CFD simulation of polydispersed bubbly two phase flow around an obstacle


CFD simulation of polydispersed bubbly two phase flow around an obstacle

Krepper, E.; Ruyer, P.; Beyer, M.; Lucas, D.; Prasser, H.-M.; Seiler, N.

This paper concerns the model of a polydispersed bubble population in the frame of an ensemble averaged two-phase flow formulation. The ability of the moment density approach to represent bubble population size distribution within a multi-dimensional CFD code based on the two-fluid model is studied. Two different methods describing the polydispersion are presented: (i) a moment density method, developed at IRSN, to model the bubble size distribution function and (ii) a population balance method considering several different velocity fields of the gaseous phase. The first method is implemented in the NEPTUNE_CFD code whereas the second method is implemented in the CFD code ANSYS/CFX. Both methods consider coalescence and break-up phenomena and momentum inter-phase transfers related to drag and lift forces.
Air-water bubbly flows in a vertical pipe with obstacle of the TOPFLOW experiments series performed at FZD are then used as simulations test cases. The numerical results, obtained with NEPTUNE_CFD and with ANSYS/CFX, allow attesting the validity of the approaches. Perspectives concerning the improvement of the models, their validation, as well as the extension of their applicability range are discussed.

Keywords: bubbly flow; CFD; population balance method; moment density method; non-drag forces; bubble breakup; bubble coalescence; model validation

Permalink: https://www.hzdr.de/publications/Publ-10920
Publ.-Id: 10920