Number density of bubbles under ultrasonic horn measured from stroboscopic images

Abstract

Although image measurement is essential in the analysis of acoustic cavitation bubbles, it is impossible to determine the position of the bubble along the optical axis of the imaging system from the images. Thus, the number density of the bubbles cannot be measured from the image. This paper proposed a method to determine bubbles’ positions along the optical axis using the bubble image brightness. The relationship among the bubble position along the optical axis, the bubble diameter, and the bubble image brightness is clarified using the bubble in the single bubble system. A measurement method of the bubble number density based on this relationship is established. Using this method, the time-averaged spatial distribution of bubble number density under ultrasonic horn is revealed.