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2026, 46(1): 011001.
doi: 10.11883/bzycj-2024-0457
Abstract:
Blasts near the water surface are one of the major threats to ships. Experiments were carried out to study the load characteristics of the shock wave on the water surface with TNT/RDX(40/60) explosives. Three typical scaled burst heights were used: contact burst, near-surface blast, and air blast. In the experiments, overpressures in air and water were obtained, and high-speed photographic was used to record the explosion images. A numerical simulation method based on a five-equation model was used to study further the explosion phenomenon and the loading characteristic of shock waves on the water surface. The numerical simulation results are in good agreement with the experimental results. The results show significant differences among contact bursts, near-surface blasts, and air blasts. In the contact burst, the detonation products drive the water surface directly, creating a hemispherical cavity, and the water at the edge of the cavity is squeezed upwards, forming a hollow water column. In the near-surface blast, the collision of the detonation products with the water surface is relatively weak, and the shock wave on the water surface mainly propagates outwards as Mach waves along the water surface. In the air blast, there are clear regular and irregular reflection zones of the shock wave on the water surface. Under the same yield conditions, the overpressure on the water surface of the contact burst is lower than that of the near-surface blast, but the pressure in the water is more stressful. Therefore, the water surface can no longer be considered a rigid plane. The formulas of overpressure and positive pressure duration of shock wave on the water surface within the range of 0.5～4.0 m/kg1/3 in the contact burst and the near-surface blast were obtained through data fitting, which provides a reference for shock wave loading calculation and analysis.
Blasts near the water surface are one of the major threats to ships. Experiments were carried out to study the load characteristics of the shock wave on the water surface with TNT/RDX(40/60) explosives. Three typical scaled burst heights were used: contact burst, near-surface blast, and air blast. In the experiments, overpressures in air and water were obtained, and high-speed photographic was used to record the explosion images. A numerical simulation method based on a five-equation model was used to study further the explosion phenomenon and the loading characteristic of shock waves on the water surface. The numerical simulation results are in good agreement with the experimental results. The results show significant differences among contact bursts, near-surface blasts, and air blasts. In the contact burst, the detonation products drive the water surface directly, creating a hemispherical cavity, and the water at the edge of the cavity is squeezed upwards, forming a hollow water column. In the near-surface blast, the collision of the detonation products with the water surface is relatively weak, and the shock wave on the water surface mainly propagates outwards as Mach waves along the water surface. In the air blast, there are clear regular and irregular reflection zones of the shock wave on the water surface. Under the same yield conditions, the overpressure on the water surface of the contact burst is lower than that of the near-surface blast, but the pressure in the water is more stressful. Therefore, the water surface can no longer be considered a rigid plane. The formulas of overpressure and positive pressure duration of shock wave on the water surface within the range of 0.5～4.0 m/kg1/3 in the contact burst and the near-surface blast were obtained through data fitting, which provides a reference for shock wave loading calculation and analysis.
2026, 46(1): 011101.
doi: 10.11883/bzycj-2025-0160
Abstract:
To understand the multiple tail-slapping the trans-media vehicle going through during the high-speed water entry, which may cause damage to the main structure and its accessories. The study was conducted to investigate the load characteristics of the main body of the trans-media vehicle and its accessories in the stages of the generation, development, and collapse of cavities under the condition of inclined water-entering with an attack angle, based on the VOF multiphase flow method. The influence of the water entry inclination angle on the tail-slapping load, cavity collapse load and the trajectory stability are revealed. The results show that the cavity collapse stage is the most dangerous working condition during the water entry process. As the water entry inclination angle increases, the axial and normal forces on the structure increase in the cavitation collapse stage, while the normal overload coefficient approaches a constant. When the inclination angle into the water increased from 60° to 90°, the pitch moment coefficient of the structure increased by 47.1%. A larger inclination angle can reduce the axial and normal loads of the horizontal rudders during the cavity collapse stage, and also improve the trajectory stability of the vehicle. However, it will increase the axial loads of the vertical rudders at the same time. When the cavity wall impacts the tail of the trans-media vehicle during the cavity collapse stage, the three-directional rotation of the body is suppressed, causing it to be in a brief state of rest.
To understand the multiple tail-slapping the trans-media vehicle going through during the high-speed water entry, which may cause damage to the main structure and its accessories. The study was conducted to investigate the load characteristics of the main body of the trans-media vehicle and its accessories in the stages of the generation, development, and collapse of cavities under the condition of inclined water-entering with an attack angle, based on the VOF multiphase flow method. The influence of the water entry inclination angle on the tail-slapping load, cavity collapse load and the trajectory stability are revealed. The results show that the cavity collapse stage is the most dangerous working condition during the water entry process. As the water entry inclination angle increases, the axial and normal forces on the structure increase in the cavitation collapse stage, while the normal overload coefficient approaches a constant. When the inclination angle into the water increased from 60° to 90°, the pitch moment coefficient of the structure increased by 47.1%. A larger inclination angle can reduce the axial and normal loads of the horizontal rudders during the cavity collapse stage, and also improve the trajectory stability of the vehicle. However, it will increase the axial loads of the vertical rudders at the same time. When the cavity wall impacts the tail of the trans-media vehicle during the cavity collapse stage, the three-directional rotation of the body is suppressed, causing it to be in a brief state of rest.
