Dynamic Behavior and Interaction Mechanisms of Double Bubbles near a Rigid Wall

In the real underwater explosion environments, the diversity of boundary conditions has a significant influence on bubble dynamics. In particular, the bubbles near rigid wall experience intensified collapse due to wall effects, leading to the formation of high-speed jets that impose stronger impacts on surrounding structures. The evolution of a double-bubble system near a rigid wall in underwater explosions is simulated using the coupled Eulerian-Lagrangian (CEL) algorithm, considering both parallel and perpendicular configurations. The validity of the model is verified by comparison with the experimental data from single-bubble cases. The results show that the dimensionless bubble-wall gap parameter α and the inter-bubble spacing parameter θ have a crucial influence on bubble morphology and jet behavior. The bubbles tend to be adhered to the wall and collapse against it when α is small, and they are no longer adhered to the wall for α > 0.5. As θ decreases, the bubbles are more likely to merge and generate strong jets, with a critical merging threshold being approximately θ = 0.6. Further analysis reveals that, the jet velocity after bubble merging is increased by 30≈ 50 under the parallel wall configuration for θ = 0.4. In contrast, The larger inter-bubble distances lead to higher jet velocities in the perpendicular wall configuration for θ < 1. The findings of this study contribute to a better understanding and prediction of bubble behavior, thereby improving the assessment of potential structural damage risks. This has important implications for designing the protective measures to mitigate the destructive effects of underwater explosions on structures.