Penetrative convection in an internally heated layer of magnetic nanofluid saturating a porous medium

A. Mahajan - M. K. Sharma

Department of Applied Sciences, National Institute of Technology Delhi, Narela, Delhi--110040, India

Abstract
In this numerical study, we applied the linear stability theory to investigate the onset of penetrative convection due to purely internal heating in a thin magnetic nanofluid layer saturating a porous medium. A model that has the combined effect of Brownian diffusion, thermophoresis, magnetophoresis and Darcy's law is considered. The Chebyshev pseudospectral method and QZ algorithm are applied to solve the resulting eigenvalue problem. The numerical results are derived for various combinations of boundary conditions on impermeable, conducting, free and with constant heat flux surfaces for water- and ester-based magnetic nanofluids. The results show that the onset of penetrative convection is advanced with an increase in Lewis number Le, concentration Rayleigh number Rn, modified diffusivity ratio N_A, but opposite is the case with an increase in value of the permeability K, Langevin parameter α_L, porosity ε, width of the magnetic nanofluid layer d, modified diffusivity ratio N′_A. Moreover, it is also observed that the modified particle density increment N_B does not significantly affect the stability of the system. Tables 1, Figs 8, Refs 42.