Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Book Part Citation - Scopus: 1Molecular Dynamics Studies on Nanoscale Gas Transport(Springer Science+Business Media, 2015) Beşkök, Ali; Barışık, Murat[No abstract available]Conference Object Molecular Modeling of Force Driven Gas Flows in Nano-Channels(International Conference on Computational Fluid Dynamics (ICCFD), 2016) Barışık, MuratNano-scale gas transport plays an important role in many micro/nanotechnology applications where the rarefied gas dynamics based solutions are frequently used by maintaining a “dynamic similarity” between low pressure (rarefied) and nano gas flows. However, such a consideration is incomplete since the surface force field effects dominant in nano-levels induce significant variations. In order to specify the surface force effects on gas transport, we define a new parameter (B) as the ratio of force penetration length to the channel height, and studied the length scales and conditions for applicability of current rarefied gas dynamics on nano-scale gas flows. Using Molecular Dynamics, force driven gas flows were characterized as a function of B parameter and Knudsen number. Results showed that for a negligible value of B parameter (B?0) transport can be described by rarefied gas dynamics in the whole Knudsen range while the velocity profiles are parabolic and the variation of mass flow rate shows the well-known Knudsen minimum around Kn=1. As the flow dimension decreases, B becomes a finite value indicating the dominancy of surface force effects over rarefaction, and gas velocities and mass transport significantly deviates from the kinetic theory predictions. © 2016 9th International Conference on Computational Fluid Dynamics, ICCFD 2016 - Proceedings. All rights reserved.Article Citation - WoS: 76Citation - Scopus: 79Near-Surface Viscosity Effects on Capillary Rise of Water in Nanotubes(American Physical Society, 2015) Vo, Truong Quoc; Barışık, Murat; Kim, BoHungIn this paper, we present an approach for predicting nanoscale capillary imbibitions using the Lucas-Washburn (LW) theory. Molecular dynamics (MD) simulations were employed to investigate the effects of surface forces on the viscosity of liquid water. This provides an update to the modified LW equation that considered only a nanoscale slip length. An initial water nanodroplet study was performed to properly elucidate the wetting behavior of copper and gold surfaces. Intermolecular interaction strengths between water and corresponding solid surfaces were determined by matching the contact angle values obtained by experimental measurements. The migration of liquid water into copper and gold capillaries was measured by MD simulations and was found to differ from the modified LW equation. We found that the liquid layering in the vicinity of the solid surface induces a higher density and viscosity, leading to a slower MD uptake of fluid into the capillaries than was theoretically predicted. The near-surface viscosity for the nanoscale-confined water was defined and calculated for the thin film of water that was sheared between the two solid surfaces, as the ratio of water shear stress to the applied shear rate. Considering the effects of both the interface viscosity and slip length of the fluid, we successfully predicted the MD-measured fluid rise in the nanotubes.