Numerical study of Newtonian fluid flow characteristics in triangle enclosure considering various obstacle geometries

Abstract

This article investigates the effect of cylindrical obstacles with different dimensions inside the triangular cavity on natural convection heat transfer. This study considers three cavities, each of which has one, two, and three-cylinder barriers embedded inside it. The use of one or two cylindrical barriers has been investigated in many research, but in this research, in addition to the number of cylindrical barriers, their dimensions and sizes have been changed, and an alternating temperature function has been used at the base of the cavity. The considered nanofluid is Al2O3H2O, which contains aluminum oxide nanoparticles with a concentration of 5 %. In all three cavities, the velocity of the nanofluid in the walls is zero. The temperature in the lateral sides of the cavity has low-temperature faces. Instead of being constant or adiabatic, the temperature at its base is an alternating function (sinusoidal function with a frequency of 1.0 Hz.). In contrast, it is considered that the surfaces of the obstacles of the cylinders have zero velocity and are adiabatic. In this study, the governing equations of nanofluid flow behavior have been solved using the Galerkin finite element method and analyzed in the Rayleigh number range of 103 to 105. Because triangular cavities with different ratios are used to optimize multiple objectives and increase thermal performance in microchannels, the results show that the multiplicity of cylindrical obstacles in the triangular cavity causes the expansion of the nanofluid velocity range in the whole area, which itself causes the increase of the heat transfer surface, and with the increase of the Rayleigh number and the buoyancy force, the magnitude of the velocity inside the triangular cavity increases. In the triangular cavity containing three cylindrical barriers, the nanofluid's velocity range is low, but according to the velocity contours, its extent is greater than the other two cavities. Also, the average Nusselt number in this cavity is higher than other cavities.