零压力梯度边界层流动中中间结构的特征长度尺度
The Characteristic Length Scale of the Intermediate Structure in Zero-Pressure-Gradient Boundary Layer Flow
AI总结：
本研究针对零压力梯度湍流边界层，确定了中间结构的两层特征长度尺度，并证明二者接近，从而挑战了经典的尾迹区域模型。
摘要：
在零压力梯度的光滑平板上方的湍流边界层中，粘性底层与自由流之间的中间结构由两层组成：一层紧邻粘性底层，另一层紧邻自由流。当自由流中的湍流水平较低时，两层之间的边界是清晰的，并且两者都具有由雷诺数相关的缩放（幂次）定律描述的自相似结构。这种结构引入了两个长度尺度：一个——壁面区域厚度——由两个中间层之间的清晰边界决定，第二个由以下条件决定：第一中间层中的速度分布是所有壁面有界流动共有的，特别是与先前为管道流动确定的缩放定律一致。利用最近的实验数据，我们确定了这两个长度尺度，并表明它们很接近。我们的结果与“尾迹区域”的经典模型不一致。
英文摘要：
In a turbulent boundary layer over a smooth flat plate with zero pressure gradient, the intermediate structure between the viscous sublayer and the free stream consists of two layers: one adjacent to the viscous sublayer and one adjacent to the free stream. When the level of turbulence in the free stream is low, the boundary between the two layers is sharp and both have a self-similar structure described by Reynolds-number-dependent scaling (power) laws. This structure introduces two length scales: one --- the wall region thickness --- determined by the sharp boundary between the two intermediate layers, the second determined by the condition that the velocity distribution in the first intermediate layer be the one common to all wall-bounded flows, and in particular coincide with the scaling law previously determined for pipe flows. Using recent experimental data we determine both these length scales and show that they are close. Our results disagree with the classical model of the "wake region".
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