Open-source finite volume solvers for the simulation of multiphase (n-phase) Newtonian/non-Newtonian fluid flows*

We present two newly developed finite volume solvers based on OpenFOAM® suitable for the numerical prediction of n-phase flows involving Newtonian and non-Newtonian fluids. These solvers introduce crucial modifications into the original multiphaseInterFoam solver, provided by OpenFOAM, considerably enhancing its efficiency and, most importantly, its accuracy for flows dominated by surface tension. The non-Newtonian solver is able to account for a wide range of rheologically complex materials which may exhibit yield stress, viscoelastic, or elasto-viscoplastic effects. This is accomplished by incorporating the RheoTool toolbox that offers numerous constitutive equations for modelling fluids with complex rheology. The new solvers are verified for several two- and three-phase benchmark flows, including dam break with an obstacle, a floating lens, a levitating drop, and a bubble rising in an ambient fluid; flows involving Newtonian, viscoplastic, or viscoelastic liquids are considered. Comparisons are performed against analytical solutions and data available in the literature, indicating that our solvers can accurately simulate three-phase flows for simple and complex liquids with significant interfacial tension effects.