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“Interface Retaining Coarsening for Multiphase Flow”
Presented by XIANYANG “TOM” CHEN
(Adviser: Prof. Gretar Tryggvason)
Multiphase flows are characterized by sharp moving phase boundaries, 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 is therefore critical to retain a sharp interface for the resolved scales. Here, a systematic process to coarsen fully resolved numerical solutions for multiphase flows while retaining a sharp interface is presented. The different phases are identified by an index function that takes different values in the different phases and is coarsened by solving a constant coefficient diffusion equation, while tracking the interface contour. Diffusion equations are also solved for the flow variables such as density and momentum, but the diffusion coefficient is modified at the interface location, to prevent diffusion across the interface. Several examples of different levels of coarsening are shown. Evolution equations for the coarsened field are derived assuming a simple homogeneous mixture model, and tested by evolving a Rayleigh-Taylor instability in time.