2026, 46(1): 011102.
doi: 10.11883/bzycj-2024-0435
Abstract:
During the underwater launch of multiple projectiles, each projectile operates within a highly complex and dynamic flow field, where its trajectory deflection is influenced by a combination of factors. These factors include initial conditions such as the projectile’s velocity and the presence of crossflow, as well as the mutual interference effects among the projectiles. To gain a deeper understanding of the cavitation evolution and trajectory interference characteristics during the underwater launch of multiple projectiles, this study develops a comprehensive numerical simulation model. The model integrates the overlapping grid technique and the finite volume method and is coupled with a six-degree-of-freedom (6-DOF) motion model. Through this model, the influence mechanisms of spatial arrangement, launch velocity, and crossflow on trajectory deflection are systematically analyzed. The results of this study reveal several important findings. First, the spatial arrangement of the projectiles has a relatively minor impact on trajectory deflection. An equilateral triangular configuration is found to be an optimal choice for practical applications, as it maximizes the efficient utilization of the launch space. Second, as the launch velocity increases, the wake interference between projectiles becomes more pronounced. This intensified interference leads to significant disturbances in the flow field and stronger mutual trajectory interference among the projectiles. Third, higher crossflow velocities exacerbate the asymmetric development of cavitation near the projectile shoulders. When the crossflow velocity exceeds 0.75 m/s, it becomes the dominant factor influencing trajectory deflection. These research findings provide a robust theoretical foundation for trajectory prediction and layout optimization in the underwater launch of multiple projectiles.
During the underwater launch of multiple projectiles, each projectile operates within a highly complex and dynamic flow field, where its trajectory deflection is influenced by a combination of factors. These factors include initial conditions such as the projectile’s velocity and the presence of crossflow, as well as the mutual interference effects among the projectiles. To gain a deeper understanding of the cavitation evolution and trajectory interference characteristics during the underwater launch of multiple projectiles, this study develops a comprehensive numerical simulation model. The model integrates the overlapping grid technique and the finite volume method and is coupled with a six-degree-of-freedom (6-DOF) motion model. Through this model, the influence mechanisms of spatial arrangement, launch velocity, and crossflow on trajectory deflection are systematically analyzed. The results of this study reveal several important findings. First, the spatial arrangement of the projectiles has a relatively minor impact on trajectory deflection. An equilateral triangular configuration is found to be an optimal choice for practical applications, as it maximizes the efficient utilization of the launch space. Second, as the launch velocity increases, the wake interference between projectiles becomes more pronounced. This intensified interference leads to significant disturbances in the flow field and stronger mutual trajectory interference among the projectiles. Third, higher crossflow velocities exacerbate the asymmetric development of cavitation near the projectile shoulders. When the crossflow velocity exceeds 0.75 m/s, it becomes the dominant factor influencing trajectory deflection. These research findings provide a robust theoretical foundation for trajectory prediction and layout optimization in the underwater launch of multiple projectiles.
2026, 46(1): 011103.
doi: 10.11883/bzycj-2024-0274
Abstract:
The pressure characteristics and structural deformation mechanism of aluminum honeycomb sandwich plates (AHSPs) under water-entry impact were investigated through experimental methods. A self-designed drop experimental platform in the water tank was established, and the water-entry impact experiments of AHSPs at different drop heights were carried out. Meanwhile, the deformation of the face sheets was measured by a 3D scanner, and the time history of water impact pressure at different measuring points was monitored. Furthermore, the repeatability of the experiment was verified. On this basis, the water impact load characteristics of AHSPs during the process of water entry were studied and compared with those of other structures in published papers. In addition, the deformation modes and permanent deflection characteristics of AHSPs were analyzed, and the fitting formulas of the permanent deflection of the face sheets and the compression of the core were proposed. Results show that the distribution of the water impact pressure on the front sheet of AHSPs is uneven. However, within the range of drop heights studied, the peak value of the water impact pressure is approximately linear with the drop height. Additionally, compared to the water entry of rigid plates, the peak value of the water impact pressure of AHSPs is smaller. Compared with the mass equivalent aluminum plates, the peak value of the water impact pressure of AHSPs is much smaller, while the pressure duration of AHSPs is longer. The deformation modes of the face sheets of AHSPs at different drop heights are almost the same. Besides, with the increase of the drop height, the permanent deflections of the front and back faces of AHSPs increase approximately in the form of a quadratic parabola with decreasing slope. Suffering from water entry impact loadings, the permanent deflections of the back sheet of AHSPs are smaller than those of the equivalent aluminum plates, indicating that the AHSPs have better impact resistance compared with the equivalent aluminum plates.
