Published 12 issues per year
ISSN Print: 1091-028X
ISSN Online: 1934-0508
Indexed in
BOUNDS FOR THE GROWTH RATE OF PERTURBATION IN A COUPLE-STRESS FLUID IN THE PRESENCE OF ROTATION AND MAGNETIC FIELD IN A POROUS MEDIUM
ABSTRACT
A layer of couple-stress fluid heated from below in a porous medium is considered in the presence of uniform vertical magnetic field and rotation. Following the linearized stability theory and normal mode analysis, the paper, through mathematical analysis of the governing equations of couple-stress fluid convection with a uniform vertical magnetic field and rotation in porous medium, for any combination of perfectly conducting free and rigid boundaries of infinite horizontal extension at the top and bottom of the fluid, established that the complex growth rate о of oscillatory perturbations, neutral or unstable for all wave numbers, must lie inside a semi-ring enclosed by the two semi-circles of radii, ε/2 { Q − √(Q2 + 4TA )} and ε/2 { Q + √(Q2 + 4TA )}, in the right half of the σr−σi plane whose centers are at the origin, where TA is the Taylor number, Q is the Chandrasekhar number, and ε is the porosity of the porous medium. Further, it has been established that the sufficient condition for the validity of the "principle of exchange of stability" in magneto-rotatory thermal convection in a couple-stress fluid in a porous medium is that Q/√(Q2 + 4TA) ≤ 1, and that the existence of oscillatory motions of growing amplitude in the present configuration depends crucially upon the magnitude of the nondimensional number Q/√(Q2 + 4TA), in the sense so long as 0<Q/(√(Q2 +4TA)) ≤ 1, no such motions are possible, and in particular principle of exhange of stability (PES) is valid.
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Nield Donald A., Bejan Adrian, Internal Natural Convection: Heating from Below, in Convection in Porous Media, 2017. Crossref