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首页> 外文期刊>Bulletin of the American Physical Society >APS -70th Annual Meeting of the APS Division of Fluid Dynamics- Event - Causal analysis of self-sustaining processes in the log-layer of wall-bounded turbulence
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APS -70th Annual Meeting of the APS Division of Fluid Dynamics- Event - Causal analysis of self-sustaining processes in the log-layer of wall-bounded turbulence

机译：APS-流体动力学APS部门第70届年会-事件-壁边界湍流对数层中自我维持过程的因果分析

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摘要

Despite the large amount of information provided by direct numericalsimulations of turbulent flows, the underlying dynamics remain elusiveeven in the most simple and canonical configurations. Most standardmethods used to investigate turbulence do not provide a clear causalinference between events, which is necessary to determine thisdynamics, particularly in self-sustaning processes. In the presentwork, we examine the causal interactions between streaks and rolls inthe logarithmic layer of minimal turbulent channel flow. Causalitybetween structures is assessed in a non-intrusive manner by transferentropy, i.e., how much the uncertainty of one structure is reduced byknowing the past states of the others. Streaks are represented by thefirst Fourier modes of the streamwise velocity, while rolls aredefined by the wall-normal and spanwise velocities. The results showthat the process is mainly unidirectional rather than cyclic, and thatthe log-layer motions are sustained by extracting energy from the meanshear, which controls the dynamics and time-scales. The well-knownlift-up effect is shown to be not a key ingredient in the causalnetwork between shear, streaks and rolls.
机译：尽管直接由湍流的数值模拟提供了大量信息，但是即使在最简单和规范的配置中，基本的动力学仍然难以捉摸。用于研究湍流的大多数标准方法并未提供事件之间的明确因果关系，这对于确定这种动力学是必要的，尤其是在自持过程中。在目前的工作中，我们研究了最小湍流通道对数层中条纹和滚动之间的因果关系。结构之间的因果关系是以非侵入性的方式通过传递熵来评估的，即，通过了解其他结构的过去状态，可以减少一种结构的不确定性。条纹由流向速度的第一傅立叶模式表示，而横滚由壁法向速度和跨度速度定义。结果表明，该过程主要是单向的而不是循环的，并且对数层运动是通过从均值表达中提取能量来维持的，该均值表达控制了动态和时间尺度。众所周知，提升作用不是剪切，条纹和轧辊之间的因果网络中的关键因素。

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