Transferred jet of a near-wall bubble induced by another in-phase bubble: A numerical study

The non-spherical collapse of a cavitation bubble near a rigid wall generates a high-speed liquid jet directed toward the surface, which has significant implications for fluid–solid interactions. The jet's direction can be controlled by introducing an in-phase bubble above the near-wall bubble. In this study, numerical simulations are employed with the compressibleInterFoam solver within the OpenFOAM framework to investigate the parametric conditions and formation mechanisms of transferred jets of near-wall bubbles that are directed away from the rigid wall. Transferred jets are classified as thin jets or regular jets based on the presence or absence of neck formation during near-wall bubble contraction. Thin jets, which develop a neck through curvature reversal at the bubble equator, exhibit significantly higher velocities owing to the high-pressure region generated by flow focusing. In contrast, regular jets, which do not form a neck, demonstrate relatively low jet velocities. Furthermore, we investigate the time integral of the forces acting on the surface of the near-wall bubble during its formation and collapse, i.e., the Kelvin impulse. By applying the momentum theorem, we establish a correlation between the Kelvin impulse and the transferred jet velocity, deriving a scaling law: Ujet*∼η/ζ, where ζ(ζ=(Rc/Rmax)3) is the dimensionless volume and η(η=1/γ22−1/(2γ1)2−1/(2γ1+γ2)2) is the distance factor. This scaling law is verified using numerical simulations. This study's findings enhance our understanding of the dynamics of non-spherical cavitation bubbles under the combined influence of multiple factors, which is of great importance.