Wall-Resolved LES and URANS simulations of an axial flow on a cantilevered rod at a moderate Reynolds number

In the context of nuclear engineering, Flow-Induced Vibration (FIV) of fuel rods can lead to mechanical wear, which can be responsible for safety issues and significant maintenance cost in Nuclear Power Plants (NPPs). In the framework of the Vibration ImpaKt In Nuclear power Generation (VIKING) consortium [1], preliminary wall-resolved Large Eddy Simulation (WR-LES) of cantilevered rods experiments have been performed at a Reynolds number equal to 60 000, with both blunt and curved rod ends. The meshes are made of 370 and 400 million hexahedra, respectively. The standard Smagorinsky model with the Van-Driest wall damping function has been used. The flow statistics and the mechanical stresses exerted over the rods are investigated, a peak of radial stresses fluctuations is observed at the rod's tip and in the recirculation zone for the curved and blunt ends, respectively. Then, WR-LES results are compared to those obtained with URANS simulations. Although k − ω SST and Elliptic-Blending Reynolds Stress Model (EBRSM) did not capture any stresses fluctuations on the curved end configuration, mean velocity and Reynolds stress profiles are in fairly good agreement with the WR-LES. With the blunt end configuration, the fluctuations captured by URANS have lower magnitude than the one predicted by WR-LES. Furthermore, the recirculations predicted downstream of the tip are longer, in particular with the EB-RSM. These CFD simulations aim at paving the way for both one-way and two-way coupling FSI simulations using ALE (Arbitrary Lagrangian Eulerian) in the context of the Go-Viking (Gathering expertise On Vibration ImpaKt In Nuclear power Generation) European project [2].