2020 Volume 34 Issue 1 Pages 222-230
The Marangoni effect on the repulsive forces on approaching interfaces, which is likely to suppress bubble coalescence due to the surfactant addition, is numerically studied. We consider a bubble-wall system and a bubble-bubble one. We perform direct numerical simulation using a boundary-fitted grid conforming to the interfacial deformation. Spatiotemporal development of the Marangoni stress and liquid film drainage are investigated for various Reynolds and Marangoni numbers. The change in the gas-liquid interface shape is categorized into three types: continuation of pimple, continuation of dimple, and repetition of pimple and dimple. When a dimple forms, the Marangoni stress induced by interface deformation suppresses the pressure drop along the film and therefore the displacement at dimple head, accounting for the mechanism of suppressing bubble coalescence.
