Investigation of Fluid Structure Interaction in Thin Fluid Gaps - Comparison Between CFD and Experiment.

Abstract

The paper concludes on the potentiality of CFD for this kind of fluid structure interaction.In nuclear reactors, structures separated by thin fluid gaps are often encountered (e.g. fast breeder reactor core, ...). The knowledge of fluid forces effects on those neighboring structures is of first importance for vibration or seismic issues since it modifies oscillation frequencies and their damping. This paper presents a numerical modeling of the fluid structure interaction occurring during the tilting of a rigid body surrounded by thin water gaps and maintained by a return spring. On the one hand, the oscillations of the structure (and especially their frequency and damping) are computed in three configurations : only expanding and compressing gaps, with lateral by-pass flow, with bottom by-pass flow. On the other hand, a mock-up, representative of the most complex configuration, is set up and provides measured displacements.The calculation of fluid structure interaction by the Star-CD CFD code is first validated for the simplest configurations with analytical formulations. The case involving lateral and bottom by-passes is then positively compared with the experimental measures.