Search

This study numerically investigates the two-dimensional natural convection in a square enclosure with an isothermal diamond elliptic array at Rayleigh numbers of 104 ≤ Ra ≤ 107. Three cases are considered, i.e., case 1 where two pairs of circular heating bodies are used inside the cavity, one is placed on the vertical centerline (VC) of the cavity and the other on the horizontal centerline (HC), case 2 where one pair of horizontal elliptic heating bodies is placed on the VC of the cavity and the other on the HC and case 3 where the horizontal elliptic heating bodies are replaced by vertical elliptic heating bodies. Numerical simulation was carried out based on the mesoscopic approach (LBM). The effects of the horizontally and vertically heated arrays were investigated. We demonstrate that, only when the Rayleigh number increases to Ra = 107, the numerical solutions reach an unsteady state for all cases. The transition of the flow regime from the unsteady state to the steady state depends on the variation in the ratio of the elliptical cylinder. [ABSTRACT FROM AUTHOR]

Three-dimensional investigation has been carried out to simulate buoyancy induced heat transfer and fluid flow as well as entropy creation inside C-shaped enclosure charged with based water CNT–Al2O3 (15–85%) hybrid nanofluid. Left side is isothermally heated while the vertical portions of the right wall are isothermally cooled. Effects of various parameters on the flow behavior and the produced irreversibilities, namely the cavity aspect ratio (0.1 ≤ Ar ≤ 0.4), Rayleigh number (103 ≤ Ra ≤ 106) and volumetric fraction of hybrid nanofluid (0 ≤ φ ≤ 0.06) have been examined. It was revealed that the aspect ratio is the main controlling parameter of thermal energy transfer and generated entropy. In addition, for specific Ra, adding hybrid nanoparticles leads to the increase of the average Nusselt number while the highest produced entropy is observed with higher Rayleigh number. Moreover, the maximum Bejan number occurred for a shape factor Ar = 0.1 and Ra = 104 disregarding the hybrid nanoparticles volume fraction showing the dominance of thermal irreversibility over the viscous dissipation irreversibility in such conditions. [ABSTRACT FROM AUTHOR]

In this paper, Lattice Boltzmann method (LBM) is proposed to simulate Magnetohydrodynamic (MHD) free convection in a two-dimensional open cavity with mixed boundary conditions (BCs). The cavity is getting under a uniform transverse magnetic field. The proposed numerical scheme solved the flow field and the temperature field using D2Q9 lattice model. So, the main aim of this study is to highlight the effectiveness of this mesoscopic model to predict the effects of pertinent parameters such as the Hartmann number varying from 0 to 150 and the Prandtl number altering in a wide range of Pr=0.025 and 0.71. Rayleigh number is fixed at moderate value of 105. This in-house numerical code used in this paper is ascertained and a good agreement with literature is highlighted. The appropriate validation with previous numerical investigations demonstrated that this attitude is a suitable method and a powerful approach for engineering MHD problems. Findings and results show the alterations of Hartman number that influence the isotherms and the streamlines widely at different Rayleigh and Prandtl numbers simultaneously. Moreover, heat transfer declines with the increment of Hartmann number. The effect of the magnetic field on the average Nusselt number at Liquid Gallium (Pr=0.025) is also highlighted. [ABSTRACT FROM AUTHOR]