Some thermal stability problems of elastico-viscous, ferromagnetic and nanofluids

Abstract

The non-Newtonian fluids are of vital importance due to their diverse applications in modern technology, industries and bio-mechanics. In the present thesis, the linearized stability theory and normal mode analysis have been used to study the effect of various important parameters on thermal and thermosolutal stability of hydrodynamic and hydromagnetic systems of various non-Newtonian fluids. The thermal stability of a layer of Walters’ B fluid heated from below permeated with suspended particles is considered to include the effect of rotation in the presence of magnetic field, porous medium and compressibility. It is found that, for stationary convection, suspended particles and compressibility have destabilizing effect whereas rotation has stabilizing effect. The magnetic field and porous medium have stabilizing/destabilizing effect under certain conditions. The principle of exchange of stabilities is satisfied in the absence of magnetic field, rotation and viscoelasticity. The presence of these parameters introduces oscillatory modes into the system. Further, the effect of suspended particles, magnetic field and rotation on thermal stability of a layer of ferromagnetic fluid heated from below have been analyzed and it is found that magnetic field, magnetization and rotation have stabilizing effect whereas suspended particles have destabilizing effect on the system. For a couple stress fluids, the effect of Hall currents and suspended particles has been considered. The couple stresses and Hall currents have stabilizing effect whereas suspended particles have destabilizing effect on the system. The magnetic field has stabilizing/destabilizing effect under certain conditions. We also studied the effect of various parameters such as Hall currents, compressibility, magnetic field, suspended particles and porous medium on thermosolutal stability of Rivlin Ericksen fluid. The compressibility, suspended particles, Hall currents and permeability have destabilizing effect whereas solute gradient and magnetic field have stabilizing effect on the system. Further, the effect of rotation on double diffusive convection in a horizontal layer of a nanofluid in porous medium has been analyzed. The rotation, concentration Rayleigh number, modified diffusivity ratio, Lewis number, Darcy number and porosity have stabilizing effect whereas solutal Rayleigh number has destabilizing effect on the system.