Abstract
In the presence of a constant heat source and sink in each layer, the Non-Darcian Triple Diffusive Convection (NDTDC) problem in a combined layer that is horizontally infinite is examined. This composite layer is rigid and adiabatic in the lower enclosure of the porous layer and free as well as isothermal in the higher enclosure of the fluid layer. The thermal Marangoni number (tMn) for two cases of thermal boundary combinations (TBCs), case (i) adiabatic–adiabatic and case (ii) adiabatic–isothermal, is determined by solving the system of ordinary differential equations obtained following normal mode analysis in closed form. The effect of important parameters on NDTDC is studied in detail and illustrated visually versus the thermal ratio. It is noticed that case (i) is observed to be stable because the Eigenvalue obtained is higher than that for case (ii) and NDTDC can be postponed by making the upper boundary of the combined layer adiabatic and the same is augmented by converting the upper boundary of the combined layer to isothermal, as isothermal boundaries support early convections.