含沙溃堤洪水数值模拟分析
Numerical Simulation and Analysis of Sandy Levee Breach Flood

为了研究复杂地形下含沙溃堤洪水的泥沙输移和床面冲淤, 分析泥沙冲淤对溃堤出流的影响, 评估水沙共同作用下的洪水风险, 建立了非结构化三角网格的二维水沙数学模型．单元界面的水动力通量采用基于近似黎曼解的Roe格式计算, 泥沙通量采用TVD-MUSCL格式求解．用小尺度的水槽动床试验数据对数值模型进行验证．将模型应用于黄河宁蒙段河道洪泛区某溃口含沙溃堤洪水的数值模拟．模拟结果表明, 溃口冲刷坑外围易形成环形泥沙淤积体, 同时洪泛区出现明显泥沙淤积．因此, 含沙溃堤洪水带来的泥沙淤积问题不容忽视．通过比较清水定床、清水动床、含沙定床和含沙动床4种数值模型的计算结果, 发现床面冲淤变化对溃堤洪水进洪流量有明显影响．
In order to study sandy sediment transport and bed deformation of sandy levee breach flood under complex terrain，this paper analyzed the impact of sediment deposition on levee breaches outflows and assessed the flood risks under combined flow and sediment action. And a two-dimensional flow-sediment mathematical model based on unstructured triangular mesh was established. The Roe scheme based on approximate Riemann solver was adopted to calculate the hydrodynamic flux，and the TVD-MUSCL scheme was adopted to solve the sediment flux. Numerical model was validated by the experimental data of the small scale flume. This model was applied to a dyke on the flood plains of Ningxia and Inner Mongolia Reach of the Yellow River. The simulation results show that annular sedimentation is easy to be formed around the scoured pit of levee burst，and obvious sedimentation is appeared in the flood plains. Therefore，the sedimentation problem that results from sandy levee breach flood cannot be ignored. By comparing the results which calculated through clear water fixed bed，clear water erodible bed，sandy flood fixed bed and sandy flood erodible bed mathematical models，it is found that variations in bed deformation have significant effect on the amount of flood in the flood levee breaches