Continuum simulations of water flow in carbon nanotube membranes

We propose the use of the Navier–Stokes equations subject to partial-slip
boundary conditions to simulate water flows in Carbon NanoTube (CNT)
membranes. The finite volume discretizations of the Navier–Stokes equations
are combined with slip lengths extracted from molecular dynamics (MD)
simulations to predict the pressure losses at the CNT entrance as well as the
enhancement of the flow rate in the CNT. The flow quantities calculated from
the present hybrid approach are in excellent agreement with pure MD results
while they are obtained at a fraction of the computational cost. The method
enables simulations of system sizes and times well beyond the present capabilities
of MD simulations. Our simulations provide an asymptotic flow rate
enhancement and indicate that the pressure losses at the CNT ends can be
reduced by reducing their curvature. More importantly, our results suggest that
flows at nanoscale channels can be described by continuum solvers with proper
boundary conditions that reflect the molecular interactions of the liquid with the
walls of the nanochannel.