Quasi-static bubble formation on submerged orifices

The static formation of air bubbles emanating from a submerged orifice was analyzed based on the principles of force balance. The analysis was corroborated by experiments using a shadow imaging technique. The influence of the Young contact angle of the three material components was investigated by identifying two modes of formation, corresponding to bubble formation at the orifice rim and spreading of the bubble base on the horizontal surface around the bubble. The characteristics of the formation process such as shape, height and volume of the bubble and the non-dimensional pressure difference at the orifice are given for both modes up to the critical equilibrium, defined by the maximum bubble volume, at which the bubble releases dynamically.