MHD Mixed Convection Stagnation-Point Flow Over a Stretching Vertical Plate in Porous Medium Filled with a Nanofluid in the Presence of Thermal Radiation

Abstract

This article deals with the study of the two-dimensional mixed convection magnetohydrodynamic boundary layer of stagnation-point flow over a stretching vertical plate in porous medium filled with a nanofluid and in the presence of thermal radiation. The stretching velocity and the ambient fluid velocity are assumed to vary linearly with the distance from the stagnation point. By means of similarity transformation, the governing partial differential equations are reduced into ordinary differential equations. The similarity equations were solved for three types of nanoparticles, namely copper, alumina and titania with water as the base fluid, to investigate the effect of the nanoparticle volume fraction parameter φ, the constant magnetic/porous medium parameter Λ, the mixed convection parameter λ, the Prandtl number Pr and the radiation parameter Rd on the flow and heat transfer characteristics. The skin-friction coefficient and Nusselt number as well as the velocity and temperature profiles for some values of the governing parameters are presented graphically and discussed. Effects of the solid volume fraction on both of assisting and opposing flows on the flow and heat transfer characteristics are thoroughly examined. It is observed that, for all three nonoparticles, the magnitude of the skin friction coefficient and local Nusselt number increases with the nanoparticle volume fraction φ for both cases of buoyant assisting and opposing flows. In addition, the velocity of fluid increases in case of assisting flow by decreasing Λ and Pr but the opposite trend is noted in the opposing flows. A similar effect on the velocity is observed when λ and Rd increases and the temperature increase by increasing Λ and Rd in both cases of buoyant assisting and opposing flows. The highest values of the skin friction coefficient and the local Nusselt number was obtained for the Cu nanoparticles compared to Al2O3 and TiO2.