Study on the evolution of near-wall jet induced by serial collapse of twin bubbles and its load amplification characteristics

Bubbles are commonly found in both natural environments and engineering applications. Since they rarely exist in isolation, more complex jet phenomena can emerge due to multi-bubble interactions. In particular, the collapse of two bubbles near a rigid wall generates high-speed jet loads directed toward the wall. These jet characteristics can be regulated by controlling bubble interactions, and the jet enhancement effect resulting from two-bubble coupling holds great promise for practical applications. This study investigates the variation in jet loads from near-wall double bubbles using both underwater spark experiments and numerical simulations. A numerical model was developed to simulate two-bubble interactions near a rigid boundary, accurately capturing the full dynamic process of bubble generation, expansion, collapse, and jet formation. It also predicts the wall loads induced during bubble coupling and collapse. The simulation results closely match the experimental observations of bubble dynamics and wall pressure, confirming the model's accuracy. On this basis, the effects of bubble–wall distance (γw), bubble–bubble distance (γb), and detonation time difference (τ) on bubble-induced loads were further explored. The results reveal that the spatial arrangement and timing of the explosions significantly influence bubble motion, jet formation, and wall pressure. Under optimal conditions (γw=1.2, γb=1, τ=1), a coordinated collapse mechanism substantially enhances the peak pressure. Additionally, a global sensitivity analysis based on the Kriging surrogate model and Sobol method was conducted to quantify the influence of spatial arrangement and initiation timing. The results indicate that the bubble–wall distance γw has the greatest influence, followed by the bubble–bubble distance γb, while the detonation time difference τ has the least effect.