The pressure characteristics and structural deformation mechanism of aluminum honeycomb sandwich plates (AHSPs) under water-entry impact were investigated through experimental methods. A self-designed drop experimental platform in the water tank was established, and the water-entry impact experiments of AHSPs at different drop heights were carried out. Meanwhile, the deformation of the face sheets was measured by a 3D scanner, and the time history of water impact pressure at different measuring points was monitored. Furthermore, the repeatability of the experiment was verified. On this basis, the water impact load characteristics of AHSPs during the process of water entry were studied and compared with those of other structures in published papers. In addition, the deformation modes and permanent deflection characteristics of AHSPs were analyzed, and the fitting formulas of the permanent deflection of the face sheets and the compression of the core were proposed. Results show that the distribution of the water impact pressure on the front sheet of AHSPs is uneven. However, within the range of drop heights studied, the peak value of the water impact pressure is approximately linear with the drop height. Additionally, compared to the water entry of rigid plates, the peak value of the water impact pressure of AHSPs is smaller. Compared with the mass equivalent aluminum plates, the peak value of the water impact pressure of AHSPs is much smaller, while the pressure duration of AHSPs is longer. The deformation modes of the face sheets of AHSPs at different drop heights are almost the same. Besides, with the increase of the drop height, the permanent deflections of the front and back faces of AHSPs increase approximately in the form of a quadratic parabola with decreasing slope. Suffering from water entry impact loadings, the permanent deflections of the back sheet of AHSPs are smaller than those of the equivalent aluminum plates, indicating that the AHSPs have better impact resistance compared with the equivalent aluminum plates.
2026, 46(1): 011104.
doi: 10.11883/bzycj-2025-0092
Abstract:
Contact explosion is an important condition in the damage and protection of underwater structures, and the pulsating bubbles generated by explosive underwater explosion are an important damage source. The current research on underwater explosion bubbles mainly focuses on the pulsating characteristics of spherical bubbles under free-field and typical boundary conditions, while there is a notable lack of research on non-spherical bubbles under contact explosion conditions. The pulsation characteristics of underwater contact explosion bubbles were systematically investigated through theoretical modeling, numerical simulations, and experiments. To address the theoretical gap in contact explosion dynamics, a hemispherical bubble dynamics model under rigid wall contact conditions was established based on incompressible and inviscid fluid assumptions. By comparing present model with the spherical bubble pulsation model in an incompressible flow field, quantitative relationships between parameters such as the maximum bubble radius, initial radius, pulsation period were obtained. Theoretical analysis reveals that the maximum radius, initial radius, and pulsation period of contact explosion bubbles are 1.26 times (theoretical scaling factor) those of free-field conditions. An error analysis was conducted to account for factors such as fluid compressibility, unstable bubble deformation, and energy dissipation induced by bubble-rigid wall interactions. Numerical simulations using LS-DYNA for underwater explosions with 0.300 g, 0.233 g, and 5.000 g TNT charges under varying water depths reveal that the scaling factors for maximum radius and pulsation period under contact explosion conditions range from 1.22 to 1.24 and 1.20 to 1.21 times those of free-field results, respectively, with simulation errors below 5% compared to theoretical predictions. Experimental validation in a water tank shows that the maximum radius and period of contact explosion bubbles are 1.10 and 1.06 times those of free-field conditions. During the experiments, plate vibrations were observed upon explosion, which significantly contributed to experimental errors. This work addresses the theoretical gap in contact explosion bubble dynamics, enhances the understanding of boundary effects in underwater explosion phenomena.
Contact explosion is an important condition in the damage and protection of underwater structures, and the pulsating bubbles generated by explosive underwater explosion are an important damage source. The current research on underwater explosion bubbles mainly focuses on the pulsating characteristics of spherical bubbles under free-field and typical boundary conditions, while there is a notable lack of research on non-spherical bubbles under contact explosion conditions. The pulsation characteristics of underwater contact explosion bubbles were systematically investigated through theoretical modeling, numerical simulations, and experiments. To address the theoretical gap in contact explosion dynamics, a hemispherical bubble dynamics model under rigid wall contact conditions was established based on incompressible and inviscid fluid assumptions. By comparing present model with the spherical bubble pulsation model in an incompressible flow field, quantitative relationships between parameters such as the maximum bubble radius, initial radius, pulsation period were obtained. Theoretical analysis reveals that the maximum radius, initial radius, and pulsation period of contact explosion bubbles are 1.26 times (theoretical scaling factor) those of free-field conditions. An error analysis was conducted to account for factors such as fluid compressibility, unstable bubble deformation, and energy dissipation induced by bubble-rigid wall interactions. Numerical simulations using LS-DYNA for underwater explosions with 0.300 g, 0.233 g, and 5.000 g TNT charges under varying water depths reveal that the scaling factors for maximum radius and pulsation period under contact explosion conditions range from 1.22 to 1.24 and 1.20 to 1.21 times those of free-field results, respectively, with simulation errors below 5% compared to theoretical predictions. Experimental validation in a water tank shows that the maximum radius and period of contact explosion bubbles are 1.10 and 1.06 times those of free-field conditions. During the experiments, plate vibrations were observed upon explosion, which significantly contributed to experimental errors. This work addresses the theoretical gap in contact explosion bubble dynamics, enhances the understanding of boundary effects in underwater explosion phenomena.
