The vapor condensation onto a thin liquid film, induced by the reflection of a weak shock wave, is studied by molecular dynamics atomistic simulations of a simple Lennard-Jones fluid. Molecular dynamics results provide reference flowfields for two models. The first one adopts a hybrid continuum-kinetic description in which the liquid phase is described by hydrodynamic equations, whereas the vapor is described by the Boltzmann equation. The structureless liquid–vapor interface is replaced by a classical kinetic boundary condition. The second model is based on the diffuse interface full continuum description of the Lennard-Jones fluid liquid, vapor, and interface regions. For both models, the required fluid thermodynamic and transport properties have been prescribed according to those of the Lennard-Jones fluid. Not unexpectedly, the results show that the continuum-kinetic model provides a good description of molecular dynamics results when the vapor is close to ideal conditions, increasingly deviating from reference data when the vapor non-ideality increases. The opposite behavior is found for the diffuse interface model. It is observed that flow conditions exist where both models fail to provide a reasonably accurate description of reference flow properties.

中文翻译：

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通过微观和连续模型模拟 Lennard-Jones 流体中激波引起的蒸汽冷凝流

通过对简单 Lennard-Jones 流体的分子动力学原子模拟，研究了由弱冲击波反射引起的薄液膜上的蒸汽冷凝。分子动力学结果为两个模型提供了参考流场。第一个采用混合连续介质动力学描述，其中液相用流体动力学方程描述，而蒸汽用玻尔兹曼方程描述。无结构的液-气界面被经典的动力学边界条件所取代。第二个模型基于 Lennard-Jones 流体液体、蒸汽和界面区域的扩散界面完整连续统描述。对于这两种模型，所需的流体热力学和传输特性已根据 Lennard-Jones 流体的特性进行了规定。没想到，结果表明，当蒸汽接近理想条件时，连续介质动力学模型提供了对分子动力学结果的良好描述，当蒸汽非理想状态增加时，与参考数据的偏差越来越大。在漫反射界面模型中发现了相反的行为。据观察，存在两种模型都无法提供对参考流动特性的合理准确描述的流动条件。