坎控底射混合流在新集水工模型中的试验研究

结合新集水利枢纽模型试验，针对其泄洪时水流佛氏数低且发生二次水跃的特点，在消力池尾部设置一定高度的跌坎后，水流过坎形成跌水与二次水跃的联合流态，即坎控底射混合流。通过对跌坎高度（共轭比）的试验比较研究了坎控底混流的运动规律、消能特性及其控制因素。试验结果表明，一次水跃后产生的坎控底混流能有效地改善下游流态及河床流速分布、提高消能效率，且在上下游水位差很小且佛氏数很低的条件下，共轭比对底射混合流的消能率大小起控制作用。

Study of Falling-sill Controlled Undershot Mixed Flow in Xinji Hydraulic Model Test

This article studies the model test of Xinji Hydro project. The Froude number of water is low and there is secondary hydraulic jump when flood discharging. The undershot mixed flow composed of hydraulic drop and secondary hydraulic jump is generated after setting up a falling-sill with a reasonable height at the empennage of the stilling pool. And then the motion law of falling-sill controlled undershot mixed flow, the characteristics of energy dissipation and its controlled factors is studied by test of different depth of falling-sills (conjugate ratio). The test results show that the undershot mixed flow which generated from the first hydraulic jump can significantly improve both the flow regime of the downstream and the flow velocity of the river bed, and increase the percentage of energy dissipation; conjugate ratio can also control energy dissipation efficiency of undershot mixed flow when the water head difference of upstream and downstream is small and the Froude number is much too low.