CAREER: Internal Waves, Turbulence and Diapycnal Mixing in Oceanic Flows

职业：海洋流中的内波、湍流和二重混合

• 批准号: 1151838
• 负责人: Subhas Venayagamoorthy
• 金额: $ 51.72万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-03-01 至 2019-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1151838&HistoricalAwards=false
• 关键词: CAREER; Internal; Waves; Turbulence; Diapycnal

The oceanic internal wave field is widely accepted to be one of the most dominant sources of energy for the sustenance of small-scale ocean turbulence. The advancement of the current state of knowledge on internal waves, turbulence and diapycnal (cross-isopycnal) mixing in oceanic flows is critical for the accurate parameterization of the processes that control the dynamics of these flows. A key example concerns the parameterization of mixing processes in ocean general circulation models, where long term predictions are highly sensitive to mixing parameterizations that can result in uncertain predictions of the ocean's role in climate change. A key related question is how should the small-scale mixing effects be incorporated into models of mixing and dispersion in stably stratified turbulence? These are fundamental research questions that the oceanographic community need to address in order to enhance the predictive capability of large scale circulation models. The subject of this CAREER project is on dissipation of internal waves linked closely to turbulence and diapycnal mixing. The primary theme and vision of this proposal is to improve understanding and modeling of geophysical flows that will lead to new generalized formulations for turbulent fluxes of momentum and scalars. A holistic approach that integrates basic and applied multi-disciplinary research with a strong educational program is proposed. In particular, the key research objectives of this CAREER project are to obtain new fundamental insights into the details of the turbulent mixing processes in geophysical stratified flows that will translate into simple effective parameterizations for use in large scale numerical models and to bridge the gap between parameterizations/models for turbulent mixing to be developed (and already developed) by the PI from fundamental numerical simulations and laboratory experiments to geophysical scale models by addressing up-scaling issues via novel model-data comparisons. To this end, high-resolution direct numerical simulations (DNS) and large-eddy simulations (LES) coupled with particle tracking of forced stably stratified turbulence and internal wave induced turbulence in Knight Inlet sill will be performed in order to gain insight into small-scale processes and develop/extend models for mixing. Second, model-data comparisons will be performed using relevant turbulence and wave measurements in the ocean that will be available through collaborations forged with field scale oceanographers. A third aspect of this research is to formulate turbulence closure schemes for use in Reynold-Averaged Navier-Stokes (RANS) models. The intellectual merit of this proposal is based on the generation of new knowledge and concepts for describing mixing and dispersion in stratified geophysical flows. State of the art turbulence simulations coupled with particle tracking will be used to build on the principal investigator's prior innovative steps to identify new ways for elucidating mixing mechanisms using a combination of Eulerian and Lagrangian analysis of fluid motion. In particular, new turbulence diagnostic tools for the separation and quantification of irreversible momentum and scalar fluxes associated with the energetics of these flows will be developed. The proposed work will seek to formulate a seamless approach to parameterize the intermingled dynamics resulting from the co-existence of internal waves and turbulence in stratified geophysical flows. The insights gained from this study will significantly improve our understanding of the key dynamical features of stably stratified flows which are ubiquitous in the ocean. The insights gained in concert with theoretical ideas will form the basis to develop better parameterizations for mixing that will be tested in non-homogeneous turbulent flows in large-scale water column models. Another novel aspect of the research methodology proposed is the use of "real world" field-scale case studies via model-data comparisons to test and provide feedback on the efficacy of mixing models thus allowing for ongoing refinement of the models.The broader impacts of this research come from the broad applicability of improved mixing parameterizations in oceanography, atmospheric science and engineering, especially concerning climate change, environmental sustainability, renewable energy and national security. Broader impact also comes from the strong integrated educational and outreach program. The principal investigator will establish an environmental fluid dynamics program at Colorado State University (CSU) with an emphasis on empowering students with skill sets required to solve complex geophysics and engineering related problems in multi-disciplinary settings. Research and education are integrated through two new graduate courses in environmental fluid mechanics. The principal investigator will recruit and train underrepresented minority and female students in the field of environmental fluid mechanics. This project will support the training of two PhD students (at least one of whom will be a female student). Outreach efforts include the principal investigator's involvement in summer camps/programs coordinated by the Women and Minorities in Engineering Program (WMEP) at CSU as well as through outreach to a local high school. The results of this project will be widely disseminated through premier international journal articles in physical oceanography and fluid mechanics as well as through seminars and presentations at scientific conferences and a dedicated website.

