NUMERICAL INVESTIGATION OF BOUNDARY SURFACE EFFECTS ON NATURAL CONVECTION IN A HORIZONTAL POROUS CAVITY BY USING NON-DARCIAN FLOW

Abstract

In this paper, Non–Darcian steady flow two-dimensional natural convective heattransfer in an rectangular and square porous cavities with two parallel walls kept atconstant different temperatures, while the other two parallel walls were well insulated,had been studied numerically. The governing equations had been solved using finitedifference method with Gauss-Seidel iteration. Results have been obtained for amodified Rayleigh number of the range of (100 – 1000), enclosure aspect ratio of (0.5 –3.0), and Darcy number( 6 4 ) 10 10− − − . The results showed (Multicellular Flow) when theaspect ratio less than one and disappeared this flow when the aspect ratio A ≥1. The rateof heat transfer was increase when the (aspect ratio and modified Rayleigh number)increased and Darcy number decreased, except when the boundary layer flow wasencountered, also for any constants modified Rayleigh number and Darcy number themaximum Nusselt number was obtained at one aspect ratio . As certain value Darcynumber, any increase in the aspect ratio will lead to appearance of boundary layer flowat low modified Rayleigh number. The increase in Darcy number enhances theboundary layer thickness. The effect of Darcy number became more significant at(Da=10-4), also the effect of the Darcy number decreases when increase the aspect ratio.The Nusselt number was found a strong function of modified Rayleigh numberandaspect ratio.