Dynamical behaviors of cavitation bubble under acoustic standing wave field

Abstract

Considering the compressibility of liquid, we investigate the dynamical behaviors of a cavitation bubble in an acoustic standing wave field by regarding water as a work medium. The motion state of the cavitation bubble at each position is simulated in the standing wave field, the influences of the primary Bjerknes force on the motion direction of the cavitation bubble at each position are also simulated with different relevant parameters. The results show that in the standing wave field, the motion state of the cavitation bubble is divided into three aspects: the cavitation bubble is of steady-state cavitation near the pressure antinode; the cavitation bubble is of transient cavitation at the position deviating from the pressure antinode; in the vicinity of the acoustic pressure node, the cavitation bubble has been moving to the acoustic pressure node due to the primary Bjerknes force, so the phenomenon of cavitation does not occur. In the standing wave field, when the acoustic pressure amplitude exceeds its upper limit, the primary Bjerknes force makes the cavitation bubble move to pressure node, it is not conducive to the occurrence of cavitation. When the acoustic frequency is smaller than the bubble resonant frequency, the primary Bjerknes force will make more cavitation bubbles move to acoustic pressure node with the increase of the acoustic pressure, so this is not conducive to the occurrence of cavitation. Especially, the height of the liquid level should not be a quarter of acoustic wavelength. For a given acoustic frequency, the larger the initial radius of cavitation bubble, the more favorable the occurrence of cavitation is. But when the initial radius of cavitation bubble exceeds the resonant radius of acoustic frequency, the bubble will be pushed to pressure node. That is to say, the acoustic pressure amplitude, the acoustic frequency, and the initial radius of cavitation bubble each have a corresponding limit. Moreover, the lower limit is conducive to the occurrence of the phenomenon of cavitation.