Magneto-convection and its effect on partially active thermal zones in a porous square domain

• A detailed numerical study of combined heat and magnetic field effects in a saturated porous square cavity in presence of a sinusoidal discrete temperature gradient is presented.
• Inclusion of an external magnetic field and electrically conducting fluid in a porous media have potential applications such as the interaction of the geomagnetic field with the fluid in the geothermal region, where the Earth’s crust serves as a porous medium.
• Conducting fluids have additional properties for slowing down or accelerating the fluid motion through the external action of an electromagnetic field.
• Also, the external applied magnetic field determines the appearance of an induced magnetic field within the fluid.
• For fixed value of Grashof number (Gr) and Hartmann number (Ha), the flow is dominated by the convection effects where the buoyancy-induced activities are appreciable and fluids are well mixed and temperature is well distributed in the bulk of the cavity.
• Increase in Prandtl number (Pr) produces increment in heat transfer for Darcy number (Da) < 1.
• It is also observed that the average Nusselt number smoothly increases as Gr increases and average Nusselt numbers are reduced as the strengths of the applied magnetic field are increased.

A numerical study of hydromagnetic mixed convective flow inside a cubical enclosure filled with a porous mixture is presented. The flow enhancement is observed due to a sinusoidal time dependent discrete temperature gradient along the boundaries. A two dimensional computational visualization technique is used to study the detailed physical insights of the thermally activated porous flows subjected to the magnetic field effects. The time history analysis is made for flow and thermal stratification for a series of fluid parameters such as Grashof number, Hartmann number and Darcy number, porosity and oscillatory frequency. The total heat transfer effects are computed for both high convection (due to magnetic field) and diffusive forces (due to temperature). The local Nusselt number is increasing along the side walls for increase of Hartmann number. Bulk average temperature is found to be maximum due to the variation of Grashof number and oscillatory frequency.