曲线型局部超高阶梯溢洪道的水力特性

中文摘要: 针对在高弗劳德 Fr、大流速的来流下，曲线型光滑溢洪道的凹岸水位严重超高，凸岸出现底板露底，进入消力池的水流流态恶劣等不良水力现象，提出一种曲线型局部超高阶梯溢洪道。该溢洪道内布置多级阶梯，每级阶梯的凹岸和凸岸底部高程不同，且凹岸高于凸岸。利用水工模型试验和3维数值模拟方法详细研究水力特性。试验依托于某水库的岸边溢洪道工程，数值模型基于RNG “ k-ε”紊流模型和VOF法。与试验测量的阶梯溢洪道沿程流速、水面线分布等数据比较表明，数值模型的可靠性和准确度满足工程计算要求。通过试验分析光滑和阶梯溢洪道内的水流流态，验证了该溢洪道在工程中应用的可行性。从3个特征横断面水面线、流速分布，以及第Ⅱ特征断面所处的阶梯平台、凹凸岸边墙和中轴线沿程流速矢量、压力分布结果可以看出，横断面的流速、水深分布趋于均匀，凸岸底板的露底现象消失，岸边的折冲水流被极大削减；负压区出现在凹岸边墙、竖立面和阶梯平台形成的3维区域内，范围较小；阶梯平台上存在横向水流，与主流共同形成3维消能区，明显加强沿程水流能量耗散，入池流速得到减缓，平稳下泄进入消力池。在曲线型溢洪道内布置局部超高阶梯能成功解决大流速、高弗劳德数急流条件下出现的恶劣流态，增加能量损失，但需要结合前置掺气坎解决空蚀空化问题。
Abstract:At high Froude number ( Fr) by large flow velocity, the water level along the concave bank of a curved smooth spillway is extremely high, and the bed of the convex bank will be exposed, and the flow status in the basin pool is poor.These poor hydraulic characteristics pose a serious threat to the project. A new curved spillway was proposedto improve the flow regimein a bend. The multistage steps werearranged in the spillway, and the bottom bed elevation of each step along the concave bank was higher than that along the convex bank.The design was verified by the hydraulic model test, and the hydraulic characteristics were studied in detail based on the three-dimensional numerical simulation.The hydraulic model test was based on a realspillway project of a reservoir,and the three-dimensional numerical model employed the RNG " k-ε" turbulence model and the VOF method.The simulationwas compared with the experimental measurement to verify the reliability and accuracy of the numerical model.The position of the mainstream zone was analyzed by using the water surface line and velocity distribution at three representative cross sections. For Section Ⅱ, the velocity vector and pressure distribution were analyzed for understanding of flow patterns and cavitation erosion in the spillway. The energy dissipation effect was analyzed according to the energy dissipation standard. The results show that the flow velocity and water depth of the cross section tend to be uniform, and the negative pressure zone is mainly located in the small triangle area formed by the wall, the vertical plane and the step surface. In addition, the energy dissipation of the flow is obviously strengthened along the path, and the deflected flow near the bank is greatly reduced, and the water flows smoothly into the pool. Combined with the pre-aerator, the problems of aerial drainage and energy dissipation of curved spillway under the flow condition of large flow velocity and high Froude number are solved.