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 analysed. The existence of both aperiodic and oscillatory modes in the gas pressure distribution along a narrow capillary is predicted. The equations are derived which define the conditions for the transitions between the modes and describe the relationship between the pressure oscillation frequency and amplitude. The effect of fast pressure oscillations on a liquid meniscus after a bubble detachment is discussed on a qualitative basis. The possibility of a qualitatively different mechanism for overcoming the maximum bubble pressure is considered. Model experiments with capillaries of different lengths and diameters are performed for pure water. The results of these experiments agree with the theoretical predictions. (C) 1998 Elsevier Science B.V. All rights reserved.