Discrete unified gas kinetic scheme for all Knudsen number flows. IV. Strongly inhomogeneous fluids.
Discrete unified gas kinetic scheme for all Knudsen number flows. IV. Strongly inhomogeneous fluids.
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DOI：
10.1103/physreve.101.043303
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
Baochao Shan;Peng Wang;Yonghao Zhang;Zhaoli Guo
中科院分区：
文献类型：
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作者：
Baochao Shan;Peng Wang;Yonghao Zhang;Zhaoli Guo
本文的工作是离散统一气体动力学格式（DUGKS）从稀薄气体动力学到强非均匀稠密流体系统的推广。对于稀薄气体，流体分子的尺寸可以忽略，而对于纳米尺度的表面受限流体流动，分子间的非局部碰撞以及固-流和流-流相互作用的竞争起着重要的作用。这种非平衡状态导致了强烈的流体结构约束的不均匀性和反常的流体流动动力学。根据先前的动力学模型[Guo等人，E71，035301（R）（2005）10.1103/PhysRevE.71.035301]，通过平均场近似来模拟分子间的长程吸引，并且通过碰撞算子中的硬球势来考虑体积排阻效应。动力学模型采用具有渐近保持、低耗散、二阶精度和多维性质的DUGKS方法求解。静态流体结构和动态流动行为的计算和验证与Monte Carlo或分子动力学结果。结果表明，随着稠密度的减小或平均流径的增大，稠密流体系统的流动趋向于稀薄气体的流动。结果表明，DUGKS方法适用于模拟这类非平衡稠密流体系统。
This work is an extension of the discrete unified gas kinetic scheme (DUGKS) from rarefied gas dynamics to strongly inhomogeneous dense fluid systems. The fluid molecular size can be ignored for dilute gases, while the nonlocal intermolecular collisions and the competition of solid-fluid and fluid-fluid interactions play an important role for surface-confined fluid flows at the nanometer scale. The nonequilibrium state induces strong fluid structural-confined inhomogeneity and anomalous fluid flow dynamics. According to the previous kinetic model [Guo et al., Phys. Rev. E 71, 035301(R) (2005)10.1103/PhysRevE.71.035301], the long-range intermolecular attraction is modeled by the mean-field approximation, and the volume exclusion effect is considered by the hard-sphere potential in the collision operator. The kinetic model is solved by the DUGKS, which has the characteristics of asymptotic preserving, low dissipation, second-order accuracy, and multidimensional nature. Both static fluid structure and dynamic flow behaviors are calculated and validated with Monte Carlo or molecular dynamics results. It is shown that the flow of dense fluid systems tends to that of rarefied gases as the dense degree decreases or the mean flow path increases. The DUGKS is proved to be applicable to simulate such nonequilibrium dense fluid systems.