冰湖溃决洪水的二维水动力学数值模拟  

Two-dimensional Mathematical Modeling of Glacier Lake Outburst Flood

作　　者：岳志远[1] 曹志先[1] 车涛[2] 李新[2] 

机构地区：[1]武汉大学水资源与水电工程科学国家重点实验室,湖北武汉430072 [2]中国科学院寒区旱区环境与工程研究所,甘肃兰州730000

出　　处：《冰川冻土》2007年第5期756-763,共8页Journal of Glaciology and Geocryology

基　　金：中国科学院知识创新工程重要方向项目(KZCX3-SW-357-02);国家自然科学基金项目(50459001)资助

摘　　要：为分析冰湖溃决洪水过程,建立了一个二维非恒定流数值模型,可以定量的开展冰湖溃决洪水预测.数值模型的基本控制方程采用二维浅水水流方程,数值方法采用可以捕捉激波的WAF TVD二阶精度格式,并用非界面追踪的方法处理干湿边界.通过理想情况下一维解析解的验证和二维复杂地形情况的数值试验,证明数值模型具有较好的精度和可靠性,并且可以适应复杂地形.将数值模型应用于一个典型的冰湖溃决事件,定量地预估了该冰湖溃决洪水过程,结果表明:水流流速很高,床面剪切应力很大,可能诱发活跃的泥沙运动,形成泥石流灾害.A two-dimensional mathematical model for unsteady free-surface flows is presented, which facilitates a quantitative approach to the analysis of glacier-lake outburst floods. The governing equa- tions of the model comprise the shallow water hydrodynamics equations closed with the Manning formulation for the boundary resistance. The second-order Total-Variation-Diminishing version of the Weighted-Average-Flux method, along with the HLL approximate Reimann Solver, is used to solve the governing equations, which can properly capture shock waves and deal with irregular boundaries. Numerical tests of dam-break flows are carried out to demonstrate the accuracy of the model under an idealized case with known analytical solution, and the ability of the model to properly reflect flow patterns under the ease of irregular to-pography. The mathematical model is applied to predict the potential flood event due to sudden outburst of a glacial-lake under a practical situation, with given DEM of the basin and initial water level in the lake. The propagation of the glacial-lake outburst flood is assessed from a quantitative perspective. The mean flood flow velocity can be as high as 15 m·s ^-1, and the local bed shear stress can be as high as 1000 N·m^-2 The highly energetic flood flow should trigger very active sediment erosion, transport and deposition, and debris flow hazards may be inevitable in the particular situation. This finding appears to characterize the need for the extension of the present mathematical model for purely unsteady flows to a coupled model for flow, sediment transport and morphological evolution.

关 键 词：冰湖溃决洪水 非恒定流 数值模型 水动力学 

分 类 号：P331.1[天文地球—水文科学]