Validation of CFD models for mono- and polydisperse air–water two-phase flows in pipes

Many flow regimes in nuclear reactor safety (NRS) research and nuclear reactor engineering are characterized by water–steam two-phase flows and require for their accurate CFD simulation the development and validation of appropriate multiphase flow models. This paper is presenting multiphase flow models for the description of mono- and polydisperse bubbly flows in the Eulerian framework of multiphase flow modeling in ANSYS CFX. The models are taking into account interphase momentum transfer due to governing drag and non-drag forces. Furthermore in case of a polydisperse air–water or water–steam bubbly flow the bubble size distribution, bubble break-up and coalescence processes as well as different gas velocities in dependency on the bubble diameter are taken into account in the newly developed inhomogeneous MUSIG model. Both multiphase flow models for mono- and polydisperse bubbly flows have thoroughly been validated and compared to experiments of MT-Loop and TOPFLOW test facilities (FZ Dresden-Rossendorf, Germany). Best practice guidelines (Menter, 2002) have been applied in order to allow for a systematic error quantification and thoroughly assessment of model formulations.