A Study on Measurement Technique for Amount of Generated Acoustic Cavitation -Investigation of Broadband Integrated Voltage by Comparing with Sound Pressure and Sonochemical Luminescence-

We have been studying a quantitative technique for measuring the amount of generated acoustic cavitation. Cavitation plays a key role in several fields. Therefore, a precise technique for measuring the amount of generated cavitation is required in order to attain a balance between safety and effectiveness. Hence, we have been investigating a measurement technique based on broadband integrated voltage (BIV). BIV is a value integrated from the high-frequency components of broadband noise in frequency spectra of a signal received from a cavitation sensor. Broadband noise is changed by the production of cavitation bubbles. In previous studies, we reported that BIV is a parameter which reflects the energy of broadband noise generated by cavitation. In this study, the spatial distribution of cavitation generation in a water vessel was measured in terms of BIV. As a result, the respective peak positions of BIV and the acoustic pressure differed in the horizontal direction. Although the acoustic pressure showed a peak at the center position, BIV was low at the same position, and the peaks of BIV were found on both sides of the acoustic pressure peak. The reason for this was the absence of cavitation bubbles at the center due to the flow of cavitation bubbles towards the water surface induced by acoustic streaming. Also, BIV was higher around the water surface in the vertical direction. The results revealed a correlation with the emission distribution of sonochemical luminescence. As a consequence, BIV has the potential to become an accurate tool for measuring the spatial distribution of cavitation generation in a water vessel.