Dynamics of single bubble between a moving spherical boundary and a plate structure

Boundary conditions significantly influence the near-field dynamics of bubbles. This study employs numerical simulations to investigate the coupling characteristics of high-pressure bubbles near solid boundaries and moving spherical boundaries. It focuses on the effects of the sinking velocity of the sphere and the initial bubble-boundary distance on bubble evolution and loading characteristics. The results indicate that an increase in the sphere's sinking velocity or a decrease in the initial bubble-boundary distance leads to bubble tearing during the collapse process. This generates high-speed water jets directed either toward the bubble center or the boundary, significantly reducing the kinetic energy of the sphere. The shock waves and water jets caused by bubble tearing temporarily impede the sphere's motion, while the lagging flow induced by bubble expansion and contraction has a relatively minor impact. As the initial bubble-boundary distance increases, the bubble tearing phenomenon gradually weakens and may even disappear. This attenuation is attributed to the suppression of the Bjerknes effect by the boundary, which reduces the tendency of the bubble to migrate toward the boundary. Furthermore, the intensity of the tearing phenomenon significantly affects the pressure distribution near the bubble region around the sphere. Strong tearing induces a double-peaked pressure profile, while weak tearing results in a single-peaked profile primarily dominated by bubble collapse. This study reveals the critical influence of bubble-boundary interactions on sphere motion and pressure distribution, providing valuable insights for engineering design and applications in related fields.