Nonlinear mixed convective nanofluid flow about a rough sphere with the diffusion of liquid hydrogen

In this paper, a study of steady nonlinear mixed convective nanoliquid flow about a rough sphere with the diffusion of liquid hydrogen is considered. The governing equations are first modelled from the current physical problem, and then, suitable non-similar transformations are applied to non-dimensionalize the model equations. The resultant nonlinear dimensionless equations are linearized by using the Quasilinearization technique. The resulting linear system of differential equations are approximated by finite differences to obtain numerical solutions. The impacts of different physical parameters involved in the problem, such as the distribution of velocity, temperature, nanoparticle volume fraction and species concentration are studied. The analysis of wall gradients is carried out, which discusses the skin friction, heat and mass transfer rates defined at the surface of the sphere. The graphs of numerical results are plotted, which reveal that the flow velocity is increased, while the fluid temperature is reduced, for increasing values of the roughness parameter. The presence of mixed convection parameter delays the occurrence of separation in the boundary layer in both the cases of an ordinary fluid and a nanofluid. For increasing values of the Schmidt number, the species concentration decreases, while the rate of mass transfer increases. Moreover, the thermophoresis parameter of the nanofluid increases the fluid's temperature, while it decreases the heat transfer rate. The fluid's temperature reduces for larger values of nonlinear convection parameter. Also, the flow velocity increases for the diffusion of liquid hydrogen. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.