The
transport mechanism of a simple liquid through nanoporous graphene
membranes (NPGMs) with pores of various diameters has been explored
by utilizing nonequilibrium molecular dynamics (NEMD) simulation.
The flow is initiated using a pressure-driven flow mechanism that
moves the specular reflection wall at a constant velocity. Both the
local density peak near the membrane and the pressure drop are dependent
on the pore diameter. For accurate calculation of the velocity profile
inside the nanopore, we implemented three boundary approaches and
local nanoscale variants to see the effect of these factors on the
nature of the nanoscale flow. We found an optimized definition of
the pore boundary, which minimizes the deviation between MD results
and slip-viscosity-modified Sampson’s prediction for nanopores
of various diameters. Additionally, we observed that with decreasing
pore size, the pore center velocity increases, as does the slip velocity,
which we attributed to van der Waals interaction between the liquid
and wall atoms inside the nanopore. However, the effects of slip velocity,
interfacial viscosity, and pore boundary decay exponentially with
increasing pore diameter because of the dominance of van der Waals
repulsive forces at the molecular level.