Multiphase flows are known for forming a wide range of scales of motion and geometries as they develop. Advancements in computation have provided the opportunity to study many aspects of multiphase flows, however it is not always possible to resolve every scale. Topology changes are one example of complex phenomena that may occur and that requires understanding how multiple scales behave. Multi-scale models provide the capacity to simulate complex flow problems without requiring high resolutions.
Several multi-scale multiphase flow problems have been studied including two-dimensional and three-dimensional flow with topology changes. A model for thin films based on mass and momentum conservation principles is developed. The simulations were done using a front-tracking/finite-volume method, where the interface is represented by connected marker points moving with the fluid, while the governing equations are solved on a fixed grid. The results are evaluated by comparison with fully resolved simulations. Low dimensional models such as this one can potentially reduce the computational cost of multi-scale and multiphase simulations.