Fokker-Planck-Poisson kinetics: multi-phase flow beyond equilibrium
Fokker-Planck-Poisson kinetics: multi-phase flow beyond equilibrium
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DOI：
10.1017/jfm.2021.461
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发表时间：
2021-06
影响因子：
3.7
通讯作者：
M. Sadr;M. Pfeiffer;M. H. Gorji
中科院分区：
文献类型：
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作者：
M. Sadr;M. Pfeiffer;M. H. Gorji
摘要多相现象是许多具有挑战性的流体动力学问题的核心。界面处的分子通量决定了相邻相的命运，但它们远离连续体的闭合需要建模。沿着动力学方法的层次，多相粒子方法设计在这项研究中。该方法紧密建立在先前关于致密气体[Phys. Fluids，第29卷（12），2017]和长程相互作用[J. COMPUT.物理、第378卷，2019年]。正是在这种背景下，目前的工作福克-普朗克-泊松模型的多相现象开始。分子间的相互作用是由白色噪声驱动的随机力和长程吸引力共同作用的结果。前者是局部的，追求分子碰撞的扩散近似，而后者由于平均场力而具有全局特征。所得到的福克-普朗克-泊松组合提供了一个有效的工作流程，物理驱动的模拟适合于远离平衡的多相现象。除了突出的计算效率的方法，各种典型的和复杂的问题，从液滴之间的温度梯度倒置的亚稳分解进行了探讨。详细讨论了分散在低/高密度背景气体中的液滴的不同特性，包括偏离傅立叶定律的热通量以及液滴在旋节相中的生长。
Abstract Multi-phase phenomena remain at the heart of many challenging fluid dynamics problems. Molecular fluxes at the interface determine the fate of neighbouring phases, yet their closure far from the continuum needs to be modelled. Along the hierarchy of kinetic approaches, a multi-phase particle method is devised in this study. This approach is built closely upon the previous studies on the kinetic method development for dense gases [Phys. Fluids, vol. 29 (12), 2017] and long-range interactions [J. Comput. Phys., vol. 378, 2019]. It is on this background that the current work on Fokker-Planck-Poisson modelling of multi-phase phenomena is initiated. Molecular interactions are expressed via stochastic forces driven by the white noise, coupled to the long-range attractions. The former is local and pursues diffusive approximation of molecular collisions, whereas the latter takes a global feature owing to mean-field forces. The obtained Fokker-Planck-Poisson combination provides an efficient work flow for physics-driven simulations suitable for multi-phase phenomena far from the equilibrium. Besides highlighting the computational efficiency of the method, various archetypical and complex problems ranging from inverted temperature gradients between droplets to spinodal decomposition are explored. Detailed discussions are provided on different characteristics of the droplets dispersed in low/high density background gases; including the departure of heat fluxes from Fourier's law as well as droplets growth in spinodal phases.