Abstract
The cavitation zone generated by a pulsed ultrasound field absorbs less acoustic energy than that generated by continuous irradiation, i.e. an acoustic clarification effect is shown to exist in a pulsed ultrasound field. The pulse modulation of an acoustic field decreases the volume concentration of bubbles in the cavitation zone. The acoustic power available for each transient bubble is increased and the energy stored by the bubbles during the expansion phase increases too. The decrease of the bubble density decreases the intensity of their interactions and provides the possibility of preserving their spherical shape down to deeper stages of collapse and so the energy concentration in the implosion is increased. This is confirmed by the increase of the sonoluminescence intensity in the pulsed ultrasound field.