Hydrodynamics of fluvial wakes past large in-stream natural objects and their implications for riverbed morphology

目前，人们通过河流水流结构控制的非生物因素的空间异质性程度来理解自然河流环境的多样性。这一主题的核心是由天然河流中的障碍物产生的水流非均质性，如巨石群、原木堵塞、河岸和水生植被及其各种组合的斑块。在河流中障碍物周围和下游形成的特定流动类型称为尾流，由于自然环境和过程的复杂性，其动力学仍未完全了解。这项拟议的研究旨在通过提供对控制因素及其对河流形态的影响的基本理论洞察，来改善尾流流体动力学的知识。在这个项目中，将在一系列水文条件下直接在实地评估由多孔河流中的障碍物在浅水、粗糙河床环境中产生的复杂环境流。通过将现场观测结果与实验室实验结果进行比较，将进一步了解这些尾流的动力学，将通过进行与尺度无关的基于现场的实验和数值模拟来研究放大问题。这些研究还将通过对天然障碍物的孔隙度进行现场调查和对河床底质进行采样来补充。这些调查将提供目前无法获得的关于河流中障碍物的基本性质的知识，并直接量化河流尾流造成的侵蚀/沉积过程。此外，收集的数据将估计尾迹对河段尺度上的总体水力特性的贡献。

The diversity of natural river environments is presently understood throughout the degree of spatial heterogeneity in abiotic factors controlled by river flow structures. Central to this topic is flow heterogeneity produced by natural in-stream obstructions such as boulder clusters, log jams, patches of riparian and aquatic vegetation and their various combinations. Specific flow types forming around and downstream of in-stream obstructions are called wakes, which dynamics are still incompletely understood because of complexities in natural environments and processes. The proposed research aims at the improvement in knowledge of wake flows hydrodynamics by providing fundamental theory-based insight into controlling factors and their implications for river morphology. In this project, complex environmental flows generated in shallow, rough-bedded river environments by porous in-stream obstructions will be assessed directly in the field at a range of hydrological conditions. Dynamics of these wake flows then will be further understood by comparing field observations with the results of lab experiments, which up-scaling issues will be examined by carrying out scale-independent field-based experiments and numerical simulations. These studies will be also complemented by in-situ surveys of porosity in natural obstructions and sampling of the riverbed substrate. These surveys will deliver presently unavailable knowledge on fundamental properties of in-stream obstructions and direct quantification of erosion/deposition processes due to fluvial wakes. Furthermore, the collected data will estimate the wakes’ contribution into the bulk hydraulic characteristics at a river reach scale.