Modelling supercritical CO2 flow in a co-rotating twin screw extruder using the level-set method

Supercritical CO2 has been used in recent years to replace conventional blowing agents in extrusion processes. So far, computational fluid dynamics analyses of such extrusion processes are relatively scarce. In this work, a multiphase model of a co-rotating twin screw extruder is presented that uses the Level Set method to describe the interface between supercritical CO2 and polypropylene - which is modelled as an inelastic, non-Newtonian fluid - under various operating conditions. The results show that the Level Set method is a promising technique to describe multiphase flow and can predict both stable and unstable processing regimes as described by experimentalists in literature.