Layer formation and relaminarisation in plane Couette flow with spanwise stratification
Layer formation and relaminarisation in plane Couette flow with spanwise stratification
复制标题
具有展向分层的平面库埃特流中的层形成和再层化
DOI：
10.1017/jfm.2019.192
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发表时间：
2018
影响因子：
3.7
通讯作者：
R. Kerswell
中科院分区：
文献类型：
--
作者：
D. Lucas;Colm‐cille P. Caulfield;R. Kerswell
本文研究了当重力沿展向作用时，稳定层结对平面Couette流的影响。当流动是湍流时，我们观察到近壁分层和相关的新的平均流的形式大规模展向扁平流向卷。这些层表现出预期的浮力比例$l_{z}\sim U/N$，其中$U$是典型的水平速度比例，$N$是浮力频率。我们将新的相干结构与平面库埃特流中著名的大尺度二次环流的分层修改相关联。我们发现，过渡到持续湍流的可能性是由这个浮力尺度的相对大小的条纹的展向间距控制。在参数空间的部分中，也可以通过该系统中新发现的线性不稳定性来启动过渡（Facchini等人，J.流体机械，第853卷，2018年，pp. 205-234）。当壁湍流可以维持时，线性不稳定性在相空间中为无穷小扰动引发湍流开辟了新的途径。当浮力尺度抑制湍流时，线性不稳定性导致更有序的非线性状态，有可能出现二次剪切不稳定性的间歇性爆发。
In this paper we investigate the effect of stable stratification on plane Couette flow when gravity is oriented in the spanwise direction. When the flow is turbulent we observe near-wall layering and associated new mean flows in the form of large-scale spanwise-flattened streamwise rolls. The layers exhibit the expected buoyancy scaling $l_{z}\sim U/N$ where $U$ is a typical horizontal velocity scale and $N$ the buoyancy frequency. We associate the new coherent structures with a stratified modification of the well-known large-scale secondary circulation in plane Couette flow. We find that the possibility of the transition to sustained turbulence is controlled by the relative size of this buoyancy scale to the spanwise spacing of the streaks. In parts of parameter space transition can also be initiated by a newly discovered linear instability in this system (Facchini et al., J. Fluid Mech., vol. 853, 2018, pp. 205–234). When wall turbulence can be sustained the linear instability opens up new routes in phase space for infinitesimal disturbances to initiate turbulence. When the buoyancy scale suppresses turbulence the linear instability leads to more ordered nonlinear states, with the possibility for intermittent bursts of secondary shear instability.
水平强制分层湍流中的层形成：将精确的相干结构与线性不稳定性联系起来
影响因子：
3.7
作者：
Lucas D
通讯作者：
Lucas D
稳定分层平面库埃特流中的精确相干结构
影响因子：
3.7
作者：
Olvera D
通讯作者：
Olvera D