A-Posteriori Assessment of Sub-Filter Scale Models for Turbulence-Interface Interaction with the Two-Fluid Formulation Considering a Single Rising Gas Bubble in Liquid

Gas-liquid flows are of great importance for a large number of different industrial applications, e.g. in energy sector or metal processing industry. From there arises a strong need for numerical tools, which help to predict dynamics of two-phase flows in technical facilities with high predictive accuracy, reasonable computational expense and without any need for initial knowledge of the present flow regime. A big challenge in investigations of such problems is the large range of interfacial and turbulent scales, which need to be accounted for in numerical simulations. A typical approach to capture all these dynamics and their interactions are multi-scale multi-regime methods, which make use of coupling of different individual modeling concepts. The overall aim is to adopt the hybrid approach of H ̈ ansch et al. (2012), which combines an Eulerian-Eulerian approach with a volume-of-fluid(VOF)-like method in a two-fluid model in order to represent interfacial structures on subgrid-scale and on grid-scale, respectively. In situations, where transitions between different morphologies occur, interfacial structures appear to be too large for an Eulerian-Eulerian model approach and, at the same time, too small for the flow dynamics to be fully resolved in a VOF-like model. In other words, in the range of mesh scale and slightly above, interfacial and turbulent structures need to be simulated in an under-resolved manner. For this to deliver physically reasonable results, modeling of subgrid-scale (SGS) dynamics becomes necessary.