Collaborative Research: New Pathways to Enhanced Turbulence and Mixing via Kelvin-Helmholtz Instability Tube and Knot Dynamics

合作研究：通过开尔文-亥姆霍兹不稳定管和结动力学增强湍流和混合的新途径

• 批准号: 2128443
• 负责人: David Fritts
• 金额: $ 74.86万
• 依托单位: GLOBAL ATMOSPHERIC TECHNOLOGIES AND SCIENCES, INC.
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-11-01 至 2024-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2128443&HistoricalAwards=false
• 关键词: Collaborative; Research; New; Pathways; Enhanced

The project seeks funding to investigate atmospheric turbulence generation. Shear layers in the atmosphere, where a layer slides over another, can result in instabilities that are commonly seen in thin cloud layers and resemble a series of ocean waves breaking on a beach. These instabilities, called Kelvin-Helmholtz instabilities, cause turbulence and mixing throughout the atmosphere and the oceans where shears are strong. Spacing between these “billows” can vary in the atmosphere from a few meters near the ground to 10 km or larger at altitudes as high as 100 km. Those seen in clouds usually have spacings (or wavelengths) from a few hundred meters to a km or so. The turbulence and mixing when these billows “break” influence the atmospheric structure and weather, especially near the ground, but their effects are not described well in weather prediction models. This research will explore a new type of instability causing breaking and turbulence that was recently discovered in thin clouds at very high altitudes that the research team expects to occur at all altitudes, and to significantly increase the turbulence and mixing due to these processes. If shown to occur for a wider range of conditions, this would significantly influence our ability to model the atmosphere near the ground and improve weather prediction that impacts all of us. The same instabilities occur in the oceans and are expected to also improve prediction of ocean circulations and structure when these processes are more fully understood. The project will involve a graduate student and a postdoctoral researcher experience in state-of-the-art modeling and super-computing. New observations of thin Polar Mesospheric Clouds and airglow layers at high altitudes (~80-90 km) have revealed the occurrence of a new type of instability leading to turbulence arising from mis-aligned Kelvin-Helmholtz (KH) billows accompanying variable geophysical forcing. These instabilities arise due to interactions among adjacent KH billow cores, rather than within single billows, and initial modeling of these dynamics have shown them to be much stronger, and to lead to much more intense turbulence, than occur in their absence. These dynamics arise from interactions between KH billow cores and large-scale vortex tubes that are excited where KH billows are mis-aligned or discontinuous due to initial conditions. Initial modeling employing direct numerical simulations that enable quantitative assessments of these dynamics, their stronger instabilities, and their more intense turbulence suggest that they may also cause enhanced turbulence and mixing in regions, and for conditions, in which turbulence was not previously expected. The research team believes that these enhanced KH billow dynamics are likely to be widespread and that they will allow us to update how these dynamics are modeled, enabling improved weather prediction, and of similar responses in the oceans. Because KH instabilities also play significant roles of other fields of physics, specifically magnetospheric physics and astrophysics, the benefits of this research may prove to be very broad.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.

该项目寻求资助大气中的大气湍流层，其中一个层在另一个层上滑动，可能会导致在研究薄云层时常见的不稳定现象，类似于一系列海浪在海滩上的破碎。称为开尔文-亥姆霍兹不稳定性，会在整个大气和海洋中引起湍流和混合，这些“巨浪”之间的间距在大气中可以从接近地面的几米到 10 米不等。在高达 100 公里的高度处，云层中可见的波涛通常具有几百米到一公里左右的距离（或波长）。这些波涛“破裂”时的湍流和混合会影响大气结构和天气。特别是在地面附近，但它们的影响在天气预报模型中并没有得到很好的描述。这项研究将探索一种新型的不稳定性，这种不稳定性会导致最近在研究小组预计会发生的极高海拔的薄云中发现的破裂和湍流。所有高度，并显着增加由于这些过程而产生的湍流和混合，如果在更广泛的条件下发生，这将显着影响我们模拟地面附近的大气并改善影响我们所有人的天气预报的能力。海洋中也存在同样的不稳定性，当人们更充分地了解这些过程时，预计也将改善对海洋环流和结构的预测。该项目将涉及一名在最先进的建模和超级方面拥有丰富经验的研究生和博士后研究员。 - 计算的新观察。高海拔（约 80-90 公里）的极地中层云和气辉层揭示了一种新型不稳定性的发生，这种不稳定性是由未对准的开尔文-亥姆霍兹 (KH) 巨浪伴随着可变的地球物理强迫而产生的湍流。相邻 KH 巨浪核心之间的相互作用，而不是单个巨浪内部的相互作用，这些动力学的初步建模表明它们要强大得多，并导致更强烈的这些动力学源于 KH 巨浪核心与大型涡流管之间的相互作用，这些涡流管在 KH 巨浪由于初始条件而未对准或不连续的情况下被激发，从而能够进行定量评估。这些动力学的特征、它们更强的不稳定性和更强烈的湍流表明它们也可能在区域和以前没有湍流的条件下引起增强的湍流和混合。研究小组认为，这些增强的 KH 巨浪动力学可能会广泛传播，并且它们将使我们能够更新这些动力学的建模方式，从而改进天气预报以及海洋中的类似响应。考虑到其他物理学领域，特别是磁层物理学和天体物理学的作用，这项研究的好处可能会被证明是非常广泛的。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进行评估，被认为值得支持标准。

项目成果

Multi-scale dynamics of Kelvin–Helmholtz instabilities. Part 2. Energy dissipation rates, evolutions and statistics

开尔文-亥姆霍兹不稳定性的多尺度动力学。

• DOI: 10.1017/jfm.2021.1086
• 发表时间: 2022-06
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: Fritts, David C.;Wang, L.;Thorpe, S.A.;Lund, T.S.
• 通讯作者: Lund, T.S.

Multi-scale dynamics of Kelvin–Helmholtz instabilities. Part 1. Secondary instabilities and the dynamics of tubes and knots

开尔文-亥姆霍兹不稳定性的多尺度动力学。

• DOI: 10.1017/jfm.2021.1085
• 发表时间: 2022-06
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: Fritts, David C.;Wang, L.;Lund, T.S.;Thorpe, S.A.
• 通讯作者: Thorpe, S.A.

Multi-scale dynamics of Kelvin–Helmholtz instabilities. Part 1. Secondary instabilities and the dynamics of tubes and knots

开尔文-亥姆霍兹不稳定性的多尺度动力学。

• DOI: 10:1017/jfm.2021.1085
• 发表时间: 2022-01
• 期刊: Journal of fluid mechanics
• 影响因子: 3.7
• 作者: Fritts, David C.;Wang, L.;Lund, T. S.;Thorpe, S. A.
• 通讯作者: Thorpe, S. A.