When gas-filled microbubbles flow into an ultrasonic wavefield, the microbu
bbles 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 for
ce and the microbubble trapping by ultrasonic-wave primary Bjerknes force a
re considered. The dynamics of microbubbles inside an ultrasonic wavefield
are observed using two different types of gas-filled microbubbles with corr
esponding mean diameters of 20 mum and 1.3 mum.