Exponential growth of lifetime of localized turbulence with its extent in channel flow
Exponential growth of lifetime of localized turbulence with its extent in channel flow
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DOI：
10.1088/1873-7005/aaa73c
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发表时间：
2019-01
影响因子：
1.5
通讯作者：
M. Shimizu;T. Kanazawa;G. Kawahara
中科院分区：
文献类型：
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作者：
M. Shimizu;T. Kanazawa;G. Kawahara
在有壁流动中，例如管道流动、平面Couette流动和通道流动，向湍流的过渡最初是作为局部湍流簇发生的。众所周知，这些局部结构是短暂的，并在无记忆过程中衰减。本文研究了局部化结构的范围与其寿命之间的关系。通过对具有小展向周期性的通道流动进行数值模拟，我们产生了流向局部但展向扩展的湍流，湍流“泡”而不是斑点。我们改变展向周期长度作为其范围的参数，以表明湍流“泡”的寿命作为雷诺数的函数在任何展向范围内呈双指数增长。研究还表明，当展向尺寸不大时，寿命作为展向尺寸的函数呈指数增长。
The transition to turbulence in wall-bounded flows, for example pipe flow, plane Couette flow and channel flow, initially occurs as localized clusters of turbulence. It is well known that these localized structures are transient and decay in a memoryless process. In this paper we investigate the relationship between the extent of a localized structure and its lifetime. By performing numerical simulations of channel flow with small spanwise periodicity we produce streamwise-localized but spanwise-extended turbulence, turbulent ‘puffs’ instead of spots. We vary the spanwise periodzation length as the parameter of its extent to show that the lifetime of turbulent ‘puffs’ increases double-exponentially as a function of the Reynolds number for any spanwise extent. It is also shown that the lifetime increases exponentially as a function of the spanwise size when it is not large.