Molecular dynamics simulations on the shear viscosity of Al2O3 nanofluids

•Viscosity of Al2O3 nanofluids was computed with EMD simulations.•Effect of particle size on viscosity was revealed.•Particle–water interaction is responsible for the specific viscosity variations.•An correlation for viscosity, particle size and temperature was proposed.

The shear viscosity of nanofluids is sensitive to the size and concentration of the added nano particles. Using equilibrium molecular dynamics (MD) simulations we studied the particle size, particle concentration and temperature dependence of the shear viscosity of Al2O3 nanofluids. Larger viscosity was predicted for the nanofluids with smaller particle size, higher particle concentration, and lower temperature, which reproduced the experimental trends. The increased viscosity is attributed to the particle–water interaction. Calculations at the density functional theory level conform that the interaction energy between Al2O3 particle and water molecule is stronger than that between water molecules. Based on the simulated results an expression was proposed to describe the mixed effect of particle size, particle concentration and temperature on the viscosity of Al2O3 nanofluids.