Lattice Boltzmann study on magnetohydrodynamic double-diffusive convection in Fe3O4–H2O nanofluid-filled porous media

Magnetohydrodynamic double-diffusive convection (MHD-DDC) in porous media has substantial significance in broad applications. However, due to the complexity of the DDC problems involving nanofluid, porous media, and external magnetic field at the same time, the MHD-DDC in nanofluid-filled porous media has rarely been studied. Besides, previous research on MHD convection problems usually focuses on magnetic fields or nanofluid effects. Effects of the thermal-to-mass properties, including the buoyancy radio (Br) and Lewis number (Le), on MHD-DDC problems have rarely been studied, seriously limiting the understanding and regulation of heat and mass transfer. Herein, we numerically study heat and mass transfer in the MHD-DDC within a square cavity containing a nanofluid of Fe3O4-H2O and a porous medium using a lattice Boltzmann method. A series of case studies are carried out to investigate the effects of Br, Le, and the medium porosity (ε) on the velocity, temperature, and nanoparticle concentration. Results indicate that Br determines the rotation pattern of the streamline, while Le and ε can be utilized to regulate the intensity of heat and mass exchange. The results of this paper present a quantitative insight into regulating heat and mass transfer patterns in MHD-DDC problems.