부산대학교 도서관

Temperature-dependent viscosity variation effect on the onset of ferroconvection in a ferrofluid horizontal layer in a Brinkman porous medium is studied in the presence of a vertical magnetic field. The variation of viscosity is expressed as an exponential function of temperature. The bounding surfaces of the ferrofluid layer are considered to be either stress free or rigid-ferromagnetic and insulated to temperature perturbations. The resulting eigenvalue problem is solved numerically using the Galerkin technique and also analytically by a regular perturbation technique for different types of velocity boundary conditions, namely, free-free, rigid-rigid as well as lower rigid and upper free boundaries. The effect of the viscosity parameter on the onset of ferroconvection in a porous medium is dual in nature depending on the choices of physical parameters. It is found that increasing the magnetic number M1 and the Darcy number Da is to hasten the onset of ferroconvection. Moreover, the nonlinearity of fluid magnetization M3 is observed to have no effect on the onset of ferroconvection in the case of fixed heat flux boundary conditions. [ABSTRACT FROM AUTHOR]