Comprehensive Verification and Validation of 2D and 3D RANS Turbulence Models in the Mixing Region of Three Parallel Channels Across Diverse Reynolds Numbers

Abstract

This research assesses the feasibility and effectiveness of utilizing Reynolds-Averaged Navier-Stokes (RANS) models to precisely ascertain the velocity profiles within the mixing region formed by the convergence of three parallel channels. In this study, the geometry of these channels is thoroughly analyzed across three distinct cases of inlet velocities, encompassing laminar, turbulent, and transitional flows, to provide a comprehensive understanding of the dynamics involved. The outcomes of this analysis will also contribute to bolstering the initial design phase for the replacement reactor at the National Institute of Standards and Technology (NIST), specifically the NIST Neutron Source (NNS). OpenFOAM v10 serves as the foundational platform for analyzing three distinct RANS turbulence models. Employing the PIMPLE algorithm, this study integrates and examinses the K-Epsilon Relizable, K-Epsilon, and KOmega SST turbulence models in its comprehensive analysis. Parameters such as velocity, pressure, vorticity, turbulent intensity are analyzed in comparison to experimental data recorded. Further, a Grid Convergence Study is performed to obtain numerical uncertainties for all models. The K-Omega SST model demonstrated superior performance compared to the other three models tested, delivering results the most closely align with the experimental data within the scope of RANS modeling. Nonetheless, significant discrepancies in transient validation highlight the limitations of RANS models in accurately simulating highly turbulent crossflow systems.