Benchmark simulation of the flow-induced vibrations for nuclear applications

Abstract

This study investigates the computational modelling of flow-induced vibrations of cantilever rods subjected to turbulent axial flow at operating conditions relevant to those of fuel rods of pressurized-water-cooled (PWR) nuclear reactors. The aim is to assemble all the modelling elements needed for a cost-effective and thus URANS-based (Unsteady Reynolds Averaged Navier–Stokes) modelling strategy, employing high-Reynolds-number models of turbulence. This objective is pursued through three stages. First, we investigate the numerical FSI (Fluid–Structure Interaction) strategy adopted, through the computation of flow-induced vibration of an elastic plate subjected to axial laminar flow. We subsequently assess the suitability of URANS models through computations of turbulent flow over a forward-facing step, for which measurements of the fluctuating wall pressure are available. On the numerical side, these explorations led to adopting a two-way FSI strategy, using a single finite-volume solver, with the Arbitrary Lagrangian–Eulerian (ALE) approach, high order convective discretization schemes and Laplacian smoothing for the displacement of the mesh in the fluid domain. On the physical modelling side, they resulted in the use of high-Reynolds-number Reynolds stress transport models. The resulting modelling strategy is subsequently validated against the experimentally investigated case of a steel cantilever rod caused to vibrate through exposure to turbulent axial flow. The resulting comparisons show that for the first time, to our knowledge, both the frequency and the amplitude of the flow induced vibrations of this case, have been reproduced with good accuracy.