消力池底板缝隙水流脉动压力频谱分析研究

Study on spectrum of fluctuating pressure under bottom slabs of stilling basins

水流脉动压力在缝隙中的传播是消力池板块失稳的主要原因。本文基于水体振荡模型的基本理论,分析了二元均匀流场板块底部与表面水流脉动压力频谱的转换关系。研究结果表明,板块底部缝隙中任意点与缝隙入口频谱转换系数并非一个常数,而是一个以频率为变量的周期函数。通过在水槽中的二元水跃实验对理论分析进行了验证,实测数据与理论分析吻合较好。文章进一步分析了固定流场中不同板块长度对缝隙内脉动压力强度的削减作用,指出了缝隙内脉动压力随板块长度增加的变化趋势,使用无量纲谱图能直观看出板块长度是否最优。试验成果对消力池板块尺寸的优选具有一定指导意义。

Transmission of fluctuating pressure in slab gaps is the major cause of slab instability. This paper analyzes the formulas for transform of a spectrum of fluctuating pressure on slab top surface into a spectrum of the gap underneath the slab. It is revealed that the transform function is periodic with its period depending on the length of gap and the velocity of eddy at the gap inlet. Verification shows that the theoretical results agree well with the measurements obtained in our model tests of two-dimensional hydraulic jump. An analysis on the effects of different slab sizes on pressure fluctuations under a given flow suggests that an optimal size can be easily found if dimensionless spectra are compared. The results presented in this paper are useful for design of stilling basin slabs.