Numerical Simulation Using Realizable k-e Turbulence Model of Jet Flow Mixing Within Rod Bundles

In this investigation, a steady state simulation of jet mixing in a rod bundle with varied jet Reynolds numbers was performed with CD-Adapco’s Star-CCM+ computational fluid dynamics (CFD) code utilizing the realizable k-ε turbulence model and two-layer y+ wall treatment. The goal of the work is to investigate the ability of the realizable k-ε turbulence model to predict phenomena expected in the exit plenum of the prismatic gas cooled reactor as well as provide a benchmark for future numerical investigation into the validity of certain turbulence models for rod bundle simulation. Numerical results were qualitatively verified against available experimental data [6]. Two injection sites were present in the rod bundle with impingement of the jets on the lower plane of the domain. The Reynolds numbers specified for the inlets varied between 6,300 and 12,700 for different cases. A mesh of over four million polyhedron cells was generated to capture critical flow characteristics within the domain. Polyhedral cells were chosen for this application because they provided a better quality mesh and reduced the total number of cells necessary to achieve accurate results [4]. The simulations carried out were defined as having reached a converged solution when all residuals reduced to less than 10⁻⁵. The simulation of the flow in the rod bundle was successful in providing insight into locations of some key recirculation zones and the dependence they have on inlet conditions. The comparison between numerical and experimental results showed similar key flow patterns as well as aided in possible points of focus for future investigation. The information obtained and conclusions drawn will be critical in future numerical benchmarks in this area of research.