Effects of Bjerknes Forces on Gas-Filled Microbubble Trapping by Ultrasonic Waves.

When gas-filled microbubbles flow into an ultrasonic wavefield, the microbubbles interact with the ultrasonic waves and aggregate into large masses of bubbles. Those bubbles are trapped against the surrounding liquid flow by ultrasonic waves. In this paper, the microbubble trapping by an ultrasonic wavefield are discussed both from theoretical and experimental viewpoints. Both, the microbubble aggregation by ultrasonic-wave secondary Bjerknes force and the microbubble trapping by ultrasonic-wave primary Bjerknes force are considered. The dynamics of microbubbles inside an ultrasonic wavefield are observed using two different types of gas-filled microbubbles with corresponding mean diameters of 20 µm and 1.3 µm.