• Response of an air-cushion vehicle skirt to underwater explosion is examined. • Coupled hydrodynamic and structural skirt behaviours are characterised. • Detonation distance deterministically affects plough-in occurrence. The skirts of air-cushion vehicles (ACVs) are subjected to highly nonlinear loads, which can compromise their stability and strength when exposed to underwater explosions. However, only a few studies have investigated the scenario of ACV skirts subjected to slamming loads or treated them as rigid bodies. Therefore, the aim of this study was to examine the hydrodynamic and structural responses of an ACV skirt under underwater explosion conditions. A numerical model was developed by coupling the control volume approach with the arbitrary Lagrangian–Eulerian method to examine these responses and was validated through a benchmark experiment. The results show that the occurrence of the plough-in phenomenon is governed by the detonation distance rather than charge weight. Given the complexity of the load, deformation, and maximum principal stress profiles, the corresponding numerical results should be used for evaluating the stability and strength of ACVs without simplification. The results of this study offer valuable guidelines for ACV design and navigation.

Investigation on bubble dynamics near curved plates with a hole subjected to underwater explosion

A compressible multi-fluid scheme based on upwind space-time Conservation Element and Solution Element method and its application to underwater detonation jet

Very-low-frequency (VLF) underwater acoustic monitoring is a primary means for monitoring specialized underwater explosions. In view of the limited availability of dedicated off-the-shelf VLF underwater acoustic monitoring equipment and related technologies, this study investigates embedded VLF underwater acoustic acquisition techniques and develops an embedded acquisition device for VLF signals generated by specialized underwater explosions. The device adopts a modular architecture that separates the sensor from the controller, and integrates a low-noise transimpedance amplification and differential conditioning circuit, a high-resolution ADS1285 analog-to-digital converter, an STM32F429 control core, and an eMMC-based storage system. Multi-node time consistency is achieved through GNSS timing combined with a PPS synchronization mechanism, while cyclic recording and plug-and-play data export are implemented using the FATFS file system and USB MSC mode. In underwater explosion experiments, the device successfully recorded the initial shock-wave arrival, bubble pulsation signals, and long-range VLF underwater acoustic signals, thereby demonstrating the capability of the system for low-noise acquisition, reliable time synchronization, and long-term autonomous monitoring. The results indicate that the device can provide long-term stable acquisition and storage capabilities, meeting the engineering requirements of VLF underwater acoustic monitoring, explosion effect assessment, and underwater acoustic experiments, and offering key technical support for the development of VLF underwater acoustic monitoring equipment.

Abstract For a cylinder shell with a heavy frame, this paper analyses the pre-stress and deformation of the cylinder shaft under the action of static water pressure, the variation of shock wave pressure during the underwater explosion shock, and the shock response of the column shell structure under the effect of underwater blast load. Under fluid static pressure, the cylindrical shell with the frame ribs produces a certain amount of pre-stress and deformation, which is maximum at the junction of the framework ribs with the shell. During the underwater explosion, the shock wave pressure reaches a maximum of 8.31MPa when reflected at the point of impact of the cylindrical shell, then spreads along the shell to both ends. Under the influence of the deformation of the structure, a negative pressure area or a local high pressure area may occur, but the peak pressure of the shock waves gradually decreases. Under the action of the explosive load, the stress response of the cylindrical shell with the frame rib reaches a maximum value of 3.19 mm at the point of impact. Under the influence of the vibration of the shell, as time increases, the overall stress level of the cylindrical shell gradually tends to be uniform.

Dynamic evolution of wall pressure reflection coefficient and structural response characteristics of stiffened cylindrical shells subjected to underwater explosion loads

Motivated by applications to underwater explosions and volcanic eruptions, this paper considers the evolution of an initial pressure disturbance in the ocean, including effects due to the dynamic and static compression of water and the free surface. In order to solve the equations of motion of a linear compressible ocean, a special inner product is introduced, which allows us to apply self-adjoint operator theory. What results is a Hilbert space in which the acoustic–gravity modes are orthogonal in the generalised sense. This allows the time-domain evolution of the free surface and subsurface pressure field resulting from an initial disturbance to be calculated. Our simulations show initial radial propagation of the pressure pulse and subsequent reflection from the water's surface and the rigid ocean floor, eventually leading to horizontal propagation away from the source point. The solutions with and without the inclusion of the static compression are compared, and the effect of static compression is shown to be small but not negligible.

ABSTRACT To rapidly and accurately predict the dynamic response of cylindrical shells subjected to far-field underwater explosion (UNDEX), this paper proposes shock response and effective plastic strain prediction models based on the conditional deep convolutional generative adversarial network (cDCGAN). The conditional inputs include charge mass, stand-off distance, shell thickness and axial offset, enabling the prediction of peak displacement, peak acceleration, peak velocity and effective plastic strain. Compared with the deep neural network (DNN) models, the proposed models reduce the root mean square error (RMSE) by 67%, 56%, 56% and 67% for , respectively. Both prediction models achieve a coefficient of determination (R²) of 0.99. These results demonstrate that the proposed cDCGAN models provide superior prediction accuracy and rapid prediction capability.

