Enhanced flow of core-softened fluids through narrow nanotubes

Abstract

We investigate through non-equilibrium molecular dynamic simulations the flow of anomalous fluids inside rigid nanotubes. Our results reveal an anomalous increase of the overall mass flux for nanotubes with sufficiently smaller radii. This is explained in terms of a transition from a single-file type of flow to the movement of an ordered-like fluid as the nanotube radius increases. The occurrence of a global minimum in the mass flux at this transition reflects the competition between the two characteristic length scales of the core-softened potential. Moreover, by increasing further the radius, another substantial change in the flow behavior, which becomes more evident at low temperatures, leads to a local minimum in the overall mass flux. Microscopically, this second transition is originated by the formation of a double-layer of flowing particles in the confined nanotube space. These nano-fluidic features give insights about the behavior of confined isotropic anomalous fluids.

Influence of disordered porous media on the anomalous properties of a simple water model

“…In order to answer these questions water-like atomistic or continuous effective potential models were explored. The confining geometries could be plates [27][28][29][30][31][32][33][34][35][36][37], one pore [38][39][40][41][42][43][44][45][46], and a disordered matrix [43,52,53,[55][56][57]. The results for the melting temperature obtained within these approaches are controversial, while results for SPC/E water show that the melting temperature for hydrophobic plates is lower than the melting for the unconfined system and higher than for the system confined by hydrophilic walls, for the mW model no difference between the melting temperatures due to the hydrophobicity [47] is found.…”

Effects of confinement on anomalies and phase transitions of core-softened fluids

“…[43][44][45][46] CS fluids confined in nanotubes also present interesting findings, similar to obtained in atomistic models for water, as the increase in diffusion coefficient and flux for narrow nanotubes associated to a layer to single-file transition and a discontinuity in the enhancement flow factor. [47][48][49] The drawback of these core-softened potentials is that due to the simplicity of the two length scales, they are not capable to reproduce the effects related to the third coordination shell of the anomalous fluid what might be relevant under confinement. 50 In addition to the relevance of the detail structure of the liquid, the structure of the confining system is also relevant since biological and physical materials do not exhibit the smoothness and regularity of the flat walls and tubes employed in the simulations.…”

Structure and Transport Properties of Water and Hydrated Ions in Nano‐Confined Channels

“…In CNTs, the water flows in spiral-like chain [77,78] or n-gonal rings, [79] where n increases with the diameter of the nanotube. [65,81,82] However, the density oscillation never disappears aside the solid walls. [80] In other materials, both tubes and slits, water can also be found to form layered structure, especially aside the solid/liquid interface.…”