论文标题
非平衡多相流的离散玻尔兹曼多尺度建模
Discrete Boltzmann multi-scale modeling of non-equilibrium multiphase flows
论文作者
论文摘要
本文的目的是双重的：首先是基于基于纵向多相流量系统的密度功能动力学理论来制定和验证多尺度离散的玻尔兹曼方法（DBM），从连续性到过渡流动状态范围；第二个是在相分离过程中对热流动力非平衡（THNE）效应提出一些新的见解。 Methodologically, DBM includes three main pillars: (i) the determination of the fewest kinetic moment relations, which are required by the description of significant THNE effects beyond the realm of continuum fluid mechanics, (ii) the construction of appropriate discrete equilibrium distribution function recovering all the desired kinetic moments, (iii) the detection, description, presentation and analysis of THNE based on the moments of the non-equilibrium distribution （$ f-f^{（eq）} $）。合并适当的额外高阶热动力学力矩的结合大大扩展了DBM处理较大液体蒸气密度比，抑制杂种电流和确保质量摩托巨型能量保护的能力。与仅一阶Thne的DBM相比（Gan等人软物质11,5336），该模型可以检索超过三阶超级博内特水平的动力学力矩，并且即使本地Knudsen数量超过$ 1/3 $，对于弱，中等和强的情况也是准确的。从物理上讲，THNE和相关物理参数之间线性关系的终点提供了一个独特的标准，可以识别系统是靠近还是远离平衡。此外，表面张力会绕过界面周围的局部thne，但可以通过界面平滑和扩大来扩展界面并增强界面的强度。
The aim of this paper is twofold: the first is to formulate and validate a multi-scale discrete Boltzmann method (DBM) based on density functional kinetic theory for thermal multiphase flow systems, ranging from continuum to transition flow regime; the second is to present some new insights into the thermo-hydrodynamic non-equilibrium (THNE) effects in the phase separation process. Methodologically, DBM includes three main pillars: (i) the determination of the fewest kinetic moment relations, which are required by the description of significant THNE effects beyond the realm of continuum fluid mechanics, (ii) the construction of appropriate discrete equilibrium distribution function recovering all the desired kinetic moments, (iii) the detection, description, presentation and analysis of THNE based on the moments of the non-equilibrium distribution ($f-f^{(eq)}$). The incorporation of appropriate additional higher-order thermodynamic kinetic moments considerably extends the DBM's capability of handling larger values of the liquid-vapor density ratio, curbing spurious currents, and ensuring mass-momentum-energy conservation. Compared with the DBM with only first-order THNE (Gan et al. Soft Matter 11,5336), the model retrieves kinetic moments beyond the third-order super-Burnett level, and is accurate for weak, moderate, and strong THNE cases even when the local Knudsen number exceeds $1/3$. Physically, the ending point of the linear relation between THNE and the concerned physical parameter provides a distinct criterion to identify whether the system is near or far from equilibrium. Besides, the surface tension refrains the local THNE around the interface, but expands the THNE range and strengthens the THNE intensity away from the interface through interface smoothing and widening.
