Dynamic characteristics of large scale spark bubbles close to different boundaries

Experiments on the pulsation of the high-voltage electrical-spark bubbles near different boundaries are conducted by means of high-speed photography. Some intriguing details are observed clearly, such as the formation of the jet (especially the contact jet formed when a bubble is quite close to the rigid boundary) and bubble splitting. The variation of the maximum radius of the bubble, bubble period, jet tip velocity, and bubble center migration is investigated with the presence of different boundaries. In the study of the bubble period, two fitting curves are obtained from the data by the author and previous references; one is for the bubble generated beneath the free surface and the other is for the bubble generated above the rigid boundary. In the study of the maximum jet tip velocity, a possible trend line is proposed to describe the variation of the jet tip velocity with γb (the non-dimensional standoff distance from the bubble center to the rigid boundary). Finally, the critical value of γb is studied, at which the migration of the bubble center is inverted.