Double Diffusive Natural Convection with Variable Properties of Nanofluid Using Lattice Boltzmann Method

Natural double diffusive convection in a square cavity employing variable thermal conductivity and viscosity of Al2O3 water based nanofluid was investigated numerically by means of the lattice Boltzmann method with the BGK operator with three distribution functions. The enclosure is subjected to constant temperatures and concentrations on its side walls while the horizontal ones are kept impermeable and adiabatic. This study presents and discusses the findings on the effects of nanoparticles volume fraction (φ = 0 and 0.05), buoyancy ratio (N = 1 and 2), and Lewis number (10−3 ≤ Le ≤ 10) on temperature, concentration, and stream function distributions, as well as the maximum stream function, and Nusselt and Sherwood numbers. The outcomes exhibit that the heat transfer rate and the mass transfer rate, respectively, increases and declines with the nanoparticles volume fraction. The opposite trend of this latter is observed with the Lewis number, while the heat and mass transfer rates increment with the buoyancy ratio.