Rotating horizontal convection
Rotating horizontal convection
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DOI：
10.1017/jfm.2013.136
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发表时间：
2013-04
影响因子：
3.7
通讯作者：
R. Barkan;K. Winters;Stefan G. Llewellyn Smith
中科院分区：
文献类型：
--
作者：
R. Barkan;K. Winters;Stefan G. Llewellyn Smith
摘要水平对流是流体在水平边界上受沿着浮力变化而产生的流动的总称。我们分两个阶段数值研究了旋转对三维HC的影响：第一阶段，斜压不稳定被抑制;第二阶段，涡被包围并形成斜压涡。我们集中在近地表边界层的厚度，分层在深度，翻转环流和流动能量学在每个阶段的变化。我们的结果表明，对于中等通量瑞利数（$O（1{0}^{11}）$），快速旋转大大改变了HC的稳态解。当流动在横向方向上被限制为均匀时，快速旋转的解不支持边界层，在所有深度处表现出较弱的翻转环流和较大的分层。在这种情况下，扩散是横向浮力通量的主导机制，随之而来的可用势能的积累导致斜压不稳定的解决方案。当这些快速旋转的气流受到扰动时，斜压不稳定性发展，斜压涡主导横向和垂直浮力通量。与非旋转HC相比，所得的统计稳定解支持边界层、更大的深层分层值和多个翻转单元。一个转换的欧拉平均方法表明，剩余环流占主导地位的准地转涡动流函数和涡动浮力通量具有不可忽略的内部非绝热分量。的动能和可用的势能是大于在非旋转的情况下，混合效率从${\sim }0。7$到${\sim }0。17美元。涡流在热边界层的形成中起着重要作用，并与负浮力羽流一起帮助建立深层分层。这些斜压活动解具有地转湍流的特征。
Abstract ‘Horizontal convection’ (HC) is the generic name for the flow resulting from a buoyancy variation imposed along a horizontal boundary of a fluid. We study the effects of rotation on three-dimensional HC numerically in two stages: first, when baroclinic instability is suppressed and, second, when it ensues and baroclinic eddies are formed. We concentrate on changes to the thickness of the near-surface boundary layer, the stratification at depth, the overturning circulation and the flow energetics during each of these stages. Our results show that, for moderate flux Rayleigh numbers ( $O(1{0}^{11} )$ ), rapid rotation greatly alters the steady-state solution of HC. When the flow is constrained to be uniform in the transverse direction, rapidly rotating solutions do not support a boundary layer, exhibit weaker overturning circulation and greater stratification at all depths. In this case, diffusion is the dominant mechanism for lateral buoyancy flux and the consequent buildup of available potential energy leads to baroclinically unstable solutions. When these rapidly rotating flows are perturbed, baroclinic instability develops and baroclinic eddies dominate both the lateral and vertical buoyancy fluxes. The resulting statistically steady solution supports a boundary layer, larger values of deep stratification and multiple overturning cells compared with non-rotating HC. A transformed Eulerian-mean approach shows that the residual circulation is dominated by the quasi-geostrophic eddy streamfunction and that the eddy buoyancy flux has a non-negligible interior diabatic component. The kinetic and available potential energies are greater than in the non-rotating case and the mixing efficiency drops from ${\sim }0. 7$ to ${\sim }0. 17$ . The eddies play an important role in the formation of the thermal boundary layer and, together with the negatively buoyant plume, help establish deep stratification. These baroclinically active solutions have characteristics of geostrophic turbulence.