Free convection of Al2O3-water nanofluid inside a hexagonal-shaped enclosure with cold diamond-shaped obstacles and periodic magnetic field

Abstract

The hydrothermal characteristics of fluid flow within a hexagonal enclosure hold immense significance due to their wide-ranging applications in various fields. Despite their potential importance, there is currently a limited understanding of free convection flow within these geometries. This study aims to tackle this aspect by considering the effect of cold diamond-shaped obstacles and periodic magnetic field. The cavity top inclined walls are uniformly heated while bottom inclined walls are considered as heaters. The straight top and bottom walls of the cavity are adiabatic. The numerical solution is obtained via finite element method. The results indicate a substantial augmentation of streamlines, x- and y-direction velocities, entropy and average Bejan number with increase in the Rayleigh number. Inducing stronger magnetic field force reduces x- and y-direction velocities, average Bejan number and entropy generation. The average Nusselt number improves by 76.16% for Rayleigh number ranging from 105 to 106 at several lengths of hot surface. Among the cases analyzed in this research, moving the diamonds from the middle (Case A) to top (Case B) and bottom (Case C) enhances and reduces the Nusselt number by 6.3% and 7.5%, respectively.