Unified modeling of bubbly flows in pipes, bubble columns, and airlift columns

- A closure model for bubbly flow is proposed.
- Including bubble forces and bubble-induced turbulence.
- It allows to treat different geometries and boundary conditions in a unified manner.
- Specifically bubbly flow in a pipe, a bubble column and an airlift column are considered.

Multiphase CFD simulation is a valuable tool in process engineering which is particularly useful to study new reactor concepts and their scale-up from laboratory to production scale. Simulations of bubbly flows up to industrial dimensions are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, for practical applications suitable closure models are needed which describe the physics on the scale of individual bubbles or groups thereof. The quest for such models with a broad range of applicability allowing predictive simulations is an ongoing venture.A set of closure relations for the fluid dynamics of bubbly flow has been collected that represents the best available knowledge and may serve as a baseline for further improvements and extensions. It is shown that this model is applicable to bubbly flows in different systems, namely pipes, bubble columns, and airlift columns. While these systems have been considered individually before, the novelty of the present work lies in their unified treatment by a single model.