ULTRASOUND FOCUSING IN SPHERICAL BUBBLE CLOUD

HIFU (High Intensity Focused Ultrasound) applications have attracted much attention recently because they are less invasive. However, the behavior of acoustic cavitation caused by high pressure amplitude at the focal region has not been clarified. In this study, it is assumed that the acoustic cavitation forms a spherical bubble cloud which consists of many micro bubbles, and ultrasound focusing in the cloud is investigated numerically. The compressibility of liquid, the evaporation and condensation of liquid at the bubble wall, heat transfer through the bubble wall are considered in the simulation. Initial cloud radius is equal to 0.5 mm, bubble radius is 1 µm, void fraction is 0.1 %, and the frequency of ultrasound extends from 5 kHz t