Sacrificial confining structures for attenuation of underwater implosion-induced pressure spikes

This paper develops and validates a fully coupled fluid–structure interaction (FSI) simulation framework to predict the underwater implosion response of cylindrical shells enclosed within sacrificial external shrouds. The simulations capture the complex nonlinear coupling between fluid motion and structural deformation, demonstrating strong agreement with experimental pressure–time histories, peak pressures, deformation profiles, and event timing. Shrouded configurations consistently mitigated implosion pressure spike severity by attenuating the initial underpressure phase and reducing the amplitude of subsequent positive pressure spikes by up to 90%, with approximately 60% reduction in early underpressure. These mitigation effects were attributed to the shroud’s influence on the fluid field, which delayed the progression of collapse, redistributed energy, and smoothed pressure evolution through dissipation mechanisms. The framework also replicated observed deformation patterns, particularly the delayed and slower radial inward motion in shrouded cases, while providing insight into internal structural behavior not visible in physical tests. High-resolution three-dimensional visualizations revealed localized fluid accelerations, vortex structures, and transient pressure gradients, including inward-directed fluid jets through shroud perforations that generated low-pressure zones and confirmed strong pressure–velocity coupling. These features highlight the simulation’s ability to resolve complex, transient FSI behavior beyond the reach of experiments. Overall, the framework offers a predictive, high-fidelity tool for evaluating implosion mitigation strategies using sacrificial encasements, supporting the development of safer, more resilient submerged systems across a range of geometries, materials, and operating conditions.