Bubble departure from cavities

An experimental investigation has been undertaken on the growth and departu re of bubbles from artificial nucleation sites. Bubbles were produced by ga s diffusion from a carbonated water solution on 0.6, 1.48 and 2.08 mm diame ter cavities in a horizontal plate. The departure size and growth time of t he bubbles produced in the experiments could not be accurately predicted us ing a force balance analysis and the assumed initial growth condition of a bubble nucleus. A numerical simulation was developed to solve these paramet ers. This showed that the bubble grows very rapidly after a neck forms, Exp eriments in which the bubbles grew to a height which was several times the cavity diameter revealed that departure occurred during the rapid growth. T he numerical simulation also predicted accurately the volume of the residua l bubble inside the cavity and the time until the succeeding bubble appeare d above the cavity opening. The effect of surface tension on the bubble dep arture diameter was found to aid departure by the formation of a bubble nec k rather than resisting departure as an adherent force that attached the bu bble to the surface, (C) 2001 Elsevier Science Ltd. All rights reserved.