Turbulence in tidal flow over rough three-dimensional topography

粗糙三维地形上的潮汐流湍流

• 批准号: 1737367
• 负责人: Sutanu Sarkar
• 金额: $ 51.22万
• 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: 2017
• 资助国家: 美国
• 起止时间: 2017-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1737367&HistoricalAwards=false
• 关键词: Turbulence; tidal; flow; over; rough

This project examines how tidal flows in the ocean interior, particularly near underwater mountains, seamounts and ridges, contribute to the generation of turbulent and other complex flows. These flows contribute to mixing of heavier, cold bottom waters with overlying lighter, warmer oceanic waters. The project uses specialized high resolution numerical simulations to describe and predict turbulent motions over idealized conical mounts. These simplified geometries are used to represent rough underwater topography, like that found in the oceans. The flows investigated, and the water temperature distribution they create, play an important role in setting weather and climate. Also, they establish the environment for marine life, and determine the conditions faced by manned and unmanned submerged vehicles, usually used for defense and ocean exploration. Results from this project will be utilized by the scientific community engaged to observations of fine-scale processes in the environment and their parameterization in numerical large-scale models. A graduate student and a postdoctoral researcher will be supported and they will gain exposure to ocean sciences, fluid mechanics, and computational science in the context of a problem of great societal interest. Ocean tides constitute a large reservoir of energy that can be converted to internal gravity waves and turbulence. Tidally modulated flows encounter submerged, three-dimensional (3D), small-scale topographic features of order 1-10 km within larger scale, nominally two-dimensional ridges, islands and headlands. These flows generate propagating internal gravity waves at the oscillation frequency and at higher harmonics, along with transient downslope jets and lee waves. The shed vortices generated interact among themselves and with the body leading to complex turbulent motions. This project will identify the relative roles of the wake vortices (sub-mesoscale eddies), formed by flow around the three-dimensional features, and the nonlinear internal wave field using high-resolution simulations. High-resolution 3D large eddy simulations (LES) of flow over a steep (supercritical slope) conical obstacle in the stratified flow regime of low topographic Froude number will be performed. The simulations and analyses aim to characterize and understand the dynamics as a function of the following non-dimensional parameters: the relative strength of mean and oscillating velocity components, the ratio of the flow excursion length to a characteristic along-flow topography length, and the shape of the horizontal cross-section of the obstacle. The simplified setting used in the simulations will allow to advance knowledge of the combined dynamics of the vortices, wake and the nonlinear internal-wave near field, and of the consequences for stratified turbulence at 3D topography. Preliminary results have shown the generation of interacting eddies, complex 3D nonlinear internal wave fields and turbulence occurring in multiple vertical layers.

该项目研究海洋内部，特别是水下山脉、海山和海脊附近的潮汐流动如何促成湍流和其他复杂流动的产生。这些流动有助于较重的冷的底层沃茨与上面较轻的温暖的海洋沃茨混合。该项目使用专门的高分辨率数值模拟来描述和预测理想化的锥形支架上的湍流运动。这些简化的几何图形被用来表示粗糙的水下地形，就像在海洋中发现的那样。所研究的水流及其产生的水温分布在天气和气候的形成中起着重要作用。此外，它们还为海洋生物建立了环境，并确定了载人和无人潜水器所面临的条件，这些潜水器通常用于国防和海洋勘探。参与观测环境中小尺度过程及其在大尺度数值模型中参数化的科学界将利用该项目的成果。 一名研究生和一名博士后研究员将得到支持，他们将在社会感兴趣的问题的背景下接触海洋科学，流体力学和计算科学。海洋潮汐构成了一个巨大的能量库，可以转化为内部重力波和湍流。潮汐调制流遇到淹没，三维（3D），小规模的地形特征，1-10公里的规模较大，名义上二维的山脊，岛屿和岬。这些流动产生以振荡频率和高次谐波传播的内部重力波，沿着瞬态下坡射流和背风波。所产生的脱落涡流相互作用，并与身体导致复杂的湍流运动。该项目将使用高分辨率模拟来确定由三维特征周围的流动形成的尾涡（亚中尺度涡旋）和非线性内波场的相对作用。 高分辨率的三维大涡模拟（LES）的流动在一个陡峭的（超临界斜率）锥形障碍物在低地形弗劳德数的分层流态将被执行。模拟和分析的目的是表征和理解的动力学作为以下无量纲参数的函数：平均和振荡速度分量的相对强度，流量漂移长度的比率的特征沿流地形长度，和障碍物的水平横截面的形状。在模拟中使用的简化设置将允许先进的知识的涡，唤醒和非线性内波近场的组合动力学，以及分层湍流在3D地形的后果。初步结果表明，相互作用的涡流，复杂的三维非线性内波场和湍流发生在多个垂直层的产生。

项目成果

Tidal Synchronization of Lee Vortices in Geophysical Wakes

• DOI: 10.1029/2020gl090905
• 发表时间: 2021-01
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Pranav S. Puthan;S. Sarkar;G. Pawlak

High Drag States in Tidally Modulated Stratified Wakes

潮汐调制层状尾流中的高阻力状态

• DOI: 10.1175/jpo-d-21-0178.1
• 发表时间: 2022
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Puthan, Pranav;Pawlak, Geno;Sarkar, Sutanu
• 通讯作者: Sarkar, Sutanu

The wake of a three-dimensional underwater obstacle: Effect of bottom boundary conditions

三维水下障碍物的尾流：底部边界条件的影响

• DOI: 10.1016/j.ocemod.2020.101611
• 发表时间: 2020
• 期刊: Ocean Modelling
• 影响因子: 3.2
• 作者: Puthan, Pranav;Jalali, Masoud;Ortiz-Tarin, Jose Luis;Chongsiripinyo, Karu;Pawlak, Geno;Sarkar, Sutanu
• 通讯作者: Sarkar, Sutanu