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| Titel |
Contributions from the geophysical flow simulation experiment ‘GeoFlow': fringe patterns of convection and their spatio-temporal behaviour in rapid rotating and non-rotating spherical shells |
| VerfasserIn |
Birgit Futterer, Sandy Koch, Christoph Egbers |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032943
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| Zusammenfassung |
| Thermally driven convective flows in spherical shells are a central issue of geophysical fluid
dynamics, i.e. discussing fluid flow of the planet’s interiors with its contribution especially to
action of dynamos in the cores. For the problem of spherical Rayleigh-Bénard convection in
a self-gravitating force field a reasonable amount of research work exists. Most of these
studies are in the area of theoretical and numerical simulation analysis. Topic of the
‘GeoFlow’ experiment is the investigation of convection in rotating, self-gravitating
spherical shells. The central symmetry buoyancy field is generated by means of a
spherical symmetric electric field acting in a dielectric insulating liquid. Herewith
microgravity conditions are necessary. The GeoFlow experiment was running in
relevant conditions inside European COLUMBUS module of International Space
Station ISS from August 2008 until January 2009, delivering data for convection in
spherical shells for no, low, intermediate and rapid rotating cases. Here we present the
experimental alignment with numerical data bases for the non-rotating and rapid rotation
case.
The non-rotating case is characterized by a co-existence of several stationary supercritical
modes, with a strong influence of initial conditions leading to axisymmetric, octahedral/cubic
or pentagonal solutions. Transition to chaos is in form of a sudden onset. Experimental data
supports the numerically validated influence of initial conditions in showing the octahedral
mode as most preferred stable state. Well-known issue of rapid rotation is the alignment of
convective cells at the tangent cylinder due to the domination of centrifugal forces against the
self-gravitating buoyancy field. This is the first time that an experiment includes both
influences. Hence experimental data reach the regimes of rapid rotation, the system
shows very clearly the centrifugal effects by patterns in form of columnar cells. |
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