Study on underwater explosion bubble dynamics in a finite open domain

Under damaged, gas-leakage, or secondary-explosion conditions, the water in liquid-containing structures, such as liquid cabins and oil tanks, may change from a liquid phase to a gas–liquid two-phase environment with dispersed microbubbles. This change can affect underwater explosion bubble evolution and bottom load transmission. To reveal the influence of an open aerated background on explosion-bubble dynamics and structural response, a transparent cylindrical water-tank experimental system was established. A 400 V high-voltage spark discharge was used to simulate the underwater explosion process. The water depth was fixed at H = 175 mm, with five relative aeration levels from non-aerated to maximum. Experiments and numerical simulations were combined to analyze bubble evolution and bottom dynamic response under different aeration levels. Results show that the maximum equivalent radius varies non-monotonically with aeration level, while the overall variation remains limited. However, it weakens the integrity of the main bubble in later cycles. The later-stage bubble evolution becomes dominated by local residual structures earlier. The maximum equivalent radius varies non-monotonically with aeration level, but the overall fluctuation is limited, from 18.65 to 21.30 mm. The bottom load response also shows non-monotonic characteristics. Under the moderate aeration condition (0.50 Q max ), the positive pressure peak reaches the maximum of 0.049 MPa. Higher and maximum aeration levels reduce the load transmission efficiency to the bottom plate. These results show that background aeration is associated with coupled, non-monotonic changes in bubble pulsation, local pressure response, and bottom-plate vibration in the finite open domain. The findings can provide a reference for blast safety assessment of liquid-containing structures under leakage or aeration conditions.