The evolution of large-scale motions in turbulent pipe flow
The evolution of large-scale motions in turbulent pipe flow
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DOI：
10.1017/jfm.2015.418
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发表时间：
2015-08
影响因子：
3.7
通讯作者：
L. Hellström;B. Ganapathisubramani;A. Smits
中科院分区：
文献类型：
--
作者：
L. Hellström;B. Ganapathisubramani;A. Smits
采用双平面快照本征正交分解（POD）方法对雷诺数为104000的圆管湍流进行了数值分析。在管道中心线上的横流平面（2D-3C）和流向平面（2D-2C）两个平面上同时采集高速粒子图像测速数据。交叉流平面分析揭示了大结构的时空范围为$1{-} 2 R $，其中$R$是管道半径。这些大规模的结构的时间演变检查使用的横流快照POD系数的时移相关性，确定负责大规模模式之间的过渡的低能量中间模式。通过有条件地平均的基础上的发生/强度的一个给定的横流快照POD模式，一个复杂的结构组成的附壁和分离的大型结构被证明是与最充满活力的模式。有一个伪对齐这些大的结构，它们一起创建一个时空范围约6 R $的结构，这似乎可以解释形成的非常大规模的运动，以前观察到的管流。
A dual-plane snapshot proper orthogonal decomposition (POD) analysis of turbulent pipe flow at a Reynolds number of 104 000 is presented. The high-speed particle image velocimetry data were simultaneously acquired in two planes, a cross-stream plane (2D–3C) and a streamwise plane (2D–2C) on the pipe centreline. The cross-stream plane analysis revealed large structures with a spatio-temporal extent of $1{-}2R$ , where $R$ is the pipe radius. The temporal evolution of these large-scale structures is examined using the time-shifted correlation of the cross-stream snapshot POD coefficients, identifying the low-energy intermediate modes responsible for the transition between the large-scale modes. By conditionally averaging based on the occurrence/intensity of a given cross-stream snapshot POD mode, a complex structure consisting of wall-attached and -detached large-scale structures is shown to be associated with the most energetic modes. There is a pseudo-alignment of these large structures, which together create structures with a spatio-temporal extent of approximately $6R$ , which appears to explain the formation of the very-large-scale motions previously observed in pipe flow.