Analysis of Self-excited Sloshing Caused by the Fluid Discharge over the Flexible Weir Including Nonlinearity

在法国示范快增殖堆超级凤凰一号上，在试验运行期间，观测到了柔性堰上方的流体排放引起的圆柱壳自激振动的两次振动。第一种是晃动耦合振动，后者称为流体弹性振动，本文提出了超级凤凰ILMFBR的晃动耦合振动分析模型。这种流体-结构系统由柔性堰和相邻的流体真空室组成，流体通过柔性堰从上游真空室排放到下游真空室。推导了堰在下游晃动频率下的系统特征方程，重点研究了矩形柔性板和两个柔性柱面堰的高阶晃动耦合振动。从理论和实验两方面分析了上下游真空室液位差和堰面刚度的影响，并对其失稳机理进行了详细的探讨。结果表明，流量和上下罐液面高度差对高阶模式不稳定性的影响也可以用所提出的解析模型来描述。

Two rypes of self-excited vibrations of a cylindrical shell caused by the fluid discharge over the flexible weir were observed in French demonstration fast breeder reactor, Super Phoenix-1 during test operations. The first type is a sloshing coupled vibration and the latter is so called a fluidelastic vibration.In this study, an analytical model for the sloshing coupled vibration as observed in Super-Phoenix-ILMFBR is proposed. This fluid-structure system is constituted by the flexible weir and adjoining fluid plenums and the fluid is discharged from the upstream plenum to the downstream plenum over the flexible weir. The characteristic equation of the system is derived for the case in which the weir vibrates at the frequency of the downstream sloshing.In this research project, special attentions were made with higher mode sloshing coupled vibrations with the case of a rectangular flexible plate and with the case of two flexible cylindrical weirs. The effects of the fluid level difference between the upstream and the downstream plenum and weir rigidity are examined both theoretically and experimentally and the mechanism for instability is discussed in detail. As a result, it was found that the effects of discharge flow rate and the liquid height difference between the upper and lower tank on the higher mode instability can also be described by the proposed analytical model.