Influence of MHD forces on Bejan’s heatlines and masslines in a doubly stratified fluid saturated Darcy porous enclosure in the presence of Soret and Dufour effects – A numerical study

•Mathematical model is developed for double diffusive natural convection process in a fluid saturated porous enclosure, under multiple interacting forces.•The medium is doubly stratified with Soret and Dufour effects under action of the magnetic forces.•A new instance of visualization of heat and mass transfer is depicted by introducing Heatline and Massline, which show trajectories of heat flux and mass flux, in addition to streamlines, isotherms and iso-concentrations in a square porous enclosure.•A detailed parametric study has been carried out by using the Finite Element Method (FEM) along with validation of the results.•Introducing the magnetic force, reduces the convective heat transfer and for higher magnetic field, disperse the isotherms and iso-concentration lines from the left bottom and right top portion of the cavity which leads to the horizontal variations in temperature and concentration substituting their vertical stratification. The present article is an analysis of heat and mass transfer phenomena for a two-dimensional magnetohydrodynamic (MHD) free convection process in a thermal and mass stratified fluid containing Darcy porous enclosure under the influence of Soret and Dufour effects. The non-dimensional form of coupled non-linear partial differential equations governing the problem is solved numerically by using finite element method. Following the energy analogy concept of Kimura and Bejan (1983) the equation governing the heat function (H) and mass function (M) are derived to facilitate the better visualization of energy and mass distribution. Obtained results are compared with those from literature and found to be in good agreement. In order to evince the characteristics and inherent structures of heat and mass transfer process in fluid flow, the obtained numerical results demonstrated graphically by cumulative heat/mass flux, streamlines, isotherms, iso-concentration plots including heatline and massline (trajectories of heat/mass flux) plots for various values of parameters involved in the problem like: Magnetic parameter (Mg), Thermal (ST) and Mass (SC) stratification, Buoyancy ratio (B), Rayleigh number (Ra), Lewis number (Le), Soret (Sr) and Dufour (Df) numbers.