On the late-time behaviour of a bounded, inviscid two-dimensional flow
On the late-time behaviour of a bounded, inviscid two-dimensional flow
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DOI：
10.1017/jfm.2015.535
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发表时间：
2015-11-01
影响因子：
3.7
通讯作者：
Marston, J. B.
中科院分区：
文献类型：
--
作者：
Dritschel, David G.;Qi, Wanming;Marston, J. B.
利用互补的高分辨率数值方法，我们研究了球面上无粘不可压缩二维流的晚时行为。从一个随机的初始涡量场开始，我们发现，与平衡统计力学的预测相反，流动并没有演变成一个大尺度的稳态。相反，显著的不稳定性持续存在，其特征是持续的小尺度涡旋与大尺度振荡四极涡旋场相互作用。此外，涡度呈阶梯状分布，由由陡峭梯度分隔的几乎均匀的区域组成。非定常的持续可以用一个简单的点涡模型来解释，该模型描述了出现的四个主要涡之间的相互作用。
Using complementary numerical approaches at high resolution, we study the late-time behaviour of an inviscid incompressible two-dimensional flow on the surface of a sphere. Starting from a random initial vorticity field comprised of a small set of intermediate-wavenumber spherical harmonics, we find that, contrary to the predictions of equilibrium statistical mechanics, the flow does not evolve into a large-scale steady state. Instead, significant unsteadiness persists, characterised by a population of persistent small-scale vortices interacting with a large-scale oscillating quadrupolar vorticity field. Moreover, the vorticity develops a stepped, staircase distribution, consisting of nearly homogeneous regions separated by sharp gradients. The persistence of unsteadiness is explained by a simple point-vortex model characterising the interactions between the four main vortices which emerge.