Study on the bubble motion control by ultrasonic wave

The behavior of a bubble in an acoustic wave field was investigated experimentally and analytically. Ultrasonic transducers were used to set up acoustic standing waves to control the bubble motion and position in a liquid column under normal and reduced gravity conditions. A single ultrasonic transducer was first used in a liquid column with a free surface to hold a bubble between a node and a loop under normal gravity. The motion and equilibrium position of the bubble were predicted numerically by solving the Rayleigh-Plesset equation and bubble motion equation in the translational direction. By using a pair of ultrasonic transducers and varying the node and loop positions in the acoustic standing wave field, the equilibrium bubble position could be changed at will. Finally, the applicability of the ultrasonic bubble control technique to the reduced-gravity condition was confirmed by conducting experiments aboard NASA's KC-135 aircraft flying parabolic trajectories. The equilibrium position of the bubble was confirmed to be at the node of the acoustic pressure field in the absence of gravity. (C) 2002 Elsevier Science Inc. All rights reserved.