Provider: National Science Library - National Research Council Canada / Bibliothèque scientifique nationale - Conseil national de recherches Canada
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TY - JOUR
TI - Numerical nonlinear analysis of subcritical Rayleigh-Bénard convection in a horizontal confined enclosure filled with non-Newtonian fluids
DO - 10.1063/1.4890829
AU - Benouared, Ouahiba
AU - Mamou, Mahmoud
AU - Messaoudene, Noureddine Ait
T2 - Physics of Fluids
SN - 1070-6631
SN - 1089-7666
VL - 26
IS - 7
SP - 073101
KW - Thermal convection
KW - Shear thinning
KW - Viscosity
KW - Shear rate dependent viscosity
KW - Boundary value problems
AB - Non-Newtonian subcritical convection in a Rayleigh-Bénard configuration was investigated numerically, using rigid boundary conditions. The flow configuration consisted of a finite aspect ratio enclosure subject to a vertical temperature gradient, which was established by heating and cooling the lower and the upper walls by either a constant heat flux or by applying constant temperatures. The non-Newtonian fluid viscosity was modeled using the Carreau-Yasuda model. The convective flow was governed by the conservation equations, which were solved numerically using a finite difference method with a time-accurate scheme. For a shallow enclosure, when the walls were subject to constant heat fluxes, an asymptotic solution was derived assuming a parallel flow behavior. A comparison between the numerical and asymptotic solutions was performed. The effects of the controlling parameters, namely, the Rayleigh and the Prandtl numbers, and the fluid rheological parameters on the onset of subcritical convective flow were investigated. The threshold for the onset of subcritical convection was found to be well below the threshold of stationary convection and decreased considerably (with the fluid rheological parameters variation) as the fluid became more and more shear thinning. Depending on the governing parameters, steady and unsteady-periodic flow solutions were possible. Within a square enclosure with slip or no-slip vertical walls, maintaining the active walls at a constant heat flux or at constant temperature, the rheological subcritical flow behavior remained qualitatively the same, but led to different subcritical convection thresholds.
PY - 2014
DA - 2014/07/31
PB - AIP Publishing
LA - eng
C1 - Collection / Collection : NRC Publications Archive / Archives des publications du CNRC
C2 - Record identifier / Identificateur de l’enregistrement : 0c45cfc1-df29-40f8-a801-852303e976c5
ER -