Nano-scale liquid film sheared between strong wetting surfaces: effects of interface region on the flow

Vo, Truong Quoc; Park, BooSeong; Park, ChoHee; Kim, BoHung

doi:10.1007/s12206-015-0340-6

Cited by 26 publications

(29 citation statements)

References 28 publications

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“…Several articles suggested that the bin size should be comparable to the atomic diameter to be able to distinctly observe the characteristics of the amorphous medium. 50,51 However, for a crystalline solid, planes are adjacently stacked with a similar spacing between layers corresponding to a particular crystal lattice. The ASD in each divided bin, which is perpendicular to the Z direction, is calculated resulting in the density distribution of the systems.…”

Section: The Proper Bin Size For Correct Measurements At Grain Bmentioning

confidence: 99%

Atomic density effects on temperature characteristics and thermal transport at grain boundaries through a proper bin size selection

Barışık

Kim

2016

The Journal of Chemical Physics

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This study focuses on the proper characterization of temperature profiles across grain boundaries (GBs) in order to calculate the correct interfacial thermal resistance (ITR) and reveal the influence of GB geometries onto thermal transport. The solid-solid interfaces resulting from the orientation difference between the (001), (011), and (111) copper surfaces were investigated. Temperature discontinuities were observed at the boundary of grains due to the phonon mismatch, phonon backscattering, and atomic forces between dissimilar structures at the GBs. We observed that the temperature decreases gradually in the GB area rather than a sharp drop at the interface. As a result, three distinct temperature gradients developed at the GB which were different than the one observed in the bulk solid. This behavior extends a couple molecular diameters into both sides of the interface where we defined a thickness at GB based on the measured temperature profiles for characterization. Results showed dependence on the selection of the bin size used to average the temperature data from the molecular dynamics system. The bin size on the order of the crystal layer spacing was found to present an accurate temperature profile through the GB. We further calculated the GB thickness of various cases by using potential energy (PE) distributions which showed agreement with direct measurements from the temperature profile and validated the proper binning. The variation of grain crystal orientation developed different molecular densities which were characterized by the average atomic surface density (ASD) definition. Our results revealed that the ASD is the primary factor affecting the structural disorders and heat transfer at the solid-solid interfaces. Using a system in which the planes are highly close-packed can enhance the probability of interactions and the degree of overlap between vibrational density of states (VDOS) of atoms forming at interfaces, leading to a reduced ITR. Thus, an accurate understanding of thermal characteristics at the GB can be formulated by selecting a proper bin size. Published by AIP Publishing. [http://dx

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Section: The Proper Bin Size For Correct Measurements At Grain Bmentioning

confidence: 99%

Atomic density effects on temperature characteristics and thermal transport at grain boundaries through a proper bin size selection

Barışık

Kim

2016

The Journal of Chemical Physics

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“…The surface effects dominate the nanoscale conduits as the force penetration distance induced by the intermolecular force fields of the wall molecules becomes comparable to the confinement dimensions. Thus, the molecular structures of the fluid and solid wall, as well as their interactions at atomistic length scales, play key roles in studying nanoscale fluid dynamics [15][16][17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

“…However, they are important in multiscale methods or nanoscale fluid flow problems, in which the continuum descriptions completely break down, and the dynamics depends on the variations on the interface or on the flow boundary layer [24,25]. Furthermore, these solidlike liquid layers influence fluid properties, resulting in a different shear rate or viscosity at the wall-fluid boundary, as well as in the channel center [4,[18][19][20]. However, these nanoscale effects on capillary action of liquid water apparently have not been characterized to date.…”

Section: Introductionmentioning

confidence: 99%

Near-surface viscosity effects on capillary rise of water in nanotubes

Barışık

Kim

2015

Phys. Rev. E

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In 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.

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“…According to the review article by Lomascolo et al [29], the thermal conductivity of a nanofluid may increase linearly with the nanoparticle volume concentration, but in some cases the increase is non-linear. Many experimental studies [61], theoretical analysis/modelling [11,61] and molecular dynamics simulations [62][63][64][65][66] have attempted to reveal the complex mechanism of the thermal conductivity of nanofluids and the heat transfer between the fluid and the nanoparticles. There have also been many studies measuring the thermal conductivity of nanofluids; proper correlations provided by these studies are useful for engineering simulations [27,67,68].…”

Section: The Heat Flux Vectormentioning

confidence: 99%

Heat Transfer and Flow of Nanofluids in a Y-Type Intersection Channel with Multiple Pulsations: A Numerical Study

Massoudi

Yan

2017

Energies

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Abstract:In this paper, we study pulsed flow and heat transfer in water-Al 2 O 3 nanofluids in a Y-type intersection channel with two inlets and one outlet. At the two inlets, two sinusoidal velocities with a phase difference of π are applied. We assume that the shear viscosity and the thermal conductivity of the nanofluids depend on the nanoparticles concentration. The motion of the nanoparticles is modeled by a convention-diffusion equation, where the effects of the Brownian motion, thermophoretic diffusion, etc., are included. The effects of pulse frequency, pulse amplitude and nanoparticles concentration on the heat transfer are explored numerically at various Reynolds numbers. The results show that the application of the pulsed flow improves the heat transfer efficiency (Nusselt number) for most of the cases studied. Amongst the four factors considered, the effect of the frequency seems to be the most important.

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Nano-scale liquid film sheared between strong wetting surfaces: effects of interface region on the flow

Cited by 26 publications

References 28 publications

Atomic density effects on temperature characteristics and thermal transport at grain boundaries through a proper bin size selection

Atomic density effects on temperature characteristics and thermal transport at grain boundaries through a proper bin size selection

Near-surface viscosity effects on capillary rise of water in nanotubes

Heat Transfer and Flow of Nanofluids in a Y-Type Intersection Channel with Multiple Pulsations: A Numerical Study

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