Space and energy-based turbulent scale-resolving simulations of flow in a 5 × 5 nuclear reactor core fuel assembly with a spacer grid

Highlights: • Turbulent flow in a 5x5 Pressurized Water Reactor fuel bundle lattice, with spacer grid and split type mixing vanes. • Application of Space and Energy based turbulent scale resolving simulations, Large eddy Simulation and Partially Averaged Navier-Stokes equations. • Possibility to use energy based filters, for incompressible Navier-Stokes equations, as bridging type modelling between RANS and LES. • Partially Averaged Navier-Stokes equations can have comparable LES resolution, with a proper choice of the cut-off energy filter, without requiring as much computational cost as LES. • Partially Averaged Navier-Stokes equations modelling can be adopted in any CFD code equipped with RANS models. - Abstract: The partially averaged Navier–Stokes turbulence model, which is a bridging model between the Reynolds averaged Navier–Stokes model and direct numerical simulation, is capable of directly resolving the turbulent scales of interest by filtering the Navier–Stokes equation using turbulent kinetic energy and dissipation based filters. In this study, comparison is made between the partially averaged Navier–Stokes and large eddy simulation models, with emphasis on the mean flow characteristics and spatio-temporal turbulent flow structures. The results show that the partially averaged Navier–Stokes modeling produces results comparable to those of large eddy simulation when the appropriate cut-off energy filter is chosen. The test case involves simulating flows in a 5 × 5 fuel rod bundle configuration with a spacer grid at a Reynolds number of 14,000. The simulation results are compared with particle image velocimetry data obtained from the scientific literature.