高扩散低收缩差动挑坎Ⅱ：收缩比对射流特性及冲坑的影响实验研究

Allotypic hybrid type flip bucket. Ⅱ. Effect of contraction ratio on hydraulic characteristics and local scour

高扩散低收缩差动式挑坎高坎顺水流扩散,低坎顺水流收缩,在空间上形成差动射流,低坎收缩比是其射流特性的一个重要影响参数,本文通过模型实验,对该型式挑坎的高低坎分流规律、高低坎坎内压力分布、射流挑距及下游最大冲坑深度进行深入研究,得出收缩比的改变对其水力特性的影响规律及估算公式。

For the allotypic hybrid type bucket, the contraction in its lower bucket and diffusion in its upper bucket cause the jet flows to cross and impact each other, so the contraction ratio of lower bucket is a key parameter to determination of the jet characteristics. Systematic model tests of this bucket were conducted under different contraction ratios to examine the variations of flow-diversion ratios of the upper and lower buckets, the pressure distributions in these buckets, etc. This paper establishes empirical formulas for estimation of various jet characteristics under different contraction ratios, and demonstrates the variations of jet trajectory length and local scour depth.