Collaborative Research: The dynamics of sediment-laden river plume and initial deposition off small mountainous rivers

合作研究：富含沉积物的河流羽流动力学和山区小河流的初始沉积

• 批准号: 0926427
• 负责人: Wayne Geyer
• 金额: $ 39.26万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0926427&HistoricalAwards=false
• 关键词: Collaborative; Research; dynamics; sediment; laden

Abstract This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This new award is for a multi-scale modeling study of the dynamics and sediment-transport processes related to the highly turbid outflows from small montane rivers. The project will contribute to the 3D wave-averaged Community Sediment Transport Modeling System (CSTMS, a suite of models based on a coupled ROMS/SWAN framework). The enhancements will address critical intra-wave processes and are primarily two-fold: a new formulation on the interaction of surface waves and stratified shear flow, and parameterizations of the influence of convection on vertical sediment flux that may significantly alter the distribution of sediment deposition. The theoretical formulation for wave-current interaction is based on a multiple scale expansion that allows arbitrary vertical current variation. The resulting formulation represents a significant modification to the numerical coupling between ROMS and SWAN. A 2DV wave-resolving RANS model which is capable of resolving sediment-laden plume dynamics, such as hyperpycnal flows and convective instability, will resolve the interaction between a sediment-laden plume and surface waves, then tested against the theoretical formulation and enhanced CSTMS in idealized simulations. A 3D turbulence-resolving simulation tool for fine sediment transport will be extended to study instabilities, coherent structures and turbulence-salinity-sediment interactions at fine scales in order to reveal physical mechanisms responsible for the occurrence of convective instability and to improve the turbulence closure of the RANS model. The enhanced CSTMS will be utilized to carry out domain-scale (up to 5 km) scenario studies using typical physical settings of small montane rivers in order to determine how the small-scale convective, turbulent, density-driven and wave-driven processes interact at the scales of actual river outflows and affect sediment deposition. The results of this study will lay the groundwork for the design of future field programs and more comprehensive model-data comparisons. The research represents a combination of fundamental fluid dynamics (stratified hydraulics, instability, wave dynamics, turbulence-sediment interaction) and sediment-transport processes (frontal trapping, hyperpycnal flows, wave-supported gravity-flows), in context with a geophysical regime of global significance. While the importance of the contribution of small mountainous rivers to the total sediment discharge into the global oceans has been recognized since the early 90's, the dynamics of sediment-laden river plumes and the corresponding sediment transport processes remain poorly understood. The contributions from this research will thus occur both in the elucidation of the individual mechanisms and in their integrated impact on the cross-margin transport of sediment. Broader Impacts: The proposed research will impact various disciplines such as sedimentary geology, earth-surface processes research, and coastal engineering. The proposed modeling activity will be incorporated as an element of the Community Surface Dynamics Modeling System, a comprehensive suite of models quantifying the processes that modify the earth's landscape. These modeling efforts will also benefit several ongoing international research activities on field studies of hyperpycnal flow of small montane rivers in New Zealand and Taiwan. Hands-on laboratory experiments on sediment-laden plume will be developed by undergraduate scholars from underrepresented groups in collaboration with RISE program at University of Delaware (UD). Undergraduate scholars will also participate in outreach programs at UD to introduce the importance of sediment source-to-sink in our everyday life to middle/high school students and teachers. Two graduate students will be supported by this project for their PhD studies at UD. A post-doctoral investigator at WHOI will gain valuable experience as a participant in this project.

摘要 该奖项由 2009 年美国复苏和再投资法案（公法 111-5）资助。这个新奖项是为了对与小山地河流高度浑浊的流出物相关的动力学和沉积物输送过程进行多尺度建模研究。该项目将为 3D 波平均社区沉积物输送建模系统（CSTMS，一套基于耦合 ROMS/SWAN 框架的模型）做出贡献。这些增强功能将解决关键的波内过程，主要有两个方面：表面波和分层剪切流相互作用的新公式，以及对流对垂直沉积物通量影响的参数化，这可能会显着改变沉积物沉积的分布。波流相互作用的理论公式基于允许任意垂直电流变化的多尺度展开。由此产生的公式代表了对 ROMS 和 SWAN 之间数值耦合的重大修改。 2DV 波解析 RANS 模型能够解析含有沉积物的羽流动力学（例如异重流和对流不稳定性），将解析含有沉积物的羽流和表面波之间的相互作用，然后根据理论公式和增强的 CSTMS 进行测试。理想化的模拟。用于精细沉积物输运的 3D 湍流解析模拟工具将扩展到精细尺度上的不稳定性、相干结构和湍流-盐度-沉积物相互作用的研究，以揭示导致对流不稳定发生的物理机制，并改善湍流闭合RANS 模型。增强型 CSTMS 将用于利用小型山地河流的典型物理环境进行域尺度（最多 5 公里）情景研究，以确定小规模对流、湍流、密度驱动和波浪驱动过程如何相互作用在实际河流流出量的范围内并影响沉积物沉积。这项研究的结果将为未来现场计划的设计和更全面的模型数据比较奠定基础。该研究结合了基本流体动力学（分层水力学、不稳定性、波浪动力学、湍流-沉积物相互作用）和沉积物输送过程（锋面捕获、异重流、波浪支撑重力流），并结合了地球物理状况全球意义。尽管自 20 世纪 90 年代初以来人们就认识到山区小河流对全球海洋沉积物排放总量的重要性，但人们对富含沉积物的河流羽流的动态以及相应的沉积物输送过程仍然知之甚少。因此，这项研究的贡献将体现在阐明各个机制及其对沉积物跨缘运输的综合影响方面。更广泛的影响：拟议的研究将影响沉积地质学、地球表面过程研究和海岸工程等各个学科。拟议的建模活动将作为社区表面动力学建模系统的一个要素纳入其中，该系统是一套全面的模型，用于量化改变地球景观的过程。这些建模工作还将有益于正在进行的多项国际研究活动，这些活动涉及新西兰和台湾小山地河流异重流的实地研究。来自代表性不足群体的本科生学者将与特拉华大学 (UD) 的 RISE 项目合作，开发关于沉积物羽流的实验室实践实验。本科生学者还将参加特拉华大学的外展项目，向中学生和教师介绍沉积物从源到汇在我们日常生活中的重要性。该项目将支持两名研究生在特拉华大学攻读博士学位。 WHOI 的博士后研究员作为该项目的参与者将获得宝贵的经验。