高精度城市雨洪漫流动力波模型研究

The climate change and the fast urbanization in China have greatly raised the risk of the urban flood. How to efficiently and reliably model the rainfall runoff and flood propagation becomes one of the key measures to mitigate urban flood disasters. However, the existing hydrologic and hydro-dynamic models fail to handle this problem. This project proposes a physically based dynamic wave model. In the dynamic wave model, key features in sub-grid scale are taken into account to increase the reliability of the model results, by means of developing anisotropic porosity method; The causes of the numerical instability for the complex unban overland flow are investigated. Accordingly, the second-order MUSCL scheme and the treatments for the slope and friction source terms are improved to preserve the robustness; The high-performance GPU parallel computing technique and the automatically optimized grid system are employed to considerably accelerate the simulation. The final goal is to develop an accurate, fast and robust 2D overland flow model for urban areas. The research outputs help to further develop the theory of hydraulics. Besides, they are also of importance for the urban flood prediction and the sponge city construction.

受气候变化和城市化的影响，我国城市内涝愈加频发，如何快速准确地模拟暴雨汇流和洪涝演进过程成为精准防控洪涝灾害的关键因素之一，然而现有的水文学和水动力学模型在模拟城市雨洪漫流时存在着可靠性差、效率低下和容易失稳的问题。基于考虑了全物理过程的动力波模拟方法，本研究将解析漫流水力特性对亚网格尺度关键地形的响应规律，并改进各项异性孔隙率法以提高模拟精度；揭示复杂城市漫流易导致计算失稳的作用机理，藉此重构二阶MUSCL格式和底坡源项、摩阻源项的处理方式；同时，在高分辨率模拟中引入并行计算性能突出的GPU技术，并在此平台上创立网格自动优化方法，以实现在不降低精度的前提下大量减少计算单元，从而极大地提高计算速度。目标是构建精度、效率和稳定性俱佳的二维城市漫流动力波模型。研究成果有助于丰富和推动水力学理论的发展，亦对洪涝预报和海绵城市建设具有重要的应用价值。

针对现有的水文学和水动力学模型在模拟城市雨洪漫流时存在着可靠性差、效率低下和容易失稳的问题，通过该项目的研究，开发了一套适用于科学研究和工程应用的具有良好模拟精度、计算效率和稳定性的二维高分辨率城市漫流动力波模型。模型通过改进摩阻源项隐式处理方法来提升薄层漫流模拟的精度和稳定性；通过实现GPU并行加速计算来提升全水动力模拟的效率。同时搭建了城市雨洪综合试验平台，采用人工模拟降雨的方式来开展城市下垫面缩尺物理模型的径流过程试验。试验研究了城市雨洪过程的机理，探究了不同地形、雨强等因素对城市下垫面稳渗率的影响；并模拟了多项LID措施的综合叠加效果。试验结果、解析解及现场实测资料被用于系统验证模型，揭示了所提出的模拟算法在计算城市漫流过程的精度、效率和稳定性有所提高。所建城市漫流动力波模型被用于模拟西咸新区沣西新城海绵城市试点建设区的雨洪过程；计算了建设前设计暴雨条件下的内涝积水风险；并协助评价海绵城市建设对内涝削减的量化效果。研究成果有助于丰富和推动水力学理论的发展，亦对城市洪涝管理和海绵城市建设效果评估具有一定的应用价值。