Investigation of pressure loss and velocity distribution in fuel assemblies with wire-wrapped rods by using RANS and LES with wall functions

Abstract Hexagonal assemblies of wire wrapped fuel rods were analyzed experimentally at Texas A&M University. CFD analysis with LES and RANS (SST k-ω) of a 61-pins experiment have already been published by using wall resolved meshing. These results are compared in this study to CFD calculations with wall functions, more precisely RANS (k-e) and LES. The presented comparison will be used as reference result in the design of RANS based models for the reactor core of sodium cooled fast breeder reactors, since the next generation core models developed at CEA will use CFD models with wall functions. It is shown that the velocity profiles of the analyzed turbulence models are in reasonable accordance to the experiment and among each other. However, RANS with wall functions overestimates the pressure loss in wire wrapped rod bundles.