ABSTRACT This study investigates the influence of aluminum powder content on the metal-driving capability and underwater explosion energy of HMX/RDX-based aluminized explosives. Through the preparation of polymer-bonded explosives (PBX) with aluminum content ranging from 0 to 15%, we conducted explosive-driven metal plate test and established JWL-Miller equation of state model incorporating aluminum secondary reactions for underwater explosion simulations using LS-DYNA. Experimental results demonstrated that increasing aluminum content in aluminized explosives resulted in a gradual decline in metal-driving capability, with an 8% reduction observed at 15% aluminum content. Underwater explosion simulations revealed that where the aluminum–oxygen ratio reached 0.15, the shock wave energy achieved 1.846 MJ/kg. Bubble energy showed positive correlation with aluminum content, when the 15% aluminum formulation exhibited prolonged bubble pulsation period (249.6 ms) and expanded bubble radius (107.4 cm). The research validates the effectiveness of the JWL-Miller equation in modeling non-ideal detonation characteristics of aluminized explosives, the impact of aluminum powder on explosive performance is not only reflected in its heat value but also in the timing of energy release. These findings provide critical theoretical guidance for the design of high-energy explosive systems requiring optimized performance.

The after flow induced by underwater explosion (UNDEX) plays an important role on the damage of ship structures, particularly in the near-field explosion. In this paper, the damage experiments of the hull girder were conducted at detonation distances of R/R0 = 6, 10, and 17, and a dynamic model was established to study the hull girder deformation considering the after flow. It shows that the numerical simulations have a good agreement with the experimental results of the hull girder deformation, which increases nonlinearly as the distance decreases due to the contribution of the after flow to the nonlinear growth of structural damage. It further demonstrates that the after flow has the most pronounced influence on the overall deformation at the closest distance (R/R0 = 6), with the after flow caused by bubble expansion playing a dominant role. Critically, due to the most contribution of the after flow to the total wall pressure and its continuous energy input, the after flow increases the maximum deformation by 79.3% compared with the numerical results that exclude it at this distance. Notably, the after flow caused by bubble expansion alone accounts for an additional 87.1% final deformation increment. This research provides significant insights into the structural damage mechanism caused by near-field UNDEX loads.

Simplified semi-analytical solutions for dynamic responses of composite cylinders subjected to far-field underwater explosions

A sharp-interface discontinuous Galerkin method for simulation of two-phase flow of real gases based on implicit shock tracking

Investigating protective mechanisms of polyurea reentrant lattice encasements on composite cylinders subjected to near-field underwater explosions

An improved SPH method for simulating near-surface underwater explosions in shallow water

Investigation on the underwater explosion coupled loads testing technique and deformation response of thin plate subjected to underwater shock and fragments

Fluid-structure interaction between shaped charge underwater explosion and sandwich composite panels

Study on Damage Characteristics of Cylindrical Shells Subjected to Underwater Explosion Shock Waves

Bubble loading characteristics in underwater explosions of CL-20-based aluminized explosives: a novel aluminum combustion energy release model

ABSTRACT Thin-walled ring-stiffened cylindrical structures are widely used in underwater vehicles for their high efficiency and robustness. This study establishes a coupled acoustic-structure model to simulate transient fluid-structure interaction under far-field UNDEX loading, considering both stationary and cruising conditions. Parametric analyses evaluate the effects of standoff distance, cruising velocity, and detonation position on stress, displacement, and internal equipment response. Results show that cruising significantly lowers overall stress and alters displacement patterns, mainly due to dynamic unloading. Although stress distributions are generally similar for different detonation positions, displacements differ markedly because of bubble pulsation loading. Using the Shock Response Spectrum (SRS) method, the study further shows that, for a 30 kg TNT charge at 15 m standoff, accelerations in the guidance and motor sections exceed BV043/85 failure thresholds, implying potential equipment functional loss even without visible structural damage. The results support shock-resistant design and underwater shock assessment.

ABSTRACT The warship’s power system is crucial for navigation. This study applies a method coupling damage tree analysis (DTA) and spatial dynamic event tree (SDET) analysis to quantify and predict the probability and status of damage to the power system. The DTA model establishes the damage logic relationship between the basic, intermediate, and top events. The innovative SDET model simultaneously considers the impacts of both spatial and temporal factors on the dynamic evolution of events. The coupled of these two methods encompasses all potential logical damage pathways.Coupled acoustic-structural analysis is used to simulate deformations at equipment installation positions under underwater explosion scenarios, in order to acquire the precise basic event probabilities of the DTA model. The computational results indicate that the coupled DTA-SDET method can effectivelypredict the damage position, and evaluate the overall damage status of the power system. The results discussed herein provide valuableguidance for warship navigations.