Self–Excited Oscillation Due to the Fluid Discharge Over a Flexible Weir (2nd Report, Excitation Mechanism of a Hydroelastic Mode)

The excitation mechanism of a self-excited oscillation due to the fluid discharge over a flexible werir was investigated both theoretically and experimentally. A new type of hydroelastic instability was discovered during test operations of the Super-Phenix LMFBR reactor in France. According to a recent report by Aita, this phenomenon includes two types of instability modes: one is the sloshing mode which means the oscillation of a weir associated with coupled sloshing modes of both feeding and restitution fluid collectors; the other is a hydroelastic mode which means the oscillation of a weir associated with fluid-shell modes. In this report, the excitation mechanism of a hydroelastic mode is discussed by calculating the excitation energy brought by discharge to the fluid-structure system. The theoretical results for the range of hydroelastic mode instability virtually agreed with the experimental data.