2026, 46(1): 011105.
doi: 10.11883/bzycj-2024-0332
Abstract:
To investigate the damage mechanism and load characteristics of caisson wharf under underwater contact and near-field explosion, a high-fidelity numerical model was conducted based on the scaled model tests of caisson wharf and verified by comparing the simulation results with the experimental data. The propagation and attenuation characteristics of shock waves inside the caisson, partition walls, and internal backfill soil were analyzed. The destruction process and typical damage mechanisms of the caisson wharf were analyzed by comparing Holmquist-Johnson-Cook constitutive model damage contour maps with experimental results. The results shows that the damage areas and characteristics of the caisson wharf are largely consistent under both underwater contact and near-field explosion. The primary damage areas are blast-facing wall and deck slab. The blast-facing wall exhibits cratering and breaching phenomena, while of the deck slab shows transverse full-length cracks at trench-slab connections, longitudinal cracks, and blow-off. The side walls and internal partitions of the caisson wharf sustain relatively minor damage. Shock wave within the caisson subjected to underwater contact and near-field explosions undergo reflection and transmission at the interfaces between the partitions and fillings within the compartments. The blast-facing wall and side walls of the wharf are subjected to shock loads. The transmitted compressive waves across the transverse bulkheads and blast-resistant back walls exhibited amplification compared to the incident waves, whereas attenuation was observed as the waves traversed the sand-filled compartments. Numerical simulation results revealed that the shock wave load within the caisson undergoes a decay rate that transitions from rapid to gradual. Damage characteristics of caisson wharf is primarily shaped during the underwater explosion shockwave phase. Neglecting large-scale macroscopic movements such as uplift and scattering post panel failure, the damage formation time slightly exceeds twice the shockwave propagation duration through the structure.
To investigate the damage mechanism and load characteristics of caisson wharf under underwater contact and near-field explosion, a high-fidelity numerical model was conducted based on the scaled model tests of caisson wharf and verified by comparing the simulation results with the experimental data. The propagation and attenuation characteristics of shock waves inside the caisson, partition walls, and internal backfill soil were analyzed. The destruction process and typical damage mechanisms of the caisson wharf were analyzed by comparing Holmquist-Johnson-Cook constitutive model damage contour maps with experimental results. The results shows that the damage areas and characteristics of the caisson wharf are largely consistent under both underwater contact and near-field explosion. The primary damage areas are blast-facing wall and deck slab. The blast-facing wall exhibits cratering and breaching phenomena, while of the deck slab shows transverse full-length cracks at trench-slab connections, longitudinal cracks, and blow-off. The side walls and internal partitions of the caisson wharf sustain relatively minor damage. Shock wave within the caisson subjected to underwater contact and near-field explosions undergo reflection and transmission at the interfaces between the partitions and fillings within the compartments. The blast-facing wall and side walls of the wharf are subjected to shock loads. The transmitted compressive waves across the transverse bulkheads and blast-resistant back walls exhibited amplification compared to the incident waves, whereas attenuation was observed as the waves traversed the sand-filled compartments. Numerical simulation results revealed that the shock wave load within the caisson undergoes a decay rate that transitions from rapid to gradual. Damage characteristics of caisson wharf is primarily shaped during the underwater explosion shockwave phase. Neglecting large-scale macroscopic movements such as uplift and scattering post panel failure, the damage formation time slightly exceeds twice the shockwave propagation duration through the structure.
2026, 46(1): 011106.
