Molecular dynamics study on drag reduction mechanism of nonwetting surfaces

Abstract In order to study the mechanism responsible for the flow drag reduction on nonwetting surfaces, molecular dynamics models of fluid flow past a smooth surface with different wettability were established in this paper. The effects of surface wettability on flow characteristics in main flow region and boundary region are simulated and analyzed. Results show that compared with the model containing the wetting surfaces, the fluid density fluctuation amplitude of the model containing nonwetting surface decreases greatly and the velocity slip length increases greatly. Skin friction coefficient is calculated to evaluate the drag reduction of surfaces, which indicates that skin friction coefficient of nonwetting decreases significantly compared with wetting surface. The boundary region fluid simulation shows that there is a low-density layer near the nonwetting surfaces. Compared with the “crystallized layer” in the wetting cases, the distribution of low-density layer atoms is sparse and disorganized. Based on the simulation results, the physical mechanism of drag reduction of nonwetting surfaces is proposed: Lower solid-liquid interaction leads to the reduction of energy dissipation on nonwetting surfaces, the energy dissipation consists of dissipation due to solid-liquid contact and energy dissipation within the boundary region.