城市化地面二维浅水模拟

2D shallow-water simulation for urbanized areas

城市地区存在密集的建筑,采用传统二维数值模拟方法模拟城市洪水,需要提取城市复杂的建筑物作为计算边界和加密计算网格,难以应用于大尺度城市洪水模拟。为此,引入容积率系数修改原始二维浅水方程,以反映建筑物对城市洪水演进的影响,并采用人工逆风通量向量分裂有限体积法构建数值计算模型,求解修改后的二维浅水方程。为了检验模型,采用两个算例进行验证,并对计算结果对比分析。研究表明,该模型不需要进行建筑边界提取和精细计算网格,精度上,完全能够满足大尺度城市洪水模拟精度要求。

Extracting urban features from dense building is essential to the simulation of urban flooding using classical two-dimensional models.These urban complex structures are parts of boundaries in the simulation domain,where the mesh may be locally refined.As a result,the large-scale urban flood simulation may not be feasible due to limited information in urban buildings.In this study,the classical two-dimension shallow water equation is improved through the introduction of a plot ratio coefficient that can represent the building influence on urban flood simulation.The modified two dimension shallow water equation is solved by a finite volume method with artificial upstream flux vector splitting.The improved model is tested in two numerical case studies.The result shows that the model is able to simulate urban floods with an acceptable accuracy.At the same time,the requirement for urban feature extractions is significantly reduced.