一维畦灌地表水流-土壤水动力学耦合模型Ⅰ:建模

Coupled surface-subsurface hydrodynamic model for border irrigation Ⅰ. Model development

畦灌地表水流-土壤水动力学耦合模型可从物理机制上综合模拟地面灌溉过程中地表水与土壤水系统之间的互动关系,为开展区域尺度地面灌溉系统性能评价提供了基础工具。利用二阶时空离散精度的混合数值解法求解一维全水动力学模型,建立了一维畦灌地表水流运动模型,并利用二阶时间离散精度有限差分法和构建的四阶空间离散精度有限体积法解算一维土壤水动力学模型。同时,以地表水和土壤水质量守恒方程交替迭代计算的地表水深收敛值为基础,利用动量守恒方程获得地表水流速场,实现了地表水-土壤水系统间的有效迭代耦合,构建起基于数值解法和迭代耦合模式同步改进的一维畦灌地表水流-土壤水动力学耦合模型。

Border coupled surface-subsurface flow model can well simulate, in physical mechanism, the non-linear interactions between surface flow and soil water, as well as soil water redistribution after border irrigation, playing an important role in large-scale border irrigation system evaluation. In this study, the one-dimensional complete hydrodynamic model was solved by the hybrid numerical method. The soil water hydrodynamic model was solved by the finite volume scheme with fourth-order accuracy for spatial discreti- zation and the finite difference scheme with second-order accuracy for temporal discretization. The conver- gence value of surface water depth was obtained from the alternately iterative processes between mass con- servation equations of complete hydrodynamic model and soil water hydrodynamic model at the same time step. The momentum conservation equation of complete hydrodynamic model was modified using the conver- gence value of surface water depth to obtain the updated velocity field. Finally, the coupled surface-subsur-face hydrodynamic model was proposed based on the improvement of numerical solution methods and itera-tive coupling method.