Abstract

This study evaluates the two-group interfacial area transport equation (2G IATE) coupled with the S-Gamma (Sγ) population balance equation (PBE) model for beyond bubbly flow regimes in a vertical large-diameter pipe. The 2G IATE framework incorporates intergroup mass transfer mechanisms and is implemented within the Sγ model, which assumes a log-normal bubble size distribution. The numerical approach is validated against experimental data from Schlegel et al. (2012), with a focus on the void fraction and interfacial area concentration (IAC) distributions. The results show that 2G IATE improves the predictions of the void fraction and IAC, although its accuracy varies with flow conditions. Dominant transport mechanisms, such as bubble interaction (IM), IAC from mass transfer between group-1 and group-2 bubbles (MT), and volume expansion (VE), are analyzed, revealing that the IM is the primary contributor to IAC variations, whereas MT effects become more significant at higher gas velocities. These findings contribute to the advancement of multiphase flow modeling, with potential applications in nuclear reactor safety, chemical processing, and CFD-based two-phase flow simulations.

Department(s)

Nuclear Engineering and Radiation Science

Publication Status

Open Access

Keywords and Phrases

beyond bubbly flows; interfacial area transport equation (IATE); large-diameter pipe; population balance; S-Gamma (Sγ)

International Standard Serial Number (ISSN)

2661-8877; 2661-8869

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2026 Springer, All rights reserved.

Publication Date

01 Jan 2026

Download

Full Text Link

Share

 
COinS