Influence of porous circular cylinder on MHD double-diffusive natural convection and entropy generation

Abstract

In this study, the significance of porous circular cylinder and magnetic field on the double-diffusive natural convection and entropy generation in an enclosure is analysed using lattice Boltzmann method. Prime objective of this study is to assess the impression of permeability, buoyancy force variation, magnetic field and its direction on the thermo-solutal convection around a porous zone. The parametric study concentrates on the effects of Buoyancy ratio (BR=−5 to 5), Darcy number (Da=10−5, 10−4, & 10−3), Hartmann number (Ha=0, 25, & 50), and magnetic field angle (γM=0∘, 45∘, & 90∘) on the flow, heat and concentration transfer, and the variation in irreversibilities in and around the porous circular cylinder with high temperature and concentration. The Darcy-Brinkman-Forchheimer model is coupled with LB flow evolution equation to acquire flow features in the porous cylinder. Results indicate that Da, BR, and γM increment improves the heat and concentration transfers. Permeability increment significantly enhances the flow-field intensity around the cylinder. Effect of Ha on the reduction in mean Nusselt number and Sherwood number can be significantly controlled by the direction of magnetic field. However, magnetic field influences trivially on the flow field in the porous cylinder. Besides, the amalgamation of Da and γM induces unsteady characteristics in the enclosure. Also, γM increment widens the range of BR for the production of unsteady traits. The entropy generation augments with Ha, when the magnetic field direction is aligned with the fluid flow. Further, the irreversibilities due to concentration transfer is observed to be higher than that of other associated irreversibilities in the enclosure. The increment in BR (positive values) tends to suppress the fluid-friction and magnetic irreversibilities.