Molecular dynamics simulations of nanochannel flows at low Reynolds numbers

Abstract

In this paper we use molecular dynamics (MD) simulations to study nanochannel flows at low Reynolds numbers and present some new interesting results. We investigated a simple fluid flowing through channels of different shapes at the nano level. The Weeks-Chandler-Anderson potentials with different interaction strength factors are adopted for the interaction forces between fluid-fluid and fluid-wall molecules. In order to keep the temperature at the required level, a Gaussian thermostat is employed in our MD simulations. Comparing velocities and other flow parameters obtained from the MD simulations with those predicted by the classical Navier-Stokes equations at same Reynolds numbers, we find that both results agree with each other qualitatively in the central area of a nanochannel. However, large deviation usually exists in areas far from the core. For certain complex nanochannel flow geometry, the MD simulations reveal the generation and development of nano-size vortices due to the large momenta of molecules in the near-wall region while the traditional Navier-Stokes equations with the non-slip boundary condition at low Reynolds numbers cannot predict the similar phenomena. It is shown that although the Navier-Stokes equations are still partially valid, they fail to give whole details for nanochannel flows.