Dynamics of bubble collapse near rigid boundaries with different curvatures

Understanding the bubble dynamics near a curved boundary is crucial for evaluating the cavitation impacts, as well as advancing the beneficial use of cavitation in real-world applications such as biofilm cleaning and environmental treatment. This study employs a high-fidelity multiphase flow model to analyze the dynamics of bubble collapse near rigid curves of varying curvatures. The numerical model employs a second-order-accurate solver within a two-dimensional axisymmetric coordinate system to solve the 5-equation model (Kapila's model). After being validated by three bubble collapse experiments, the model is applied to examine the bubble morphology and jet characteristics near different curved boundaries at varying standoff distances. The results reveal that as curvature increases, the jet momentum decreases due to the decrease in the jet volume, while the bubble jet velocity gradually increases in scenarios of downward jetting. Smaller standoff distances lead to bubbles with higher transverse to longitudinal ratio, insufficient longitudinal contraction, and reduced jet velocity. Finally, we summarize the changes in bubble morphology, jet velocity, jet momentum, and peak pressure with curvatures and standoff distances and fit the boundary for different bubble collapse patterns. This study establishes a clear correlation between bubble jet momentum and bubble type, finding that downward jetting can enhance jet momentum.