Boundary condition at a gas-liquid interphase

Meland, Roar; Ytrehus, Tor

doi:10.1063/1.1407612

Cited by 4 publications

(5 citation statements)

References 5 publications

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“…II and our previous study [14]. The same phenomenon has also been observed in the MD simulations of argon [15,21]. Although we appreciate that this result needs to be confirmed by MD simulations with much larger numbers of molecules, we believe that the traditional approach to the formulation of the boundary conditions in kinetic modelling, when the distribution function of the evaporated molecules is assumed to be isotropic Maxwellian with the same temperatures for all velocity components, needs to be investigated more carefully.…”

Section: Velocity Distribution Functionsupporting

confidence: 75%

“…Alternatively, the velocity distribution function could be found by transforming the differential fluxes [15], but this approach has various numerical problems [21]. It has not been used in our analysis.…”

Section: Velocity Distribution Functionmentioning

confidence: 99%

“…[15,21,24,25]. In our previous papers when dealing with heating and evaporation of n-dodecane (C 12 H 26 ), in Diesel engine-like conditions, we used the kinetic boundary condition (KBC) in the form of Eq.…”

Section: Kinetic Boundary Conditionmentioning

confidence: 99%

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Molecular dynamics study of the processes in the vicinity of the n-dodecane vapour/liquid interface

2011

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Abstract:Molecular dynamics simulation is used to study the evaporation and condensation of n-dodecane (C 12 H 26 ), the closest approximation to Diesel fuel. The interactions in chain-like molecular structures are modelled using an optimised potential for liquid simulation (OPLS). The thickness of the transition layer between the liquid and vapour phases at equilibrium is estimated. It is shown that molecules at the liquid surface need to obtain relatively large translational energy to evaporate. The vapour molecules with large translational energy can easily penetrate deeply into the transition layer and condense in the liquid phase. The evaporation/condensation coefficient is estimated and the results are shown to be compatible with the previous estimates based on the molecular dynamics (MD) analysis and the estimate based on the transition state theory. The velocity distribution functions of molecules at the liquid-vapour equilibrium state are found in the liquid phase, interface and the vapour phase. These functions in the liquid phase and at the interface are shown to be close to isotropic Maxwellian for all velocity components. The velocity distribution function in the vapour phase is shown to be close to bi-Maxwellian with the temperature for the distribution normal to the interface being larger than the one for the distribution parallel to the interface.

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Section: Velocity Distribution Functionsupporting

confidence: 75%

Section: Velocity Distribution Functionmentioning

confidence: 99%

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Molecular dynamics study of the processes in the vicinity of the n-dodecane vapour/liquid interface

2011

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“…However, its physical validity still remains to be established, and the related studies on the basis of the molecular dynamics (MD) method have just been started. [3][4][5][6] In the present paper, we investigate the validity of this type of kinetic boundary condition at the interface of a polyatomic vapor and its own liquid phase by MD method, with particular emphasis on the functional form of the evaporation part.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics study of kinetic boundary condition at an interface between a polyatomic vapor and its condensed phase

2004

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The kinetic boundary condition for the Boltzmann equation at an interface between a polyatomic vapor and its liquid phase is investigated by the numerical method of molecular dynamics, with particular emphasis on the functional form of the evaporation part of the boundary condition, including the evaporation coefficient. The present study is an extension of a previous one for argon [Ishiyama, Yano, and Fujikawa, Phys. Fluids 16, 2899 (2004)] to water and methanol, typical examples of polyatomic molecules. As in the previous study, molecular dynamics simulations of vapor-liquid equilibrium states and those of evaporation from liquid into a virtual vacuum are carried out for water and methanol. In spite of the formation of molecular clusters in the vapor phase and the presence of the preferential orientation of molecules at the interface, essentially the same results as in the previous study are obtained. When the bulk liquid temperature is relatively low, the evaporation part is the product of the half range Maxwellian for the translational velocity of molecules of saturated vapor at the temperature of the bulk liquid phase, the equilibrium distribution of rotational energy of molecules at the temperature, and the evaporation coefficient (or the condensation coefficient in the equilibrium state). The evaporation coefficients of water and methanol are determined without any ambiguity as decreasing functions of the temperature, and are found to approach unity with the decrease of the temperature.

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“…However, its physical validity still remains to be established, and the related studies on the basis of the molecular dynamics (MD) method have just been started [4,5,6,7]. In a previous paper [7], to study the kinetic boundary condition at an interface between argon vapor and its condensed phase, we have carried out MD simulations of vapor-liquid (or solid) equilibrium states (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics study on the evaporation part of the kinetic boundary condition at the interface between water and water vapor

Ishiyama¹,

Yano²,

Fujikawa³

2005

AIP Conference Proceedings

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Abstract. Molecular dynamics simulations of vapor-liquid equilibrium states and those of evaporation from liquid phase into a virtual vacuum are performed for water. In spite of the formation of molecular clusters in the vapor phase and the presence of the preferential orientation of molecules at the interface due to uneven sharing of the bonding electron pair, essentially the same results as in our previous study for argon are obtained. That is, when the bulk liquid temperature is relatively low, the distribution function of evaporation can be expressed as the product of the equilibrium distribution of saturated vapor at the temperature in the bulk liquid phase and a well-defined evaporation coefficient, which is determined as a decreasing function of the liquid temperature, and is found to approach unity with the decrease of the temperature.

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Boundary condition at a gas-liquid interphase

Cited by 4 publications

References 5 publications

Molecular dynamics study of the processes in the vicinity of the n-dodecane vapour/liquid interface

Molecular dynamics study of the processes in the vicinity of the n-dodecane vapour/liquid interface

Molecular dynamics study of kinetic boundary condition at an interface between a polyatomic vapor and its condensed phase

Molecular dynamics study on the evaporation part of the kinetic boundary condition at the interface between water and water vapor

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