Abstract
In the present research the effect of magnetic field on the mixed convection was carried numerically in lid driven composite two dimensional square cavity ,this cavity composed of two layers : a Cu-water nanofluid layer superposed a porous media ,the porous media saturated with the same nanofuid The left and right walls are thermally insulated ,However the bottom wall which is in contact with porous media is isothermally hot while the top wall which is in contact with nanofluid layer is isothermally cold and being lid driven in constant velocity to right. The governing equations in this study were normalized and solved numerically by finite difference method. The convection term of the momentum and energy equations were treated by upwind scheme, while the diffusion and source terms were treated by central difference. Gauss-siedel iteration method were used for solution vorticity and energy equations and Successive Over Relaxation method were used for solution of stream function equation.. In this study the following parameters were considered: Hartman number (Ha) from (0 to 60), nanoparticles volume fraction (0.01, 0.03, 0.05), Richardson number (Ri) (0.1, 1, 5), Darcy number (Da) (10-3, 10-4, 10-5) and porous layer thickness (Wp) (0.3, 0.5, 0.7) at constant Reynolds number (Re=100) and Prandtl number (Pr=6.24). The results show that increasing Hartman number causes a reduction in mixed convection heat transfer and this effect reduced by increased the porous layer thickness. In increased of Hartman number from 0 to 60 with Wp (0.3, 0.5, 0.7) a reduction in convection heat transfer. Moreover an increase in Richardson number ( Ri ) enhanced the convection heat transfer for all Hartman number , Also the increase of nanoparticles volume fraction improve the heat transfer and this effect reduced as Hartman number increased. It is noticed that increasing Hartman number to 30 gives highest value of Nusselt number at lower thickness of porous layer.
