Double-Diffusive Effects on the Onset of Rayleigh-Benard Convection of Water-Based Nanofluids

Abstract

A numerical study on the Rayleigh–Benard convection in a shallow cavity filled with different metal-oxide water-based nanofluids is presented through a two-phase model, which accounts for the effects of the Brownian diffusion and thermophoresis, at variable properties with temperature. Numerical simulations are executed for different values of the average volume fraction of the nanoparticles, different aspect ratios of the enclosure, as well as for temperature difference between the bottom and the top walls. It is found that the dispersion of the nanoparticle into the base fluid increases the stability of the nanofluid layer, determining the conditions for the onset of convection also with reference to the confinement of the nanofluid.

Keywords

• nanofluids
• Rayleigh–Benard convection
• onset of convection
• critical Rayleigh number