The main purpose of this study is to investigate the interactions among convection, magnetic field, Darcy effect, thermal radiation, Brownian diffusion, and thermophoresis when a nanofluid containing carbon nanotubes in a water-base fluid flows over a stretching horizontal plate through a porous medium. Governing equations are solved using a numerical method to analyze the impact of the Darcy effect on boundary layer development. This work concurrently accounts for Darcy effect, Brownian diffusion, thermophoresis, and nanoparticle volume fraction, offering a more complete description of carbon nanotubes (CNTs) – water nanofluid transport. The combined consideration of Brownian motion and thermophoresis further clarifies their roles in nanoparticle distribution and mass transfer phenomena. The results reveal that a higher Darcy number results in lower flow velocity and thus in the boundary layer having a higher temperature and concentration. Increasing nanoparticle volume fraction corresponds to an increase in the boundary layer of temperature and a decrease in nanoparticle concentration at the wall. A higher Brownian motion parameter reduces the surface heat transfer rate, while increasing the mass transfer rate near the wall and producing a larger concentration gradient. In addition, a higher Schmidt number results in the accumulation of more nanoparticles near the wall. The local Nusselt number and Sherwood number are lower when the Darcy number is higher. A higher Brownian motion parameter results in a lower local Nusselt number but higher Sherwood number. Sherwood number is lower when the thermophoretic parameter is higher; whereas it is higher when volume fraction is higher as well.
Huang et al. (Tue,) studied this question.