跌扩型底流消能流态转捩及消能机理研究

Energy dissipator by hydraulic jump with vertical drop and sudden enlargement is a new type which is based on a typical energy dissipator. It has has wide application prospect in hydropower project. However, present researches are based on engineering for single type, or only study some basic hydraulic characters influenced on by vertical drop or sudden enlargement. In terms of energy declining mechanism, the results are few. Except that, the studies on flow pattern control are remain on the stage of qualitative analysis. In other words, the present results can not reflect the law of flow pattern transition and energy dissipation mechanism for energy dissipator. Present research will be aimed at energy dissipator by hydraulic jump with vertical drop and sudden enlargement, using theory analysis, model experiments and numerical simulation methods to study the hydraulic characters, which considering drop and enlargement at the same time. Through series experiments, the law of energy declining for jet with vertical drop and sudden enlargement is analysed, and the declining theory is built also. Based on the experimental and numerical results, the main and minor influence factors on pattern turning are confirmed. Comparative analysis on the degree of influence by single index or multi indexes is carried on, with building the quantitative relations between influence factors and flow pattern transition. It is also built the quantitative relations between upstream conditions and hydraulic indexes at downstream for energy dissipator by hydraulic jump with vertical drop and sudden enlargement, and the energy dissipation mechanism is revealed on different types condition. The studies will have a strong technological support for designing of energy dissipator, which will promote the use and development for this type better.

跌扩型底流消能工是一种建立在常规底流消能工基础上的新型消能工，在水电工程中具有较广阔的应用前景。但现有研究成果或是依托工程，研究体型单一，或是仅限于突跌或突扩一些基本水力参数的分析，射流能量衰变机理研究较少，同时流态控制研究还停留在定性分析上，不能系统反映跌扩底流消能工的流态转捩规律及消能机理。本项目将以跌扩型底流消能工为研究对象，采用理论分析、物理试验与数值模拟相结合的方法，同时考虑突跌和突扩的影响，开展系列研究，分析跌扩射流能量衰变规律，建立跌扩型底流消能射流能量衰变理论；确定流态发生转捩的主要影响因素和次要影响因素，进行单指标和多指标影响程度对比分析，建立影响因素与流态转捩之间相应的定量关系；分析消力池内水力学指标沿程变化规律，建立不同体型下跌扩底流消能相应指标定量关系式，揭示跌扩型底流消能工消能机理。研究成果可为消能工的设计提供有力的技术支持，将更好地促进该体型的应用及发展。

高水头、大流量的消能防冲问题是高坝建设中需要解决的一个重大技术问题，直接关系到整个泄水建筑物工程的安全与经济。跌扩型底流消能方式是一种新型消能方式，下游水流紊动剧烈，流态相当复杂。“跌扩型底流消能流态转捩及消能机理研究”在已有工程实地调研及试验研究成果的基础上，采用物理试验、数值计算及理论研究等手段，对跌扩型底流消能射流能量衰变规律及流态转捩规律等系列问题进行了研究，分析了水力指标沿程衰变规律，进而揭示了消能机理，为跌扩型底流消能的应用提供了理论依据与技术支持。具体研究成果如下：①以动量方程及连续方程为基础，提出了跌扩型底流消能共轭水深和消能率等的定量关系式，结合模型试验与数值计算结果，探讨了跌扩型底流消能流态的影响因素；②基于射流衰变规律和消能机理研究，分析了跌坎型底流消力池流态转捩与影响因素的关系，提出了有效控制消力池内流态的措施，改善了消力池临底水力学指标；③研究了不同体型下跌扩型底流消能工水力特性的变化规律，分析了突扩比、入流间距和跌坎高度等因素对消力池内漩涡运动的影响机制，进而揭示了其消能机理。