CFD-Modeling of fluid domains with embedded monoliths with emphasis on automotive converters

•New approach for calculating flow domains with embedded monoliths.•Domain coupling allows exclusion of monolith and usage of different models in domains.•Approach works perfectly and leads to valuable results.•RANS modeling leads to good results but transition behind monolith cannot be predicted.•LES yields all details of flow and captures transition from laminar to turbulent flow.