Digitale Medien
New York, NY
:
American Institute of Physics (AIP)
Physics of Fluids
2 (1990), S. 2157-2163
ISSN:
1089-7666
Quelle:
AIP Digital Archive
Thema:
Physik
Notizen:
Direct numerical simulations of two-dimensional high Rayleigh (Ra) number, base-heated thermal convection in large aspect-ratio boxes are presented for infinite Prandtl number fluids, as applied to the Earth's mantle. A transition is characterized in the flow structures in the neighborhood of Ra between 107 and 108. These high Ra flows consist of large-scale cells with strong intermittent, boundary-layer instabilities. For Ra exceeding 107 it is found that the heat-transfer mechanism changes from one characterized by mushroom-like plumes to one consisting of disconnected ascending instabilities, which do not carry with them all the thermal anomaly from the bottom boundary layer. Plume–plume collisions become much more prominent in high Ra situations and have a tendency of generating a pulse-like behavior in the fixed plume. This type of instability represents a distinct mode of heat transfer in the hard turbulent regime. Predictions of this model can be used to address certain issues concerning the mode of time-dependent convection in the Earth's mantle.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.857802
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