Wall-resolved LES and Low-Reynolds Number URANS combined to an Arbitrary Lagrangian Eulerian approach for Predicting Water Cross-Flow Induced vibrations of a Single Flexible Tube in a Normal Square Tube Array

In the context of nuclear engineering, Flow-Induced Vibration (FIV) in steam generators can lead to mechanical damage, responsible for safety issues and significant maintenance costs in Nuclear Power Plants (NPPs). In the framework of the Vibration ImpaKt In Nuclear power Generation (VIKING) consortium, Wall-Resolved LES (WR-LES) and Low-Reynolds Number UnsteadyRANS (LRN-URANS) combined to an Arbitrary Lagrangian Eulerian (ALE) approach have been used to predict FIV of a Single Flexible Tube in a Normal Square Tube Array. The pitch-to-diameter ratio is P/D=1.44. The cylinder motion uses a mass-spring-damper model, and a strong two-way coupling is performed. In all cases, the flow is fully turbulent, the computations are 3D and the transverse length is equal to 2D with periodic boundary conditions. WR-LES is performed on a restricted computational domain containing 3x7 tubes using a very fine mesh with a gap velocity of 1.5 m/s corresponding to a gap Reynolds number of 33 000. 3 corresponds to the number of tubes in the stream-wise direction for which a periodic boundary condition is applied. LRN-URANS are performed on the full 7x7 configuration at 1.5 m/s and 2.5 m/s. The LES is used as reference results for the low gap velocity. A strong dependency to the URANS model and the numerical options is highlighted. It is still not possible do discriminate the models but the advanced Eddy Viscosity Model (the BLv^2k) and the second moment closure (EB-RSM) seem to exhibit a more satisfactory qualitative behavior. Finally, the presence of a bifurcation in the BLv^2k computations is shown.