CAREER: Towards understanding and modeling Turbulent Buoyant Flows

1056142当重流体置于轻流体之上时，会出现Blananjor Rayleigh-Taylor不稳定性。轻流体由于浮力而上升，并且在许多情况下，流动迅速转变为湍流。由于其固有的性质，瑞利-泰勒不稳定性在各种各样的工程应用和自然现象（惯性约束聚变，熔炉，意外火灾，恒星内的热传递，超新星形成，水下热喷口，石油泄漏）中发现。关于Rayleigh-Taylor不稳定性的初始和长期增长，人们已经做了大量的工作。然而，很少有人知道的结构内的湍流浮力混合层。一个很好的例子是观察到的尺度的各向异性与建立良好的柯尔莫哥洛夫理论直接矛盾，目前仍然无法解释任何理论模型。为了获得湍流的精细细节，将进行各种“受控实验”的直接数值模拟。这些配置跨越所有制度的湍流浮力流，从弱浮力为主的湍流。这些数据将用于分析瑞利-泰勒不稳定性的增长，浮力流中尺度各向异性的出现，以及理查森和阿特伍德数的影响。结果是多方面的，包括制定一个新的理论框架统一湍流非浮力和浮力流。这是第一个将尺度的各向异性和能谱与湍流结构的Richardson数相关联的模型。该项目还将导致专门为湍流浮力流的大涡模拟设计的新的次网格尺度模型的开发。这个研究项目与教育计划紧密结合。选择了三项关键任务，每项任务都针对一个真实的社会问题。这包括在学生对科学失去兴趣的时候在中学进行动手实验。这包括让本科生参与研究项目，并为他们提供继续攻读研究生的知识和技能。最后，这包括与公众接触，以确保我们的工作不会默默无闻。此外，研究计划将确保跨学科（工程和非工程）的科学家直接从研究项目中受益。除了建立被动的数据交换手段外，还与其他大学和国家实验室的人员开展了明确的合作。

1056142 Blanquart Rayleigh-Taylor instabilities appear when a heavy fluid is placed on top of a light fluid. The light fluid rises as a result of buoyancy forces, and in many cases, the flow transitions rapidly to turbulence. Due to their intrinsic nature, Rayleigh-Taylor instabilities are found in a large diversity of engineering applications and natural phenomena (inertial confinement fusion, furnaces, accidental fires, heat transfer within stars, supernova formation, underwater hot vents, oil spill). A lot of work has been done on the initial and long term growth of Rayleigh-Taylor instabilities. However, little is known about the structure of the turbulence inside buoyant mixing layers. A perfect example is the observed anisotropy of scales in direct contradiction with the well established Kolmogorov theory and which remains currently unexplained by any theoretical models. In order to gain access to the fine details of turbulence, Direct Numerical Simulations of various "con-trolled experiments" will be performed. These configurations span all regimes of turbulent buoyant flows, from weak buoyancy to buoyancy-dominated turbulence. The data will be used to analyze the growth of Rayleigh-Taylor instabilities, the emergence of scale anisotropy in buoyant flows, and the effects of Richardson and Atwood numbers. The outcome is multiple and includes the formulation of a novel theoretical framework unifying turbulent non-buoyant and buoyant flows. This first-of-a-kind model will correlate the anisotropy of scales and the energy spectra to the Richardson number of the turbulent structures. The project will result also in the development of new subgrid scale models specifically designed for Large Eddy Simulations of turbulent buoyant flows. This research project is integrated closely with an educational plan. Three key tasks have been chosen, and each task is targeting a real social problem. This includes performing hands-on experiments in middle school at a time when students lose interest in science. This includes engaging undergraduate students in research projects and providing them with the knowledge and skills to continue to graduate school. Finally, this includes reaching out to the general public to ensure that our work does not remain unknown. In addition, the research plan will ensure scientists across disciplines (engineering and non-engineering) benefit directly from the research project. In addition to establishing passive means of exchanging data, explicit collaborations have been initiated with personnel in other universities and national laboratories.