Interfacial Area Transport Equation for Bubble Coalescence and Breakup: Developments and Comparisons

Abstract

Bubble coalescence and breakup play important roles in physical-chemical processes and bubbles are treated in two groups in the interfacial area transport equation (IATE). This paper presents a review of IATE for bubble coalescence and breakup to model five bubble interaction mechanisms: bubble coalescence due to random collision, bubble coalescence due to wake entrainment, bubble breakup due to turbulent impact, bubble breakup due to shearing-off, and bubble breakup due to surface instability. In bubble coalescence, bubble size, velocity and collision frequency are dominant. In bubble breakup, the influence of viscous shear, shearing-off, and surface instability are neglected, and their corresponding theory and modelling are rare in the literature. Furthermore, combining turbulent kinetic energy and inertial force together is the best choice for the bubble breakup criterion. The reviewed one-group constitutive models include the one developed by Wu et al., Ishii and Kim, Hibiki and Ishii, Yao and Morel, and Nguyen et al. To extend the IATE prediction capability beyond bubbly flow, two-group IATE is needed and its performance is strongly dependent on the channel size and geometry. Therefore, constitutive models for two-group IATE in a three-type channel (i.e., narrow confined channel, round pipe and relatively larger pipe) are summarized. Although great progress in extending the IATE beyond churn-turbulent flow to churn-annual flow was made, there are still some issues in their modelling and experiments due to the highly distorted interface measurement. Regarded as the challenges to be addressed in the further study, some limitations of IATE general applicability and the directions for future development are highlighted.

HiGee Microbubble Generator: (II) Controllable Preparation of Microbubbles

“…Thus, it caused the shallow depth of field (48 μm) and small observation area (4 × 4 mm 2 ); on the other hand, the microbubbles might be difficult to coalesce because of their own characteristics. The coalescence of bubbles was generally considered to be affected by the collision frequency and coalescence efficiency. − In the absence of external force, the collision frequency of microbubbles was very low, causing difficulty for them to coalesce . However, the coalescence efficiency of microbubbles calculated by either the film drainage theory or the relative velocity theory was very high.…”

A Coupled CFD-DEM Study on the Effect of Basset Force Aimed at the Motion of a Single Bubble

“…As for the motion of a single bubble in a multiphase system, it is essential for us to take full consideration on the coupling relationship in order to realize the unsteady coupling process [ 24 ]. Therefore, in this work, a coupled model is constructed with Fluent software (ANSYS Inc., Canonsburg, PA, USA) for the continuous phase and EDEM software (DEM Solutions Ltd., Edinburgh, UK) for the discrete phase, where the fluid and the bubble are discretized in the Eulerian and Lagrangian framework, respectively.…”

“…(b) It has been identified that interfacial area transport equations (IATE) can handle all bubbles in two groups: the spherical/distorted bubble group and the cap/slug bubble group [ 38 , 39 , 40 ]. Moreover, 1 mm bubbles belong to Group I bubbles (spherical/distorted bubbles) in bubbly flow, which are treated in one-group IATE rather than two-group IATE [ 24 , 41 ]. Therefore, the coalescence and breakup of 1 mm bubbles are neglected in the dilute phase flow, and it is reasonable [ 24 ].…”

“…Moreover, 1 mm bubbles belong to Group I bubbles (spherical/distorted bubbles) in bubbly flow, which are treated in one-group IATE rather than two-group IATE [ 24 , 41 ]. Therefore, the coalescence and breakup of 1 mm bubbles are neglected in the dilute phase flow, and it is reasonable [ 24 ]. (c) Water is turbulent incompressible Newtonian fluid and initially at rest.…”

Collisions of Two-Phase Liquid Droplets in a Heated Gas Medium

“…The processes developing from the collisions of droplets [4,5] containing gas or vapor bubbles are comparable to the micro-explosive destruction of liquid [6,7]. However, in that case, the second phase in a water droplet emerges as a result of fast boiling liquid passing through a pipeline [8] and continuing its movement in a high-temperature gas medium [9]. Gas bubbles can also end up in liquid droplets when they collide during spraying [10].…”