Scale interactions in turbulent plane Couette flows in minimal domains
Scale interactions in turbulent plane Couette flows in minimal domains
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最小域内湍流平面库埃特流中的尺度相互作用
DOI：
10.1017/jfm.2020.1063
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发表时间：
2021
影响因子：
3.7
通讯作者：
Tsukahara Takahiro
中科院分区：
文献类型：
--
作者：
Kawata Takuya;Tsukahara Takahiro
近几年来，人们对壁湍流的尺度间能量传递进行了深入的研究，发现了湍流能量的正向传递（即从大尺度到小尺度）和反向传递，但其相应的物理现象尚未得到揭示。在本研究中，我们进行直接数值模拟的湍流平面Couette流与减小尺寸的计算域，其中无论是流向或展向域的大小减少到其最小长度，旨在阐明在每个方向上的规模相互作用的作用。我们的计算结果与流向最小域表明，流向细长条纹和小于流向最小长度的涡之间的相互作用是必不可少的尺度相互作用的内部和外部结构。我们进一步表明，这些流向独立的和较小的尺度结构交换能量通过正向和反向的尺度间能量转移，和反向的能量转移保持在较大的尺度上的能量生产。基于观测到的涡应力输运与自持循环的相似性，我们推测正向和反向能量输运分别主要代表条纹不稳定性和流向涡的再生。此外，与展向最小域的计算表明，一维展向谱分析所观察到的尺度间能量转移可能与每个内部和外部结构的单独动力学，而不是代表它们的相互作用。
Interscale energy transfer in wall turbulence has been intensively studied in recent years, and both forward (i.e. from larger to smaller scales) and reversed transfers of turbulent energy have been found, although their corresponding physical phenomena have not been revealed. In the present study, we perform direct numerical simulations of turbulent plane Couette flow with reduced-size computational domains, where either the streamwise or the spanwise domain size is reduced to its minimal length, aiming to elucidate the role of scale interactions in each direction. Our computational results with the streamwise-minimal domain suggest that the interplays between streamwise-elongated streaks and vortices smaller than the streamwise minimal length are the essential scale interactions for both the inner and the outer structures. We further show that these streamwise-independent and smaller-scale structures exchange energy through forward and reversed interscale energy transfers, and the reversed energy transfer maintains the energy production at larger scales. Based on the resemblance between the observed Reynolds-stress transport and the scenario of the self-sustaining cycle, we conjecture that the forward and reversed energy transfers mainly represent the streak instabilities and regeneration of streamwise vortices, respectively. Furthermore, the computation with the spanwise-minimal domain indicates that the interscale energy transfers observed by one-dimensional spanwise spectral analysis are likely related to the individual dynamics of each inner and outer structure, rather than representing their interactions.
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