Bubble dynamics under the influence of the Marangoni force induced by a stratified field of contamination

Abstract

The Marangoni effect assumes significance in bubbly flows when temperature or concentration gradients exist in the domain. This study investigated the hydrodynamics of single bubbles under the influence of the Marangoni force induced by stratified fields of dissolved sugar, providing a numerical framework for examining these phenomena. A laboratory-scale bubble column and high-speed imaging were utilized to analyze the bubble behavior. The OpenFOAM-based geometric volume of the fluid solver was extended by incorporating the solutocapillary Marangoni effect, and a passive scalar transport equation for the sugar concentration was solved. The results revealed that small bubbles entering regions with elevated sugar concentrations experienced deceleration, transitioning into linear paths, while those departing from regions with high sugar concentrations exhibited fluctuations and meandering. Furthermore, the concentration gradient leads larger bubbles to meander throughout the entire column, without a notable increase in their velocity. The intensity of these behaviors is governed by the magnitude of the Marangoni force. The findings provide a better understanding of single bubble hydrodynamics in complex environments.