Resonant oscillations of air bubbles driven by a time varying electric field

Summary form only given. We investigate the effects of a time varying electric field on air bubbles submerged in water. For a sufficiently strong applied field, a large electrical stress, arising from the dielectric nature of water, can violently deform the volume and shape of the submerged bubble. This deformation may drastically alter the internal pressure and polarization of the bubble, potentially lowering the electrical breakdown voltage within its volume. Such a result would have a broad impact on the viability of liquid plasma based technologies, which tend to suffer from prohibitively high voltage requirements.The linear response of a bubble driven by a uniform D.C. field has been studied extensively, but few experimental investigations exist for a time varying field, which may yield a host of new interesting phenomena, including field induced resonant oscillations and wave growth on the bubble surface. Bubbles with radius 0.5-3 mm are trapped in the node of a 40 kHz underwater acoustic field while either A.C. or pulsed voltages of 10-20 kV are applied across their volume. Bubble response is captured using a high speed camera (10,000 frames per second) and a high sensitivity hydrophone, and mapped as a function of bubble size, field frequency, and field strength. Voltage and current traces are obtained with a high voltage probe and Pearson coil respectively.