土坝溃决跌坎水流水动力特性数值模拟

黏性土坝漫顶溃决涉及多学科交叉，过程极其复杂，尽管国内外大量物理模型试验成果表明其溃决多以“跌坎式”溯源冲蚀为主要特征，然而对该冲蚀发展形式下的水流-坝体微观作用机制尚不清晰。水流作为漫顶溃决的冲刷主动力，对坝体溃决发展起着主导性作用，采用RNG k-ε紊流模型和VOF自由液面捕捉技术针对黏性土坝漫顶溃决代表性水流结构——溃决跌坎水流开展了三维数值模拟研究，对跌坎水流的水流结构、流态、水力特性指标等进行了细致分析，揭示了不同工况下坝体跌坎上的剪切应力、流速分布规律，进而从水动力学的角度对坝面进行受力分析，初步推断了黏性土坝漫顶溃决过程中各级跌坎的主要合并方式为“台阶水平面刷深下切”。研究成果为进一步掌握黏性土坝漫顶溃决发展演变机理提供了理论基础。

Numerical study of hydrodynamic characteristics of dam-break headcut flow

The dam-break process of clay soil dam under overtopping condition, related to multi-disciplines, is very complex. Although a large number of domestic and foreign physical model test results show that the headcut erosion caused by overtopping is the main breach process of most clay soil dams, the micro mechanism between water flow and dam body in the form of erosion is still not clear. The water flow plays a leading role in the development of dam break as it's the active force during overtopping failure. In the study, 3D numerical simulation research is carried out on the representative flow structure—the headcut flow, by using the RNG k-ε turbulence model and the volume of fluid (VOF) method. The flow structure, flow pattern and hydraulic characteristics of the dam headcut are analyzed in detail. Also, the distributions of shear stress and flow velocity in different working conditions are revealed. By using the research results, the analysis of the forces on dam body can be carried out from the point of view of hydrodynamics. The main way of all-level headcuts merged is inferred initially. The research results can help to make a clear understanding of the dam-break process.