Simulation of unsteady fluid forces on a single rod downstream of mixing grid cell

This article provides an extensive analysis of the capabilities of CFD to estimate the fluctuating fluid forces exerted by the turbulent flow with high Reynolds inside a fuel rod bundle with mixing grids. It benefits from high accuracy experimental results obtained through an original device developed at CEA2 and providing a direct measurement of the fluctuating pressure on the surface of the rods, allowing the characterization of the turbulence scales and effects close to the walls and therefore establishing a valuable data of reference for the analysis of turbulence in fuel assemblies. The validation of CFD simulations is very important in order to then assess the turbulent excitation forces, more particularly in areas of great turbulence not accessible to measurements, for example in the feet of the assemblies.