Salinas Jorge, Balachandar S, Shringarpure Mrugesh, Fedele Juan, Hoyal David, Cantero Mariano
Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611;
Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611.
Proc Natl Acad Sci U S A. 2020 Aug 4;117(31):18278-18284. doi: 10.1073/pnas.2008959117. Epub 2020 Jul 20.
Long-running gravity currents are flows that are submerged beneath a deep layer of quiescent fluid and they travel over long distances along inclined or horizontal surfaces. They are driven by the density difference between the current and the clear ambient fluid above. In this work we present results on highly resolved direct numerical simulations of turbid underflows that involve nearly 1 billion degrees of freedom. We assess the effect of bed slope on the flow statistics. We explore the turbulence dynamics of the interface in the classical sub- and supercritical regimes. We investigate the structure of interfacial turbulence and its relation to the turbulence statistic. A transcritical regime is identified where intermittent cascading interfacial instabilities appear. We investigate how departure from the self-sustaining equilibrium state may be the mechanism responsible for this cyclic evolution of the transcritical regime.
长期存在的重力流是淹没在静止深层流体之下的流动，它们沿着倾斜或水平表面长距离流动。它们由重力流与上方清澈环境流体之间的密度差驱动。在这项工作中，我们展示了涉及近10亿自由度的浑浊底流高分辨率直接数值模拟的结果。我们评估了河床坡度对流动统计量的影响。我们探索了经典亚临界和超临界状态下界面的湍流动力学。我们研究了界面湍流的结构及其与湍流统计量的关系。识别出了一个跨临界状态，其中出现间歇性级联界面不稳定性。我们研究了偏离自持平衡状态如何可能是导致跨临界状态这种循环演化的机制。
