Experimental study of strong pressure pulses radiated by oscillating spark bubbles

Pressure pulses radiated by spark generated bubbles are examined with an aim to determine whether shock fronts developed in them. A rise time of a leading edge of the pressure pulse is used as a suitable indicator of the shock front presence. Only pressure pulses radiated by bubbles having maximum radii of approximately 45 mm are considered. It has been found that for moderate intensities of bubble oscillations (pzp1 < 90) no shock fronts developed in the pressure pulses. However, if the bubbles oscillate with a sufficiently high intensity (pzp1 > 90) the rise time becomes as short as 1 ?s, indicating that the limits given by the hydrophone are reached. The procedure used in this study does not allow determining if the pressure pulse deformation is due to finite amplitude wave effects or due to shock front presence. To resolve this question new experiments are being prepared.