Molecular dynamics study of kinetic boundary condition at an interface between a polyatomic vapor and its condensed phase
Molecular dynamics study of kinetic boundary condition at an interface between a polyatomic vapor and its condensed phase
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DOI：
10.1063/1.1811674
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发表时间：
2004-12-01
影响因子：
4.6
通讯作者：
Fujikawa, S
中科院分区：
文献类型：
--
作者：
Ishiyama, T;Yano, T;Fujikawa, S
用分子动力学数值方法研究了多原子汽液界面Boltzmann方程的动力学边界条件，着重讨论了边界条件中蒸发部分的函数形式，包括蒸发系数。本研究是先前对氩的研究[Ishiyama，Yano，and Fujikawa，Phys.Fluids 16，2899（2004）]扩展到水和甲醇，多原子分子的典型实例。在以前的研究中，分子动力学模拟的汽液平衡状态和从液体蒸发到虚拟真空进行了水和甲醇。尽管在气相中的分子簇的形成和在界面处的分子的优先取向的存在下，基本上相同的结果，在以前的研究中获得。当液相温度较低时，蒸发部分是液相温度下饱和蒸汽分子平动速度的半程麦克斯韦方程、该温度下分子转动能的平衡分布和蒸发系数（或平衡状态下的冷凝系数）的乘积。水和甲醇的蒸发系数作为温度的递减函数被确定，没有任何歧义，并发现随着温度的降低接近1。(C)美国物理学会.
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. (C) American Institute of Physics.