水利工程溢洪道底流消能水力特性分析

合理地选择溢洪道建筑物消能型式,是关系到整个水利工程安全与经济的重要问题.通过溢洪道设计规范进行消能方式水力学计算,结合物理模型试验对传统底流消能与跌坎型底流消能水力特性进行了对比分析,结果表明:传统底流消能在校核洪水下泄流量时,底流消能方水流进入消力池后产生一定程度的远驱式水跃,消力池消能主要位于消力池后部,消力池后部及出口水面壅高较大,且波动剧烈,没有形成相对稳定的消能水体,消力池消能效果不太好,需要增加消力池长度;跌坎型底流消能消力池底板高程降低1 m,但是临底流速较底流消能得到大幅度降低,池内水流扩散充分,剪切明显,消力池后段形成了稳定的水体,消能效果良好,出水渠内水流流态得到改善,不容易对消力池冲刷破坏.跌坎型底流消能空化数增大相对不容易发空蚀,可能避免消力池空蚀破坏,最大水跃位置向前移动7 m,水流不会冲击底板和尾坎,水流垂直溅起,因此消力池内流态稳定,雾化影响较小,具有适应性强,消能效率高、流态稳定等优点.

Analysis of hydraulic characteristics of spillway underflow energy dissipation in hydraulic engineering

Reasonable selection of energy dissipation type of spillway building structure is an important issue related to the safety and economy of the whole water conservancy project. The hydraulic calculation of energy dissipation mode is carried out by spillway design code, and the hydraulic characteristics of traditional underflow energy dissipation and sill type underflow energy dissipation are compared and analyzed by combining with physical model test. The results show that when the traditional underflow energy dissipater checks the discharge of flood, the flow of underflow energy dissipater will produce a certain degree of far drive hydraulic jump after it enters the stilling basin. The energy dissipation of stilling basin is mainly located in the back of stilling basin. The backwater of the back and outlet of stilling basin is high and fluctuates violently. There is no relatively stable energy dissipation water body. The energy dissipation effect of the stilling basin is not very good, so the length of the stilling basin needs to be increased. The floor elevation of the plunge sill type underflow stilling basin is reduced by 1 m, but the flow velocity near the bottom is significantly lower than that of the underflow stilling basin. The flow in the stilling basin is fully diffused and the shear is obvious. The stable water body is formed in the back section of the stilling basin, and the energy dissipation effect is good. The flow pattern in the outlet channel is improved, and it is not easy to scour and destroy the stilling basin. The increase of cavitation number of the bottom flow energy dissipation of the falling still type is relatively not easy to cause cavitation, which may avoid the cavitation damage of stilling basin. The maximum hydraulic jump position moves forward 7 m, the water flow will not impact the bottom plate and tail sill, and the water flow will splash vertically. Therefore, the flow pattern in the stilling basin is stable, the inference of atomization is small, and it has the advantages of strong adaptability, high energy dissipation efficiency and stable flow pattern.