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International Journal of Technology
Year : 2016, Volume : 6, Issue : 2
First page : ( 233) Last page : ( 238)
Print ISSN : 2231-3907. Online ISSN : 2231-3915.
Article DOI : 10.5958/2231-3915.2016.00036.5

MHD stability of a nanofluid layer using Darcy model: Introduction of oscillatory motions for bottom heavy configuration

Ahuja Jyoti1, Gupta Urvashi2,*, Sharma Veena3

1Energy Research Centre, Panjab University, Chandigarh-160014, India

2Dr. S.S. Bhatnagar University Institute of Chemical Engineering and Technology, Panjab University, Chandigarh-160014, India

3Department of Mathematics and Statistics, Himachal Pradesh University, Summer Hill, Shimla-171005

*Corresponding Author Email: dr_urvashi_gupta@yahoo.com

Online published on 2 February, 2017.

Abstract

The impact of vertical magnetic field on the thermal instability of a horizontal porous nanofluid layer using Darcy model is considered for free-free boundaries. Brownian motion and thermophoretic forces are introduced due to the presence of nanoparticles and Lorentz's force term is added in the momentum equation along with the Maxwell's equations due to magnetic field. Normal mode technique and single term Galerkin approximation is employed to investigate the instability and derive the eigen value problem. It is found that the mode of instability is through oscillatory motions for bottom heavy suspension of nanoparticles. The reason for the existence of oscillatory motions is due to the occurrence of two opposite buoyancy forces i.e. density variation due to heating and density gradient of nanoparticles at the bottom of the layer. The thermal Rayleigh number increases with the increase of Chandrasekhar number and decreases with the increase of porosity. The effect of Lewis number, modified diffusivity ratio, concentration Rayleigh number and heat capacity ratio on the onset of thermal convection has been investigated analytically and presented graphically.

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