A description of turbulent wall-flow vorticity consistent with mean dynamics
A description of turbulent wall-flow vorticity consistent with mean dynamics
复制标题
与平均动力学一致的湍流壁流涡度的描述
DOI：
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发表时间：
2013
影响因子：
3.7
通讯作者：
J. Klewicki
中科院分区：
文献类型：
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作者：
J. Klewicki
本文在平均动力学方程所承认的自相似性质的范围内，描述了湍流壁流中的平均涡度结构和脉动涡度结构。从一个相对广泛的数值和物理实验的数据被用来探索和澄清的结构假设。揭示了平均动力学的四层制度的发病的平均涡度指标。随着雷诺数的增加，平均涡度分离成两个越来越明确的域。一半的平均涡度集中在宽度（相对于总流动宽度）的近壁区域，该区域与雷诺数的平方根倒数成比例减小。其余的平均涡度分布在一个接近高雷诺数时总流动宽度的外部区域上，振幅逐渐减小。涡度拉伸和重定向被推测为占平均和波动涡度的内域行为的特征机制。通过平流输送的涡度弥散被推测为在外部区域的特征机制。在这一区域内，脉动涡度拟能随雷诺数的增加而趋于瞬时涡度拟能。这就支持了均值和均方根之间的自相似性。平均速度剖面为对数的区域内的涡量。与涡量场相关的一些属性的雷诺数依赖性进行了探索和量化。研究结束时，简要介绍了湍流壁流的涡结构和平均动力学结构。
Abstract A depiction of the mean and fluctuating vorticity structure in turbulent wall flows is presented and described within the context of the self-similar properties admitted by the mean dynamical equation. Data from a relatively wide range of numerical and physical experiments are used to explore and clarify the structure postulated. The mean vorticity indicator for the onset of the four-layer regime of the mean dynamics is revealed. With increasing Reynolds number, the mean vorticity is shown to segregate into two increasingly well-defined domains. Half of the mean vorticity concentrates into a near-wall region of width (relative to the overall flow width) that diminishes proportionally to the inverse square root of Reynolds number. The remainder of the mean vorticity is spread, with diminishing amplitude, over an outer domain that approaches the overall flow width at high Reynolds number. Vorticity stretching and reorientation are surmised to be the characteristic mechanisms accounting for the inner domain behaviour of both the mean and fluctuating vorticity. Vorticity dispersion via advective transport is surmised to be the characteristic mechanism in the outer domain. In this domain, the fluctuating enstrophy approaches that of the instantaneous enstrophy with increasing Reynolds number. This underpins an emerging self-similarity between the mean and r.m.s. vorticity in the domain where the mean velocity profile is logarithmic. The Reynolds number dependence of a number of properties associated with the vorticity field is explored and quantified. The study closes with brief account of the combined vortical and mean dynamical structure of turbulent wall flows.