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| Titel |
Topographic instability of flow in a rotating fluid |
| VerfasserIn |
K. I. Patarashvili, Z. J. Tsakadze, M. V. Kalashnik, V. O. Kakhiani, R. J. Chanishvili, J. I. Nanobashvili, M. A. Zhvania |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 13, no. 2 ; Nr. 13, no. 2 (2006-06-21), S.231-235 |
| Datensatznummer |
250011738
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| Publikation (Nr.) |
 copernicus.org/npg-13-231-2006.pdf |
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| Zusammenfassung |
| Here are presented the results of experimental and theoretical studies on a
stability of zonal geostrophic flows in the rotating layer of the shallow
water. In the experiments, a special apparatus by Abastumani Astrophysical
Observatory Georgian Academy of Science was used. This apparatus represents
a paraboloid of rotation, which can be set in a regulable rotation around
the vertical axis. Maximal diameter of the paraboloid is 1.2 m, radius of
curvature in the pole is 0.698 m. In the paraboloid, water spreads on walls
as a layer uniform on height under the period of rotation 1.677 s. Against a
background of the rotating fluid, the zonal flows are formed by the
source-sink system. It consists of two concentric circular perforations on
the paraboloid bottom (width is 0.3 cm, radiuses are 8.4 and 57.3 cm,
respectively); water can be pumped through them with various velocities and
in all directions. It has been established that under constant vertical
depth of the rotating fluid the zonal flows are stable. There are
given the measurements of the radial profiles for the water level and
velocity in the stationary regime. It has been found that zonal flows may
lose stability under the presence of the radial gradient of full depth
formed by a change of angular velocity of paraboloid rotation. An
instability origin results in the loss of flow axial symmetry and in the
appearance of self-excited oscillations in the zonal flow. At the given
angular velocity of rotation, instability is observed only in the definite
range of intensities of the source-sink system.
The theoretical estimations are performed in the framework of the equations
of the shallow water theory, including the terms describing the bottom
friction. It has been shown that the instability of zonal flows found
experimentally has a topographical nature and is related with non-monotone
dependence of the potential vorticity on radius. |
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