权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Effects of internal waves on mixing and transport by gravity currents

内波对重力流混合和传输的影响

基本信息

批准号：
1634389
负责人：
Jeffrey Koseff
金额：
$ 34.84万
依托单位：
Stanford University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-09-01 至 2020-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634389&HistoricalAwards=false
关键词：
Effects internal waves mixing transport

项目摘要

Because of increased global water scarcity governments are increasingly considering the contribution made by desalination as a primary source of drinking water. Thus, the fate of dense brine effluent from coastal discharges is becoming an increasingly acute issue. The areal extent over which brine plumes from desalination facilities impact the coastal ocean remains a major uncertainty, particularly because there are energetic internal wave fields which can cause significant mixing in many coastal oceans where desalination facilities are present or proposed. Fundamental understanding of the mixing of the plume with the ambient receiving waters is thus critical to predicting the concentrations of brine and chemical additives in the plume and surrounding waters. In particular, determining the pathways and mechanisms in which the mixing and dilution of dense gravity-current underflows down slopes are influenced by oncoming internal waves is an outstanding question. Although our understanding of how waves on slopes break and how gravity currents descend through stratified environments have independently moved forward considerably in recent years, surprisingly little work has been done on the increasingly important coupling problem. This project will address this need using laboratory experimentation in combination with complementary numerical simulations and theoretical modeling. The experiments and theoretical approach extends gravity current analysis to the important setting of breaking interfacial waves in the environment. Understanding the influence of this kind of ambient motion on dispersion in gravity currents is important to many industrial and scientific fields. For example, the results of this work will enable industry and other stakeholders to make better assessments of the environmental impacts of desalination design alternatives, including the potential creation of GIS-based tools. Summer research students will be engaged through the Department of Civil and Environmental Engineering?s Research Experience for Undergraduates Program and the Stanford Summer Engineering Academy run by the School of Engineering. This project will also directly support the training and education of a post-doctoral researcher and one graduate student, who will both be involved in teaching undergraduates.The proposed laboratory experiments and numerical simulations will establish what happens to a gravity current that descends down a slope through an ambient that has a two-layer density profile and internal gravity waves. Numerical simulations of the same experimental setup will be validated against the laboratory observations, and then used to further investigate parameter regimes unattainable in the laboratory. A theoretical framework based on the potential energy required to change the density profile within the current will be created to understand the detrainment observations from first principles. The investigation will be performed using internal wave tank and numerical modeling facilities, and will examine the physics of how interfacial waves influence inclined gravity currents. Shoaling internal waves have different regimes of breaking, including non-breaking seiches on steep slopes; coherent boluses; less-coherent and more turbulent boluses; and turbulent surges. Gravity currents descending through two-layer ambients can either form intrusions at the pycnocline; form underflows which penetrate beneath the lower layer; or split into an intruding and an under flowing part. When gravity currents and internal waves are present at the same time, however, much less is known. This project will lead to substantial new insight in two ways: by identifying and systematically cataloging the ways that internal waves can influence the physics of gravity currents, and by building and validating mathematical models of the mechanisms by which they do so. Three key parameters (the wave Froude number, the Iribarren number, and the density Richardson number of the current) will be used to define the parameter space of the investigation.

由于全球水资源日益短缺，各国政府越来越多地考虑将海水淡化作为饮用水的主要来源所作的贡献。因此，沿海排放的浓盐水的命运正成为一个日益尖锐的问题。海水淡化设施的卤水羽流影响沿海海洋的面积范围仍然是一个主要的不确定性，特别是因为存在高能的内波场，这可能会在许多已有或拟设立海水淡化设施的沿海海洋造成重大混合。因此，对羽流与周围接收水混合的基本了解对于预测羽流和周围水域中卤水和化学添加剂的浓度至关重要。特别是，确定密集重力流下坡混合和稀释受即将到来的内波影响的路径和机制是一个突出的问题。尽管我们对斜坡上的波浪如何破裂以及重力流如何通过分层环境的理解在最近几年取得了相当大的进展，但令人惊讶的是，在日益重要的耦合问题上所做的工作很少。该项目将利用实验室实验结合补充的数值模拟和理论建模来满足这一需求。实验和理论方法将重力流分析扩展到环境中破碎界面波的重要设置。了解这种环境运动对重力流中弥散的影响，对于许多工业和科学领域具有重要意义。例如，这项工作的结果将使工业和其他利益攸关方能够更好地评估海水淡化设计替代方案的环境影响，包括创造基于地理信息系统的工具的可能性。暑期研究学生将通过土木工程与环境工程系？S本科生研究经验计划和工程学院举办的斯坦福大学暑期工程学院进行招聘。该项目还将直接支持一名博士后研究人员和一名研究生的培训和教育，他们都将参与本科生的教学工作。拟议的实验室实验和数值模拟将确定通过具有两层密度分布和内部重力波的环境下坡下的重力流会发生什么。相同实验装置的数值模拟将与实验室观测结果进行验证，然后用于进一步研究实验室无法获得的参数范围。我们将建立一个基于改变海流中密度分布所需势能的理论框架，以从第一性原理理解偏离观测。这项研究将使用内波池和数值模拟设施进行，并将检查界面波如何影响倾斜重力流的物理学。浅海内波有不同的破碎模式，包括陡坡上的不间断波；连贯的波；不太连贯和更湍急的波；以及湍急的涌浪。流经双层大气的重力流既可以在跃层形成侵入，也可以形成穿透下层的潜流，也可以分裂为侵入部分和潜流部分。然而，当重力流和内波同时存在时，我们所知的要少得多。该项目将在两个方面带来实质性的新见解：通过确定和系统地分类内波可以影响重力流物理的方式，以及通过建立和验证内波影响重力流物理的机制的数学模型。三个关键参数(波的弗劳德数、艾伯伦数和水流的密度理查森数)将被用来定义调查的参数空间。