Simulation of Multiple Pass Perforated Tube Silencers Based on the Method of Characteristics

Abstract

Based on the method of characteristics, a time domain non-linear model for unsteady compressible flow is used to simulate the flow in multi-pass perforated tube silencers. In the present work, the flow in both two and three pass anechoically terminated silencers will be simulated for low sound pressure level excitation. The temporal solution is first transferred into the frequency domain using FFT, and then processed by the two-microphone technique in order to evaluate the transmission loss. Derivation of necessary one-dimensional equations, which are used to implement the method of characteristics along with the mathematical formulation of length corrections and different boundary conditions, are presented. Resorting to the white noise excitation, a significant reduction in the computational effort is achieved compared to the step-by-step frequency excitation. The paper uses data from previously published experimental and numerical work for the sake of comparison. A good agreement is verified for the frequency range where the one-dimensional assumption is justified.