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

Abstract

A new approach for calculating flow domains with embedded monoliths is presented, focusing on a system suitable for an automotive converter. Using appropriate boundary conditions, the monolith itself can be excluded from the CFD computational domain, leaving two mapped computational domains upstream and downstream of the monolith. The resulting method enables more detailed results of the downstream flow profile than afforded by the commonly used porous body approach for simulating a monolith, but without the complexities of a full 3D calculation of the entire domain, including the monolith. The present approach was validated with experimental flow data from the literature collected with a prismatic (planar) monolith with approximately 4500 channels. Sensitivity studies were performed to check the influence of the downstream turbulence model, inlet turbulence boundary conditions, and spatial discretization schemes. RANS turbulence models (k-ω SST and k-ε) generally predict the experimentally measured flow profile downstream of the monolith although the transition to turbulence cannot be reproduced correctly. Currently, LES is the best approach for adequately describing the characteristics of flow downstream of monoliths.