Investigation of Recirculating Marangoni Flow in Three-Dimensional Geometry of Aqueous Micro-Foams

Abstract

Experimental investigations of Marangoni flow in micro-foams have faced challenges due to the inherent difficulties in detecting and measuring this flow. The Marangoni flow manifests as small spots within the lamellae films, which makes it hard to accurately analyze. Hence, to elucidate Marangoni flow characteristics, this study introduces and investigates comprehensive three-dimensional models of flow in microscale foams. The geometric models contained Plateau Borders (PB), nodes, and films. The recirculating Marangoni flow was simulated and studied for different interfacial mobilities. Inside the foams, the Marangoni flow velocities were at the same scale with the PB flow velocity for mobile interfaces. However, for a more rigid interface, the magnitude of the Marangoni flow was considerably less than that of the PB owing to the combined effect of high surface hydraulic resistance on the Marangoni flows and nature of the Marangoni flow as a surface-only flow type. Furthermore, the effect of the film thickness on the Marangoni flow was analyzed. Thicker films have a stronger effect in reducing the Marangoni flow than PB flow. This is due to the higher ratio of gravity body force to the Marangoni-driven surface force for thicker films. Finally, the combined effect of the liquid–air interfacial mobility and film thickness on the Marangoni velocity was studied.