溃口近区二维数值模拟与溃坝洪水演进耦合

基于黏土心墙砂石坝的溃决过程,以及溃坝洪水传播和运动的特性,建立黑河金盆水库大坝溃口近区二维数值模型和下游地区溃坝洪水演进耦合数学模型。使用DAMBRK法计算逐渐溃坝,并应用其结果进行后续模拟。采用Abbott-Ionescu六点隐式有限差分格式求解一维模型,采用单元中心的有限体积法求解二维模型方程。采用侧向连接方式,将黑河两岸计算水位点与二维网格单元相连,实现一、二维模型的耦合。采用所建立的二维模型对溃口近区进行计算与模拟,得到计算区域某一时刻的水深及流速分布。应用所建耦合模型对黑河金盆水库万年一遇入库洪水漫顶致溃坝洪水进行数值模拟,得到一维河道内各断面的水位和流量变化过程,以及二维计算区域内不同时刻的水深分布图、流速矢量图和淹没范围变化过程。溃口的形成过程不仅包括漫顶水流的直接作用,同时包括溃口形成过程中两侧漩涡状水流的反冲刷作用。耦合模型可以同时兼顾河道内的水流变化以及河道外计算区域内的洪水演进过程,从而减少由于计算结果偏大或偏小所带来的防洪资源浪费和防洪措施不利等不良影响。

2D numerical simulation of breach area and coupling simulation of dam breach flood

Based on the breach process of the clay-core wall sandy dam, as well as the characteristics of dam breach flood propagation and movement, the 2-D numerical simulation of breach area and the coupling simulation of the dam-breach flood of Heihe Jinpen reservoir dam are presented in this paper. The method of DAMBRK is used to calculate gradual dam breach, and the results of DAMBRK model are used in the following simulation. A one-dimensional model is solved by the Abbott-Ionescu six points implicit finite difference scheme. The unit centered finite volume method is adopted to solve a two-dimensional model equation. To achieve the coupling of 1-D and 2-D model, the lateral connections are used to connect the level calculation points and the two-dimensional grid unit of both sides of Heihe River. The 2-D model is developed to calculate and simulate the breach area. The instantaneous water depth and the velocity distribution of the calculation region are given by the 2-D model. Taking the flood with frequency of 0.01% for example, the simulating results, such as water level and discharge process of each cross-section within the one-dimensional river course and water depth profile, velocity vector diagram and submerged range changing process of two-dimensional computational domain are presented by the coupling simulation. The formation process of the breach area includes not only the direct effects of overtopping flow, but also the anti-erosion effect of the spiral flow on both sides in the process of breach. Both flows change inner river and flood evolution of the calculation area in the outer river, which could be simultaneously taken into account by the coupling simulation.In conclusion, the adverse effects from wasting flood resources and the inappropriate flood protection measures which are brought by too large or too small calculation results have been reduced. In engineering practice, for complex river network region, it is recommended to apply the coupling model in calculation in order to improve simulation accuracy.