HYDRODYNAMIC PROCESSES IN DYNAMIC BUBBLE PRESSURE EXPERIMENTS PART 3 - OSCILLATORY AND APERIODIC MODES OF PRESSURE VARIATION IN THE CAPILLARY

The effect of the process of bubble separation from the capillary tip on the hydrodynamic flow in maximum bubble pressure experiments is ana lysed. The existence of both aperiodic and oscillatory modes in the ga s pressure distribution along a narrow capillary is predicted. The equ ations are derived which define the conditions for the transitions bet ween the modes and describe the relationship between the pressure osci llation frequency and amplitude. The effect of fast pressure oscillati ons on a liquid meniscus after a bubble detachment is discussed on a q ualitative basis. The possibility of a qualitatively different mechani sm for overcoming the maximum bubble pressure is considered. Model exp eriments with capillaries of different lengths and diameters are perfo rmed for pure water. The results of these experiments agree with the t heoretical predictions. (C) 1998 Elsevier Science B.V. All rights rese rved.