Underwater explosions (UNDEXs) represent a significant threat to marine vessels, motivating the analysis of their resulting dynamic response and damage. Conducting experimental investigations on full-scale ships, while being the most consistent strategy, is not always feasible due to obvious economic constraints. Consequently, researchers usually rely on scaled models designed to replicate real-world scenarios in laboratory environments. Despite the widespread use of this approach, the scaling laws between prototypes and models are not yet satisfactory due to the complexity of the UNDEX phenomena and the variability in boundary conditions. To address this aspect, the present study focuses on the scalability of a simplified vessel, termed a simplified hull girder (SHG). This study is conducted numerically and originates from a comparison with experiments available in the literature. This work has two objectives: firstly, it provides a practical approach to simulating the behaviour of complex architectures that undergo severe deformation due to blast loads, a critical challenge for state-of-the-art computational methods. Secondly, this work aims to assess the reliability of the scaling laws commonly used in UNDEX scenarios and to highlight the importance of strain-rate effects.

This paper develops a numerical methodology to evaluate the influence of seabed properties on the acceleration response of resiliently mounted equipment subjected to underwater explosions (UNDEX). The approach is based on a coupled acoustic–structural analysis (CASA), implemented in ABAQUS CAE, to simulate the transient response of a foundation–resilient–mass system installed on a patrol vessel. The study considers multiple seabed configurations, including rigid, rock, sand, muddy, and muddy-over-sand conditions, with the objective of quantifying how reflected shock waves modify the dynamic loading environment. A far-field non-contact UNDEX scenario is modelled, accounting for both incident and seabed-reflected pressure waves. The response of the mounted equipment is evaluated in terms of transmitted accelerations at different installation locations along the hull. The results demonstrate that seabed characteristics play a dominant role in shaping the vibration response. Rigid and rock seabeds induce significant amplification of acceleration levels, reaching values up to twice those of the free-field condition, whereas softer seabeds lead to a marked attenuation effect. The proposed framework enables a systematic assessment of seabed-induced effects on onboard equipment and provides quantitative support for the design and placement of resilient mounting systems in naval applications.

This research explores the application of model order reduction (MOR) techniques for blast wave propagation and mitigation. Blast waves, with their rapid pressure changes and highly nonlinear behavior, pose significant challenges for predictive modeling. MOR, a mathematical dimensionality reduction technique, offers a solution by simplifying the complexity of large-scale dynamical systems described by differential equations. These systems can be computationally expensive to solve through conventional numerical schemes. MOR creates a reduced-order model (ROM) that retains the essential features and behavior of the original system but with fewer degrees of freedom. Unlike traditional high-fidelity simulations that are accurate but computationally expensive, MOR allows for multi-query scenarios. This approach significantly reduces computational demands without sacrificing accuracy, making it a valuable tool for engineers and professionals in safety engineering and defense planning. The study also enables the creation of reduced-order models based on high-fidelity simulations of blast wave interactions with structures, promoting their broader adoption in safety planning and structural assessments.