Meandering Morphodynamics and Related Fluvial Processes

本研究项目旨在提高对直流和曲流河流水流输沙过程的认识和分析处理，从而改进此类河流中发生的关键大规模过程的数学模型。在接下来的五年里，研究将沿着两个主题进行：曲流流平面演化的动力学和建模（主题A）和大尺度湍流（主题B）。主题A的研究重点是克服曲流建模及其与河流可动边界相互作用的尚未解决的问题。在主题B下，关于大尺度湍流的知识将被扩展到包括对大尺度水平相干结构的动力学和形态学后果的初步理解。具体目标如下：(1)建立一个有效的二维流动力计算模型，包括适当的三维效应参数化；(2)开发新的岸蚀分析公式；(3)建立曲流长期平面演化计算的数值模型，并对目标1和目标2研究所得的流量和冲岸新公式进行检验、完善和验证；(4)深入研究在直流或近直流中发生的大尺度湍流水平相干结构的生命周期动力学，并深入了解其形态学后果。目前，我们将在大型设施中进行一系列广泛的实验室实验，包括两个不同的1米宽、50厘米深的通道，由三个连续的曲流环组成，用于曲流研究，以及一个21米长、宽度从1到2米可调的直水槽用于湍流研究。最先进的设备将用于获得床的详细记录和规划形状形态调整，并测量瞬时和时间平均流速场，以及当地的泥沙输送率。将收集文献中的实地数据和与水有关的机构提供的未发表的数据，以便进一步了解正在调查的过程，并能够进一步测试这项研究产生的计算机模型。从建议的研究中获得的新知识和工具将直接适用于广泛的河流工程研究和项目的可行性分析、设计和优化，以及制定健全的河流管理指南和协议。该研究将培养5名博士、2名硕士和3名理学士学生，他们将获得水力物理和数值模拟方面的高级技能，并对河流工程和管理的社会、经济和环境方面有深刻的认识。

This research program aims at advancing the understanding and analytical treatment of flow and sediment transport processes in straight and meandering rivers, leading to an improved mathematical modelling of key large-scale processes taking place in such rivers. Over the next five years, the research will be carried out along two themes: the dynamics and modeling of the planimetric evolution of meandering streams (Theme A) and large-scale turbulence (Theme B). The research under Theme A focuses on overcoming unresolved issues related to the modeling of meandering flow and its interaction with the stream movable boundary. Under Theme B, the knowledge on large-scale turbulence will be extended to include a first understanding of the dynamics and morphological consequences of large-scale horizontal coherent structures. The specific objectives are as follows: (1) to develop an efficient 2-D hydrodynamic model for the computation of meandering flow, including appropriate parametrizations of three-dimensional effects; (2) to develop new analytical formulations of bank erosion; (3) to develop a numerical model for the computation of long-term planimetric evolution of meandering streams, and use it to test, refine and validate the new formulations of flow and bank erosion resulting from research carried out under objectives 1 and 2; and (4) to penetrate the dynamics of the life-cycle of large-scale turbulence horizontal coherent structures occurring in straight or nearly straight streams, and gain insight into their morphological consequences.For the present purposes, extensive series of laboratory experiments will be conducted in large-scale facilities, including two different 1 m wide, 50 cm deep channels formed by three consecutive meander loops for the meandering studies, and a 21m-long straight flume with adjustable width from 1 to 2m for the turbulence studies. State-of-the-art equipment will be used to obtain detailed records of bed and plan shape morphological adjustments, and measure instantaneous and time-averaged flow velocity fields, and local sediment transport rates. Field data from the literature and unpublished data available from water-related agencies will be gathered, to get further insights into the processes under investigation and enable further testing of the computer models resulting from this research.The new knowledge and tools resulting from the proposed research will be directly applicable to the feasibility analysis, design and optimization of an extensive array of river engineering studies and projects and the development of sound river management guidelines and protocols. The research will result in the training of 5 PhD, 2 MSc and 3 BSc students, who will acquire highly desired, advanced skills in hydraulic physical and numerical modeling, and a deep appreciation of the social, economic and environmental aspects of river engineering and management.