Onset of vortex structures in rotating plane Couette flow
Onset of vortex structures in rotating plane Couette flow
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DOI：
10.1017/jfm.2021.283
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发表时间：
2021-05
影响因子：
3.7
通讯作者：
M. Nagata;Baofang Song;D. Wall
中科院分区：
文献类型：
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作者：
M. Nagata;Baofang Song;D. Wall
摘要通过数值计算，发现了旋转平面Couette流（RPCF）中两种新的不稳定流动：斜涡流动和斜涡流动。到目前为止，人们一直认为，层流状态的前几个分叉序列已被很好地理解，即，具有二维滚动单元（2dRC）结构的流向独立流动首先分叉，然后是波涡流动（WVF）的分叉。目前的研究表明，2dRC，事实上，从它的发病不稳定，新发现的倾斜涡流接管的地方2dRC。在层流-湍流转捩的早期阶段，存在着旋涡流动。新流动的存在可以通过Hiwatashi等人（Phys. Fluids，第19卷，2007，048103）和Kawata & Alfredsson（J. Fluid Mech.，vol.791，2016，191-213）。
Abstract Two new flows, a tilted-vortex flow and a periodic-vortex flow, are found numerically at the onset of instability in rotating plane Couette flow (RPCF). It has hitherto been believed that the first few bifurcation sequences from the laminar state are quite well understood, namely, that a streamwise-independent flow with a two-dimensional roll-cell (2dRC) structure bifurcates first, followed by the bifurcation of a wavy-vortex flow (WVF). The present study shows that the 2dRC is, in fact, unstable from its onset, and that the newly found tilted-vortex flow takes over in place of 2dRC. It is further found that the periodic-vortex flow takes part in the early stages of laminar–turbulent transition. The existence of the new flows can be verified by careful examinations of the experimental observations in Hiwatashi et al. (Phys. Fluids, vol. 19, 2007, 048103) and Kawata & Alfredsson (J. Fluid Mech., vol. 791, 2016, 191–213).