doi: 10.11883/bzycj-2024-0515
Abstract:
Underwater explosions in deep-sea environments involve complex interactions, making both theoretical modeling and experimental validation particularly challenging. While previous research has provided valuable insights into the basic features of shock wave propagation and bubble dynamics in underwater explosions, most existing studies are limited to shallow water scenarios or narrowly defined environmental parameters. Systematic research on the laws governing shock wave loads from deep-sea explosions and their associated bubble pulsation under varying operational conditions holds critical academic significance. Numerical simulations were conducted utilizing a zoned solution algorithm for shock waves derived from the unified equation for bubble dynamics theoretical model. The algorithm enabled numerical simulation of shock wave peak pressure and pressure attenuation processes under diverse initial conditions. Comparative analysis with experimental data confirmed model reliability, demonstrating a mere 0.5% deviation between simulated and measured peak pressures and excellent agreement in pressure attenuation processes. The simulations specifically investigated the influence of water depth, stand-off distance, and explosive charge mass on the peak pressure of the underwater explosion shock wave and explored the variation patterns of the shock wave under different initial conditions through an in-depth analysis of the shock wave impulse and specific shock wave energy. Furthermore, employing the same theoretical model, the bubble pulsation characteristics within a single cycle under varying water depths and explosive charge masses were comparatively analyzed. Traditional empirical formulas were employed to analyze the numerical simulation results, and dimensionless treatment was conducted on the parameters. The results reveal that the peak pressure of the shock wave is primarily influenced by the charge mass and stand-off distance, and increases with water depth at an approximate rate of 1% per kilometer. In contrast, both shock wave impulse and specific shock wave energy decrease with increasing water depth and stand-off distance, but show a positive correlation with charge magnitude. The bubble pulse radius is primarily determined by both the charge weight and the water depth, with the bubble pulsation phenomenon becoming attenuated in deep-water environments. Compared to the traditional Cole empirical formula, the simulated bubble pulse radius is reduced in the range of 0.1 to 10 km. The simulation indicates an asymmetry in the pulsation cycle: the expansion phase consistently lasts slightly longer than the collapse phase. These findings contribute to a more nuanced understanding of underwater explosion phenomena in deep-sea environments and have practical implications for naval engineering, subsea structural safety assessment, and explosive ordnance disposal in complex oceanic settings.
Underwater explosions in deep-sea environments involve complex interactions, making both theoretical modeling and experimental validation particularly challenging. While previous research has provided valuable insights into the basic features of shock wave propagation and bubble dynamics in underwater explosions, most existing studies are limited to shallow water scenarios or narrowly defined environmental parameters. Systematic research on the laws governing shock wave loads from deep-sea explosions and their associated bubble pulsation under varying operational conditions holds critical academic significance. Numerical simulations were conducted utilizing a zoned solution algorithm for shock waves derived from the unified equation for bubble dynamics theoretical model. The algorithm enabled numerical simulation of shock wave peak pressure and pressure attenuation processes under diverse initial conditions. Comparative analysis with experimental data confirmed model reliability, demonstrating a mere 0.5% deviation between simulated and measured peak pressures and excellent agreement in pressure attenuation processes. The simulations specifically investigated the influence of water depth, stand-off distance, and explosive charge mass on the peak pressure of the underwater explosion shock wave and explored the variation patterns of the shock wave under different initial conditions through an in-depth analysis of the shock wave impulse and specific shock wave energy. Furthermore, employing the same theoretical model, the bubble pulsation characteristics within a single cycle under varying water depths and explosive charge masses were comparatively analyzed. Traditional empirical formulas were employed to analyze the numerical simulation results, and dimensionless treatment was conducted on the parameters. The results reveal that the peak pressure of the shock wave is primarily influenced by the charge mass and stand-off distance, and increases with water depth at an approximate rate of 1% per kilometer. In contrast, both shock wave impulse and specific shock wave energy decrease with increasing water depth and stand-off distance, but show a positive correlation with charge magnitude. The bubble pulse radius is primarily determined by both the charge weight and the water depth, with the bubble pulsation phenomenon becoming attenuated in deep-water environments. Compared to the traditional Cole empirical formula, the simulated bubble pulse radius is reduced in the range of 0.1 to 10 km. The simulation indicates an asymmetry in the pulsation cycle: the expansion phase consistently lasts slightly longer than the collapse phase. These findings contribute to a more nuanced understanding of underwater explosion phenomena in deep-sea environments and have practical implications for naval engineering, subsea structural safety assessment, and explosive ordnance disposal in complex oceanic settings.
2026, 46(1): 011107.
