Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.
We compare both new and commonly-used boundary conditions for generating pressure-driven ﬂows through carbon nanotubes (CNTs) in molecular dynamics (MD) simulation. Three systems are considered: a ﬁnite CNT membrane with streamwise periodicity and gravity forcing; a non-periodic ﬁnite CNT membrane with reservoir pressure control; and an inﬁnite CNT with periodicity and gravity forcing. The ﬁrst system is simple to implement in common MD codes, while the second system is more complex to implement, and the selection of control parameters is less straightforward. The required level of user-input for such a system was found to be largely dependent on selection of state controllers used in the reservoirs. A large pressure difference is required across the realistic membrane system reservoirs to compensate for large pressure losses at the entrance and exit of the nanotube. Despite a dramatic increase in computational efﬁciency, an inﬁnite length CNT does not account for these signiﬁcant inlet and outlet effects, suggesting that a much lower pressure gradient is required to achieve a speciﬁed mass ﬂow rate. Use of an inﬁnite channel also restricts naturalﬂow developmentthroughthe CNT due to explicitcontrol of the ﬂuid. Observation of radial density proﬁles suggest that this results in over-constraint of the water molecules in the channel.