钱塘江涌潮多尺度时空演变及驱动机制研究

The existence of a tidal bore is based upon an interactional balance between the upstream movement of tidal flow, river runoffs and riverbed evolution. This balance may be easily disturbed by some changes in the boundary conditions, especially the impact of human activity on these changes. For example, a number of tidal bores disappeared because of river training, dredging and damming. Some man-made interventions led to the loss of several bores with often adverse impacts onto the estuarine eco-systems. Previous work about the temporal-spatial evolution and trend prediction of tidal bore based on long-term measured data falls short of full knowledge and understanding, and makes restrictions on comprehensive management of the Qiantang River estuary and protection of tidal bore. An application of theoretical research, field observation, numerical simulation and data analysis are studied comprehensively to approach the characteristics of time variation, space distribution and driving mechanisms of tidal bore by means of the theories and methods of estuary dynamics, soil mechanics and mathematical statistics. Based on the OpenFOAM, an advanced multi-physics and multi-scale model will be established to achieve the global coupling simulation between tidal flow and river bed system. This research will sort out the intrinsic link between far/near-field flow structures, the pore water pressure response in soil mass and bed form changes. Based on functional data analysis, a multi parameter statistical model will be established to investigate the relationship between patterns and main controlling factors of tidal bore, and realize the short-term forecast and long-term prediction of the strong tidal bore in the Qiantang River. The research findings would have an important significance to the understanding of the hydrodynamic changes and its internal mechanisms, resources protection and disaster prevention of the tidal bore in a macro-tidal estuary.

涌潮的存在是潮流上溯、径流入海和河床演变三者相互作用平衡的结果，其平衡性易受边界条件，特别是人类活动的影响。目前对钱塘江涌潮长系列时空变化特征与趋势预测还缺乏充分认识和理解，使得钱塘江河口综合治理开发与涌潮保护受到诸多限制。本项目运用理论研究、现场观测、数值模拟和数据分析等手段，结合河口动力学、土力学和数理统计等跨学科的理论和方法，对人类活动影响下钱塘江涌潮形态的时间变化和空间分布特征及驱动机制进行综合研究。基于OpenFOAM平台进行程序设计，开展多物理场、多尺度耦合与仿真，理清远/近场水流结构、土体孔压响应与床面形态变化之间的内在联系，实现涌潮水流与河床系统整体耦合的数值模拟；基于函数型数据分析原理建立多参数统计模型，探明涌潮形态与主控因子之间的关系，实现钱塘江强涌潮的短时预报和长期预测。研究成果对深入认识强潮河口水动力变化规律及其内在机理、涌潮资源保护和防灾等具有重要的意义。

涌潮是入海河流河口段的一种特殊潮汐现象，是潮波前锋浅水变形的结果。日益加剧的人类活动和自然环境的变化，影响涌潮的生成和演变。钱塘江河口大规模的治江围涂，导致河口江道渐趋缩窄和口门下移，引起涌潮起潮点和上溯强度的变化。目前针对钱塘江涌潮长系列的时空演变趋势及驱动机制的系统研究还比较缺乏，使得钱塘江河口综合治理开发与涌潮保护受到诸多限制。以钱塘江涌潮基本特性研究为核心，结合河口动力学、土力学和数理统计等学科的基本理论和方法，揭示了人类活动影响下钱塘江涌潮形态的时间变化和空间分布特征，探索了钱塘江涌潮对变化条件的响应过程和驱动规律；采用X波段雷达、无人机摄影测量和高频声学多普勒流速剖面仪等仪器设备进行了涌潮形态变化、潮头水流结构和三维流场的实时观测；建立了基于OpenFOAM平台的涌潮水流与河床系统整体耦合的数值模型及基于多源数据融合的函数型数据分析统计模型，开展了钱塘江涌潮的时空演变趋势的预测。项目收集了钱塘江河口长系列的涌潮观测资料，分析了治江围涂等人类活动影响下涌潮多时空尺度的形态及变幅；利用X波段雷达对大范围水域表面成像，建立使用互相关算法的雷达影像匹配方法，用于中分辨率X波段雷达图像分析，反演了涌潮的传播过程和速度；涌潮水动力学模型采用基于重整化群理论的RNGk-ε模型，用于模拟涌潮局部近场的两相不可压缩流动运动，耦合涌潮和河床之间界面上的动态水压力，求解河床响应的动力学方程，研究了不同时空尺度下钱塘江涌潮演变过程的驱动规律；采用实测资料分析和数学模型计算相结合的方法，研究了影响钱塘江涌潮时空变化的主要控制因子；建立了基于水文时间序列和滩槽空间位置的面板数据库，采用函数型数据分析统计模型，分析预测了主要因素影响下钱塘江涌潮的时空演变趋势。项目的开展为钱塘江河口治理开发与涌潮保护提供理论依据和技术支持。