HYDROMAGNETIC INSTABILITY OF A CONTINUOUSLY STRATIFIED FLUID LAYER IN A POROUS MEDIUM WITH A VARIABLE OBLIQUE MAGNETIC FIELD

The paper deals with the theoretical investigation of the effect of dust/suspended particles on a layer of electrically conducting micropolar fluid heated and dissolved from below in the presence of a uniform vertical magnetic field in a porous medium. The presence of coupling between thermosolutal and micropolar effects and magnetic field brings oscillatory motions in the system. A dispersion relation governing the effects of solute gradient, magnetic field, and suspended particles is obtained for a fluid layer contained between two free boundaries using linear stability theory and normal mode technique. Graphs have been plotted by giving numerical values to various parameters involved to depict the stability characteristics for both cases of stationary convection and overstability. It has been found that, for permissible values of various parameters under consideration, the effect of magnetic field and solute gradient is stabilizing and that of medium permeability, suspended particles, and micropolar coefficient is destabilizing. Further it is found that the Rayleigh number for overstability is always less than that for stationary convection except for high values of suspended particle factor.

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The effect of an oblique magnetic field on the surface instability of a finite conducting fluid layer

Acta Mechanica ◽

10.1007/bf01274246 ◽

1996 ◽

Vol 119 (1-4) ◽

pp. 165-180 ◽

Cited By ~ 8

Author(s):

N. Rudraiah ◽

B. S. Krishnamurthy ◽

R. D. Mathad

Keyword(s):

Magnetic Field ◽

Fluid Layer ◽

Surface Instability ◽

Conducting Fluid ◽

Oblique Magnetic Field

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Magneto Binary Nanofluid Convection in Porous Medium

International Journal of Chemical Engineering ◽

10.1155/2016/9424036 ◽

2016 ◽

Vol 2016 ◽

pp. 1-8 ◽

Cited By ~ 4

Author(s):

Jyoti Sharma ◽

Urvashi Gupta ◽

R. K. Wanchoo

Keyword(s):

Magnetic Field ◽

Heat Transfer ◽

Porous Medium ◽

Comparative Analysis ◽

Galerkin Method ◽

Fluid Layer ◽

Layer System ◽

Water Based ◽

The Stability ◽

Mode Technique

The effect of an externally impressed magnetic field on the stability of a binary nanofluid layer in porous medium is considered in this work. The conservation equations related to the system are solved using normal mode technique and Galerkin method to analyze the problem. The complex expressions are approximated to get useful results. Mode of heat transfer is stationary for top heavy distribution of nanoparticles in the fluid layer and top heavy nanofluids are very less stable than regular fluids. Oscillatory motions are possible for bottom heavy distribution of nanoparticles and they are not much influenced by properties of different nanoparticles. A comparative analysis of the instability of water based nanofluids with metallic (Cu, Ag) and semiconducting (TiO2, SiO2) nanoparticles under the influence of magnetic field is examined. Semiconducting nanofluids are found to be more stable than metallic nanofluids. Porosity destabilizes the layer while solute difference (at the boundaries of the layer) stabilizes it. Magnetic field stabilizes the fluid layer system significantly.

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Magnetofluidconvection in a Rotating Porous Layer Under Modulated Temperature on the Boundaries

Journal of Heat Transfer ◽

10.1115/1.2712851 ◽

2006 ◽

Vol 129 (7) ◽

pp. 835-843 ◽

Cited By ~ 11

Author(s):

B. S. Bhadauria

Keyword(s):

