On the Origin of Streaks in Turbulent Shear Flows
On the Origin of Streaks in Turbulent Shear Flows
复制标题
湍流剪切流条纹的起源
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
J. Hamilton
中科院分区：
文献类型：
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作者：
F. Waleffe;John Kim;J. Hamilton
结果表明，基于线性理论的选择性放大和直接共振的思想并没有为在壁边界湍流剪切流中观察到的约100个壁单位（以下简称100+）的明确条纹间距提供选择机制。直接共振理论（Benney & Gustaysson，1981；fang et al.，1986）表明，条纹是由垂直速度的非线性自相互作用产生的，而不是由直接强制的垂直涡度产生的。然后提出选择机制本质上必须是非线性的并且对应于自我维持的过程。条纹的形成只是整个机制的一个阶段，不能与该过程的其余部分分开。 100+ 值应被视为该自维持机制的关键雷诺数。对于平面泊肃叶流的情况，基于中心线速度和通道半宽度，100+ 准则对应于 1250 的临界雷诺数，该值接近通常引用的约 1000 的值。在平面库埃特流中，基于半速度差和半宽度，它对应于 625 的临界雷诺数。
It is shown that the ideas of selective amplification and direct resonance, based on linear theory, do not provide a selection mechanism for the well-defined streak spacing of about 100 wall units (referred to as 100+ hereafter) observed in wall-bounded turbulent shear flows. For the direct resonance theory (Benney & Gustaysson, 1981; fang et al., 1986), it is shown that the streaks are created by the nonlinear self-interaction of the vertical velocity rather than of the directly forced vertical vorticity. It is then proposed that the selection mechanism must be inherently nonlinear and correspond to a self-sustaining process. The streak formation is only one stage of the complete mechanism and cannot be isolated from the rest of the process. The 100+ value should be considered as a critical Reynolds number for that self-sustaining mechanism. For the case of plane Poiseuille flow the 100+ criterion corresponds to a critical Reynolds number of 1250, based on the centerline velocity and the channel half-width, which is close to the usually quoted value of about 1000. In plane Couette flow, it corresponds to a critical Reynolds number of 625, based on the half velocity difference and the half-width.