Probing multibubble cavitation fields under different experimental conditions.

The understanding and control of the spatial distribution and the type of cavitation bubbles are crucial for the efficient use of cavitation bubbles in these applications. A semi-quantitative comparison of the spatial distribution of the cavitation activity has been carried out using the images of sonoluminescence, sonophotoluminescence, and sonochemiluminescence at various ultrasound frequencies and at various acoustic amplitudes. The sonochemically active cavitation zones have been found to be much larger than the sonoluminescence cavitation zones. Also, the sonochemically active bubbles have been observed at relatively lower acoustic amplitudes than that required for sonoluminescence bubbles to appear. The acoustic power required for the observation of the initial cavitation bubbles increases with an increase in the ultrasound frequency. These observations highlight the complexities involved in acoustic cavitation. Multibubble sonoluminescence-based experimental technique has also been used for the detection and the control of type of cavitation at low and high ultrasound frequencies.