Evaluation of Length Scales and Meshing Requirements for Resolving Two-Phase Flow Regime Transitions Using the Level Set Method

New criteria for fully resolving two-phase flow regime transitions using direct numerical simulation with the level set method for interface capturing are proposed. A series of flows chosen to capture small scale interface phenomena are simulated at different grid refinements. These cases include droplet deformation and breakup in a simple shear field, the thin film around a Taylor bubble, and the rise of a bubble towards a free surface. These cases cover the major small scale phenomena observed in two-phase flows: internal recirculation, interface curvature, interface snapping, flow of liquid in thin films, and drainage/snapping of thin films. The results from these simulations and their associated grid studies were used to develop new meshing requirements for simulation of two-phase flow using interface capturing methods, in particular the level set method. When applicable, the code used in this work, PHASTA, was compared to experiments in order to contribute to the ongoing validation process of the code. Results show that when the solver meets these criteria, with the exception of resolving the nanometer scale liquid film between coalescing bubbles, the code is capable of accurately simulating interface topology changes.