Modeling thin-film dynamics in multiscale volume-of-fluid simulations

In two-phase flow simulations utilizing the volume-of-fluid (VOF) method for interface capturing, the mesh size limits the characteristic length of the smallest resolvable features, which hinders the prediction of breakup. We present a computational framework to couple the VOF method to a thin-film model in underresolved fluid regions to accurately predict the thickness evolution of the film. A two-plane interface reconstruction in each cell and a connected-component labeling method for film identification facilitate a seamless transition between the VOF representation and the thin-film model. We demonstrate our method on a liquid sheet that thins down to subgrid scale due to flow kinematics and discuss implications for bag breakup modeling.