Load characteristics of large-scale underwater explosion bubble pair near a wall using the smoothed particle hydrodynamics method

The two-bubble coupling dynamics near a boundary is always complicated due to the inter-bubble interaction and the boundary effect, and relevant research is still very limited. Benefit from the Lagrangian properties, smoothed particle hydrodynamics (SPH) has distinct superiority in handling the bubble fusion, tearing, and fragmentation. Using the SPH method, this work numerically simulates the nonlinear interactions of two large-scale underwater explosion bubbles near an upper wall and investigates the shock characteristics of the bubble pair. Given the superiority of Riemann solvers to handle discontinuities, an accurate multiphase Riemann-SPH method with the monotone upwind-centered scheme for conservation laws reconstruction is adopted. Through this method, the experiment of an out-of-phase bubble pair interaction near the wall is first modeled, and the reliability of the present model is proven by the comparison of the experimental data with the SPH results. Subsequently, the influence of several key factors, including the distance between the bubble pair (γbb), the distance from the bubble to the wall (γbw), and the phase difference of two bubbles (θ), on the dynamic bubble behavior, the jet mode, and the load characteristics are systematically discussed. In this study, four bubble jet patterns are discovered, namely, “merging-upward jet,” “merging-downward jet,” “upward-downward jet,” and “upward-counter jet.” Compared to the cases of θ = 0 and θ = 0.5, the bubble pair under θ = −0.5 always exerts a stronger impact on the wall regarding the pressure peak and impulse, with the upward-downward jet mode posing the greatest load to the wall.