海洋内波场被广泛认为是维持海洋小尺度湍流最主要的能量来源之一。关于海洋流动中的内波、湍流和横等密度线混合的现有知识的进步对于控制这些流动动态的过程的精确参数化至关重要。一个重要的例子涉及海洋环流模型中混合过程的参数化，长期预测对混合参数化非常敏感，这可能导致海洋在气候变化中的作用的不确定预测。一个关键的相关问题是如何将小尺度混合效应纳入稳定分层湍流的混合和扩散模型？这些都是海洋学界需要解决的基本研究问题，以提高大尺度环流模式的预测能力。这个CAREER项目的主题是关于与湍流和底流混合密切相关的内波耗散。该提案的主要主题和愿景是提高对地球物理流的理解和建模，这将导致动量和标量湍流通量的新的广义公式。提出了一种整体的方法，将基础和应用多学科研究与强大的教育计划相结合。特别是，这个CAREER项目的主要研究目标是，获得关于地球物理分层流中湍流混合过程细节的新的基本见解，这些基本见解将转化为用于大尺度数值模型的简单有效的参数化，并弥合有待开发的湍流混合参数化/模型之间的差距PI通过新颖的模型-数据比较解决尺度放大问题，从基础数值模拟和实验室实验到地球物理尺度模型（已经开发）。为此，高分辨率的直接数值模拟（DNS）和大涡模拟（LES）加上粒子跟踪强制稳定分层湍流和内波诱导湍流在骑士入口门槛将进行深入了解小规模的过程和开发/扩展模型的混合。第二，将利用海洋中的相关湍流和波浪测量结果进行模型数据比较，这些测量结果将通过与实地尺度海洋学家的合作获得。本研究的第三个方面是制定湍流封闭方案，用于雷诺平均纳维尔-斯托克斯（RANS）模型。这一建议的智力价值是基于新的知识和概念的产生，用于描述分层地球物理流的混合和分散。最先进的湍流模拟加上粒子跟踪将被用来建立在主要研究者的先前创新步骤，以确定新的方法来阐明混合机制，使用流体运动的欧拉和拉格朗日分析相结合。特别是，将开发新的湍流诊断工具，用于分离和量化与这些流动的能量学相关的不可逆动量和标量通量。拟议的工作将寻求制定一个无缝的方法来参数化的混合动力学所造成的共存的内波和湍流的分层地球物理流。从这项研究中获得的见解将显着提高我们的理解的关键动力学特性的稳定分层流是无处不在的海洋。与理论思想一致获得的见解将形成基础，以开发更好的混合参数化，将在大规模水柱模型的非均匀湍流中进行测试。提出的研究方法的另一个新颖方面是通过模式-数据比较使用"真实的世界"实地尺度案例研究，以测试混合模式的有效性并提供反馈，从而允许不断改进模式。这项研究的更广泛影响来自海洋学、大气科学和工程中改进的混合参数化的广泛适用性，特别是在气候变化方面，环境可持续性、可再生能源和国家安全。更广泛的影响还来自强大的综合教育和推广计划。首席研究员将在科罗拉多州立大学（CSU）建立一个环境流体动力学项目，重点是使学生具备在多学科环境中解决复杂物理学和工程相关问题所需的技能。研究和教育通过两个新的研究生课程在环境流体力学相结合。首席研究员将征聘和培训环境流体力学领域人数不足的少数民族学生和女生。该项目将支持培训两名博士生（其中至少一名为女生）。外联工作包括主要研究员参与由科罗拉多州立大学妇女和少数民族工程方案协调的夏令营/方案，以及通过外联到当地一所高中。该项目的成果将通过物理海洋学和流体力学方面的主要国际期刊文章以及通过研讨会和科学会议上的介绍和一个专门网站广泛传播。