Significance of a permeable semi-circular body and magnetic field on thermo-solutal natural convection and irreversibilities

Abstract

This study explores the intriguing phenomenon of thermo-solutal buoyancy-driven traits in the presence of a magnetic force within a square cold enclosure housing a soluted and heated permeable semi-circular cylinder. The amalgamation of flat and curved edges, alongside the permeable characteristics, serves as the driving motivation behind this investigation. The primary objective is to scrutinize the impact of magnetic force and its orientation, buoyant force, permeability on the thermo-solutal convection occurring within and around the permeable body. To achieve this, a thorough parametric investigation is carried out, focusing on the significance of Hartmann number (Ha), magnetic field angle (γM), buoyancy ratio (BR), and Darcy number (Da), concerning flow, heat, concentration transfer, and the variation in irreversibilities. The Darcy-Brinkmann-Forchheimer equation as a source term in lattice Boltzmann technique is utilized to accurately solve the intricate porous medium flow. The investigation reveals that escalating the buoyant force, and permeability, and magnetic field angle yields favourable heat and concentration traits. Additionally, aligning the magnetic force opposite to gravity diminishes the inhibitory effects on the thermal and solutal transfers exerted by the magnetic force. Notably, unsteady behaviour is predominantly observed when the BR assumes a negative value, with the amplitude and frequency of these phenomena amplified by the Da and γM. Also, a few anomalous spikes in the NuM and ShM are witnessed, attributed to the development of a robust uni-vortex in the top region of the cavity. Interestingly, the irreversibilities induced by the magnetic field diminish as the BR increases. Among these irreversibilities, entropy generation due to concentration emerges as the dominant contributor, with the exception of cases exhibiting atypical rises, where fluid entropy resulting from friction takes precedence.