CAREER: Interaction between Turbulence Structures and Suspended Sediment in Rivers

泥沙的紊流输移对许多地质和环境问题都很重要。在大多数情况下，悬浮泥沙浓度下降非常迅速地远离沉积床。因此，在预测悬浮泥沙通量的最重要的因素是一个准确的估计悬浮泥沙非常接近的沉积床。 已经引入了许多公式来预测这种近床浓度，但这些公式的估计值差异很大。目前还没有定性或定量的模型来描述悬浮泥沙颗粒从水力粗糙流的河床上被夹带和分离的实际过程。 该奖项的主要目标之一是发展的过程中悬浮泥沙夹带和disentrage从水力粗糙床的推移质输运的理解。据推测，夹带和disentrainment过程不仅是由近床湍流结构与积极的，垂直向上的速度，但也通过在床面的悬浮颗粒的可用性。其有效性可能受床面悬浮颗粒的折返和埋藏控制。 为了理解这一过程，一些定量可视化实验将在实验室水槽中使用高速视频系统，激光片，和一套新颖的混合PIV-PTV算法进行。将通过计算大量推移质和悬浮颗粒的同时运动，对整个卷吸和消卷进行数值模拟。运动将由时间和空间上真实的湍流结构驱动。 最后，悬浮泥沙输运场将耦合到发生在河道中的大尺度横向湍流结构。 横向结构将在实验室流表和在河流中使用PIV PTV测速技术进行调查。然后计算建筑物对输沙场的影响。 将在研究生和本科生的帮助下建立一个学生地球表面流体实验室。该实验室将包括一个用于地下水流调查的hele-shaw单元，一个用于水流和河道变化调查的流表，以及一个用于泥沙输运实验的泥沙循环水槽。 此外，该实验室将配备工具和材料，以建立其他小型实验设备的学生指导的项目。 将为每个实验室装置编写一套流动结构解析数值程序。将开设一门地表流体实验课程。 该课程将提供如何构建、设置和测量流动结构的实践经验。课程的重点将是发展学生指导的研究项目。一个新推出的泥沙输运力学课程的研究生将继续发展与材料纳入本拟议的研究结果。 此外，将继续为地质学本科生开发一个新的“影子课程”，辅导学生完成家庭作业，同时介绍微积分和物理学的地质应用。

The transport of sediment in suspension by turbulent flows is important to a large number of geologic and environmental problems. In most instances, the suspended sediment concentration decreases very rapidly moving away from the sediment bed. Therefore, the most important factor in predicting the suspended sediment flux is an accurate estimate of suspended sediment very near the sediment bed. Numerous formulas have been introduced to predict this near-bed concentration, but estimates from these formulas vary considerably. There exists no qualitative or quantitative model for the actual process by which suspended sediment grains are entrained and disentrained from the bed of a hydraulically rough flow. One of the primary goals of this award is to develop an understanding of the process of suspended sediment entrainment and disentrainment from a hydraulically rough bed with simultaneous bedload transport. It is hypothesized that the entrainment and disentrainment process is governed not only by near-bed turbulence structures with positive, vertically upward velocities, but also by the availability of suspended-size particles at the bed surface. The availability is presumably controlled by the exhumation and burial of suspended-size particles at the bed surface. To understand this process, a number of quantitative visualization experiments will be conducted in a laboratory flume using a high-speed video system, laser light sheet, and a suite of novel hybrid PIV-PTV algorithms. A numerical simulation of the overall entrainment and disentrainment will be performed by calculating the simultaneous motions of a very large number of bedload and suspended-size particles. The motions will be driven by temporally and spatially realistic turbulent structures. Finally, the suspended sediment transport field will be coupled to large-scale lateral turbulent structures occurring in river channels. The lateral structures will be investigated in a laboratory stream table and in a river using PIV-PTV velocimetry techniques. Then the modification of the sediment transport field by the structures will be calculated. A Student Earth Surface Fluid Laboratory will be built with the help of graduate and undergraduate students. The laboratory will consist of a hele-shaw cell for ground-water flow investigations, a stream table for flow and channel change investigations, and a sediment recirculating flume for sediment transport experiments. Also, the lab will be equipped with tools and materials to build other small experimental devices for student directed projects. A set of flow-structure-resolving numerical routines will be written for each of the laboratory devices. A course in earth surface fluid experiments will be developed. The course will provide hands-on experience of how to build, setup, and take measurements of flow structures. The focus of the class will be on developing student directed research projects. A newly introduced sediment transport mechanics course for graduate students will continue to be developed with material incorporated from results of this proposed research. Also, a new "shadow course" for geology undergraduates will continue to be developed that tutors students with their homework while introducing geologic applications of calculus and physics.