CAREER: Towards understanding and modeling Turbulent Buoyant Flows

1056142将重流体放在轻流体上时，会出现布兰夸特瑞利-泰勒不稳定性。由于浮力的作用，轻质流体会上升，在许多情况下，流动会迅速转变为湍流。由于瑞利-泰勒不稳定性的本质，瑞利-泰勒不稳定性广泛存在于各种工程应用和自然现象中(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)。关于Rayleigh-Taylor不稳定性的初始和长期发展，人们已经做了大量的工作。然而，关于浮力混合层内的湍流结构却知之甚少。一个很好的例子是观察到的尺度的各向异性，这与公认的柯尔莫戈洛夫理论直接矛盾，目前还没有任何理论模型来解释。为了获得湍流的细微细节，将进行各种“控制实验”的直接数值模拟。这些构型跨越了所有湍流浮力流动的区域，从弱浮力到以浮力为主的湍流。这些数据将被用来分析瑞利-泰勒不稳定性的增长，浮力流动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，包括提出了一个新的理论框架，将湍流、非浮力流动和浮力流动统一起来。这一首开先河的模型将把尺度的各向异性和能谱与湍流结构的理查森数联系起来。该项目还将导致开发专门为湍流浮力流动的大涡模拟而设计的新的次网格尺度模型。这项研究项目与教育计划紧密结合在一起。选择了三项重点任务，每项任务都针对一个现实的社会问题。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，并为他们提供继续深造所需的知识和技能。最后，这包括接触公众，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(工程学和非工程学)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，还开始与其他大学和国家实验室的人员进行明确的合作。

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.