Showing papers by "Sarith P. Sathian published in 2017"

Water flow in carbon nanotubes: The effect of tube flexibility and thermostat.

Abstract: Although the importance of temperature control in nonequilibrium molecular dynamics simulations is widely accepted, the consequences of the thermostatting approach in the case of strongly confined fluids are underappreciated. We show the strong influence of the thermostatting method on the water transport in carbon nanotubes (CNTs) by considering simulations in which the system temperature is controlled via the walls or via the fluid. Streaming velocities and mass flow rates are found to depend on the tube flexibility and on the thermostatting algorithm, with flow rates up to 20% larger when the walls are flexible. The larger flow rates in flexible CNTs are explained by a lower friction coefficient between water and the wall. Despite the lower friction, a larger solid-fluid interaction energy is found for flexible CNTs than for rigid ones. Furthermore, a comparison of thermostat schemes has shown that the Berendsen and Nose-Hoover thermostats result in very similar transport rates, while lower flow rates are found under the influence of the Langevin thermostat. These findings illustrate the significant influence of the thermostatting methods on the simulated confined fluid transport.

Thermophoretic transport of ionic liquid droplets in carbon nanotubes

Abstract: Thermal-gradient induced transport of ionic liquid (IL) and water droplets through a carbon nanotube (CNT) is investigated in this study using molecular dynamics simulations. Energetic analysis indicates that IL transport through a CNT is driven primarily by the fluid-solid interaction, while fluid-fluid interactions dominate in water-CNT systems. Droplet diffusion analysis via the moment scaling spectrum reveals sub-diffusive motion of the IL droplet, in contrast to the self-diffusive motion of the water droplet. The Soret coefficient and energetic analysis of the systems suggest that the CNT shows more affinity for interaction with IL than with the water droplet. Thermophoretic transport of IL is shown to be feasible, which can create new opportunities in nanofluidic applications.

Effect of axial electric field on the Rayleigh instability at small length scales.

Abstract: The effect of an electric field along the longitudinal axis of a nanoscale liquid thread is studied to understand the mechanism of breakup. The Rayleigh instability (commonly known as the Plateau--Rayleigh instability) of a nanosized liquid water thread is investigated by using molecular dynamics simulations. The breakup mechanism of the liquid nanothread is studied by analyzing the temporal evolution of the thread radius. The influence of the temperature of the liquid nanothread and the electric-field strength on the stability and breakup is the major focus of the study. The results show that the axial electric field has a stabilizing effect even at nanoscale. The results from the simulations are in good agreement with the solutions obtained from the dispersion relation developed by Hohman et al. for the liquid thread. The critical electric-field strength necessary to avoid the breakup of the liquid thread is calculated and other effects such as the splaying and whipping instability are also discussed.