Collaborative Research: Multiscale modeling of internal tides at topographic generation sites: turbulence and wave energetics:

协作研究：地形生成地点内潮汐的多尺度建模：湍流和波浪能量学：

• 批准号: 1459774
• 负责人: Sutanu Sarkar
• 金额: $ 33.49万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-02-15 至 2019-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1459774&HistoricalAwards=false
• 关键词: Collaborative; Research; Multiscale; modeling; internal

Turbulent processes associated with internal waves occurring at or near the generation sites of internal tides are key ingredients in maintaining and regulating the global ocean circulation which is a crucial component of the climate system affecting simultaneously the uptake of carbon dioxide into the ocean and the meridional transport of heat. Accurate computation of the magnitude and spatial distribution of turbulent dissipation is necessary for the development of physically based parameterizations of conversion and dissipation rates in the near-field. Qualitative changes in turbulence occur when geometry, barotropic forcing and environmental parameters change. The spatial and temporal scales of the physical processes that drive the turbulent energy dissipation during the generation of internal waves span several orders of magnitude. To address these knowledge gaps, a multi-scale approach is necessary to span the disparity between scales: from the scale of the outgoing low-mode internal tide (vertical scale is of order one kilometer, horizontal scale is of order tens of kilometers, time is of order hours) through the nonlinear formation of higher wave number modes to, finally, the turbulence events (spatial scale of meters and time scale of minutes). The integration of models across disparate scales is not only relevant to ocean sciences but also of great interest in many areas of science and engineering, e.g., the representation of turbulent boundary layer processes in medium- and long-term weather forecasting. The broader community interested in developing or applying parameterizations will have access to the simulation data and the numerical model code. Two graduate students will be trained and gain valuable experience in applying cutting edge numerical tools to a complex ocean problem. A numerical investigation of the generation process of internal waves by barotropic tidal flow over an isolated topographic feature scales with the relevant non-dimensional parameters will be conducted. The driving hypothesis is that only the inclusion of turbulence in a realistic way can provide a correct description of the dissipation rates during generation and near-field propagation of internal waves at these sites. The scale-separation will be handled through a novel hierarchical approach that combines Large Eddy Simulation (LES) at small scales with the Stratified Ocean Model with Adaptive Refinement (SOMAR) for the large scales. The LES model, equipped with a sophisticated subgrid-scale model, is capable of providing a faithful description of turbulence, without the need of tunable parameters. The non-hydrostatic SOMAR is specifically optimized to deal with the anisotropy of the internal wave problem. The goal is to implement a two-way nested SOMAR-LES model so that the LES is driven with realistic forcing, and SOMAR receives realistic turbulent feedbacks. We will do so for a model triangular ridge at oceanic scales over a wide range of key non-dimensional parameters: overall Excursion number, obstacle criticality, inner Excursion number and length of critical slope. The simulations will be analyzed to ascertain (i) the dependence of internal wave energetics on the non-dimensional parameters, and (ii) a better understanding of stabilities, turbulence and associated dissipation rates in the near-field.

与内潮汐产生地点或附近发生的内波相关的湍流过程是维持和调节全球海洋环流的关键因素，而全球海洋环流是气候系统的重要组成部分，同时影响二氧化碳进入海洋的吸收和热量的经向输送。准确计算湍流耗散的幅度和空间分布对于开发近场转换和耗散率的基于物理的参数化是必要的。当几何形状、正压强迫和环境参数发生变化时，湍流就会发生质的变化。内波生成过程中驱动湍流能量耗散的物理过程的空间和时间尺度跨越几个数量级。为了解决这些知识差距，需要采用多尺度方法来跨越尺度之间的差异：从流出的低模式内潮的尺度（垂直尺度为一公里量级，水平尺度为数十公里量级，时间为小时量级）到更高波数模式的非线性形成，最后到湍流事件（空间尺度为米和时间尺度为分钟）。不同尺度的模型集成不仅与海洋科学相关，而且在科学和工程的许多领域也具有很大的意义，例如中长期天气预报中湍流边界层过程的表示。对开发或应用参数化感兴趣的更广泛的社区将能够访问模拟数据和数值模型代码。两名研究生将接受培训，并获得将尖端数值工具应用于复杂海洋问题的宝贵经验。将利用相关无量纲参数对孤立地形特征尺度上正压潮汐流产生内波的过程进行数值研究。驱动假设是，只有以现实的方式包含湍流才能正确描述这些地点的内波生成和近场传播期间的耗散率。尺度分离将通过一种新颖的分层方法来处理，该方法将小尺度的大涡模拟（LES）与大尺度的分层海洋模型与自适应细化（SOMAR）相结合。 LES 模型配备了复杂的亚网格尺度模型，能够忠实地描述湍流，而不需要可调参数。非静水力SOMAR专门针对处理内波的各向异性问题进行了优化。目标是实现双向嵌套 SOMAR-LES 模型，以便 LES 通过真实的强迫驱动，并且 SOMAR 接收真实的湍流反馈。我们将针对海洋尺度的三角山脊模型在各种关键无量纲参数上进行此操作：总体偏移数、障碍物临界度、内部偏移数和临界斜率长度。将分析模拟以确定（i）内波能量学对无量纲参数的依赖性，以及（ii）更好地理解近场中的稳定性、湍流和相关耗散率。

项目成果

Energetics and mixing in buoyancy-driven near-bottom stratified flow

浮力驱动的近底部分层流中的能量和混合

• DOI: 10.1017/jfm.2019.184
• 发表时间: 2019
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: Puthan, Pranav;Jalali, Masoud;Chalamalla, Vamsi K.;Sarkar, Sutanu
• 通讯作者: Sarkar, Sutanu