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Dynamics of flow structures and surface shapes in the surface switching of rotating fluid

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Title: Dynamics of flow structures and surface shapes in the surface switching of rotating fluid
Authors: Iima, M. Browse this author
Tasaka, Y. Browse this author →KAKEN DB
Keywords: instability
vortex flows
waves/free-surface flows
Issue Date: Feb-2016
Publisher: Cambridge University Press
Journal Title: Journal of fluid mechanics
Volume: 789
Start Page: 402
End Page: 424
Publisher DOI: 10.1017/jfm.2015.753
Abstract: We present a study of the dynamics of the free-surface shape of a flow in a cylinder driven by a rotating bottom. Near the critical Reynolds number of the laminar-turbulent transition of the boundary layer, the free surface exhibits irregular surface switching between axisymmetric and non-axisymmetric shapes, and the switching often occurs with a significant change in the free-surface height. Although such surface deformation is known to be caused by the flow structures, the detailed flow structures of a rotating fluid with a large surface deformation have yet to be analysed. We thus investigate the velocity distribution and surface shape dynamics and show that the flow field during the loss of its axisymmetry is similar to that predicted by the theory of Tophoj et al. (Phys. Rev. Lett., vol. 110, 2013, 194502). The slight difference observed by quantitative comparison is caused by the fact that the basic flow of our study contains a weak rigid-body rotation in addition to the potential flow assumed by the theory. Furthermore, the observed non-axisymmetric surface shape, which has an elliptic horizontal cross-section, is generally associated with a quadrupole vortex structure. It is also found that the relative position between the free surface and the flow structure changes before and after the detachment of the free surface from the bottom. The change just after the detachment is drastic and occurs via a transient dipole-like vortex structure.
Type: article (author version)
URI: http://hdl.handle.net/2115/62447
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 田坂 裕司

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