&nbsp;&nbsp;The joint CEA-EDF-EPRI project is designed to produce accurate thermal-hydraulic experimental data on 5x5 rod bundles at PWR conditions. The dataset includes single-phase pressure drop, flow field (axial velocity), wall temperature and thermal mixing in adiabatic and heated conditions obtained from experiments carried out in MANIVEL and OMEGA loops. This study presents the CFD modeling of the adiabatic rod bundle test (MANIVEL) with a Simple Support Grids (SSG) at a Reynolds number of 100000.&nbsp;NEPTUNE_CFD was used for all CFD simulations with RANS turbulence models. Calculations are carried out on grid using a one block fully hexahedral mesh. To reduce the computational power requirements, the computational domain is limited to one span with SSG. The inlet is a fully developed turbulent flow obtained using periodic computations. The periodic computations are based on the same momentum sources which assure a constant mean axial mass flow rate with periodic conditions in axial direction but applied on two different domains. The two different domains represent respectively an inlet box (rod bundle without SSG with a height of few hydraulic diameter based on sub-channel) and one span with SSG (span box).&nbsp;This axial periodic boundary condition is used to impose realistic flow conditions at the inlet of the test section. The mean axial velocity distribution at different localization along the SSG downstream flow and pressure drop are compared with measurements. The influence of the type of periodic inlet conditions (inlet box or span box) is negligible on pressure drop, both underestimate the pressure drop. Significant discrepancies about the mean velocity distributions are observed between the two types of periodic inlet conditions. The influence of the height of inlet box is evaluated.&nbsp;Results of the span box&nbsp;seems to be in better agreement according to the reference experimental data. For the span box inlet condition, the evolution of axial flow field along the grid wake is well reproduced with variation amplitudes, which are closer to the experimental axial velocity profiles. Sensitivity studies were performed on mesh with a total number of cells between 1 to 4 million per span and turbulence models (RANS k-epsilon, k-epsilon linear production).&nbsp;The influence of turbulence models is negligible.&nbsp;The influence of SSG is not negligible and is still present downstream. The application of periodic conditions generated on one span with SSG seems to be more appropriate with the better agreement with experimental data.&nbsp;&nbsp;&nbsp;

Influence of Inlet Turbulent Flow Generated by Periodic Computations on the Pressure Drop and Axial Velocity Distribution Predictions

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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