3D EFFECTS IN FLUID FLOW DURING 2D VIBRATIONS: EXPERIMENTAL ANALYSIS OF FSI FOR AN ENCLOSED HEXAGONAL ASSEMBLY

摘要

The purpose of this study is to improve the knowledge about the core behavior of a sodium fast breeder reactor (Na-FBR) through the fluid-structure interaction analysis during vibrations of short time scale (shutdown of Phenix reactor) as well as long time scale (earthquakes for ASTRID Project). We designed a test-rig, PISE-1a, composed by one hexagonal assembly enclosed by an hexagonal containment with a narrow gap. The experimental test-rig PISE-la is used to determine the dynamic characteristics of the assembly, to calibrate instrumentation and for validating our numerical model. Free vibration experiments in water allow to assess the added mass and added damping effect on the frequency. The fluid flow is affected by a 3D effect - named down-stroke flow - at the top and the base of the assembly. This effect produces a higher frequency than the 2D theoretical value. Investigation on this phenomena are provided by PIV methodology, which allows to show the displacement of the fluid as predicted by the theoretical analysis.