2018 Volume 32 Issue 1 Pages 80-88
For a bubble approaching a flat plate, the Marangoni effect on the drainage suppression of a liquid film and the wall repulsive force are numerically studied. We investigated the driving force of gas-liquid interface. We carry out direct numerical simulation using a boundary-fitted grid conforming to the interfacial deformation. Spatiotemporal development of Marangoni stress and liquid film drainage are quantitatively investigated for various Marangoni numbers. The simulated results reveal that the repulsive force on the wall increases with increasing of the Marangoni number, indicating the suppression of the bubble-wall coalescence owing to the surfactant-driven Marangoni effect. For the sufficiently high Marangoni number, the repulsive force reaches at plateau. Such a saturated force is attributed to an excessive addition of the surfactant, which is likely to make the gas-liquid interface non-slip. The inertial force due to the flow in the liquid film and the Marangoni effect are significant for the deformation of the gas-liquid interface to the dimple shape. The dominant driving force of the interface deformation is not the Laplace pressure but the flow pressure.
