Assessment of RANS turbulence model performance in tight lattice LWR fuel subchannels

Reynolds-averaged Navier-Stokes simulations have been performed of the turbulent flow (Re = 48000) through a tight lattice (P/D = 1.194) subchannel typical of those found in nuclear thermal-hydraulic applications. A wide range of turbulence models (linear eddy-viscosity, non-linear eddy-viscosity and stress-transport) and the use of different near-wall treatments (low-Re, standard and analytical wall-functions) have been considered. The results demonstrate both the failure of the standard wall function approach in reproducing flows with significant near-wall convection and pressure-gradient effects, and the limitations of using linear eddy-viscosity approaches in flows with anisotropic effects. Although models utilizing low-Re near-wall approaches demonstrated superior overall performance, the analytical wall-function tested offers improvements over the standard 'log-law' based formulation.