Periodic boundary conditions for the simulation of uniaxial extensional flow of arbitrary duration
Periodic boundary conditions for the simulation of uniaxial extensional flow of arbitrary duration
复制标题
任意持续时间的单轴拉伸流模拟的周期性边界条件
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
T. Hunt
中科院分区：
文献类型：
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作者：
T. Hunt
在分子动力学和其他模拟技术中，应用Lees-Edwards周期性边界条件（PBCs）来模拟剪切流是非常常见的。然而，在拉伸流动下，复杂液体的行为可能完全不同。模拟单元及其周期性图像的简单变形仅允许对这些流进行短持续时间的模拟。对于平面拉伸流的模拟，人们认识到Kraynik和Reinelt的PBCs [Int. J. Multiphase Flow 1992;18：1045]可用于模拟任意持续时间的这种流。然而，在工业应用和实验中非常常见的拉伸流动是单轴拉伸流动。Kraynik和Reinelt发现，他们的方法不能直接推广到这种流动，因为缺乏在单轴拉伸过程中自我复制的晶格。PBCs在这篇文章中，它避免了这个问题，找到一个格子，这是兼容的流动，找到约化的基础上的格子在任何时候，并使用这个基础时，计算的位置和分离的颗粒。使用这些新的PBCs，我们进行非平衡分子动力学模拟的一个简单的液体，并表明该技术给出的结果与那些从模拟使用简单变形的PBCs。
It is very common with molecular dynamics and other simulation techniques to apply Lees–Edwards periodic boundary conditions (PBCs) for the simulation of shear flow. However, the behaviour of a complex liquid can be quite different under extensional flow. Simple deformation of a simulation cell and its periodic images only allows for simulations of these flows with short duration. For the simulation of planar extensional flow, it was recognised that the PBCs of Kraynik and Reinelt [Int. J. Multiphase Flow 1992;18:1045] could be used to perform simulations of this flow with arbitrary duration. However, a very common extensional flow in industrial applications and experiment is uniaxial extensional flow. Kraynik and Reinelt found that their method could not be directly generalised to this flow because of the lack of a lattice which reproduces itself during uniaxial extension. PBCs are presented in this article, which avoid this problem by finding a lattice which is compatible with the flow, finding the reduced basis to the lattice at all times and using this basis when calculating the position and separation of particles. Using these new PBCs, we perform nonequilibrium molecular dynamics simulations of a simple liquid and show that the technique gives results which agree with those from simulations using simply deforming PBCs.