The onset of Brinkman ferroconvection using a thermal non-equilibrium model

The onset of ferroconvection in a horizontal layer of ferrofluid saturated Brinkman porous medium heated uniformly from below in the presence of a uniform vertical magnetic field is investigated when the solid and fluid phases of the porous medium are in local thermal non-equilibrium (LTNE) using linear stability theory. The modified Brinkman-Forchheimer-extended Darcy equation is employed to describe the flow in the porous medium and a two-field model for energy equation each representing the solid and fluid phases separately is used. It is established that the principle of exchange of stability is valid. The authenticity of LTNE model over LTE model and also the ferromagnetic effects on the stability of the system are discussed in detail. The system is found to be more stable when the magnetic forces alone are present. Asymptotic analysis for both small and large values of scaled inter-phase heat transfer coefficient 1 1 is presented and the results are found to be in good agreement with those obtained from the exact formula. The established results in the literature have been reproduced as particular cases from the present study. (C) 2011 Elsevier Ltd. All rights reserved.