Atomistic hybrid DSMC/NEMD method for nonequilibrium multiscale simulations

Gu, Kai; Watkins, C. B.; Koplik, Joel

doi:10.1016/j.jcp.2009.10.035

Cited by 27 publications

(15 citation statements)

References 24 publications

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“…However, the time step in this microscopic simulation is several femtoseconds, which is far smaller than that in the mesoscopic simulation based on the Boltzmann equation (the mean collision time of gas molecules is about a few fraction of one nanosecond). This greatly limits the application of the MD or even hybrid MD-direct simulation Monte Carlo methods (Gu et al 2001;Liang et al 2013;Liang & Ye 2014;Watvisave et al 2015). Some attempts have been made to model the gas-surface interaction also at the mesoscopic level.…”

Section: Introductionmentioning

confidence: 99%

Assessment and development of the gas kinetic boundary condition for the Boltzmann equation

Struchtrup

2017

J. Fluid Mech.

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Gas-surface interactions play important roles in internal rarefied gas flows, especially in micro-electro-mechanical systems with large surface area to volume ratios. Although great progresses have been made to solve the Boltzmann equation, the gas kinetic bound- ary condition (BC) has not been well studied. Here we assess the accuracy the Maxwell, Epstein, and Cercignani-Lampis BCs, by comparing numerical results of the Boltzmann equation for the Lennard-Jones potential to experimental data on Poiseuille and thermal transpiration flows. The four experiments considered are: Ewart et al. [J. Fluid Mech. 584, 337-356 (2007)], Rojas-C ́ardenas et al. [Phys. Fluids, 25, 072002 (2013)], and Yam- aguchi et al. [J. Fluid Mech. 744, 169-182 (2014); 795, 690-707 (2016)], where the mass flow rates in Poiseuille and thermal transpiration flows are measured. This requires the BC has the ability to tune the effective viscous and thermal slip coefficients to match the experimental data. Among the three BCs, the Epstein BC has more flexibility to adjust the two slip coefficients, and hence in most of the time it gives good agreement with the experimental measurement. However, like the Maxwell BC, the viscous slip coefficient in the Epstein BC cannot be smaller than unity but the Cercignani-Lampis BC can. Therefore, we propose to combine the Epstein and Cercignani-Lampis BCs to describe gas-surface interaction. Although the new BC contains six free parameters, our approxi- mate analytical expressions for the viscous and thermal slip coefficients provide a useful guidance to choose these parameters

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Section: Introductionmentioning

confidence: 99%

Assessment and development of the gas kinetic boundary condition for the Boltzmann equation

Struchtrup

2017

J. Fluid Mech.

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“…On the other hand, a model such as the proposed LJPA model will reproduce the collision dynamics better thereby leading to a better prediction of the energy (or velocity) distribution of the molecules and hence the microstructure of the thin films. The LJPA model is also an ideal model for use with hybrid MD/DSMC methods, similar to those reported by Gu et al, 21 since MD methods are typically based on the LJ intermolecular potential between molecules.…”

Section: Transport Coefficientsmentioning

confidence: 63%

“…Since the MD interaction is often based on the LJ potential, the use of a LJ scattering model in the DSMC region of these hybrid simulations would ensure better compatibility at the interface than using purely repulsive interaction models. The atomistic simulation using hybrid DSMC/MD method by Gu et al 21 used a modified form of the GSS model referred to as the MGSS model. The total cross section of the original GSS model is given by …”

Section: Introductionmentioning

confidence: 99%

Binary scattering model for Lennard-Jones potential: Transport coefficients and collision integrals for non-equilibrium gas flow simulations

Venkattraman

Alexeenko

2012

Physics of Fluids

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A Lennard-Jones (LJ) binary interaction model for dilute gases is obtained by representing the exact scattering angle as a polynomial expansion in non-dimensional collision variables. Rigorous theoretical verification of the model is performed by comparison with exact values of diffusion and viscosity cross sections and related collision integrals. The collision quantities given by the polynomial approximation model agree within 3.5% with those of the exact LJ scattering. The proposed model is compared in detail with the generalized soft sphere (GSS) model which is the closest in terms of fidelity among existing direct simulation Monte Carlo collision models. The GSS model's performance for the collision integral used in the first approximate of viscosity coefficient is comparable to the proposed model for most reduced temperatures. However, other collision integrals deviate significantly, even at moderate reduced temperatures. The high fidelity of the proposed model at low reduced temperatures enables non-equilibrium simulations of gases with deep LJ potential well such as metallic vapors. The model is based on the scattering angle as opposed to viscosity or diffusion coefficients and provides a direct link to molecular dynamics simulations.

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“…They used event driven MD for polymer particles and DSMC for solvent particles. Gu et al [7] developed a hybrid MD-DSMC method for Knudsen layer type gas flows. They have used real number of molecules for both the MD and DSMC regions.…”

Section: Introductionmentioning

confidence: 99%