Convective instabilities in binary mixtures in a porous medium

1983 ◽  
Vol 119 (1-2) ◽  
pp. 327-338 ◽  
Author(s):  
H. Brand ◽  
V. Steinberg
Keyword(s):  
Porous Medium ◽  
Binary Mixtures ◽  
Convective Instabilities

Three-dimensional absolute and convective instabilities at the onset of convection in a porous medium with inclined temperature gradient and vertical throughflow

2009 ◽  
Vol 641 ◽  
pp. 475-487 ◽  
Author(s):  
LEONID BREVDO
Keyword(s):  
Porous Medium ◽  
Rayleigh Number ◽  
Temperature Gradient ◽  
Three Dimensional ◽  
Onset Of Convection ◽  
Convective Instabilities ◽  
Homogeneous Porous Medium ◽  
Vertical Throughflow ◽  
Speed Of Propagation ◽  
Inclined Temperature Gradient

By using the mathematical formalism of absolute and convective instabilities, we study in this work the nature of unstable three-dimensional localized disturbances at the onset of convection in a flow in a saturated homogeneous porous medium with inclined temperature gradient and vertical throughflow. It is shown that for marginally supercritical values of the vertical Rayleigh numberRvthe destabilization has the character of absolute instability in all the cases in which the horizontal Rayleigh numberRhis zero or the Péclet numberQvis zero. In all the cases in whichRhandQvare both different from zero, at the onset of convection the instability is convective. In the latter cases, the growing emerging disturbance has locally the structure of a non-oscillatory longitudinal roll, and its group velocity points in the direction opposite the direction of the applied horizontal temperature gradient, i.e. parallel to the axis of the roll. The speed of propagation of the unstable wavepacket increases withQvand generally increases withRh.

Convective instabilities induced by exothermic reactions occurring in a porous medium

1994 ◽  
Vol 6 (9) ◽  
pp. 2907-2922 ◽  
Author(s):  
Sudhakar Subramanian ◽  
Vemuri Balakotaiah
Keyword(s):  
Porous Medium ◽  
Exothermic Reactions ◽  
Convective Instabilities

scholarly journals Roll convection of binary fluid mixtures in porous media

2010 ◽  
Vol 649 ◽  
pp. 165-186 ◽  
Author(s):  
R. UMLA ◽  
M. AUGUSTIN ◽  
B. HUKE ◽  
M. LÜCKE
Keyword(s):  
Porous Medium ◽  
Binary Mixtures ◽  
Fluid Layer ◽  
Boussinesq Approximation ◽  
Fluid Mixtures ◽  
New Type ◽  
The Stability ◽  
Binary Fluid Mixtures ◽  
Rayleigh Benard ◽  
Bénard System

We investigate theoretically the nonlinear state of ideal straight rolls in the Rayleigh–Bénard system of a fluid layer heated from below with a porous medium using a Galerkin method. Applying the Oberbeck–Boussinesq approximation, binary mixtures with positive separation ratio are studied and compared with one-component fluids. Our results for the structural properties of roll convection resemble qualitatively the situation in the Rayleigh–Bénard system without porous medium except for the fact that the streamlines of binary mixtures are deformed in the so-called Soret regime. The deformation of the streamlines is explained by means of the Darcy equation which is used to describe the transport of momentum. In addition to the properties of the rolls, their stability against arbitrary infinitesimal perturbations is investigated. We compute stability balloons for the pure fluid case as well as for a wide parameter range of Lewis numbers and separation ratios that are typical for binary gas and fluid mixtures. The stability regions of rolls are found to be restricted by a crossroll, a zigzag and a new type of oscillatory instability mechanism, which can be related to the crossroll mechanism.

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