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Localization of toroidal motion and shear heating in 3‐D high Rayleigh number convection with temperature‐dependent viscosity
Author(s) -
Balachandar S.,
Yuen D. A.,
Reuteler D. M.
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl03046
Subject(s) - rayleigh number , viscosity , rayleigh scattering , convection , mechanics , dissipation , toroid , temperature dependence of liquid viscosity , shear (geology) , physics , materials science , thermodynamics , natural convection , relative viscosity , optics , composite material , plasma , quantum mechanics
We have applied spectral‐transform methods to study three‐dimensional thermal convection with temperature‐dependent viscosity. The viscosity varies exponentially with the form exp(‐BT), where B controls the viscosity contrast and T is temperature. Solutions for high Rayleigh numbers, up to an effective Ra of 6.25×10 6 , have been obtained for an aspect‐ratio of 5×5×1 and a viscosity contrast of 25. Solutions show the localization of toroidal velocity fields with increasing vigor of convection to a coherent network of shear‐zones. Viscous dissipation increases with Rayleigh number and is particularly strong in regions of convergent flows and shear deformation. A time‐varying depth‐dependent mean‐flow is generated because of the correlation between laterally varying viscosity and velocity gradients.