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

Serge Delafontaine (1)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)

The CALIFS study is part of a program that will combine hydraulic tests on 5 × 5 mock up of a fuel rod bundle and CFD simulations to evaluate the fluctuating fluid forces exerted at high Reynolds number in PWR fuel rod bundles. In this study, we consider a first intermediate geometry of the calibration bench, implementing one single rod and one grid equipped with mixing vanes. 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.

Mots clés: Fuel assembly of pressurized water reactor; Fluid-structure interaction; Pressure load on fuel rodsTurbulent flow; Computational fluid dynamics (CFD)

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

Serge Delafontaine. Simulation of unsteady fluid forces on a single rod downstream of mixing grid cell. Nuclear Engineering and Design, 2017, 332, pp.38-58. ⟨10.1016/j.nucengdes.2018.03.010⟩. ⟨cea-02418718⟩