Throughflow effects on convective instability in superposed fluid and porous layers
Resource
Journal of Fluid Mechanics 231: 113-133
Journal
Journal of Fluid Mechanics
Pages
113-133
Date Issued
1990
Date
1990
Author(s)
Abstract
We implement a linear stability analysis of the convective instability in superposed horizontal fluid and porous layers with throughflow in the vertical direction. It is found that in such a physical configuration both stabilizing and destabilizing factors due to vertical throughflow can be enhanced so that a more precise control of the buoyantly driven instability in either a fluid or a porous layer is possible. For �a = 0.1 (�a, the depth ratio, defined as the ratio of the fluid-layer depth to the porous-layer depth), the onset of convection occurs in both fluid and porous layers, the relation between the critical Rayleigh number R c m and the throughflow strength �^ m is linear and the Prandtl-number ( Pr m ) effect is insignificant. For �a ? 0.2, the onset of convection is largely confined to the fluid layer, and the relation becomes R c m �� �^ 2 m for most of the cases considered except for Pr m = 0.1 with large positive �^ m where the relation R c m �� �^ 3 m holds. The destabilizing mechanisms proposed by Nield (1987 a , b ) due to throughflow are confirmed by the numerical results if considered from the viewpoint of the whole system. Nevertheless, from the viewpoint of each single layer, a different explanation can be obtained.
Other Subjects
Flow of Fluids--Porous Materials; Fluid Mechanics; Heat Transfer--Stability; Convective Instability; Destabilizing Mechanisms; Heat Transfer; convective instability; fluid layer; porous layer; throughflow effect
Type
journal article
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