To enhance the controllability of transport phenomena where magnetic fields are coupled with other multiphysics, a concept of multi-banding distribution of the magnetic field is presented in this work. For this study, a typical differentially heated convective system (of square shape) is considered with porous media saturated Cu–Al2O3/water hybrid nanofluid. The isothermal heating and cooling applied on the sidewalls of the system induce a buoyant flow, which is resisted by porous media and is dampened intermittently by the banded form of application of magnetic fields. The multi-banding distribution of magnetic fields is illustrated using four-band, two-band, and one-band configurations (all having the same effective length of the magnetic field). The results are generated by an in-house code adopting the finite volume method and the Brinkman-Forchheimer-Darcy model. For a set of selective parameters of the Hartmann number, Darcy number, hybrid nanofluid concentration, and Darcy-Rayleigh number, the study reveals that the multi-banding of the magnetic field through different numbers of bands has significant effects on transport phenomena and heat transfer. Heat transfer with the two-banded magnetic field is found more. Overall, the multi-banding technique is energy efficient compared to the whole domain magnetic field. This technique could be a prospective tool to control convective transports effectively and could open an area of potential researches in the area of multi-physical applications.

The paper presents a pertinent modification to the wall-moving thermal systems (classically represented by lid-driven cavity) by introducing a partial motion of the boundary walls. The effect of partial wall motion is investigated under magnetohydrodynamic (MHD) mixed convection in the cavity filled with porous medium. The corner heating arrangement is chosen for this investigation. The heater is placed at the right-bottom corner of the cavity, whereas the halves of the adjacent sides (which are moving) of the top-left corner are utilized for cooling. The present MHD thermofluid flow in porous cavity under partially driven condition is solved numerically using Brinkman-Forchheimer-Darcy model and analyzed using heatlines, streamlines, isotherms and average Nusselt number. The detailed insights of partially driven cavity are captured for different values of Richardson number (Ri = 0.1-100), Reynolds number (Re = 10-500), Hartmann number (Ha = 0-100), Darcy number (Da = 10 −7 to 10 −3) and porosity (ε = 0.1-1.0). The result reveals that the partial wall motion and its direction have a significant impact on the thermofluid flow structures and heat transfer rate.

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Application of partial magnetic field can be useful for controlling thermal convective processes occurring in magneto-thermal devices/systems. The present work aims to demonstrate the implementation of a partial magnetic field using a typical thermal system. This study explores both local transport phenomena and global heat transfer rates. The partial magnetic fields involving multiphysical conditions find many applications in electronic industries, medical, and health science. The paper presents a conceptual finding from the use of a partial magnetic field on a classical porous cavity comprising Cu−Al2O3/water hybrid nanoliquid heated differentially. The partial magnetic field is functional either horizontally or vertically. The finite volume technique is employed to the coupled transport equations subjected to particular boundary situations using a developed computing code. The simulations are accomplished to a great extent with different variables such as the Darcy-Rayleigh number (Ram), Darcy number (Da), Hartmann number (Ha), and hybrid nanoparticles concentrations ( φ). The effects of magnetic field widths and their positional variations in horizontal and vertical directions are also analyzed. The study found that the convective transport process could effectively be modulated by setting the appropriate position, widths, directions, and intensity of the imposed magnetic fields. The partial magnetic field causes a decrease in heat transfer ∼17.15% or 9.71% less compared to the whole length horizontal or vertical magnetic field. The application of partial magnetic fields significantly alters local thermo-fluid flow phenomena and advancement in heat transfer characteristics in comparison to the magnetic fields acting over the entire domain. Furthermore, the heatline visualization tools reveal the insight of the heat flow dynamics, which dictates the selection of appropriate parametric values and magnetic field configurations.