Laminar-Turbulent Patterning in Transitional Flows
Laminar-Turbulent Patterning in Transitional Flows
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DOI：
10.3390/e19070316
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发表时间：
2017-07-01
期刊：
影响因子：
2.7
通讯作者：
Manneville, Paul
中科院分区：
文献类型：
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作者：
Manneville, Paul
在雷诺数R（自然控制参数）的一定范围内，壁面边界流动经历了一个向湍流的过渡，其特征是层流和湍流区域共存。这种过渡状态发生在上阈值Rt和下阈值Rg之间，在上阈值Rt之上，湍流是均匀的（无特征的），在下阈值Rg之下，任何形式的湍流都可能在过长的混沌瞬态结束时衰减。最具代表性的情况下，流沿着平板过渡到/从湍流根据这种情况进行审查。共存通常是以带的形式，交替层流和湍流，并相对于总的流动方向倾斜定向。在Rg的带的最后衰减点的相关性的定向渗流和临界的意义上的物理相变。在Rt的过渡带的形式的性质仍然有些神秘，并不容易适合在层流背景下增加控制参数的图案形成不稳定性的计划。与此相反，带出现在Rt出一个均匀的湍流背景在一个减少的控制参数。一个可能的理论层流湍流图案的成分进行了讨论。
Wall-bounded flows experience a transition to turbulence characterized by the coexistence of laminar and turbulent domains in some range of Reynolds number R, the natural control parameter. This transitional regime takes place between an upper threshold Rt above which turbulence is uniform (featureless) and a lower threshold Rg below which any form of turbulence decays, possibly at the end of overlong chaotic transients. The most emblematic cases of flow along flat plates transiting to/from turbulence according to this scenario are reviewed. The coexistence is generally in the form of bands, alternatively laminar and turbulent, and oriented obliquely with respect to the general flow direction. The final decay of the bands at Rg points to the relevance of directed percolation and criticality in the sense of statistical-physics phase transitions. The nature of the transition at Rt where bands form is still somewhat mysterious and does not easily fit the scheme holding for pattern-forming instabilities at increasing control parameter on a laminar background. In contrast, the bands arise at Rt out of a uniform turbulent background at a decreasing control parameter. Ingredients of a possible theory of laminar-turbulent patterning are discussed.