OpenFOAM-Hybrid: A Morphology Adaptive Multifield Two-Fluid Model

Industrial multiphase flows are typically characterized by coexisting morphologies. Modern simulation methods are well established for dispersed [e.g., Euler-Euler (E-E)] or resolved [e.g., volume-of-fluid (VOF)] interfacial structures. Hence, a morphology adaptive multifield two-fluid model is proposed that is able to handle dispersed and resolved interfacial structures coexisting in the computational domain with the same set of equations. An interfacial drag formulation for large interfacial structures is used to describe them in a VOF-like manner. For the dispersed structures, the baseline model developed at Helmholtz-Zentrum Dresden-Rossendorf is applied. The functionality of the framework is demonstrated by investigating a single rising gas bubble in a stagnant water column, a two-dimensional stagnant stratification of water and oil sharing a large-scale interface that is penetrated by micro gas bubbles, and an isothermal countercurrent stratified flow case. Recent developments focus on the transition region, where bubbles are overresolved or underresolved either for E-E or for VOF. Furthermore, a concept is presented for the transition of oversized dispersed bubbles into the resolved phase.