Antoine Antebas , Francisco Denia , Eva Sánchez-Orgaz , Francisco Fuenmayor

In this work, a finite element approach has been developed to study the acoustic behaviour of perforated dissipative mufflers with heterogeneous absorbent material and the presence of mean flow. The heterogeneous properties can appear, for example, during the manufacturing processes of the dissipative muffler or due to the flow of soot particles within the absorbent material. A uniform mean flow is considered within the central passage and a perforated duct separates this flow from the outer dissipative chamber. First, the finite element method is applied to the wave equation for a stationary non-homogeneous medium (outer chamber) and a moving homogeneous medium (central passage). The absorbent material is characterized as an equivalent fluid, by means of its complex density and speed of sound. To introduce the variations of these properties within the material, a coordinate-dependent function is proposed for the filling density. This yields a heterogeneous resistivity, which produces spatial modifications of the equivalent properties. The acoustic impedance of the perforated duct has been also modified to include the heterogeneous properties of the dissipative medium. Finally, the effect of the mean flow Mach number, filling density and porosity of the perforated duct on the acoustic attenuation of the muffler is studied.

Mots clés: muffler; finite element approach; heterogeneous absorbent material; mean flow

Domaines: Acoustique [physics.class-ph]

Antoine Antebas, Francisco Denia, Eva Sánchez-Orgaz, Francisco Fuenmayor. Numerical transmission loss calculations for perforated dissipative mufflers containing heterogeneous material and mean flow. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00810633⟩