River morphodynamics and its mathematical modelling

该研究计划将冲积河流河床和河岸变形中涉及的水流和泥沙输运机制的理论和实验研究与基于物理的高精度数值模型的开发相结合，用于模拟和预测河流形态变化。这些变化可能是自然发生的，也可能是对人类直接或间接干预河流的反应。本研究的重点是：1-大尺度湍流相干结构及其形态后果; 2-曲流中河床形态变化和河岸迁移。 一系列广泛的实验将在一个20米长的直通道中进行，通道宽度可从1米到2米调节。在这些实验中，将记录大尺度相干结构的产生、增长和衰减的事件及其形态学后果。这项研究预计将产生一个更好的理解的发展大规模的床的形式（交替和多个酒吧）和发展的初期流偏离直线，最终导致曲折或编织。它还将为今后模拟这些过程奠定基础。 此外，还将研究弯曲河流中河床和河岸变形所涉及的水流和泥沙输运机制。为此目的，初始（非平衡）实验室曲流流躺在一个21米长，7米宽的砂盆，将受到各种流动条件和它们的时间演变将被监测。新的数据和见解将用于开发两个数值模型：（一）用于计算曲流床地形及其时间演变的三维模型;（二）用于模拟曲流的长期平面演变和预测曲流迁移率的模型。这些模型预计将构成宝贵的工具，以评估自然和人为引起的蜿蜒形态变化对物理环境的影响。 该研究项目将培养3名博士。学生，3名硕士生和1名B.Sc学生。

This research program combines the theoretical and experimental research of mechanisms of flow and sediment transport involved in the deformation of bed and banks of alluvial streams with the development of physically-based, high-accuracy numerical models for the simulation and prediction of river morphological changes. These changes may occur naturally or as a response to direct or indirect human river interventions. The research focuses on: 1- large-scale turbulence coherent structures and their morphological consequences; and 2- bed morphological changes and bank migration in meandering streams.       An extensive series of experiments will be carried out in a 20m-long straight channel having an adjustable width from 1m to 2m. In these experiments, events of generation, growth and decay of large-scale coherent structures and their morphological consequences will be recorded. This study is expected to yield a better understanding of the development of large-scale bed forms (alternate and multiple bars) and the development of incipient stream deviations from straight alignment eventually leading to meandering or braiding. It will also constitute a foundation for the future modelling of these processes.       Additionally, the mechanisms of flow and sediment transport involved in bed and bank deformation in meandering streams will be investigated. For this purpose, initial (non-equilibrium) laboratory meandering streams lying on a 21m-long, 7m-wide sand basin, will be subjected to a variety of flow conditions and their time-evolution will be monitored. The new data and insights will be used to develop two numerical models:(i) a 3-D based model for the computation of meandering bed topography and its time-evolution; and (ii) a model for the simulation of the long-term planimetric evolution of meanders and prediction of meander migration rates. These models are expected to constitute valuable tools to assess the impact on the physical environment of both natural and man-induced meandering morphological changes.       This research program will result in the training of 3 Ph.D. Students, 3 M.Sc. students and 1 B.Sc student.