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Stability of gravitationally unstable double diffusive transient boundary layers with variable viscosity in porous media
Author(s) -
Sabet Nasser,
Hassanzadeh Hassan,
Abedi Jalal
Publication year - 2017
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.15626
Subject(s) - viscosity , transient (computer programming) , porous medium , instability , lewis number , mechanics , boundary (topology) , convection , boundary layer , rayleigh number , boundary value problem , thermodynamics , stability (learning theory) , physics , porosity , natural convection , chemistry , mathematical analysis , mathematics , mass transfer , organic chemistry , quantum mechanics , machine learning , computer science , operating system
We study the double diffusive convection (DDC) in porous media through linear stability analysis (LSA) and direct numerical simulations (DNS). Unlike the previous studies that assume static solutal or thermal fields, the developed model is able to capture the transient behavior of both fields. We show that under the assumption of static field, the role of Lewis number cannot be distinguished. Under transient fields, we conclude that higher Lewis numbers result in earlier instability of the boundary layers. Moreover, the effect of viscosity contrast is explained in terms of the mobility of the boundary layer. The DNS results confirm the validity of LSA predictions. We also obtain the critical Rayleigh number and show that in the presence of viscosity contrast, it can be much smaller than the conventional limit of 4π 2 . This study provides a better understanding of the transient nature of DDC in the presence of viscosity variations. © 2017 American Institute of Chemical Engineers AIChE J , 63: 2471–2482, 2017