Mixed convection of nanofluid by two-phase model in an inclined cavity with variable aspect ratio

Abstract

In this numerical study, the laminar mixed cross-convection of incompressible nanofluid in a two-dimensional inclined cavity with various aspect ratios is investigated. A nonhomogeneous Buongiorno's model is taken into account. Transport mechanisms incorporating the effects of Brownian motion, thermophoresis diffusion, Soret-Dufour effect are analyzed. The energy governing equation includes both regular diffusion and cross-diffusion terms. The numerical analysis is performed by the collocation spectral method (CSM) based on the fast cosine transformation (FCT). The improved projection scheme (IPS) is specially modified with help of FCT to decouple the pressure and the velocities. The combined effects of inclined cavity angle γ, aspect ratio A, thermophoresis parameters Nt, Brownian motion parameter Nb, Dufour diffusicity Df, Soret diffusicity Sr, along with Re, Gr, Pr, Le, Ln and buoyancy ratios Br, Nb, Nr, etc., on the developments of streamlines, isotherms, solutal isoconcentrations and nanoparticle isoconcentrations as well as on the average Nusselt and Sherwood numbers, are analyzed and discussed in detail. The results indicate that the above parameters, especially γ and A, have substantial effects on the flow, heat and mass transfer. The distributions of temperature, solutal concentration and nanoparticle concentration are changed completely. The cross-diffusive effects including Dufour-Soret effect can't be ignored.