Modelling dissipative silencers using point collocation

Abstract

Dissipative silencers are widely used in ducts to attenuate broad band noise. Silencers may assume many different shapes and sizes, ranging from a relatively compact automotive exhaust silencer, to a much larger HVAC splitter silencer. To accommodate such a wide range of silencer geometries it is convenient to use numerical methods such as the finite element method, although for many silencers the use of a fully three dimensional approach may computationally be too expensive. A convenient alternative is to use a method known as point collocation which seeks to mesh only the cross-section of a silencer (assuming a uniform cross-section in the axial direction) and then numerically matches continuity conditions at discrete transverse locations over the inlet and outlet planes of the silencer. This paper examines the suitability of using point collocation to compute the transmission loss for a wide range of silencer configurations. The robustness and flexibility of the method is reviewed with a view to adopting this technique as a single, efficient, design tool for studying dissipative silencers of any cross-sectional shape and size.