Session: Flow Visualization and Regular Poster Session

Paper Number: 170461

170461 - Bubble Interactions in Slug Flows: Unmasking the Master-Slave Relationship 

Abstract: 

Bubble Interactions in Slug Flows: Unmasking the Master-Slave Relationship

Shahriyar G. Holagh, Wael H. Ahmed

School of Engineering, University of Guelph, Guelph, ON N1G 2W1, Canada

Abstract:

In 2014, Fabre and Figueroa-Espinoza uncovered an "unexpected" phenomenon in counter-current slug flow—what they termed the master-slave interaction between small and Taylor bubbles. Surprisingly, this captivating behavior has remained unexplored in subsequent investigations, leaving a critical question: Can a small bubble really become the master of a long Taylor bubble? If so, under what circumstances? Our recent detailed experimental work on slug flow, utilizing flow visualization of gravity-driven concurrent slug flows in a vertical pipe, revealed a fascinating insight into this often-overlooked phenomenon. Using a Phantom M320 camera recording at 1000 fps, we captured the flows at 30D downstream from the pipe entrance. The flow images reveal that when a small bubble possesses two essential traits—being slightly larger than average and adopting an oblate shape, generating a strong wake—it can trap the nose of a trailing Taylor bubble within its wake. This interaction distorts the Taylor bubble's nose and neck, introducing significant instabilities that ultimately enslave the Taylor bubble, forcing it to align its trajectory with the small bubble. As gas accumulates in high-velocity regions of the wake, the Taylor bubble's nose sharpens, reducing its radius of curvature and accelerating the bubble, causing a deviation from the linear trajectory predicted by inviscid theory. Nonetheless, not all small bubbles exhibit master-like behavior—those lacking the critical size and oblate geometry produce weaker wakes, incapable of exerting dominance. Interestingly, the master bubble's influence diminishes as it transitions from an oblate to a prolate or spherical shape. When this transformation occurs, the Taylor bubble is released from its "slave" state, even as the former master bubble drifts nearby. The master-slave interaction induces rapid, frame-by-frame fluctuations in the Taylor bubble's shape, introducing an attractive high-frequency event within the flow.

Keywords:  Slug flow; Small Bubbles; Taylor Bubbles; Master-Slave Relationship

Presenting Author: Shahriyar Ghazanfari Holagh University of Guelph

Presenting Author Biography: Shahriyar Ghazanfari Holagh is a Ph.D. candidate in Mechanical Engineering at the University of Guelph, Canada. His research focuses on multi-phase transport phenomena in gas-liquid systems, with applications in CO₂ capture. He earned his bachelor's degree in Mechanical Engineering from the University of Tabriz, Iran, in 2015, and completed his master's degree at Iran University of Science and Technology. Prior to his doctoral studies, Shahriyar accumulated nearly four years of industrial experience, primarily in the oil and gas sector. Throughout his academic career, Shahriyar has authored over 40 journal articles and conference papers, which have been cited more than 1,500 times globally. He has also contributed to two book chapters and has served as a peer reviewer for approximately 100 manuscripts across various journals.