Continuum-particle hybrid coupling for mass, momentum, and energy transfers in unsteady fluid flow
Continuum-particle hybrid coupling for mass, momentum, and energy transfers in unsteady fluid flow
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DOI：
10.1103/physreve.67.046704
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发表时间：
2003-04-01
影响因子：
2.4
通讯作者：
Coveney, PV
中科院分区：
文献类型：
--
作者：
Delgado-Buscalioni, R;Coveney, PV
混合方法在模拟中的目的是在不同的时间和长度尺度上交流区域。这里，在内部区域P内的原子级描述的流体耦合到由连续流体动力学描述的外部区域C。这两种物质描述的匹配是在一个重叠的区域进行的，通常由一个双向耦合方案(C--&P和P-->；C)组成，它传递质量、动量和能量流。在此提出的混合方案的贡献是双重的。首先，它处理非定常流动，更重要的是，它处理C和P区域之间的能量交换。这里使用具有不同质量、动量和能量交换率的定常和非定常流动来测试C--&P耦合的实现。尤其是，由线性流体动力学(横波和纵波)描述的松弛流是最有启发性的，因为它们构成了一整套水动力模式。在初始扰动开始后应用混合耦合格式，P区流动变量(速度、密度、内能、温度和压力)的单元平均傅立叶分量的演变与流体动力学趋势非常一致。结果还表明，该方案保持了正确的信息熵产生速率。我们讨论了由特征微观尺度和水动力尺度引起的对粗粒度长度和时间尺度的一般要求。
The aim of hybrid methods in simulations is to communicate regions with disparate time and length scales. Here, a fluid described at the atomistic level within an inner region P is coupled to an outer region C described by continuum fluid dynamics. The matching of both descriptions of matter is made across an overlapping region and, in general, consists of a two-way coupling scheme (C-->P and P-->C) that conveys mass, momentum, and energy fluxes. The contribution of the hybrid scheme hereby presented is twofold. First, it treats unsteady flows and, more importantly, it handles energy exchange between both C and P regions. The implementation of the C-->P coupling is tested here using steady and unsteady flows with different rates of mass, momentum and energy exchange. In particular, relaxing flows described by linear hydrodynamics (transversal and longitudinal waves) are most enlightening as they comprise the whole set of hydrodynamic modes. Applying the hybrid coupling scheme after the onset of an initial perturbation, the cell-averaged Fourier components of the flow variables in the P region (velocity, density, internal energy, temperature, and pressure) evolve in excellent agreement with the hydrodynamic trends. It is also shown that the scheme preserves the correct rate of entropy production. We discuss some general requirements on the coarse-grained length and time scales arising from both the characteristic microscopic and hydrodynamic scales.