CAREER: Integrated Experimental and Numerical Modeling Study of Non-uniform Sediment Transport in Meandering Channels

河槽泥沙运动的科学认识来源于河槽试验。 在弯曲河道中，沉积物与高度三维的水流相互作用，诱发点沙坝和曲流地貌的演化。到目前为止，没有理论能够令人满意地解释和量化的流动（平均和湍流），泥沙输运的粒度，点酒吧动力学和弯曲的顺序迁移之间的相互作用。在许多应用于弯曲和曲折的渠道，泥沙输运配方的粒径分数已从直实验室水槽的数据为基础，从来没有测试与弯曲的渠道。 目前对曲折河道沉积物分选的理解限制了数值模型模拟河床物质级配、河床形态和弯曲平面形态演变的能力。 为了全面了解河曲泥沙输运，本项目旨在解决以下问题：水流如何影响泥沙输运？泥沙输移与近床平均流的偏差有多大？ 输沙量的空间分布是怎样的？推移质、表面和底质的级配是什么？它们如何与泥沙输移率的粒度级相关？空间变化的泥沙通量如何构成点沙动力学？曲流迁移如何响应点沙坝的生长或抑制？实验将在几个系列的自形成的弯曲河道，弯曲度从1.25到3.7。将级配良好的沉积物混合物送入这些蜿蜒的河道，以研究三维水动力流场、表面和基质物质的分布、流向和横向不同粒径组分的沉积物输运特性、尖端和河道交叉处附近的点坝和池的逐渐形成、生长和阻尼、河岸侵蚀和点坝进展时的平面形态演变。 实验结果将被整合到一个数值模型中，以模拟实验水槽和天然河流中的弯曲迁移过程。研究结果将有助于科学认识河曲，并为河曲修复设计提供有价值的指导。 其优点不仅在于基础研究，而且在于工程实践。该项目将获得新课程所需的实验设施和计算机模型，让本科生参与研究，为女学生建立长期指导方案，为科学博物馆开发计算机动画展览，并向高中生推广。其目标是鼓励创造力和创新，强调工程教学中的计算，提高妇女在工程领域的知名度，并吸引最有才华的高中毕业生从事土木工程。

AbstractThe scientific knowledge on sediment transport in alluvial channels stems from experiments in straight channels. In curved channels, sediment interacts with highly three-dimensional flow and induces point bars and meandering planform evolution. To date, no theory is able to satisfactorily explain and quantify the interactions among flow (mean and turbulence), sediment transport by size fractions, point bar dynamics and the sequential migration of bends. Among many numerical models applied to curved and meandering channels, formulations for sediment transport by size fractions have been based on data from straight laboratory flumes and never tested with sinuous channels. Current understanding of sediment sorting through meandering channels limits the capability of numerical models in simulating the evolution of bed material gradation, bed morphology, and bend planform. Towards a complete understanding of sediment transport in meanders, this project aims to address the following questions: How does flow influence sediment transport? How much does sediment transport deviate from the near-bed mean flow? What are the spatial distributions of sediment load? What are the size gradations of bed load, surface, and substrate material? How do they correlate to sediment transport rate by size fraction? How does spatially varied sediment flux constitute point bar dynamics? How does meandering migration response to the growth or dampening of point bars?Experiments will be conducted in several series of self-formed meandering channels with sinuosities ranging from 1.25 to 3.7. Well-graded sediment mixtures will be fed into these sinuous channels to enable investigation of three-dimensional hydrodynamic flow field, distributions of surface and substrate material, sediment transport characteristics for different size fractions at the streamwise and lateral directions, gradual formation, growth, and dampening of point bars and pools near the apex and channel crossing, planform evolution as bank erodes and point bar progresses. The experimental results will be integrated into a numerical model to simulate the processes of meandering migrations in both experimental flumes and a natural river. The results of this research will contribute to scientific understanding of river meanders and provide valuable guidance in river restoration design. The merit is not only in basic research but also in engineering practice. The project will acquire an experimental facility and a computer model needed for new courses, engage undergraduates in research, establish a longer-standing mentoring program for women students, develop a computer animation exhibition for science museums, and outreach to high school students. The objectives are to encourage creativity and innovation, stress computing in engineering teaching, increase the visibility of women in engineering, and attract most talented high school graduates to Civil Engineering.