Statistical State Dynamics of Weak Jets in Barotropic Beta-Plane Turbulence
Statistical State Dynamics of Weak Jets in Barotropic Beta-Plane Turbulence
复制标题
正压β平面湍流中弱射流的统计状态动力学
DOI：
10.1175/jas-d-18-0148.1
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发表时间：
2017
影响因子：
3.1
通讯作者：
P. Ioannou
中科院分区：
文献类型：
--
作者：
N. Bakas;N. Constantinou;P. Ioannou
正压装置中的纬向急流通过均匀湍流态的成流不稳定性(纬地转不稳定性)从均匀湍流中产生，这种不稳定是随着湍流强度的增加而发生的。这一点已经用统计状态动力学(SSD)框架在二阶闭包下进行了演示。此外，对于小的超临界情况，流动不稳定性遵循Ginzburg-Landau(G-L)动力学。在这里，SSD框架被用来研究这种小超临界造流不稳定性的平衡。首先，我们比较了弱非线性G-L动力学和完全非线性SSD动力学在较大参数范围内二阶闭合的预测。揭示了喷流平衡的一个新分支，它不是与G-L分支相连的。与G-L分支相比，这个新的弱超临界分支涉及的喷流幅度更大。此外，即使对于线性成流不稳定性的亚临界值，这一新的分支仍在继续。由此揭示了均匀湍流中的一种新的非线性造流不稳定性。其次，我们研究了线性成流不稳定性和新的非线性成流不稳定性是如何平衡的。我们确定了射流平衡背后的物理过程，以及在每个过程中贡献的涡流类型。第三，我们对G-L动力学的扩散系数进行了修正，使之能够在线性造流不稳定性的边缘尺度(边带不稳定性)以外的尺度上捕捉弱喷流的演化。
Zonal jets in a barotropic setup emerge out of homogeneous turbulence through a flow-forming instability of the homogeneous turbulent state (zonostrophic instability), which occurs as the turbulence intensity increases. This has been demonstrated using the statistical state dynamics (SSD) framework with a closure at second order. Furthermore, it was shown that for small supercriticality the flow-forming instability follows Ginzburg–Landau (G–L) dynamics. Here, the SSD framework is used to study the equilibration of this flow-forming instability for small supercriticality. First, we compare the predictions of the weakly nonlinear G–L dynamics to the fully nonlinear SSD dynamics closed at second order for a wide range of parameters. A new branch of jet equilibria is revealed that is not contiguously connected with the G–L branch. This new branch at weak supercriticalities involves jets with larger amplitude compared to the ones of the G–L branch. Furthermore, this new branch continues even for subcritical values with respect to the linear flow-forming instability. Thus, a new nonlinear flow-forming instability out of homogeneous turbulence is revealed. Second, we investigate how both the linear flow-forming instability and the novel nonlinear flow-forming instability are equilibrated. We identify the physical processes underlying the jet equilibration as well as the types of eddies that contribute in each process. Third, we propose a modification of the diffusion coefficient of the G–L dynamics that is able to capture the evolution of weak jets at scales other than the marginal scale (side-band instabilities) for the linear flow-forming instability.
二维分层湍流中浮力层形成的菲利普斯机制统计状态动力学分析
影响因子：
3.7
作者：
Fitzgerald, Joseph G.;Farrell, Brian F.
通讯作者：
Farrell, Brian F.
二维分层湍流中垂直剪切水平流的统计状态动力学
影响因子：
3.7
作者：
Fitzgerald, Joseph G.;Farrell, Brian F.
通讯作者：
Farrell, Brian F.
分层湍流中垂直剪切水平流动的不稳定性：统计状态动力学平衡的解析线性稳定性分析
影响因子：
3.1
作者：
Fitzgerald, Joseph G.;Farrell, Brian F.
通讯作者：
Farrell, Brian F.