PRELIMINARY INVESTIGATION OF CYLINDRICAL BUBBLE MODELS FOR CONFINED CAVITY INDUCED BY HYDRODYNAMIC RAM

Abstract

Hydrodynamic ram (HRAM) phenomena, triggered by high-velocity projectiles impacting water-filled containers, induce confined cavities whose evolution is strongly influenced by container constraints. This study integrates experimental data, numerical simulations using LS-DYNA’s ALE method, and theoretical models—including a model developed by the authors (Ji model) and both incompressible and compressible cylindrical bubble models— to investigate cavity evolution. While simulations accurately capture the initial expansion phase, they underestimate contraction dynamics. Theoretical analysis reveals that, under a specific energy condition, the Ji and incompressible cylindrical bubble models yield equivalent predictions, and the compressible model shows superior agreement with experiments compared to its incompressible counterpart. These results emphasize the critical role of initial conditions and pressure parameters in modeling confined cavities and provide quantitative insights into the asymmetrical expansion and contraction phases observed experimentally.