CAREER: Interaction between Turbulence Structures and Suspended Sediment in Rivers

职业：湍流结构与河流悬浮沉积物之间的相互作用

• 批准号: 0134924
• 负责人: Mark Schmeeckle
• 金额: $ 32.51万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-02-01 至 2003-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0134924&HistoricalAwards=false
• 关键词: CAREER; Interaction; between; Turbulence; Structures

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.

湍流中悬浮液中沉积物的运输对于大量地质和环境问题很重要。在大多数情况下，悬浮的沉积物浓度降低了从沉积床迅速移动。因此，预测悬浮沉积物通量的最重要因素是非常在沉积物床附近的悬浮沉积物的准确估计。 已经引入了许多公式来预测这种近床的浓度，但是这些公式的估计差异很大。对于实际过程中，没有定性或定量模型，悬浮的沉积物颗粒被夹带并从液压流的床层中脱离。 该奖项的主要目标之一是对悬挂的沉积物夹带和与同时发生运输的液压粗糙床的夹带和脱离过程的过程了解。假设夹带和解剖过程不仅受近床的湍流结构的控制，这些结构具有正垂直，向上速度，而且还受床表面悬挂尺寸的颗粒的可用性。该可用性大概是由床表面的悬浮大小颗粒的挖掘和埋葬控制的。 为了了解这一过程，将使用高速视频系统，激光灯片和一套新型混合PIV-PTV算法在实验室水槽中进行许多定量可视化实验。通过计算大量的床负荷和悬浮大小的颗粒的同时运动，将对整体夹带和解剖进行数字模拟。这些动作将由时间和空间上现实的湍流结构驱动。 最后，悬浮的沉积物运输场将与河道中发生的大规模侧向湍流结构耦合。 将使用PIV-PTV Velocimotry技术在实验室桌和河流中研究横向结构。然后将计算通过结构对沉积物传输场的修饰。 将在研究生和本科生的帮助下建造学生地面流体实验室。该实验室将由用于地下水流量研究的Hele-shaw细胞组成，流量和通道变化研究的流桌以及用于沉积物传输实验的沉积物循环水槽。 此外，该实验室还将配备工具和材料，以制造其他针对学生定向项目的小型实验设备。 将为每个实验室设备编写一组流量结构的数值例程。将开发地面流体实验中的课程。 该课程将提供有关如何构建，设置和进行流程结构测量的实践经验。班级的重点将放在开发学生定向研究项目上。通过这项拟议研究的结果结合的材料，将继续开发针对研究生的新型沉积物运输力学课程。 此外，将继续为地质本科生提供新的“影子课程”，以便在介绍微积分和物理学的地质应用同时为学生提供家庭作业。