Computational study of thermal dependence of accommodation coefficients in a nano-channel and the prediction of velocity profiles

Prabha, Sooraj K.; Sathian, Sarith P.

doi:10.1016/j.compfluid.2012.07.021

Cited by 11 publications

(5 citation statements)

References 28 publications

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“…When the gas is bounded with solid wall, the variation of number density of fluid atoms near the wall is significant. 10,11 In this study the attempt is to calculate the mean free path by tracking the trajectory of a molecule and detecting collisions.…”

Section: Introductionmentioning

confidence: 99%

The effect of system boundaries on the mean free path for confined gases

et al. 2013

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The mean free path of rarefied gases is accurately determined using Molecular Dynamics simulations. The simulations are carried out on isothermal argon gas (Lennard-Jones fluid) over a range of rarefaction levels under various confinements (unbounded gas, parallel reflective wall and explicit solid platinum wall bounded gas) in a nanoscale domain. The system is also analyzed independently in constitutive sub-systems to calculate the corresponding local mean free paths. Our studies which predominate in the transition regime substantiate the boundary limiting effect on mean free paths owing to the sharp diminution in molecular free paths near the planar boundaries. These studies provide insight to the transport phenomena of rarefied gases through nanochannels which have established their potential in microscale and nanoscale heat transfer applications.

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Section: Introductionmentioning

confidence: 99%

The effect of system boundaries on the mean free path for confined gases

et al. 2013

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“…The reason why only E/MACs on bottom wall are reported here is for a further comparison with experimental data which are in the same temperature range. As it is shown in [15,18], the temperature gradient between two walls causes only a minor reduction in obtained values for E/MACs on the bottom wall. Therefore, this can be neglected.…”

Section: Resultsmentioning

confidence: 59%

“…Herein, the gas molecules are not coupled to an external heat bath, and their temperature change is caused only via collisions with other particles (gas and solid particles). As it will be discussed in detail in the proceeding section, in order to obtain reliable results for E/MACs, a large number of collisions between gas molecules and the wall surface are required: 100,000 collisions have been considered here, as it has been recommended in previous studies [15,18] for a similar simulation setup. Increasing the number of collisions can be achieved by either extending the walls surface area or increasing the gas number density.…”

Section: Molecular Dynamics (Md) Simulationsmentioning

confidence: 99%

“…These coefficients can be fed into semi-empirical GSI models such as Maxwell's model [10] or Cercignani-Lampis-Lord (CLL) model [11] that can be employed as boundary conditions for higher-scale simulation techniques such as Direct Simulation Monte Carlo (DSMC) [12], Lattice Boltzmann method (LBM) [13], and method of moments (MoM) [14] to describe heat and mass flow at macroscopic level under rarefied condition. In literature there are various numerical studies in which MD simulations are employed to determine accommodation coefficients for different gas-solid surface combinations [15][16][17][18][19][20][21][22]. The general objective of all such investigations is to find the correlation between the energy and momentum accommodation coefficients and input parameters such as the gas temperature or purity, gas molecular weight (MW), surface condition (i.e., surface roughness, cleanness, temperature and chemistry), as well as the gas-surface interaction strength.…”

Section: Introductionmentioning

confidence: 99%

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The Influence of Gas–Wall and Gas–Gas Interactions on the Accommodation Coefficients for Rarefied Gases: A Molecular Dynamics Study

et al. 2020

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Molecular dynamics (MD) simulations are conducted to determine energy and momentum accommodation coefficients at the interface between rarefied gas and solid walls. The MD simulation setup consists of two parallel walls, and of inert gas confined between them. Different mixing rules, as well as existing ab-initio computations combined with interatomic Lennard-Jones potentials were employed in MD simulations to investigate the corresponding effects of gas-surface interaction strength on accommodation coefficients for Argon and Helium gases on a gold surface. Comparing the obtained MD results for accommodation coefficients with empirical and numerical values in the literature revealed that the interaction potential based on ab-initio calculations is the most reliable one for computing accommodation coefficients. Finally, it is shown that gas-gas interactions in the two parallel walls approach led to an enhancement in computed accommodation coefficients compared to the molecular beam approach. The values for the two parallel walls approach are also closer to the experimental values.

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“…On the other hand, using the extended Navier-Stokes equations form is not practical from a general CFD user point of view, applying vendor CFD codes with no such extensions available to the user. More complex numerical model were also derived, based on molecular dynamics simulations [22], and the solution of the Boltzmann equations that can be used in order to compute the fluid flow around a microparticle [23,24] even in cases of high Knudsen number values. However, these models are not directly applicable in the context of CFD.…”

Section: Introductionmentioning

confidence: 99%

A specific slip length model for the Maxwell slip boundary conditions in the Navier–Stokes solution of flow around a microparticle in the no-slip and slip flow regimes

Wedel

Štrakl

Ravnik

et al. 2022

Theor. Comput. Fluid Dyn.

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In the case of microscopic particles, the momentum exchange between the particle and the gas flow starts to deviate from the standard macroscopic particle case, i.e. the no-slip case, with slip flow occurring in the case of low to moderate particle Knudsen numbers. In order to derive new drag force models that are valid also in the slip flow regime for the case of non-spherical particles of arbitrary shapes using computational fluid dynamics, the no-slip conditions at the particle surface have to be modified in order to account for the velocity slip at the surface, mostly in the form of the Maxwell’s slip model. To allow a continuous transition in the boundary condition at the wall from the no-slip case to the slip cases for various Knudsen (Kn) number value flow regimes, a novel specific slip length model for the use with the Maxwell boundary conditions is proposed. The model is derived based on the data from the published experimental studies on spherical microparticle drag force correlations and Cunningham-based slip correction factors at standard conditions and uses a detailed CFD study on microparticle fluid dynamics to determine the correct values of the specific slip length at selected Kn number conditions. The obtained data on specific slip length are correlated using a polynomial function, resulting in the specific slip length model for the no-slip and slip flow regimes that can be applied to arbitrary convex particle shapes. Graphic abstract

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Computational study of thermal dependence of accommodation coefficients in a nano-channel and the prediction of velocity profiles

Cited by 11 publications

References 28 publications

The effect of system boundaries on the mean free path for confined gases

The effect of system boundaries on the mean free path for confined gases

The Influence of Gas–Wall and Gas–Gas Interactions on the Accommodation Coefficients for Rarefied Gases: A Molecular Dynamics Study

A specific slip length model for the Maxwell slip boundary conditions in the Navier–Stokes solution of flow around a microparticle in the no-slip and slip flow regimes

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