台阶式溢流坝后消力池压强特性

本文通过物理模型试验,研究了台阶式溢流坝在3种坡度下消力池底板上的时均压强、峰值动水压强、脉动压强强度及其形成的特点,提出了计算时均压强的经验公式。研究表明,时均压强、峰值动水压强和脉动压强强度最大值出现在水流冲击消力池底板处,位于x/hk=1.2～2.5,其值随泄槽坡度和流量增加而增大,时均压强的yp/hk最大可达5.4,脉动压强强度可达其相应时均压强的80%,峰值动水压强与时均值的比值可达5～8倍。压强最小值位于x/hk=2.5～5.1之间,时均压强偶会出现负值。脉动压强优势频率在冲击区为4Hz～8Hz,水跃区2Hz～5Hz,跃后区一般在2Hz以下。

Pressure characteristics in stilling basin of stepped spillways

Through physical model tests,this work studies behaviors of pressures,i.e.time-average pressure,peak hydrodynamic pressure and pressure fluctuating intensity,on the stilling basin floor of stepped spillways under three different chute slopes,and puts forth empirical formula for calculation of average pressure.Results show that peak average pressure,peak hydrodynamic pressure and maximum pressure fluctuation occur at the jet nape impinging location x/hk=1.2~2.5.These peak values increases as the chute slope or flow rate increases.An average pressure peak of yp/hk=5.4,a hydrodynamic pressure peak of 5~8 times the average value,and a fluctuating intensity peak of 80% of average pressure,were measured.The lowest pressure appears around x/hk=2.5~5.1,and occasional negative values of average pressure may show up.The dominant frequencies of fluctuations are 4Hz~8Hz in impinging zone,2Hz~5Hz in hydraulic jump roller zone,and generally below 2Hz downstream of the hydraulic jump.