Nanofluids containing silver (Ag) nanoparticles have been used in three dimensional ink-jet printing (3DP) in recent years. Rheological properties of the nanofluids, for example, viscosity, play significant roles during the application. In this paper, viscosity of Ag-water nanofluid has been predicted using the equilibrium molecular dynamics method. The influencing factors of the viscosity, including temperature, nanoparticle size, nanoparticle concentration and nanoparticle aggregation, have been investigated. By screening the existing water models, TIP4P/2005 model is found the most suitable for viscosity calculation under the temperature range. The weight fraction of the nanoparticles, which proves more appropriate, is used during the study of the concentration effect instead of volume fraction. The results show that the viscosity of the nanofluid goes up by decreasing temperature or increasing nanoparticle concentration. Furthermore, as the nanoparticles get smaller, or aggregate, the viscosity increases slightly.
