Thickness of the liquid film formed by a growing bubble in a narrow gap between two horizontal plates

An experiment was performed to measure the thickness of the liquid film formed by a growing flattened bubble in a narrow gap whose width ranged from 0.1 to 0.4 mm. High-speed photographs were also taken to measure the bubble growth velocity in order to validate an investigation into the mechanism of the liquid film formation, From the experimental results, it was clarified that the liquid film thickness was controlled by the viscous boundary layer thickness or the capillary number according to whether the Bond number was greater or smaller than 2.