Computational approach for the acoustic modelling of large aftertreatment devices with multimodal incident sound fields

The influence of multimodal incident sound fields on the acoustic behaviour large aftertreatment devices incorporating a monolith is modelled and analysed in detail. analytical mode matching method applied to compatibility conditions three-dimensional at device geometric discontinuities, leading computation complex wave amplitudes all subdomains involved corresponding transmission loss. To have realistic model, propagation must be considered inlet/outlet ducts chambers, while one-dimensional has assumed along small capillaries (such catalytic converters particulate filters); therefore, can replaced by plane four-pole transfer matrix from an acoustical point view. On other hand, for inlet such as those found heavy-duty off-road engines, usual models with excitation are not accurate since onset higher order modes duct expected frequency range interest. Therefore, variation attenuation performance likely occur depending these modes, similar results previously case dissipative silencers. Results presented three different field hypotheses: equal modal amplitude, power energy density. A relevant test problems current investigation.