CAS: Estimates of the decay of diffusion induced flows in strongly stratified fluids and ergodic mixing properties of solutes driven by randomly moving walls in viscous fluids.

CAS：对强分层流体中扩散诱导流的衰减以及粘性流体中随机移动壁驱动的溶质的遍历混合特性的估计。

• 批准号: 2308063
• 负责人: Richard McLaughlin
• 金额: $ 32万
• 依托单位: University of North Carolina at Chapel Hill
• 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: 2023-07-15 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2308063&HistoricalAwards=false
• 关键词: CAS; Estimates; decay; diffusion; induced

The oceans play a central role in absorbing and sequestering carbon from the Earth's atmosphere. As such, understanding how this process works is crucial to predicting the future evolution of the planet's climate. The basic mechanism is one in which dissolved carbon-dioxide gas from the atmosphere is converted by phytoplankton, through photosynthesis, into solid carbon, which then sinks to the ocean bottom, where it is eventually turned into oil over the eons. Precisely how this solid sinking carbon forms into large particle clusters is not well understood, and it is a focus of this award. The PIs have recently experimentally discovered and theoretically explained a novel mechanism for the creation of particle clusters in stratified waters which only relies upon the presence of density stratification and gravitation. They established that particles suspended in stratified waters can create their own fluid flows, which draw other nearby particles into forming larger cluster aggregations. This phenomenon offers a possible mechanism for how the so-called Marine Snow, agglomerates of sedimenting carbon-rich "flakes," may form in ocean waters. Understanding the details of particle aggregate formation is necessary for predicting how much and how fast the ocean can absorb carbon, and this award seeks to improve our understanding of this fundamental process. The project also provides research training opportunities for graduate students. Recent discoveries by the PIs, involving self-assembly in stratified fluids and ergodic behavior of diffusing solutes advected by random shear layers, have identified many new fundamental questions regarding the underlying mechanisms responsible for these phenomena. For the case of self-assembly, diffusion-induced flows for single and multiple bodies will be studied analytically, computationally, and experimentally with the goal of developing a uniformly valid asymptotic expansion at both low and high Peclet numbers. This will include an in-depth study of the mechanisms and forces at play for the finite time collapse of coupled spheres experimentally observed by the PIs. Our work is the first step in understanding how large-scale aggregates may form in stratified waters. In the context of the ergodicity, new asymptotic theories using center manifold techniques will be applied to non-flat walls randomly moving in viscous fluids. We explore how randomness, injected through the wall motion, propagates into the fluid and into dissolved solutes to better understand mixing in physically realizable non-sheared flows. The study of both mixing and self-assembly by diffusion-induced flows is expected to improve our knowledge of ocean aggregate formation, which ultimately sets the timescales for carbon sinking in the ocean.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.

海洋在吸收和隔离地球大气中的碳中起着核心作用。 因此，了解该过程的工作原理对于预测地球气候的未来演变至关重要。 基本机制是从大气中溶解的二氧化碳气体通过光合作用转化为固体碳的一种机制，然后将其下沉到海底，最终将其变成eons上的油。 确切地说，这种固体下沉的碳如何形成大型粒子簇中尚不清楚，这是该奖项的重点。 PI最近在实验中发现了PI，理论上解释了一种新的机制，用于在分层水中创建粒子簇，这仅依赖于密度分层和引力的存在。 他们确定悬浮在分层水中的颗粒可以产生自己的流体流，从而将附近的其他颗粒吸引到形成较大的簇聚集中。 这种现象提供了一种可能在海水中形成所谓的海洋积雪，含碳富含碳的“薄片”的结合。 了解粒子骨料形成的细节对于预测海洋可以吸收碳的速度和多快是必要的，并且该奖项旨在提高我们对这一基本过程的理解。该项目还为研究生提供了研究培训机会。 PI的最新发现，涉及随机剪切层延伸的溶质的分层流体和奇异行为，已经确定了许多有关负责这些现象的基本机制的许多新的基本问题。对于自组装的情况，将通过分析，计算和实验研究为单个物体进行扩散诱导的流，其目的是在低和高的peclet数字上开发均匀有效的渐近扩张。这将包括对PIS实验观察到的耦合球的有限时间崩溃的作用机理和力的深入研究。我们的工作是了解大规模聚集体在分层水中如何形成的第一步。 在恐怖性的背景下，使用中心歧管技术的新渐近理论将应用于随机在粘性流体中随机移动的非平板壁。 我们探讨了如何通过壁运动注入的随机性，将其传播到流体中并溶解溶质，以更好地理解在物理上可实现的非剪切流中的混合。 通过扩散引起的流对混合和自我组装的研究有望提高我们对海洋骨料形成的了解，这最终使海洋中的碳沉没的时间表量表。该奖项反映了NSF的法定任务，并通过使用该基金会的智力功能和广泛的影响来评估Criteria criteria criteria criteria。