长江中游洞庭湖防洪系统水流模拟——Ⅰ．建模思路和基本算法

针对长江中游洞庭湖防洪系统规模庞大、水流复杂、资料短缺和预报时限紧迫的实际条件,提出了具有层次和模块结构特点、一维与二维水流模拟、水力学与水文学方法、理论模型与补充信息相结合的建模途径.所建模型的湖泊部分采用无结构网格二维非恒定流高性能有限体积格式,以适应湖区复杂的边界形状和保持水量平衡;河网部分采用一维非恒定流守恒型显格式,避免隐格式矩阵算法的复杂性,同时有利于与二维模型的耦合及与各种复杂连通关系的显式连接.这种一、二维混合非恒定流模型可用于长江干流、洞庭湖河网及湖泊、堤垸区的洪水演进和防洪调度的水流仿真.

Flow Modelling of the Middle Yangtze River Dongting Lake Flood Control System——Ⅰ.Modelling Procedures and Basic Algorithms

For the large-scale flood control system of the middle Yangtze River-Dongting Lake, featuring by complex flow conditions, data scarcity, and a limited lead time, a hierarchical and modular flow simulation model has been proposed, combining together 1-D with 2-D flow models, hydraulic with hydrologic methods, numerical algorithms with supplementary information. A finite-volume method for calculating 2-D unsteady flows on an unstructured mesh is used for the lake of a complex configuration, to preserve mass balance. A conservative explicit difference scheme is applied to simulate branched and looped network unsteady flows, to avoidtedious matrixcal culations caused by using implicit schemes, and facilitate the 2-D model and various flow connections. This hybrid unsteady flow model has been utilized to flood routing for the system connected through sub-lakes, river networks, and flood-plains.