Influence of permeable circular body and CuO−H2O nanofluid on buoyancy-driven flow and entropy generation

•CuO−H2O nanofluid natural convection from a porous circular body is examined using LBM.•Momentum of the nanofluid strongly influenced by volume fraction and permeability.•Nanofluid suppresses the adverse effect of heat transfer offered by rich permeable body.•Amalgamation of nanofluid and permeability produces more irreversibilities.•Location of maximum entropy strongly relies on the permeability value. A numerical analysis has been performed to demonstrate the impression of an isothermal circular permeable body on free-convection and thermo-dynamic irreversibilities in a square cavity by employing lattice Boltzmann technique. CuO-water nanofluid is considered as a working fluid, and the dynamic values of effective properties are evaluated by Koo-Kleinstreuer-Li (KKL) model. Primary aim of the present work is to evaluate the effects of Darcy number (Da), Rayleigh number (Ra), and nanofluid volume fraction (Φ) on flow and heat transfer characteristics in and around the permeable zone. Also, variation of entropy generation and mean Bejan number (BeM), thermal-mixing and its uniformity are analysed. The ranges of Da, and Ra considered in this analysis are, 10−6 ≤ Da ≤ 10−2, and 103 ≤ Ra ≤ 106, respectively, for the nanofluid volume fraction values of 0%-4%. It has been observed that the momentum of the fluid in the enclosure intensifies while increasing Da and nanofluid volume fraction. Also, the flow variation produced by different values of nanofluid volume fraction significantly modifies the thermal traits. Further, the location of maximum entropy generation depends on the permeability of the cylinder. It is found that the volume fraction of nanofluid governs the dominance of thermal and/or fluid-friction irreversibility. Permeability enrichment increases the thermal-mixing and reduces the temperature uniformity.