In this work, a dynamic internal boundary condition is used as subgrid model in a two-dimensional (2D) model based on the shallow water equations in order to model narrow regions in the domain. In this way, computational savings are sought, since it is not necessary to discretize these regions with cells of reduced size. The new internal boundary condition simplifies other works where 1D–2D coupled models were presented, since the 1D model is a subgrid for the 2D mesh, so the coupling between both models is simple and direct. The coupling is performed using mass conservation, simplifying the calculation in the transfer between both models. Test cases are studied to validate the implemented boundary condition, and a mountain catchment as a realistic case. The results obtained with a fully 2D mesh and a 2D mesh with rills in narrow regions are very similar, with a large reduction in computational cost when using rills, both in test cases and in the realistic case. Thus, the use of the implemented internal boundary condition is an effective tool to study regions with narrow regions by reducing the computational cost with little loss of accuracy in the results.

中文翻译：

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亚网格尺度地形具有一维内部边界条件的二维浅水流模型


在这项工作中，动态内部边界条件被用作基于浅水方程的二维 (2D) 模型中的子网格模型，以便对域中的狭窄区域进行建模。通过这种方式，可以节省计算量，因为不需要用尺寸减小的单元来离散化这些区域。新的内部边界条件简化了提出一维-二维耦合模型的其他工作，因为一维模型是二维网格的子网格，因此两个模型之间的耦合简单而直接。使用质量守恒进行耦合，简化了两个模型之间传递的计算。研究测试用例以验证所实施的边界条件，并将山区流域作为现实案例。使用全 2D 网格和狭窄区域中带有细沟的 2D 网格获得的结果非常相似，无论是在测试案例还是在实际情况中，使用细沟时计算成本都会大大降低。因此，使用所实现的内部边界条件是研究狭窄区域的有效工具，可以减少计算成本，而结果的准确性几乎没有损失。