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ISSN Online: 2377-424X

ISBN Print: 0-85295-345-3

International Heat Transfer Conference 10
August, 14-18, 1994, Brighton, UK

OSCILLATORY DOUBLE DIFFUSIVE NATURAL CONVECTION IN A TWO-LAYER SYSTEM

Get access (open in a dialog) DOI: 10.1615/IHTC10.3590
pages 67-72

Sinopsis

When a two-layer system which consists of water (upper layer) and an aqueous solution (lower layer) is heated from a vertical side wall and cooled from an opposing side wall, convection starts in each layer. Computations with a Galerkin finite element method were carried out for the Prandtl number Pr=6, the Lewis number Le=100, the aspect ratio A=4, the buoyancy ratio N=3 and the Rayleigh numbers Ra=104 , 105 and 106. At Ra=104 the average Nusselt number Nuave on each wall varies always monotonously with time. At Ra=105 the Nuave exhibits double periodic oscillation. Then a long periodic oscillation corresponds to the periodical change of the concentration distribution in a layer and a short periodic oscillation corresponds to the flow oscillation. At Ra=106 Nuave has single periodic oscillation with much higher frequency in the flow velocity. These oscillatory phenomena seem to be caused by the periodic collapse of the balance of two kinds of buoyancies, and the subsequent mixing contributes to the uniformity of concentration in a layer. Oscillatory convection is observed experimentally.