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Awasthi M.K.,Graphic Era University | Yadav D.,Indian Institute of Technology Roorkee | Agrawal G.S.,Manglayatan University
Journal of Applied Fluid Mechanics | Year: 2014

A linear analysis of Rayleigh-Taylor instability in the presence of tangential electric field has been carried out using viscous potential flow theory. In viscous potential flow theory, viscosity is not zero but viscous term in the Navier-Stokes equation is zero as vorticity is zero. Viscosity enters through normal stress balance and tangential stresses are not considered in viscous flow theory. A dispersion relation has been obtained and stability criterion has been given in the terms of critical value of electric field. It has been observed that tangential electric field influences stability of the system. A comparison between the results obtained by viscous potential analysis and inviscid potential flow has been made and found that viscosity reduces the growth of instability.


Yadav D.,Indian Institute of Technology Roorkee | Bhargava R.,Indian Institute of Technology Roorkee | Agrawal G.S.,Manglayatan University
International Journal of Thermal Sciences | Year: 2012

The effect of internal heat source on the onset of Darcy-Brinkman convection in a porous layer saturated by nanofluid is studied. The boundaries are considered to be free-free, rigid-rigid and lower-rigid and upper-free boundaries. The Brinkman-Darcy equation with fluid viscosity different from effective viscosity is used to characteristic the nanofluid motion. The model used for nanofluid includes the effects of Brownian motion and thermophoresis. The linear stability theory is employed and the resulting eigenvalue problem is solved numerically using the Galerkin technique with the Rayleigh number as the eigenvalue. The influence of internal heat source strength, nanoparticle Rayleigh number, modified particle-density increment, modified diffusivity ratio, Lewis number, Darcy number and the porosity on the stability of the system is investigated graphically. It is found that the internal heat source, nanoparticle Rayleigh number, modified diffusivity ratio and Lewis number have a destabilizing effect while Darcy number and the porosity show stabilizing effects on the system. © 2012 Elsevier Masson SAS. All rights reserved.


Awasthi M.K.,University of Petroleum and Energy Studies | Asthana R.,Munjal University | Agrawal G.S.,Manglayatan University
International Journal of Heat and Mass Transfer | Year: 2014

We study the linear Kelvin-Helmholtz instability of the interface between two viscous and incompressible fluids, when the phases are enclosed between two horizontal cylindrical surfaces coaxial with the interface in presence of mass and heat transfer across the interface. Here we use an irrotational theory known as viscous correction for the viscous potential flow theory; in which the discontinuities in the irrotational tangential velocity and shear stress are eliminated in the global energy balance by taking viscous contributions to the irrotational pressure. Both asymmetric and axisymmetric disturbances have been studied and stability criterion is given in terms of a critical value of relative velocity. It has been shown that the irrotational viscous flow with viscous correction gives rise to exactly the same dispersion relation as obtained by the dissipation method in which the viscous effect is accounted for by evaluating viscous dissipation using the irrotational flow. It has been observed that heat and mass transfer has destabilizing effect while irrotational shearing stresses stabilize the system. © 2014 Elsevier Ltd. All rights reserved.


Tiwari D.K.,P.A. College | Awasthi M.K.,University of Petroleum and Energy Studies | Agrawal G.S.,Manglayatan University
Ain Shams Engineering Journal | Year: 2015

A linear analysis of capillary instability of a cylindrical interface in the presence of axial magnetic field has been carried out when there is heat and mass transfer across the interface. Both fluids are taken as incompressible, viscous and magnetic with different kinematic viscosities and different magnetic permeabilities. Viscous potential flow theory is used for the investigation and a dispersion relation that accounts for the growth of axisymmetric waves is derived. Stability criterion is given by critical value of applied magnetic field as well as critical wave number and stability is discussed theoretically as well as numerically. Various graphs are drawn showing the effect of various physical parameters such as magnetic field strength, heat transfer capillary number, and permeability ratio, on the stability of the system. It has been observed that the axial magnetic field and heat and mass transfer both have stabilizing effect on the stability of the system. © 2015 Faculty of Engineering, Ain Shams University.


Yadav D.,Indian Institute of Technology Roorkee | Bhargava R.,Indian Institute of Technology Roorkee | Agrawal G.S.,Manglayatan University
International Journal of Heat and Mass Transfer | Year: 2013

Thermal instability of a nanofluid layer heated from below in the presence of rotation is investigated. The lower boundary of the nanofluid layer is considered to be rigid, while the upper boundary is assumed to be either rigid or free. The effects of Brownian motion and thermophoresis have been included in the model of nanofluid. The 6-term Galerkin method is used to obtain the eigenvalue equation, which is then solved numerically. The effects of rotation and other physical parameters on the onset of convection are analyzed and compared for two types velocity boundary conditions considered. Besides, some known results available in the literature are compared with those obtained from the present study and good agreement is found. © 2013 Elsevier Ltd. All rights reserved.

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