High-resolution subgrid models: background, grid generation, and implementation
High-resolution subgrid models: background, grid generation, and implementation
复制标题
高分辨率子网格模型：背景、网格生成和实现
DOI：
10.1007/s10236-014-0693-x
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发表时间：
2014
期刊：
影响因子：
2.3
通讯作者：
C. Lippert
中科院分区：
文献类型：
--
作者：
A. Sehili;G. Lang;C. Lippert
子网格模型的基本思想是在计算中使用子网格级别的可用高分辨率水深数据，这些数据在相对粗糙的网格上执行，允许大的时间步长。为此，Casulli （Int J number Method Fluids 60:391-408, 2009）和Casulli和Stelling （Int J number Method Fluids 67:441-449, 2010）推导出了一种能够正确表示发生干湿的区域的精确质量平衡的算法。计算网格单元允许是湿的、部分湿的或干燥的，并且不需要干燥阈值。基于子网格技术，实现了各种场景的实际应用，包括德国易北河口水位、盐度和温度的业务预测模型。网格生成过程允许在子网格级别进行详细的边界拟合。计算网格由流对齐的四边形组成，必要时包括几个三角形。用户自定义的网格细分在子网格级别允许一个正确的体积表示到测量精度。底部摩擦需要特殊处理。在传递方法的基础上，进行了适当的经验修正。上述特点使得子网格技术非常高效、鲁棒和准确。将预测水位与分辨率较高的经典非结构网格模型进行了比较，结果表明两者吻合良好。由于使用子网格技术，计算性能的加速大约是20倍。一个典型的每日预报可以在一个标准的类似pc的硬件上在不到10分钟内完成。因此，子网格技术是一种很有前途的框架，可以以低计算成本对海岸和河口流动和运输过程进行精确的时空大尺度模拟。
The basic idea of subgrid models is the use of available high-resolution bathymetric data at subgrid level in computations that are performed on relatively coarse grids allowing large time steps. For that purpose, an algorithm that correctly represents the precise mass balance in regions where wetting and drying occur was derived by Casulli (Int J Numer Method Fluids 60:391–408, 2009) and Casulli and Stelling (Int J Numer Method Fluids 67:441–449, 2010). Computational grid cells are permitted to be wet, partially wet, or dry, and no drying threshold is needed. Based on the subgrid technique, practical applications involving various scenarios were implemented including an operational forecast model for water level, salinity, and temperature of the Elbe Estuary in Germany. The grid generation procedure allows a detailed boundary fitting at subgrid level. The computational grid is made of flow-aligned quadrilaterals including few triangles where necessary. User-defined grid subdivision at subgrid level allows a correct representation of the volume up to measurement accuracy. Bottom friction requires a particular treatment. Based on the conveyance approach, an appropriate empirical correction was worked out. The aforementioned features make the subgrid technique very efficient, robust, and accurate. Comparison of predicted water levels with the comparatively highly resolved classical unstructured grid model shows very good agreement. The speedup in computational performance due to the use of the subgrid technique is about a factor of 20. A typical daily forecast can be carried out in less than 10 min on a standard PC-like hardware. The subgrid technique is therefore a promising framework to perform accurate temporal and spatial large-scale simulations of coastal and estuarine flow and transport processes at low computational cost.