Influence of travelling surface waves on nanofluidic viscosity

The viscosity of nanofluidics in the presence of travelling surface wave has been investigated systematically by molecular dynamics (MD) simulations in this paper. The travelling surface wave propagating on the walls of nanochannel can affect the viscosity of nanofluidics sufficiently. The nanoscale fluid mechanism in nanochannels has been influenced by both amplitude and frequency of travelling surface wave, and the hydrodynamic characteristics have been affected significantly including the degree of boundary slip and mass flow rate (MFR). The MD results show that the viscosity of fluid at the nanoscale is an increasing function of the amplitude of travelling surface wave, but is reduced dramatically at the ultra-high frequency of travelling surface wave. The boundary slip illustrates the same trend as the variation of nanofluidic viscosity. For the mass flow rate, it depends on both the apparent viscosity of fluid and slip length at the boundary. Usually the viscosity and slip length are both independent on the pressure gradient, but are enlarged as the increment of pressure gradient in the presence of travelling surface wave. In contrast, when the travelling surface wave propagates on the walls of nanochannel, the mass flow rate is reduced as the pressure gradient increases. It has also been found that the viscosity, slip length and mass flow rate are influenced easily by the travelling surface wave on the hydrophobic surface (weak fluid-wall interaction). In addition, the stress distribution of fluid across the nanochannel has been shown, which indicates that the averaged total stress has been decreased under the condition of travelling surface wave. It can be concluded that our results provide the apparent viscosity of nanofluidics and hydrodynamic characteristics in the presence of travelling surface wave.