The effects of local thermal nonequilibrium and MFD viscosity on the onset of Brinkman ferroconvection

The simultaneous effect of local thermal nonequilibrium (LTNE) and magnetic field dependent (MFD) viscosity on thermal convective instability in a horizontal ferrofluid saturated Brinkman porous layer in the presence of a uniform vertical magnetic field is studied analytically. The results indicate that the onset of Brinkman ferroconvection is delayed with increasing MFD viscosity parameter but the critical wave number is found to be independent of this parameter. When compared to the simultaneous presence of buoyancy and magnetic forces, it is observed that the onset of Brinkman ferroconvection is delayed more when the magnetic forces alone are present. Asymptotic solutions for both small and large values of scaled inter-phase heat transfer coefficient Ht are compared with those computed numerically and good agreement is found between them. Besides, the influence of magnetic and LTNE parameters on the stability characteristics of the system is also discussed. The available results in the literature are recovered as particular cases from the present study.