Collaborative Research: The interactions of waves, tidal currents and river outflows and their effects on the delivery and resuspension of sediments in the near field

合作研究：波浪、潮流和河流流出的相互作用及其对近场沉积物输送和再悬浮的影响

• 批准号: 1334641
• 负责人: Gangfeng Ma
• 金额: $ 11.63万
• 依托单位: Old Dominion University Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1334641&HistoricalAwards=false
• 关键词: Collaborative; Research; interactions; waves; tidal

This study will focus on the mechanisms for sediment resuspension and removal in the near field of a river mouth plume characterized by a combination of strong freshwater discharge, significant vertical shear resulting from stratification, and strong surface wave conditions. It is hypothesized that the dispersal pathway of river-borne sediment is possibly more often governed by resuspension events in the region of sediment trapping, as opposed to only being an a priori property of the riverine discharge. Further, surface waves are hypothesized to be an important component of the overall physical mechanism of bottom stress and sediment resuspension in river mouths and coastal inlets, leading to greatly enhanced potential for sediment transport. In order to address these hypotheses, the researchers will further develop and utilize a nonhydrostatic model (NHWAVE) with capabilities to handle salinity stratification and suspended sediment in both wave-resolving and wave-averaged forms, using, in particular, results from ongoing NSF-funded work on river plume dynamics. The model will be validated against a high-resolution data set for instabilities in sheared buoyant plume flow in order to establish the accuracy of the formulation at high resolution, and against a larger scale transect of data from the Mouth of the Columbia River (MCR) to verify basic wave and circulation processes in the model. The model will be applied to the MCR in order to study the interplay of tidally pulsed river plume and waves and the resulting removal and resuspension of sediments in the vicinity of ebb-tidal plume liftoff, and will be further used in interpreting results from the ONR-sponsored RIVET-II experiment, conducted in June 2013.Estuaries and river mouths provide the pathway for riverine supply of sediments to the coast and the distribution of sediments to the shelf and deep ocean. This project will study the influence and coupling of tidal currents, river discharges and surface waves in determining the sediment transport regime in coastal inlets. The first task will be to develop and test both wave-resolving and wave averaged versions of a flexible, parallelized nonhydrostatic model NHWAVE, which has recently been extended to incorporate density stratification and the presence of a suspended sediment load, thus providing the basic tools needed for high resolution process studies. The further development of the model is important for several reasons. First, the strong vertical components of motion associated with the tidal genesis of fronts in surface advected plumes, and the occurrence of strong resuspension events near regions of plume liftoff, require the application of fully nonhydrostatic models. In addition, wave processes in strongly sheared flows associated with surface-advected plumes are not adequately described by either existing wave resolving models or by theory for wave-averaged flows in weakly sheared environments as presently used in standard coastal ocean models, thus requiring improved model formulations.This research will advance the understanding of sedimentation processes at the intersection of river and coastal environments. The model development effort will further the recent trend towards use of nonhydrostatic formulations in coastal ocean models by incorporating wave-resolving capabilities, leading to the ability to represent a full range of wave, current, stratification, turbulence and sediment processes in a common computational framework utilized at realistic scales. The resulting model will greatly enhance the community's ability to assess the effect of complex, irregular wave processes on bottom stress and sediment resuspension, leading to a better understanding of the pathways for sediment motion from river to shelf. The resources from the grant will partially support three doctoral graduate researchers, and undergraduate summer fellows through an existing REU program. The PIs will continue their efforts to promote science and research to a K-12 population through continued and expanded participation in University of Delaware programs such as Coast Day, Engineering Cool Stuff Camp and Young Engineers Camp.

这项研究将着重于在河口羽流的近场中重新悬浮的机制，其特征是结合了强大的淡水排放，分层导致的明显垂直剪切以及强烈的表面波条件。假设，河流沉积物的分散途径可能更常见于沉积物捕获区域的重悬事件，而不是仅是河流排放的先验性质。此外，假设表面波是河流和沿海入口的底部压力和沉积物重悬的总体物理机理的重要组成部分，从而大大增强了沉积物运输的潜力。为了解决这些假设，研究人员将进一步开发和利用具有能力处理盐度分层和悬浮沉积物的非遗水模型（NHWAVE），尤其是使用持续的NSF资助的NSF资助的River Plume Dynamics上的NSF资助的作品产生的。该模型将在剪切浮力羽流中的不稳定性的高分辨率数据集进行验证，以确定在高分辨率下制剂的准确性，并与从哥伦比亚河口（MCR）口（MCR）较大的数据进行验证，以验证模型中基本波浪和循环过程。该模型将应用于MCR，以研究潮汐脉冲的河羽和波的相互作用，以及由此导致的潮汐羽流升降附近的沉积物的去除和重新悬浮，并将进一步用于解释2013年6月的沿海和河流的沿海景点，以解释沿海的河流和沿岸的河流。将沉积物分布到架子和深海。该项目将研究潮流，河流排放和表面波的影响和耦合，以确定沿海入口的沉积物运输状态。第一个任务是开发和测试柔性，并行的非遗水模型NHWAVE的波浪分解和波平均版本，该版本最近已扩展以结合密度分层和存在悬浮的沉积物负载，从而提供了高分辨率过程研究所需的基本工具。由于几个原因，该模型的进一步发展很重要。首先，与表面对流羽流的潮汐起源相关的强大运动成分，以及在羽状升降区域附近发生强的重悬事件的发生，需要应用完全非遗传模型。此外，现有的波浪解析模型或理论上，在弱剪切的环境中，在弱剪切的环境中使用现有波浪平均流量的强烈剪切流中的波过程无法充分描述，因为目前在标准的沿海海洋模型中使用了，因此需要改进的模型配方。这些研究将提高对河流和沿海地区层面和沿海地区的沉积过程的理解。模型开发工作将进一步通过结合波浪分辨能力来进一步在沿海海洋模型中使用非静态配方的趋势，从而在逼真的尺度上使用的通用计算框架中代表各种波浪，电流，分层，湍流和沉积物过程的能力。最终的模型将极大地增强社区评估复杂，不规则波过程对底部压力和沉积物重悬的影响的能力，从而更好地理解从河流到架子的沉积物运动的途径。赠款的资源将部分支持三位博士研究生研究人员，并通过现有REU计划的本科夏季研究员。 PI将通过继续参与特拉华大学计划，例如海岸日，工程酷炫的东西营和年轻工程师训练营，继续努力为K-12人口促进科学和研究。