Towards a unified approach for modelling uniform and non‐uniform bubbly flows

TLDR

Closure relations for the Euler–Euler two‑fluid model depend on turbulent fluctuation descriptions, but existing literature models disagree on their treatment across scales, leaving a unified perspective absent. The authors assemble a set of closure relations for bubbly flow fluid dynamics that represents the best available knowledge and provides a baseline for future improvements. These relations, applied to data from non‑uniform and uniform bubble‑column flows dominated by large‑scale fluctuations and bubble‑induced turbulence, include bubble forces and a turbulence model that accounts for bubble‑induced turbulence modifications. The resulting model, validated in pipes and bubble columns, successfully captures bubble forces and turbulence modifications due to bubbles.

Abstract

Abstract An important ingredient of closure relations for the Euler‐Euler two‐fluid model is the description of turbulent fluctuations. Models proposed in the literature disagree concerning the treatment of such on all scales. The large‐scale fluctuation structures as well as the bubble‐induced turbulence might be neglected, resolved, and/or modelled respectively in different ways. Each treatment has been demonstrated to work for a certain application but a unified perspective is lacking so far. To this end 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. This model comprises a set of bubble forces as well as a turbulence model including turbulence modification due to the bubbles and has been successfully validated for bubbly flows in pipes and bubble columns. Here it is applied to two sets of data representing non‐uniform and uniform flows in bubble columns which are dominated by large‐scale fluctuations and bubble‐induced turbulence respectively.