Collaborative Research: Self-organization and transitions in anisotropic turbulence

合作研究：各向异性湍流的自组织和转变

• 批准号: 2308338
• 负责人: Keith Julien
• 金额: $ 18.7万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2308338&HistoricalAwards=false
• 关键词: Collaborative; Research; Self; organization; transitions

The impact of rotation and thermal driving on stellar and planetary bodies is clearly visible in far-field optical observations. Such observations reveal the presence of differentially rotating fluid atmospheres with embedded features in the form of large-scale eddies and jets that greatly influence the climate on the celestial body. On Earth the impact of the high latitude jet stream on weather and the destructive impact of hurricanes due to climate change is evident. Within the Jovian atmosphere, the recent discovery by the Juno mission of polar vortices illuminates the longevity of vortical structures. Theory, experimentation, and numerical simulations strongly suggest that the generation of large-scale jets and vortices is common in fluid turbulence within thin layers like the Earth’s atmosphere and on rapidly rotating celestial bodies such as Jupiter. Focusing on these paradigms, this project is dedicated to elucidating the basic mechanism behind the formation of such large-scale structures from small-scale turbulent fluctuations and its disruption via the generation of isolated, weakly-interacting, mesoscale shielded vortices, and to extending this understanding to more realistic models that introduce higher level physics such as the effects of water vapor and internal heating via latent heat release. This understanding will inform more detailed studies such as those based on realistic Global Ocean and Atmospheric Circulation Models and offers hope for understanding the conditions favoring the formation of both large-scale structures and of the smaller-scale shielded vortices. The modeling strategy taken provides a foundation upon which greater discipline-specific complexity can be built. The project will support and train one graduate student and one postdoctoral researcher in the physical understanding of energy transfer between scales in systems of geophysical relevance, asymptotic and other modeling techniques, as well as direct numerical simulations of rapidly rotating fluid layers, appropriate for planetary-scale phenomena on and within the Earth.The aim of this project is to classify different regimes of instability-driven turbulence in two dimensions (2D) as a function of the energy input and dissipation parameters, and to explore how these states evolve when three-dimensional (3D) fluctuations become increasingly important as the height of the turbulent layer increases. Particular emphasis will be placed on the recently discovered regime of shielded mesoscale vortices whose generation may disrupt the inverse energy cascade familiar from 2D turbulence with random stirring. Properties of the resulting chiral mesoscale vortex gas will be studied as a function of the layer height, as will the transition to a vortex crystal that takes place at high vortex density in 2D. The Reynolds number will be varied systematically to bridge the gap between these phenomena and related states in bacterial suspensions at low Reynolds numbers. The possibility of an analogous state in rapidly rotating 3D turbulence will be investigated in detail using a new reformulation of the Navier-Stokes fluid equations, extending direct numerical simulations to smaller Rossby numbers, together with a theoretical analysis dissecting the amplitude-phase relationships between large-scale structures and small-scale turbulence.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.

在远场光学观测中，旋转和热驱动对恒星和行星体的影响是清晰可见的。这样的观测揭示了存在差异旋转的流体大气，其嵌入的特征是大范围涡流和喷流，这些特征极大地影响了天体上的气候。在地球上，高纬度急流对天气的影响以及由于气候变化造成的飓风的破坏性影响是显而易见的。在木星大气中，朱诺任务最近发现的极地涡旋说明了涡旋结构的长寿。理论、实验和数值模拟有力地表明，在地球大气层等薄层内的流体湍流中，以及在快速旋转的天体(如木星)上，大规模射流和涡流的产生是常见的。围绕这些范例，这个项目致力于阐明小尺度湍流涨落形成这种大尺度结构的基本机制，以及它通过产生孤立的、弱相互作用的中尺度屏蔽涡而破坏的基本机制，并将这一理解扩展到更现实的模式，这些模式引入了更高层次的物理，如水蒸气和通过潜热释放的内部加热的影响。这一理解将有助于开展更详细的研究，如基于现实的全球海洋和大气环流模型的研究，并为理解有利于形成大尺度结构和小尺度屏蔽涡的条件提供了希望。所采用的建模策略提供了一个基础，在此基础上可以构建更大的特定于规程的复杂性。该项目将支持和培训一名研究生和一名博士后研究人员，了解与地球物理相关的系统中尺度之间的能量转移的物理理解，渐近和其他建模技术，以及适用于地球上和地球内部的行星尺度现象的快速旋转流体层的直接数值模拟。该项目的目的是将不稳定驱动的湍流在二维(2D)中作为能量输入和耗散参数的函数进行分类，并探索当三维(3D)涨落随着湍流层高度的增加变得越来越重要时，这些状态是如何演变的。重点将放在最近发现的屏蔽中尺度涡旋区域，它们的产生可能会扰乱与随机搅动的2D湍流相似的逆能量级联。所产生的手性中尺度涡旋气体的性质将作为层高度的函数来研究，以及在2D中高涡旋密度下发生的向涡旋晶体的转变。雷诺数将系统地变化，以弥合这些现象与低雷诺数细菌悬浮液中相关状态之间的差距。在快速旋转的3D湍流中，类似状态的可能性将通过一种新的重新表述的Navier-Stokes流体方程进行详细研究，将直接数值模拟扩展到较小的Rossby数，并结合理论分析剖析大尺度结构和小尺度湍流之间的幅相关系。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为是值得支持的。