Assessment of multi-phase CFD methods for gas-laden liquid flows in centrifugal pumps with particular emphasis on the change of flow morphology

Three-dimensional gas-liquid flow simulations of a volute-type centrifugal pump are performed with OpenFOAM. The Euler-Euler two-fluid (EE2F) model and the Volume-of-Fluid (VOF) model are compared and assessed with recent experimental data. A scale-adaptive turbulence model is employed. In the EE2F model simulations, locations of gas accumulation within flow separations at the blade suction side are captured, but transport processes at sharp interfaces between accumulated gas and the liquid phase can not be resolved. The VOF simulations are inherently grid-dependent since the scale of just resolved void structures and gas-liquid interfaces correlates with the spatial grid resolution. For the VOF method, the grid size typically employed for centrifugal pump flow simulations is too coarse for an adequate interface resolution and a prediction of gas accumulations and thus head drop. These results suggest the development of a hybrid multi-phase flow solver, which dynamically and locally blends the EE2F with the VOF model what will be the subject of future studies.