Interface retaining coarsening of multiphase flows
Interface retaining coarsening of multiphase flows
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DOI：
10.1063/5.0058776
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发表时间：
2019-11
影响因子：
4.6
通讯作者：
Xianyang Chen;Jiacai Lu;G. Tryggvason
中科院分区：
文献类型：
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作者：
Xianyang Chen;Jiacai Lu;G. Tryggvason
多相流的特点是尖锐的移动界面，分离不同的流体或相。在许多情况下，界面的动态决定了流动的行为。因此，在粗略或降阶模型中，为解析的尺度保留清晰的界面可能很重要。在这里，研究了一种在保留清晰界面的同时粗化或过滤不可压缩多相流的完全解析数值解的过程。不同的相通过索引函数来识别，该索引函数在每个相中取不同的值，并通过求解常数系数扩散方程来粗化，同时跟踪界面轮廓。通过求解另一个扩散方程，将界面移动时留下的一相的小流量尺度嵌入到另一相中，该扩散方程在界面位置处为零，以防止扩散，加上一个类似压力的方程以强制粗速度场的不可压缩性，该扩散系数在界面位置为零。显示了不同粗化级别的示例。粗略模型的模拟（其中小尺度被视为均匀混合物）产生的解类似于早期瑞利-泰勒不稳定性的过滤完全解析场。
Multiphase flows are characterized by sharp moving interfaces, separating different fluids or phases. In many cases the dynamics of the interface determines the behavior of the flow. In a coarse, or reduced order model, it may therefore be important to retain a sharp interface for the resolved scales. Here, a process to coarsen or filter fully resolved numerical solutions for incompressible multiphase flows while retaining a sharp interface is examined. The different phases are identified by an index function that takes different values in each phase and is coarsened by solving a constant coefficient diffusion equation, while tracking the interface contour. Small flows scales of one phase, left behind when the interface is moved, are embedded in the other phase by solving another diffusion equation with a modified diffusion coefficient that is zero at the interface location to prevent diffusion across the interface, plus a pressure like equation to enforce incompressibility of the coarse velocity field. Examples of different levels of coarsening are shown. A simulation of a coarse model, where small scales are treated as a homogeneous mixture, results in a solution that is similar to the filtered fully resolved field for the early time Rayleigh-Taylor instability.