Vol.19, No.2, 2019, pp.86–93
UDC 537.311.35:519.87

In this paper, the effect of vertical AC electric field on the onset of electrohydrodynamic thermal instability in a horizontal layer of an elastico-viscous nanofluid saturated by a porous medium stimulated by the dielectrophoretic force due to the variation of dielectric constant with temperature is investigated. Walters’ (model B') elastico-viscous fluid model is used to describe rheological behaviour of nanofluid and for porous medium, the Darcy model is employed. The model used for nanofluid incorporates the effects of thermophoresis and Brownian diffusion. It is assumed that nanoparticle flux is zero on the boundaries. Linear stability analysis based on perturbation theory and normal mode analysis method is applied. The resulting eigenvalue problem is solved for isothermal free-free boundaries analytically and numerically by using the Galerkin method. For the case of stationary convection, it is observed that Walters’ (model B') elastico-viscous nanofluid behaves like an ordinary nanofluid. The oscillatory convection does not exist under the realistic boundary conditions.

Keywords: nanofluid, AC electric field , Rayleigh number , Walters’ (model B'), electrohydrodynamic