Fluid
transport through carbon nanotubes have shown remarkable flow properties,
with measured flow rates orders of magnitude larger than the expected
from standard continuum flow theories. Related studies have indicated
that the observed high flow rates were driven by the extreme smoothness
of the cylindrical nanotubes used in the experiments. In this work,
we consider several types of nanochannels far from the cylindrical
geometries. Using a combination of simulation techniques, such as
molecular dynamics and the lattice Boltzmann method, we study the
flow behavior under tortuous and rough channels, which are of fundamental
relevance either for optimizing carbon nanotubes for nanofiltering
applications, as well as for characterizing nanoporous organic media.
We show that, although both features have a detrimental effect on
flow rates, when nanochannels have both roughness and tortuosity simultaneously,
shorter length-scales associated with surface roughness have a deeper
impact, dominating the overall properties of the flow.