University of Illinois Urbana-Champaign

High rayleigh number convection at infinite prandtl number with temperature-dependent viscosity

Balachandar, S.; Yuen, David A.; Reuteler, David M.

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https://hdl.handle.net/2142/112454

Description

Title
High rayleigh number convection at infinite prandtl number with temperature-dependent viscosity
Author(s)
  • Balachandar, S.
  • Yuen, David A.
  • Reuteler, David M.
Issue Date
1994-07
Keyword(s)
  • Temperature Dependent Viscosity
  • Infinite Prandtl Number
  • High Rayleigh Number Convection
Abstract
The effects of high Rayleigh number convection for temperature-dependent viscosity at infinite Prandtl number are studied with three-dimensional direct numerical simulations (using a fully spectral method) in a wide box with dimensions 5 X 5 X 1. The form of the temperature-dependent viscosity decreases exponentially with the temperature. Solutions for an volumetrically averaged Rayleigh numbers up to 6.25 X 106 have been obtained for a viscosity contrast of 25. Both models with and without viscous dissipation and adiabatic heatings have been considered. There is a distinct difference in the plume dynamics between models with a dissipation number D=O and D=0.3. At zero dissipation number the hot plumes extend up to the top, while plumes at D=0.3 are cooled due to adiabatic expansion and do not extend throughout the entire layer. The cold descending flows occur in sheets and they form longer wavelength networks and can reach the bottom, regardless of the value of D. At high Rayleigh number there is a transition in the surface toroidal velocity field to a coherent network of river-like structures and compact vortices. Viscous dissipation is found to increase with the Rayleigh number and is particularly strong in regions of downwelling flows. A time- varying depth-dependent mean horizontal flow is produced from the correlation between the laterally varying viscosity field and the velocity gradients.
Publisher
Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report Name or Number
  • TAM R 761
  • 1994-6017
ISSN
0073-5264
Type of Resource
text
Language
eng
Permalink
http://hdl.handle.net/2142/112454
Sponsor(s)/Grant Number(s)
National Science Foundation 94/07
Copyright and License Information
Copyright 1994 Board of Trustees of the University of Illinois

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