CAREER: Sheared stratified turbulence: novel mechanisms and models of complex wave-vortex interactions that impact our environment

职业：剪切分层湍流：影响我们环境的复杂波涡相互作用的新机制和模型

基本信息

批准号：
2042346
负责人：
Andrew Bragg
金额：
$ 50万
依托单位：
Duke University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-01-01 至 2025-12-31
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2042346&HistoricalAwards=false
关键词：
CAREER Sheared stratified turbulence novel

项目摘要

Environmental turbulent flows are strongly influenced by stratification of air or water density, complex interactions between shearing motions, internal waves, and turbulence. Such flows may be categorized as Sheared, Stably Stratified Turbulence (SSST). Understanding SSST is crucial for a plethora of environmental problems, such as accurately describing vertical mixing in ocean circulation models, which are key for climate predictions, for weather forecasting, for predicting the dispersion of pollutants in the atmosphere or harmful plankton blooms in water systems. However, many fundamental questions about the physics of SSST remain, and robust, physics-based models are lacking. These issues must be addressed in order to make progress in predicting SSST and its role in environmental applications. This research will lead to new discoveries about the fundamental physics of SSST, and the development of predictive models for solving environmental flow problems. Outreach and education activities will include undergraduate summer projects, exciting and interactive new lessons and mini-projects for K-12 children, and public lectures that explain the fascinating and important subjects of turbulence and complexity science through connections with art. While aspects of SSST have been investigated, recalcitrant fundamental questions remain. When both stratification and shear are large, the flow may be composed of patches of turbulent and non-turbulent motion. How this “patchy” behavior originates/interacts with the kinetic and potential energy cascade mechanisms, and its implications for the transport of scalars and particles, remains a frontier to be confronted here. The research objective is to provide transformative insights into the fundamental mechanisms governing the energy cascades, intermittency, mixing efficiency, and particle transport in SSST, through new analysis, models, and Direct Numerical Simulations. Specific goals are - Goal 1: Conduct a new analysis of the kinetic and potential energy cascade mechanisms using filtering and slow-fast manifold decompositions to unravel contributions from internal waves, mean-shear, and nonlinearity. Goal 2: Use new Navier-Stokes-based, Lagrangian models for the filtered fluid velocity and density gradients to capture the nonlinear term exactly and which are robust for arbitrary Reynolds and Prandtl numbers. Goal 3: Develop new models of particle transport, that extend and apply the models of Goal 2 to predict multi-scale clustering and particle orientations. One of the undergraduate summer internship projects will involve coupling the models of Goal 2 to the Weather Research and Forecasting (WRF) model to predict turbulence at scales not resolved by WRF and explore the impact of variations in large-scale flow conditions on these unresolved scales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

环境湍流受空气或水密度分层、剪切运动、内波和湍流之间复杂的相互作用的强烈影响，此类流动可归类为剪切稳定分层湍流 (SSST)，了解 SSST 对于许多环境至关重要。问题，例如准确描述海洋环流模型中的垂直混合，这对于气候预测、天气预报、预测大气中污染物的扩散或有害物质的扩散至关重要。然而，关于SSST物理学的许多基本问题仍然存在，并且必须解决这些问题才能在预测SSST及其在环境应用中的作用方面取得进展。将带来关于 SSST 基础物理的新发现，以及开发解决环境流动问题的预测模型，外展和教育活动将包括本科生暑期项目、令人兴奋的互动新课程和 K-12 儿童的迷你项目。公开讲座解释了令人着迷的虽然 SSST 的各个方面已经得到研究，但当分层和剪切力都很大时，流动可能由湍流和非湍流运动组成。 “斑驳”行为起源于动能和势能级联机制/相互作用，及其对标量和粒子输运的影响，仍然是这里需要面对的前沿。通过新的分析、模型和直接数值模拟，对控制 SSST 中的能量级联、间歇性、混合效率和粒子输运的基本机制产生变革性的见解。具体目标是 - 目标 1：对动能和势能进行新的分析。使用滤波和慢-快流形分解的级联机制来揭示内波、平均剪切和非线性的贡献。目标 2：使用新的基于纳维斯托克斯的、用于过滤流体速度和密度梯度的拉格朗日模型，以准确捕获非线性项，并且对于任意雷诺数和普朗特数都具有鲁棒性。目标 3：开发新的粒子输运模型，扩展并应用目标 2 的模型来预测多粒子。本科生暑期实习项目之一将涉及将目标 2 的模型与天气研究和预报 (WRF) 模型相结合，以预测 WRF 无法解决的尺度上的湍流。探索大规模流动条件的变化对这些未解决的尺度的影响。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。