Liquid flow in surface-nanostructured channels studied by molecular dynamics simulation

Abstract

Molecular dynamics simulations have been carried out to investigate the fluid wetting and flow in nanochannels whose surfaces are structured by an array of nanoscale triangular modules. We find that the surface nanostructures have a dual effect on the boundary slip and friction of the liquid nanoflow. On the one hand, the nanostructures can enhance the surface hydrophilicity for a hydrophilic liquid-solid interaction, and can increase the hydrophobicity for a hydrophobic interaction due to a nanoscale lotus effect. In particular, the nanostructured surface may show superhydrophobicity and lead to the large velocity slip of the liquid flow. On the other hand, simultaneously, the nanostructures distort the nanoscale streamlines of the liquid flow near the channel surfaces and block the nanoflow directly, which decreases the apparent slip length equivalently. The dual effect of the nanostructures on the surface wettability and the hydrodynamic disturbance results in a nonmonotonic dependence of the slip length on the nanostructure size. The simulations imply that the surface nanostructures can be applied to control the friction of liquid micro-and nanoflows.

Flows of Polymer Melts through Nanopores: Experiments and Modelling

“…Then we believe the shear rate plays a subordinate role in inducing the rheological behavior of polymer melts during the flowing through nanopores. As for the wall slip it is believed that the slip length vanishes for a completely wetting surface, but increases with the contact angle [33]. When the contact angle goes to 180°, the slip length diverges as [34,35] s L σ~(…”

Fullerene-water nanofluid confined in graphene nanochannel

“…Here the Poiseuille flows are induced by subjecting the water molecules to an external driving field in the flow direction, i.e., a driving acceleration of g x in x direction is applied on each water molecules of NFs. 34 Figure 8 illustrates the snapshots of the fullerene molecules within the NFs at different driving accelerations. It can be observed that the fullerene molecules are accumulated at the central region in the channel width direction for the relatively small driving acceleration of 6.5 × 10 11 m/s 2 while they can dispersed by the larger driving acceleration of 1.5 × 10 12 m/s 2 .…”

Investigation on entrance length for electroosmotic flow in circular and noncircular cross section nanochannel

“…But in a nanochannel, this physical phenomenon is different because the EDL becomes comparable to the channel height. Furthermore, it has been theoretically shown that the hydrodynamic slippage at wall surface in the nanometric range are sufficient to increase the EO velocity, in which suggested nanostructures can be applied to control the friction of liquid flow in micro-and nanochannel (5). Like in a pressure-driven flow, an electroosmotic flow also can be distinguished into two zones, the developing and fully developed zone.…”

“…While E is the induced electric field is given by, V E (5) where V is the electric potential. These equations solve the velocity field and pressure for an electroosmotic flow inside the channel.…”