Magnetic Field ◽

Porous Medium ◽

Prandtl Number ◽

Thermal Instability ◽

Fluid Layer ◽

Saturated Porous Medium ◽

Critical Rayleigh Number ◽

Temperature Modulation ◽

Brinkman Model ◽

Vertical Magnetic Field

Thermal instability in an electrically conducting fluid saturated porous medium, confined between two horizontal walls, has been investigated in the presence of an applied vertical magnetic field and rotation, using the Brinkman model. The temperature gradient between the walls of the fluid layer consists of a steady part and a time-dependent oscillatory part. Only infinitesimal disturbances are considered. The combined effect of permeability, rotation, vertical magnetic field, and temperature modulation has been investigated using Galerkin’s method and Floquet theory. The value of the critical Rayleigh number is calculated as function of amplitude and frequency of modulation, Chandrasekhar number, Taylor number, porous parameter, Prandtl number, and magnetic Prandtl number. It is found that rotation, magnetic field, and porous medium all have a stabilizing influence on the onset of thermal instability. Further, it is also found that it is possible to advance or delay the onset of convection by proper tuning of the frequency of modulation of the walls’ temperature. In addition the results corresponding to the Brinkman model and Darcy model have been compared for neutral instability.

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Ferromagnetic Convection in a Densely Packed Porous Medium with Magnetic-Field-Dependent Viscosity – Revisited

Zeitschrift für Naturforschung A ◽

10.1515/zna-2017-0215 ◽

2018 ◽

Vol 73 (3) ◽

pp. 181-189

Author(s):

Jyoti Prakash ◽

Pankaj Kumar ◽

Kultaran Kumari ◽

Shweta Manan

Keyword(s):

Magnetic Field ◽

Porous Medium ◽

Fluid Layer ◽

Critical Rayleigh Number ◽

Wave Number ◽

Free Boundaries ◽

Medium Permeability ◽

Field Dependent ◽

Mfd Viscosity ◽

Dependent Viscosity

AbstractThe effect of magnetic-field-dependent (MFD) viscosity on the thermal convection in a ferromagnetic fluid in the presence of a uniform vertical magnetic field is investigated for a fluid layer saturating a densely packed porous medium using the Darcy model. A correction is applied to the model by Sunil et al. [Z. Naturforsch. 59, 397 (2004)], which is very important to predict the correct behaviour of MFD viscosity. A linear stability analysis is carried out for stationary modes. The critical wave number and critical Rayleigh number for the onset of instability, for the case of free boundaries, are determined numerically for sufficiently large values of the magnetic parameter M1. Numerical results are obtained and illustrated graphically. It is shown that MFD viscosity has stabilizing effect on the system, whereas medium permeability has a destabilizing effect.

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The Effect Of A Magnetic Field Dependent Viscosity On The Thermal Convection In A Ferromagnetic Fluid In A Porous Medium

Zeitschrift für Naturforschung A ◽

10.1515/zna-2004-7-802 ◽

2004 ◽

Vol 59 (7-8) ◽

pp. 397-406 ◽

Cited By ~ 1

Author(s):

◽

Pavan Kumar Bharti ◽

Divya Sharma ◽

R. C. Sharma

Keyword(s):

Magnetic Field ◽

Porous Medium ◽

Thermal Convection ◽

Fluid Layer ◽

Wave Number ◽

Medium Permeability ◽

Field Dependent ◽

Stabilizing Effect ◽

Ferromagnetic Fluid ◽

Mfd Viscosity

The effect of the magnetic field dependent (MFD) viscosity on the thermal convection in a ferromagnetic fluid in the presence of a uniform vertical magnetic field is considered for a fluid layer in a porous medium, heated from below. For a ferromagnetic fluid layer between two free boundaries an exact solution is obtained, using a linear stability analysis. For the case of stationary convection, the medium permeability has a destabilizing effect, whereas the MFD viscosity has a stabilizing effect. In the absence of MFD viscosity, the destabilizing effect of magnetization is depicted, but in its presence the magnetization may have a destabilizing or stabilizing effect. The critical wave number and critical magnetic thermal Rayleigh number for the onset of instability is determined numerically for sufficiently large values of the magnetic parameter M1. Graphs are plotted to depict the stability characteristics. The principle of exchange of stabilities is valid for a ferromagnetic fluid heated from below and saturating a porous medium.

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