RESEARCH ON DYNAMICS OF DOUBLE BUBBLES IN ELASTIC CAVITY DRIVEN BY ULTRASOUND

In practical applications of ultrasonic cavitation, bubbles may be confined within a small enclosed cavity. Under such conditions, the surrounding liquid cannot be treated as an unbounded medium, and the dynamic behaviors of the bubbles are influenced by the cavity walls. This study investigates the dynamics of two bubbles in a spherical elastic cavity driven by ultrasound based on numerical simulations. The effects of driving sound pressure amplitude and frequency, outer radius and initial inner radius of cavity, initial bubble positions and bubble ambient radii on the translations and pulsations double bubbles are systematically examined and analyzed. The results indicate that increasing the driving sound pressure amplitude will enhance the secondary Bjerknes force between double bubbles, therefore accelerates the translational motions of bubbles. Additionally, when the driving frequency is low or within certain optimal ranges, the bubbles also exhibit fast translational velocities. These findings suggest that the manipulation of movable bubbles within an elastic cavity can be achieved by adjusting the driving ultrasound. Analysis of bubble dynamics under varying cavity dimensions reveals that increasing the outer radius of the cavity affects bubble velocities in a complex manner, but this impact diminishes once the outer radius exceeds a certain threshold. Besides, increasing the initial inner radius of the cavity firstly enhances the bubble translation speed but subsequently slows it down in general. Furthermore, the initial positions and ambient radii of the bubbles significantly influence their motions. Bubbles that are symmetrically positioned relative to the cavity center and have identical ambient radii exhibit fast approach velocities. It is due to that under this condition, secondary Bjerknes force between bubbles is apparently significant. This study provides a theoretical foundation for precisely controlling motions of bubbles in closed elastic cavity with ultrasound, and is conducive to promoting the practical application and popularization of ultrasonic cavitation.