Abstract:All-atom molecular models of ultrathin hydrous diesel oil film were built based on molecular dynamics simulation method,and the lubrication properties of the oil films with different water cuts under Couette flow were investigated.The microstructure,velocity distribution,global orientational order parameter and shear viscosity of the ultrathin lubrication film under the same shear velocity were researched.The results show that for the anhydrous oil film,its behavior is solidlike without fluidity,and it shows a shear thinning property during the shear process.However,for the hydrous ultrathin oil film,the film shows a layered structure and its flow velocity is confirmed to Couette flow.When the water cut is raised,the layered structure becomes more obvious and the chain hydrocarbons are more ordered.These lead to a lower shear viscosity of the ultrathin film,which shows a nonNewtonian fluid property,and the inherent shear thinning property of the oil film is weakened.This research shows that,because of the strong intermolecular force,the water molecules can rearrange the organic molecules in the oil film,thus greatly changs the lubrication properties of the ultrathin oil film.