阶梯溢流面与WES曲面的衔接方式对宽尾墩+阶梯溢流坝+消力池消能工水力特性的影响研究

The energy dissipater of flaring gate pier combined with stepped spillway and stilling basin has been widely used in release structure which with high head and large flow. In order to increase aeration concentration of stepped surface, and ensure smooth transition for the flow, the connection forms between the stepped spillway and the WES surface often makes use of pre- aerator and transitional steps. Though the pre-aerator and transitional steps improved aerated condition and energy dissipation rate, the hydraulic characteristics of the dam surface also have been changed. At present, a lot of research for pre-aerator and transitional steps have been done since people began to recognize how importance the impacts were for the connection forms between the stepped spillway and the WES surface to flow condition, aeration and energy dissipation, energy dissipation, and the single-wide discharge. But researchers have not generated uniform explanation for the transitional forms of between the stepped spillway and the WES surface, as well as the combination of pre- aerator and transition steps. This research focuses on the influencing rule of connection forms between the stepped spillway and the WES surface to hydraulic characteristics in energy dissipater of flaring gate pier combined with stepped spillway and stilling basin. And to explore the reasonable connection forms, seek ways to improve the single- wide flow, which has certain significance to the development of hydraulic engineering for high head and large flow.

高水头大流量电站常采用宽尾墩+阶梯溢流坝+消力池的一体化消能方式，为了增大阶梯面掺气浓度，保证出墩水流平稳的过渡，工程应用中常在阶梯溢流坝与WES曲面间增设前置掺气坎和过渡阶梯。前置掺气坎和过渡阶梯增设虽然改善了阶梯面掺气条件，提高了消能率，但坝面水力特性也发生了变化。目前工程实践中已认识到阶梯溢流坝与WES曲面衔接方式对水流流态，掺气和消能、坝面空蚀空化及下泄单宽流量影响的重要性，也对前置掺气坎和过渡阶梯进行了大量研究和工程应用。但对阶梯溢流坝与WES曲面的衔接过渡形式及前置掺气坎和过渡阶梯的联合应用方式还没有形成统一认识，阶梯溢流坝与WES曲面衔接方式的系统性研究不够。本课题重点研究阶梯溢流坝与WES曲面衔接过渡段对宽尾墩+阶梯溢流坝+消力池一体化消能方式水力特性的影响规律，探讨阶梯溢流坝与WES曲面的合理衔接形式，寻求提高单宽流量的途径，对泄水建筑物向高水头大流量发展具有一定的意义。

高水头大流量电站常采用宽尾墩+阶梯溢流坝+消力池的一体化消能方式，为了增大阶梯面掺气浓度，保证出墩水流平稳的过渡，工程应用中常在阶梯溢流坝与WES曲面间增设前置掺气坎和过渡阶梯。工程实践中已认识到阶梯溢流坝与WES曲面衔接方式对水流流态，掺气和消能、坝面空蚀空化及下泄单宽流量影响的重要性。项目通过均匀台阶的阶梯溢流坝与WES曲面直接连接型式、前置掺气坎、过渡阶梯和阶梯溢流坝与WES曲面衔接过渡段等四种体型对宽尾墩+阶梯溢流坝+消力池的一体化消能方式的水力特性影响的水工模型实验和数值模型模拟研究，对比分析库水位、坝面坡度、挑坎和阶梯溢流坝面坡度、前置掺气坎、首级阶梯高度和台面角、圆角形和外凸式过渡阶梯、不同体型的过渡阶梯、掺气坎与不同过渡阶梯体型等对宽尾墩+阶梯溢流坝+消力池一体化消能方式水力特性的影响规律。通过实验和数值模拟结果的对比，我们得到，WES曲面与阶梯溢流坝的衔接过渡段中掺气坎对宽尾墩+阶梯溢流坝+消力池一体化消能方式水力特性的影响较大，其次是掺气坎后的首阶阶梯的大小，再次是首阶阶梯后可掺气空腔面积的大小，最后是首阶大阶梯后的阶梯突出坝面的距离。得到了结构合理的11.3°1m掺气坎+33.3mm×25mm首级大台阶+2个16.7mm×18.75mm阶梯构成的过渡阶梯为宽尾墩+阶梯溢流坝+消力池一体化消能方式中WES曲面与阶梯溢流坝的衔接过渡段。该体型衔接过渡段与原10°1m掺气坎+6个16.7mm×12.5mm阶梯构成的过渡阶梯的方案的消力池最大水深增大了2.92%，消力池最大时均压强增大了2.53%，最大临底流速减小了7.22%，消力池末端临底流速减少了29.55%，最大负压减小69.88%，空腔长度增加了55.56%，消能率增加了3.73%。项目得到的阶梯溢流坝与WES曲面的合理衔接形式，对泄水建筑物向高水头大流量发展具有一定的意义。