doi: 10.11883/bzycj-2025-0180
Abstract:
The evaluation method of ship’s explosion shock resistance is challenged by some key mechanical problems, such as strong nonlinear fluid-structure coupling, large-deformation and failure evolution of solid structure. By coupling the respective advantages of peridynamics (PD) and smoothed particle hydrodynamics (SPH), an efficient PD-SPH numerical method suitable for underwater explosion shock simulations was developed. The SPH method was employed to simulate underwater shock wave propagation and fluid-structure interaction, while the PD method accurately characterized the complete mechanical behavior of solid structures from elastic deformation to progressive damage failure. A PD-SPH numerical model was established for non-explosive underwater shock loading devices. In the non-ordinary state-based peridynamics (NOSB-PD) framework, the Johnson-Cook damage model was introduced. To suppress the occurrence of numerical instability, the artificial stiffness form was introduced by increasing the internal constraints between particles. To improve the computational efficiency in large-scale simulations, a multi-GPU (graphics processing unit) parallel computing framework based on domain decomposition and data-communication mechanisms was established. The domain decomposition was carried out through the Eulerian format. When particles move from one domain to another, the physical quantities of the particles were exchanged for information. Model validation and parallel efficiency tests demonstrate that the proposed method can accurately predict shock wave wall pressure and target dynamic deformation, successfully reproduce typical crack propagation patterns in thin-plate structures and simulate the entire damage process of complex grid sandwich structure. In complex fluid-structure coupling scenarios with more than 5 million particles, the 8*RTX4090 achieved an acceleration ratio of 4.13 compared to a single RTX4090, with a parallel efficiency of 51.6%. The actual computation time can be reduced to nearly 1 hour. Meanwhile, compared with traditional CPU (central processing unit) parallelism, the multi-GPU parallelism can achieve an acceleration ratio of more than 9 times. The research outcomes provide a high-precision and efficient numerical analysis tool for the design of explosion-resistant naval structures, offering significant reference value for engineering applications of fluid-structure interaction in underwater explosion problems.
The evaluation method of ship’s explosion shock resistance is challenged by some key mechanical problems, such as strong nonlinear fluid-structure coupling, large-deformation and failure evolution of solid structure. By coupling the respective advantages of peridynamics (PD) and smoothed particle hydrodynamics (SPH), an efficient PD-SPH numerical method suitable for underwater explosion shock simulations was developed. The SPH method was employed to simulate underwater shock wave propagation and fluid-structure interaction, while the PD method accurately characterized the complete mechanical behavior of solid structures from elastic deformation to progressive damage failure. A PD-SPH numerical model was established for non-explosive underwater shock loading devices. In the non-ordinary state-based peridynamics (NOSB-PD) framework, the Johnson-Cook damage model was introduced. To suppress the occurrence of numerical instability, the artificial stiffness form was introduced by increasing the internal constraints between particles. To improve the computational efficiency in large-scale simulations, a multi-GPU (graphics processing unit) parallel computing framework based on domain decomposition and data-communication mechanisms was established. The domain decomposition was carried out through the Eulerian format. When particles move from one domain to another, the physical quantities of the particles were exchanged for information. Model validation and parallel efficiency tests demonstrate that the proposed method can accurately predict shock wave wall pressure and target dynamic deformation, successfully reproduce typical crack propagation patterns in thin-plate structures and simulate the entire damage process of complex grid sandwich structure. In complex fluid-structure coupling scenarios with more than 5 million particles, the 8*RTX4090 achieved an acceleration ratio of 4.13 compared to a single RTX4090, with a parallel efficiency of 51.6%. The actual computation time can be reduced to nearly 1 hour. Meanwhile, compared with traditional CPU (central processing unit) parallelism, the multi-GPU parallelism can achieve an acceleration ratio of more than 9 times. The research outcomes provide a high-precision and efficient numerical analysis tool for the design of explosion-resistant naval structures, offering significant reference value for engineering applications of fluid-structure interaction in underwater explosion problems.
2026, 46(1): 011108.
doi: 10.11883/bzycj-2024-0455
Abstract:
To select the shaped charge structure suitable for large-distance non-contact penetration damage in water, three typical shaped-charge structures, explosively formed projectile (EFP), jetting projectile charge (JPC), and shaped charge jet (SCJ), were selected. The velocity tests of different penetrators before entering water, before hitting the target, and after penetrating the target were carried out, and the penetration tests of double-layer spaced targets in water were conducted. Firstly, a comparative test of penetration of three types of shaped charges in the air was carried out to verify the rationality of the structure of shaped charges. The air explosion height of 35 cm was selected to meet the penetration requirements of the three shaped charges. At the same time, the velocity of the shaped charges before penetrating water was measured, which provides the basis for the underwater penetration test. Secondly, the penetration test of three types of shaped charges on an underwater double-layer spaced target was carried out when the air height was 35 cm, and the length of the water medium in front of the target was 20, 45, and 100 cm. The reflected pressures were measured by the wall pressure sensor and PVDF sensor. The velocities of the penetrator at the time of water entry, before the target, and after the target were measured by double-layer on-off net targets.The damage performance of three shaped charge structures on the double-layer spaced target plate was respectively obtained when the water medium in front of the target was at short range, medium range and long range.Based on the projectile-target structure used in the experiment, a two-dimensional finite element model of shaped charge penetrating a double-layer spaced target in water was established using ANSYS/LS-DYNA finite element software. The measured velocity values of the shaped charge penetrator before entering the water, before hitting the target, and after passing through the target were compared with the numerical simulation results to verify the accuracy of the model. The error rate is about 3%. Based on the verified finite element model, the time series characteristics of the underwater damage element of the shaped charge, the peak characteristics of the forward shock wave in the water, the variation law of the penetration velocity in the water, and the penetration performance of the shaped charge against the double-layer spaced target in the water were studied. The results show that the forward shock wave reaches the target plate before the penetrator. As the length of the water medium increases, the peak pressure of the forward shock wave at the front target plate decreases linearly, and the peak pressure of the forward shock wave at the rear target plate decreases nonlinearly. The velocities of EFP, JPC, and SCJ decrease nonlinearly with the increase of water medium, and the velocity in front of the SCJ target is about twice that of JPC. When the length of the water medium in front of the target is not more than 25 cm, the maximum perforation diameter formed by EFP on the front target plate reaches 5 cm, which is 1.3 times the perforation diameter of JPC and 3 times the perforation diameter of SCJ. When the length of the water medium in front of the target is not more than 100 cm, JPC and SCJ have better penetration effect on the double-layer spacer target, and the penetration performance of JPC is better than that of SCJ.
