琴键堰泄流水力特性与体型参数优化研究

In recent years, due to the climate change , the frequency of extreme floods becomes higher and the inadequate of flood discharge capacity comes to be an important factor in the risk of dam safety. The spillway risk comes also from the operation and management of the dam such as sluice gate failure. The Piano Key Weir (PKW) is a new type of nonlinear (labyrinth-type) weir using overhangs to reduce the footprint of the foundation and it can be directly placed on a dam crest. Together with its high discharge capacity under low heads and wider specific flow range, this geometry makes the PKW can be applied more widdly in hydraulic engineering and it can provide a free over flow solution with low cost and free security risk for dams. However, the Piano Key Weir is a new type of weir with complex flow patterns, furthermore, its geometry involves a lot of parameters, so that we have no sufficient understanding about its hydraulic characteristics and don not have general design guidelines. In this project, we intend to study the flow characteristics over Piano Key Weirs systematically, using the physical model experiments and three-dimensional numerical simulations. The research schemes will be designed by orthogonal rotation regression design method. We plan to reveal different flow pattern over PKW and its critical conversion features; analyze the feeding mechanism at different parts of crest , and its influence on the discharge capacity of PKW; investigate the influence of the geometric parameters on the discharge capacity,its sensitivity and optimization range; explore new geometrical improvement and establish a new method to evaluate the discharge effectiveness of the PKW . This study will not only has important theoretical significance for deepening the understanding of the hydraulic characteristics of the PK weir, but also will lay a solid foundation for the establishment of the design criteria for the PKW.

近年来，气候变化及人为致害因子导致极端洪涝灾害频发，泄洪能力不足及运行风险（如闸门故障）成为威胁大坝安全的重要因素。琴键堰是一种全新的迷宫堰型，上下游倒悬的设计使基座大为减小，可直接安置在混凝土坝的坝顶上，且适应单宽流量成倍增加，超泄能力更强，为各类大坝泄洪提供了一种经济安全的自由溢流解决方案。然而琴键堰流态复杂，体型参数多，对其水力特性的认识还很不充分，更缺乏通用的设计准则。本项目拟采用正交旋转回归实验法设计方案，通过实验与三维数值模拟，对琴键堰的泄流流态，体型参数，泄流能力进行较为系统的研究，揭示不同泄流流态及其临界转换条件，分析不同流态下溢流前沿不同部分的泄流机制及其对泄流能力影响的规律，探讨各几何参数对琴键堰泄流能力影响的程度、敏感性及优化范围；基于不同溢流前沿泄流机制不同的事实，采用叠加原理建立琴键堰泄流能力的表达式；根据不同泄流阶段泄流效率的差异，提出评价整个泄流过程整体效率的方法。本研究不仅对于深化琴键堰水力特性的认识具有重要的意义，也将为琴键堰设计准则的确立打下坚实的理论基础。

近年来，气候变化及人为致害因子导致极端洪涝灾害频发，泄洪能力不足及运行风险（如闸门故障）成为威胁大坝安全的重要因素。琴键堰是在迷宫式溢洪道的基础上改进的创新性堰型，它能在较小水头下有效提升泄流能力和泄洪效率，且基础长度小，可以直接放置在新建或已建坝的坝顶，被认为是大坝泄洪能力不足的安全有效且经济性很高的解决方案，在新建水库的有效库容优化方面和在病险水库的除险加固方面均有着广阔的应用前景。本项目首先按照原计划任务，通过物理模型实验与三维数值模拟，获得了琴键堰过流流场的精细结构，对琴键堰的泄流水力特性，关键体型参数和泄流能力进行了系统的研究。此外，根据国外研究最新动态，本项目进一步对琴键堰的辅助体型参数（如堰鼻形状和护栏墙的高度）和其下游的冲刷形态也进行了一系列的研究。物理模型试验和数值模拟结果揭示了不同水头工况下的泄流流态及各流型之间的临界转换条件；基于琴键堰各溢流前缘的泄流特性和对总泄流量的贡献，深入分析了各溢流前沿的泄流机制及其对总泄流能力的影响规律；探讨了各几何参数对琴键堰泄流能力影响的程度、敏感性及优化范围；并根据模型试验和数值模拟结果，拟合了标准琴键堰模型的多项式泄流式，并在此基础上增加了琴键堰的主要参数--上下游倒悬比，拟合了含倒悬比和相对水头的双精度琴键堰泄流系数，为琴键堰的设计和应用打下坚实的理论基础。