Asynchronous-coupled large-eddy simulation of Langmuir turbulence and the atmospheric surface layer

海洋表面附近的空气和水的耦合流动影响到海洋对人为数量(例如二氧化碳)的封存、生物量的分散以及许多其他具有科学重要性的问题。当海浪的方向和盛行的大气风共同排列时，在海洋层内就会出现反向旋转的滚动圈。这些单元格被称为朗缪尔湍流，在海洋表面表现为细长的条纹。通常的做法是假设海洋表面受到均匀的大气强迫，而实际上大气本身是由涡动阵风组成的，这会导致风应力的空间变异性。高保真的计算机模拟将被用来描述大气压力的真实空间不均一性如何影响朗缪尔湍流的演变。该项目为多相、多尺度、大尺度湍流的基础研究提供了机会。该项目的成果将用于促进旨在提高研究生水平STEM项目的多样性和包容性的外联活动。研究人员将继续为德克萨斯州和俄克拉何马州的研究生组织为期一天的年度流体力学研讨会。海洋混合层中的朗缪尔湍流是施加的大气表面阻力和波浪轨道运动造成的聚集漂移的产物。朗缪尔湍流是一种微尺度现象，它调节动量、热量和其他量的垂直(气-海)交换。朗缪尔环流是一种反向旋转的漩涡，在空间上围绕着与盛行风向一致的主要输送方向蜿蜒而行，显示出数十至数千米的长度。朗缪尔湍流一般用湍流朗缪尔数来定义，它是大气剪切速度除以斯托克斯漂移量级的平方根。对于用于计算湍流朗缪尔数的聚合值，施加的大气应力在空间和时间上表现出显著的变化。这种变化是由高空大气表面层中连贯的动量块通过--即所谓的大范围运动--推动的，这些运动本身在空间上蜿蜒曲折，显示出长达数千米的长度。大气表层-海洋混合层的高保真异步耦合大涡模拟将被用来量化这种大规模大气运动如何调制深海(不受底部边界层影响)朗缪尔湍流的空间和动力学特征。这一奖项反映了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，被认为值得支持。

Coupled flows of air and water near the ocean surface ocean affect ocean sequestration of anthropogenic quantities (e.g., CO2), dispersion of biomass, and a host of other issues of scientific importance. When the direction of ocean waves and the prevailing atmospheric winds are coaligned, counter-rotating roll cells emerge within the ocean layer. These cells – known as Langmuir turbulence – manifest on the ocean surface as elongated streaks. It is common practice to assume uniform atmospheric forcing on the ocean surface, when in fact the atmosphere itself is composed of eddying gusts that induce spatial variability in wind stresses. High-fidelity computer simulations will be used to characterize how realistic spatial heterogeneity in atmospheric stress affects evolution of Langmuir turbulence. This project offers opportunities for fundamental research in multiphase, multiscale, large-scale turbulence. The results of this project will be used to promote outreach activities directed to improve diversity and inclusion in graduate-level STEM programs. The investigator will continue to organize an annual one-day fluid dynamics symposium for graduate students throughout Texas and Oklahoma.Langmuir turbulence in the ocean mixed layer is the product of imposed atmospheric surface drag and the aggregate drift due to wave orbital motion. Langmuir turbulence is a microscale phenomenon that regulates vertical (air-sea) exchanges of momentum, heat, and other quantities. Langmuir cells – counter-rotating vortices, meandering spatially about a predominant transport direction aligned with the prevailing wind direction – exhibit lengths of tens to thousands of meters. Langmuir turbulence is generally defined with the turbulent Langmuir number, which is the square root of atmospheric shear velocity divided by Stokes drift magnitude. The imposed atmospheric stress exhibits dramatic spatial and temporal variation about the aggregate value used to compute the turbulent Langmuir number. Such variability is driven by the passage of coherent parcels of momentum in the aloft atmospheric surface layer – so called large-scale motions, which themselves meander spatially and exhibit lengths up to thousands of meters. High fidelity asynchronously-coupled large-eddy simulations of the atmospheric surface layer-ocean mixed layer will be used to quantify how such large-scale atmosphere motions modulate the spatial and dynamical characteristics of deep ocean (unaffected by bottom-boundary layer) Langmuir 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.