DYNAMICS AND MODELLING OF LARGE-SCALE RIVER ADJUSTMENTS OF EQUILIBRIUM

这项研究计划将冲积河流河床和河岸变形所涉及的水沙运动机理的理论和试验研究与开发基于物理的高精度数值模型相结合，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，也可能是对人类河流直接或间接干预的反应。拟开展的研究主要集中在：1-大尺度湍流相干结构及其形态后果；以及曲折河流中的两床形态变化和岸滩迁移。 将在一条21米长、宽度从1米到2米可调的直槽中进行一系列广泛的实验。在这些实验中，将记录大规模相干结构的产生、生长和衰变事件及其形态后果。这项研究有望更好地了解大规模河床形态(交替和多个沙洲)的发展，以及河流初期偏离直线走向最终导致曲折或辫状。它还将构成今后对这些进程进行建模的基础。此外，还将探讨曲流河河床和岸坡变形过程中的水流泥沙运动机制。为此，位于21米长、7米宽的沙盆上的初始(非平衡)实验室曲折河流将受到各种水流条件的影响，并将对其时间演变进行监测。这些新的数据和见解将被用来开发一个2D/3D组合数值模型，用于模拟和预测曲流河床变形和横向运移随时间的耦合。这一模型有望成为评估自然和人为引起的曲折形态变化对自然环境的影响的宝贵工具。 拟议的研究将导致培养4名博士、2名硕士。和5 B.Sc.学生将获得在河流工程研究和实践中应用的高度期望的高级技能。

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 proposed 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 21m-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 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 a combined 2D/3D numerical model for the simulation and prediction of coupled meandering bed deformation and lateral migration over time. This model is expected to constitute a valuable tool to assess the impact on the physical environment of both natural and man-induced meandering morphological changes. The proposed research will result in the training of 4 Ph.D., 2 M.Sc. and 5 B.Sc. students, who will acquire highly desired, advanced skills with application in river engineering research and practice.