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

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。这个新的奖项是一个多尺度的动力学和沉积物输运过程的建模研究，与高浑浊的流出小型山区河流。该项目将有助于三维波浪平均社区沉积物输运建模系统（CSTMS，一套基于ROMS/SWAN耦合框架的模型）。增强将解决关键的波内过程，主要是双重的：一个新的提法的相互作用的表面波和分层剪切流，参数化对流的影响，垂直沉积通量，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是基于多尺度扩展，允许任意的垂直电流变化。由此产生的配方代表了一个显着的修改ROMS和SWAN之间的数值耦合。能够解决含沉积物羽流动力学（例如超密流和对流不稳定性）的2DV波浪解析RANS模型将解决含沉积物羽流与表面波之间的相互作用，然后在理想化模拟中针对理论公式和增强的CSTMS进行测试。一个用于细颗粒泥沙输运的三维相干分辨模拟工具将扩展到研究细尺度的不稳定性、相干结构和相干-盐度-泥沙相互作用，以揭示造成对流不稳定的物理机制，并改进RANS模式的湍流封闭性。将利用增强的科学、技术和监测系统，利用山区小河流的典型物理环境，进行区域尺度（最多5公里）的情景研究，以确定小尺度对流、湍流、密度驱动和波浪驱动过程如何在实际河流流出尺度上相互作用，并影响沉积物沉积。这项研究的结果将奠定基础，为未来的现场方案的设计和更全面的模型数据comparation.The研究的基本流体动力学（分层水力学，不稳定性，波浪动力学，粘性沉积物的相互作用）和沉积物输运过程（前沿捕获，hyperpycnal流，波支持重力流）的组合，在全球意义的地球物理制度的背景下。虽然自90年代初以来已认识到山区小河流对全球海洋沉积物排放总量的重要性，但对载有沉积物的河流羽流的动态和相应的沉积物输运过程仍知之甚少。因此，这项研究的贡献将发生在阐明的个别机制，并在其综合影响的跨界运输sediment.Broader影响：拟议的研究将影响各个学科，如沉积地质学，地球表面过程的研究，和海岸工程。拟议的建模活动将作为社区表面动力学建模系统的一个组成部分，这是一套全面的模型，量化了改变地球景观的过程。这些模拟工作也将有利于几个正在进行的国际研究活动，在新西兰和台湾的山区小河流的hypercnal流的实地研究。来自代表性不足群体的本科学者将与特拉华州大学（UD）的RISE项目合作，开发关于载有沉积物的羽流的动手实验室实验。本科生学者也将参加在UD的推广计划，介绍沉积物源在我们的日常生活中的重要性，以初中/高中学生和教师。本项目将资助两名研究生在UD攻读博士学位。WHOI的博士后研究员将作为该项目的参与者获得宝贵的经验。

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.