泄水建筑侧墙与底板联合掺气减蚀水力特性研究

How to protect release works with high-speed flow against cavitation erosion is one of the key problems in the high dam constructions. Cavitation control by aeration is proved by a great of projects to be an important, a useful and an economical technique for preventing cavitation damage. Behavior, mechanism and application of air entrainment for cavitation damage control have been investigated for more than 60 years. However, severe cavitation damage happened due to complex mechanism of air entrainment. Under some special hydraulic and geometry boundary conditions, cavitation erosions may be occurred both on the sidewalls and on the bottom of release works. So the aeration facilities both on the sidewalls and on the bottoms of the discharge works should be explored to protect the concrete surface of the dischanrge works from cavitation damage. But until now, systematic research work on these problems is not reliable. The effects of air entrainment are related to many factors, including geometric parameters, hydraulic parameters and entrained air manners, especially for air entrained from lateral and bottom cavities after the sidewall and the bottom aeration facilities at the same time. The mechanism of how air entrained into the flow water in the lateral cavity is sure difference from that in the bottom cavity of the aerator on the bottom of the discharge works. .In this research project, the hydraulic characteristics of flow after the aeration facilities both on the sidewalls and on the bottoms of release works will be investigated by the experiment, theory analysis and numerical simulation in order to reveal the aeration mechanism on the sidewalls and the interaction with the bottom aerator and to reveal the difference between them. Satisfactory comprehensive hydraulic characteristics after the side and the bottom aeration facilities will be optimized. The results of this research project are expected to promote the development of the technology of cavitation control by aeration. This research project is of obvious realistic significance and theory value..The research work foundation and conditions that we already had will make this research project be completed smoothly.

防止泄水建筑物的空蚀破坏是高坝建设中的关键问题之一。掺气减蚀被大量工程实践证明是有效而经济的防空蚀破坏技术。在特殊的水力及边界条件下，不仅流道的底板而且边墙也会遭空蚀破坏。为避免泄水建筑物全过水断面受到空蚀破坏，必需采用侧墙和底板联合掺气减蚀措施。但是，目前缺乏这方面的系统而有效的研究。本项目拟通过试验、理论分析并结合紊流数值模拟的方法开展侧墙与底板联合掺气减蚀的水力特性研究，揭示侧掺气机理与底掺气的差异，研究侧掺气和底掺气设施联合作用时二者的相互影响及作用的基本规律、研究泄水建筑物侧墙和底部联合掺气的综合水力特性，获得三维或全断面良好的掺气水力特性，提高全断面掺气设施的有效性并探讨联合掺气设施的有效保护范围。研究成果对解决三维掺气减蚀技术难题及更好的应用该技术具有促进意义。研究项目具有较为重要的理论意义及应用价值。已初步具备的研究工作基础及条件可保证该研究项目的顺利实施。

水利工程中泄水建筑物在下泄高速水流时常会遭受空蚀破坏。掺气减蚀已被理论和大量的工程实践证明是一种相对简单、经济和行之有效的减蚀措施。在特殊的水流及边界条件下，不仅流道的底板，而且其边墙也会受到空蚀破坏。采用侧墙和底板联合掺气设施是避免泄水建筑物全过水断面遭受空蚀破坏的一种重要途径。由于底、侧掺气设施会相互影响，使得底侧联合掺气设施的掺气水流特性比单独的底掺气或侧掺气水流特性更为复杂。本项目研究主要采用理论分析、模型试验和数值模拟相结合的方法，对有压洞出口突扩突跌掺气设施和陡槽底、侧联合掺气坎的掺气水流特性进行研究。主要研究了突扩突跌掺气设施水流流态、临界工作水头及影响因素、底侧空腔长度及相互影响关系、过流底板和侧墙的脉动压力特性，水流掺气浓度分布规律以及底板和侧墙掺气保护长度。对明流陡槽，主要研究了自掺气水流特性、单独侧掺气坎和底掺气坎掺气水流特性、底侧联合掺气坎掺气水流特性，包括底、侧掺气空腔及影响因素、陡槽底板、侧墙壁面的时均压力和脉动压力特性。得出突扩突跌掺气设施后形成良好掺气水流流态的临界工作水头随明槽底坡的增大而减小。突扩宽度对底空腔长度有明显影响，而突跌高度对侧空腔长度几乎无影响。掺气设施后底板和侧墙的脉动压力特性随流动区域不同而发生变化，稳定区的脉动压力分布更接近于正态分布。侧掺气量和底掺气量在不同的流动区域对水流总掺气量的贡献率不同，且随流量的变化而发生变化。陡槽中，由与单独底坎和单独侧坎构成的联合掺气坎的保护长度为单独底坎的1.1倍、为单独侧坎的1.8~2.0倍。紊流数学模型数值模拟结果与试验结果吻合较好，表明紊流数学模型能较好的模拟掺气水流特性，但掺气浓度的模拟结果误差相对较大，数值模拟方法还需进一步改进。本研究所得结果对更好的了解和揭示底侧联合掺气设施的掺气水力特性有较好的促进作用，也可为底、侧联合掺气设施更好地服务于实际工程提供有益的借鉴。