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.

湍流对悬浮沉积物的输送对于许多地质和环境问题都很重要。在大多数情况下，悬浮沉积物浓度随着远离沉积物床而迅速降低。因此，预测悬浮泥沙通量的最重要因素是准确估计非常靠近沉积床的悬浮泥沙。 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。对于悬浮沉积物颗粒从水力粗糙流床中夹带和脱离的实际过程，不存在定性或定量模型。 该奖项的主要目标之一是加深对悬浮沉积物夹带和从水力粗糙床中分离以及同时进行床质输送的过程的了解。据推测，夹带和脱出过程不仅受具有正垂直向上速度的近床湍流结构的控制，而且还受床表面悬浮尺寸颗粒的可用性的控制。其可用性大概是由床表面悬浮颗粒的折返和埋藏控制的。 为了了解这一过程，将使用高速视频系统、激光光片和一套新颖的混合 PIV-PTV 算法在实验室水槽中进行大量定量可视化实验。通过计算大量床质和悬浮颗粒的同时运动，可以对整体夹带和脱离进行数值模拟。这些运动将由时间和空间上的真实湍流结构驱动。 最后，悬浮泥沙输送场将与河道中发生的大规模横向湍流结构耦合。 将使用 PIV-PTV 测速技术在实验室流台和河流中研究横向结构。然后计算建筑物对泥沙输运场的影响。 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研究的 Hele-shaw 单元、一个用于流量和河道变化研究的河流表以及一个用于沉积物输送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，为学生指导的项目构建其他小型实验设备。 将为每个实验室设备编写一组流结构解析数值例程。将开设地球表面流体实验课程。 该课程将提供如何构建、设置和测量流动结构的实践经验。该课程的重点是开发学生主导的研究项目。新推出的研究生沉积物输送力学课程将继续开发，其中的材料来自这项拟议的研究结果。 此外，还将继续为地质学本科生开发一门新的“影子课程”，指导学生完成作业，同时介绍微积分和物理学的地质应用。