灌溉渠系-畦田地表水动力学耦合模拟方法研究

Irrigation channels and basin surface form a continuous system. However, until now, a useful numerical tool is rare which can be used to simulate the finely temporal-spatial distribution of irrigation water, and analyze the overall effect of irrigation and water saving of water transmission, distribution and farmland irrigation engineering from hydrodynamic perspective. For this purpose, we explore extensively the hydrodynamic mechanisms of water flow in channels and basin surface, and accurately analyze the mathematical expressions for gravitational diffusion effect, inertia advection effect and geometrical constraint advection effect of channel cross-section. A novel expression of full hydrodynamic equation is constructed for special phenomenon of irrigation. Then the full hydrodynamic models for channels and basin surface water flow with high resolution and full explicit scheme are proposed under circumstance of complex wet - dry boundary. Based on these two models, a full coupled hydrodynamic model for irrigation channels and basin surface is established. Field prototype observation experiments are carried out and the observation data are used to validate the simulation performance of the full coupled model which is finally used to analyze practical problem. The proposed full coupled model has important theoretical and practical significance to improve the comprehensive ability of water saving of irrigation engineering as well as harmony between water saving of irrigation and water demand of ecological environment.

灌溉渠系和畦田地表是承载灌溉水流运动的一个连续系统，然而迄今鲜见能以动力学方式模拟获得该系统中灌溉水流精细时空分布、并能从全局视角精细地分析渠系输配水工程和田间工程综合节水灌溉能力的模型工具。本项目拟基于已有的灌溉水动力学成果，通过深入探究驱动灌溉渠系和畦田地表水流运动的特有物理机制，精确解析重力扩散效应、惯性对流效应和渠道横断面几何约束对流效应的数学表述，获得灌溉特有物理现象下全水动力学方程的全新结构表达式，建立灌溉特有复杂干湿边界动态时空域下高精度隐式渠系输配水和畦灌全水动力学模型。在此基础上，构造渠系输配水和畦灌全水动力学方程时空离散式的全耦合整体矩阵，建立灌溉渠系-畦田地表水动力学全耦合模型。开展野外原型观测试验，系统地验证全耦合模型的模拟性能，并对其进行应用。本研究对提高灌溉工程的整体节水灌溉能力、实现灌区节水和生态环境需水之间的和谐具有重要的理论与现实意义。

畦灌作为应用广泛的灌溉方法，迄今仍缺乏能用于实际模拟评价和分析的二维地表水流运动模拟模型及软件工具，这与其采用的全水动力学方程直接源于明渠水力学密切相关。明渠水力学的地表浅水运动是惯性对流和重力扩散两种运动往往不分伯仲，其全水动力学方程被表达成具有源项的对流形式。与之相比，畦灌地表水流运动通常以重力扩散运动为主，但局部时空域内必须考虑惯性对流运动。本项目在以往研究全水动力学方程的成果基础上，深入探究了畦田地表水流运动的物理机制，通过精确解析重力扩散效应和惯性对流效应的数学表述，建立了以重力扩散为主、惯性对流为辅的新的全水动力学方程，使得畦灌地表水流运动物理过程与数学描述方法协调一致。在此基础上，建立了全水动力学方程新表达形式的数值解法。基于黑龙江锦西灌区的地理信息和水力学与几何参数等数据，对模型的效果进行了验证。