The Prediction of Silencer Acoustical Performances by 1D, 1D-3D and quasi-3D Non-Linear Approaches G. Montenegro a , A. Onorati a , A. Della Torre a a Politecnico di Milano, Department of Energy, via Lambruschini 4, 20156, Milano, Italy Abstract The design of silencers for internal combustion (I.C.) engines is a key issue to attenuate or emphasize certain spectral components of tailpipe noise. The op- timization of complex shape silencing systems is generally a time-consuming operation, which must be carried out by means of concurrent experimental measurements and numerical simulations. This paper describes the develop- ment and application of different non-linear models: a coupled 1D-multiD model and a coupled 1D-quasi-3D model, to predict the silencer behavior in the time and frequency domains. Second order time and space discretization were adopted in the 3D and quasi-3D approaches, whereas specific coupling strategies were developed to realize the interface between them and the 1D model. In particular, since the 3D relies on a collocated grid discretization, a Riemann solver based method was developed to realize the coupling with the 1D code while a cell overlapping procedure was exploited to interface the 1D code with the quasi-3D method in order to fit with the pseudo staggered grid arrangement. Both a white noise and a single impulse boundary conditions have been imposed upstream of the pipe system to excite the wave motion. The integrated 1D-multiD and the 3Dcell approaches were applied to predict the transmission loss of reactive and dissipative mufflers in which the pressure Preprint submitted to Computer & Fluids June 13, 2014