To select the shaped charge structure suitable for large-distance non-contact penetration damage in water, three typical shaped-charge structures, explosively formed projectile (EFP), jetting projectile charge (JPC), and shaped charge jet (SCJ), were selected. The velocity tests of different penetrators before entering water, before hitting the target, and after penetrating the target were carried out, and the penetration tests of double-layer spaced targets in water were conducted. Firstly, a comparative test of penetration of three types of shaped charges in the air was carried out to verify the rationality of the structure of shaped charges. The air explosion height of 35 cm was selected to meet the penetration requirements of the three shaped charges. At the same time, the velocity of the shaped charges before penetrating water was measured, which provides the basis for the underwater penetration test. Secondly, the penetration test of three types of shaped charges on an underwater double-layer spaced target was carried out when the air height was 35 cm, and the length of the water medium in front of the target was 20, 45, and 100 cm. The reflected pressures were measured by the wall pressure sensor and PVDF sensor. The velocities of the penetrator at the time of water entry, before the target, and after the target were measured by double-layer on-off net targets.The damage performance of three shaped charge structures on the double-layer spaced target plate was respectively obtained when the water medium in front of the target was at short range, medium range and long range.Based on the projectile-target structure used in the experiment, a two-dimensional finite element model of shaped charge penetrating a double-layer spaced target in water was established using ANSYS/LS-DYNA finite element software. The measured velocity values of the shaped charge penetrator before entering the water, before hitting the target, and after passing through the target were compared with the numerical simulation results to verify the accuracy of the model. The error rate is about 3%. Based on the verified finite element model, the time series characteristics of the underwater damage element of the shaped charge, the peak characteristics of the forward shock wave in the water, the variation law of the penetration velocity in the water, and the penetration performance of the shaped charge against the double-layer spaced target in the water were studied. The results show that the forward shock wave reaches the target plate before the penetrator. As the length of the water medium increases, the peak pressure of the forward shock wave at the front target plate decreases linearly, and the peak pressure of the forward shock wave at the rear target plate decreases nonlinearly. The velocities of EFP, JPC, and SCJ decrease nonlinearly with the increase of water medium, and the velocity in front of the SCJ target is about twice that of JPC. When the length of the water medium in front of the target is not more than 25 cm, the maximum perforation diameter formed by EFP on the front target plate reaches 5 cm, which is 1.3 times the perforation diameter of JPC and 3 times the perforation diameter of SCJ. When the length of the water medium in front of the target is not more than 100 cm, JPC and SCJ have better penetration effect on the double-layer spacer target, and the penetration performance of JPC is better than that of SCJ.
2026, 46(1): 013101.
doi: 10.11883/bzycj-2024-0388
Abstract:
In a reinforced concrete (RC) box structure, the dissipation of blast waves is restricted, and damage to the structure can be intensified due to multiple reflections. To thoroughly investigate the load characteristics and dynamic behavior of internal explosions in an RC box structure, the applicability of the finite element method was verified by replicating internal explosion tests on fully enclosed and semi-enclosed (with venting openings) RC box structures. Based on this, numerical simulations of internal explosions were conducted for the prototypical RC box structure and the type of terrorist bombing attacks specified by the Federal Emergency Management Agency under three explosion scenarios and four venting areas. The influence of venting area on the load characteristics at the inner surfaces and corners, the load distribution on the inner surfaces, and the time histories of displacement and velocity at the centers of the inner surfaces under internal explosion loads were explored. Additionally, a formula for calculating the total impulse of the structure’s inner surface was proposed, considering both the venting area and the spatial distribution of the impulse. The results show that the venting area has a negligible effect on the overpressure, while the impulse decreases exponentially with increasing venting area. The load distribution characteristics on the structure’s inner surface are significantly influenced by the structural dimensions, exhibiting an indented or W pattern. The maximum displacement at the centers of walls and slabs is reduced by about 50% as the venting coefficient changes from 0.457 to 1.220. Finally, based on the total impulse and maximum displacement response of each component under free-field explosion loads, a calculation method for the impulse and damage enhancement coefficient was proposed based on the venting area, effectively predicting the internal explosion load and the structure’s dynamic behavior at various venting coefficients.
