Self-Excited Sloshing Due to the Fluid Discharge over a Flexible Weir: 1st Report, Excitation Mechanism of Instability in the Rectangular Model

This paper presents an analytical model for the fluid-elastic instability as observed in Super-Phenix-1 LMFBR. This fluid-structure system is constituted by the flexible cylindrical weir and adjoining annular fluid plenums, and the fluid is discharged from the upstream plenum to the downstream plenum over the flexible weir. In this report, to clarify the mechanism for instability, we analyzed the case in which the rectangular reservior was divided into the upstream and the downstream plenums by a flexible plate weir. The characteristic equation of the system is derived. The effects of the discharged fluid on the downstream plenum sloshing and the effects of the fluid level difference between the upstream and the downstream plenums are examined, and the mechanism for instability is discussed.