Study on the dynamics of underwater explosion bubbles near elastic–plastic cylindrical shells

The dynamic behavior of underwater explosion bubbles is largely dependent on their boundary conditions. The pulsation behavior of bubbles near free surfaces or rigid boundaries has been extensively studied, while the rich mechanical mechanisms behind the pulsation behavior and jet development of bubbles near elastic–plastic boundaries have not yet been systematically investigated. In this paper, underwater explosion bubbles are first generated using experimental methods, and their pulsation behaviors under different conditions are recorded using high-speed photography. Subsequently, the arbitrary Lagrange–Euler method and the Cowper–Symonds material model are employed to accurately simulate the pulsation process of the bubbles and the dynamic response of the structures. It is shown that the pulsation behavior of bubbles near elastic–plastic cylindrical shells has been categorized into six distinct types based on varying dimensionless distance parameter γL. With an increase in γL from 0.01 to 3.20, the maximum bubble dimensionless volume V* increased from 0.75 to 0.93, while the pulsation dimensionless period T* increased from 0.78 to 1.00. Furthermore, it has been demonstrated that jets are generated by bubbles in proximity to an elastic–plastic cylindrical shell, and these jets propel away from the shell. During the developmental phase of these jets, two broader jets with a dimensionless speed v* of 0.82 have been observed to converge and form a narrower jet with a dimensionless speed v* of 5.45, resulting in an escalation of energy within the narrower jet. This phenomenon elucidates the mechanical mechanism underlying the rapid acceleration of bubble jet velocity to tens of meters per second. Additionally, the effects of buoyancy parameters and boundary conditions on both bubble pulsation and jet velocity have been examined, providing valuable insights for investigations into the pulsation of underwater explosion bubbles in the vicinity of cylindrical shells.