In a reinforced concrete (RC) box structure, the dissipation of blast waves is restricted, and damage to the structure can be intensified due to multiple reflections. To thoroughly investigate the load characteristics and dynamic behavior of internal explosions in an RC box structure, the applicability of the finite element method was verified by replicating internal explosion tests on fully enclosed and semi-enclosed (with venting openings) RC box structures. Based on this, numerical simulations of internal explosions were conducted for the prototypical RC box structure and the type of terrorist bombing attacks specified by the Federal Emergency Management Agency under three explosion scenarios and four venting areas. The influence of venting area on the load characteristics at the inner surfaces and corners, the load distribution on the inner surfaces, and the time histories of displacement and velocity at the centers of the inner surfaces under internal explosion loads were explored. Additionally, a formula for calculating the total impulse of the structure’s inner surface was proposed, considering both the venting area and the spatial distribution of the impulse. The results show that the venting area has a negligible effect on the overpressure, while the impulse decreases exponentially with increasing venting area. The load distribution characteristics on the structure’s inner surface are significantly influenced by the structural dimensions, exhibiting an indented or W pattern. The maximum displacement at the centers of walls and slabs is reduced by about 50% as the venting coefficient changes from 0.457 to 1.220. Finally, based on the total impulse and maximum displacement response of each component under free-field explosion loads, a calculation method for the impulse and damage enhancement coefficient was proposed based on the venting area, effectively predicting the internal explosion load and the structure’s dynamic behavior at various venting coefficients.
2026, 46(1): 013201.
doi: 10.11883/bzycj-2024-0483
Abstract:
To enhance the damage efficiency of fluoropolymer-based reactive fragments and broaden their application range, a novel core-shell composite structure active fragment has been proposed. To improve the strength of the matrix material, carbon fiber was introduced via a wet mixing method. Under specific sintering conditions, two types of samples were prepared: PTFE/Al/CF tungsten powder and PTFE/Al/CF tungsten ball. The basic mechanical properties of these samples were tested. The addition of tungsten powder was found to increase the dynamic compressive strength of the composite. Penetration tests were conducted on 3 mm+3 mm+2 mm+2 mm multi-layer interval aluminum targets using both types of fragments. The experimental data were automatically processed using a Python-based program, yielding the perforation area, deformation volume, and reaction light intensity for each layer of the target plate. The damage characteristics of the multi-interval target under different velocity and constraint conditions were compared and analyzed. The results show that the core-shell type fragment exhibits superior penetration ability. It can penetrate all four layers of the target plates at low speeds, although the perforation area is relatively small, with a perforation diameter approximately 0.95 times the fragment diameter. In contrast, the homogeneous fragment has a larger perforation area but weaker penetration ability. Its perforation diameter is about 1.21 times the fragment diameter, and it can only penetrate three layers of target plates at high speeds. The steel shell constraint significantly enhances the punching and penetration capabilities of the fragments. The primary active reaction of the fragment occurs during impact with the second layer of the target. The energy release reaction has a limited effect on improving the punching effect. The differences in damage characteristics are mainly attributed to the mechanical properties of the fragments. These findings provide valuable insights for the structural design and damage effect evaluation of reactive fragments.
To enhance the damage efficiency of fluoropolymer-based reactive fragments and broaden their application range, a novel core-shell composite structure active fragment has been proposed. To improve the strength of the matrix material, carbon fiber was introduced via a wet mixing method. Under specific sintering conditions, two types of samples were prepared: PTFE/Al/CF tungsten powder and PTFE/Al/CF tungsten ball. The basic mechanical properties of these samples were tested. The addition of tungsten powder was found to increase the dynamic compressive strength of the composite. Penetration tests were conducted on 3 mm+3 mm+2 mm+2 mm multi-layer interval aluminum targets using both types of fragments. The experimental data were automatically processed using a Python-based program, yielding the perforation area, deformation volume, and reaction light intensity for each layer of the target plate. The damage characteristics of the multi-interval target under different velocity and constraint conditions were compared and analyzed. The results show that the core-shell type fragment exhibits superior penetration ability. It can penetrate all four layers of the target plates at low speeds, although the perforation area is relatively small, with a perforation diameter approximately 0.95 times the fragment diameter. In contrast, the homogeneous fragment has a larger perforation area but weaker penetration ability. Its perforation diameter is about 1.21 times the fragment diameter, and it can only penetrate three layers of target plates at high speeds. The steel shell constraint significantly enhances the punching and penetration capabilities of the fragments. The primary active reaction of the fragment occurs during impact with the second layer of the target. The energy release reaction has a limited effect on improving the punching effect. The differences in damage characteristics are mainly attributed to the mechanical properties of the fragments. These findings provide valuable insights for the structural design and damage effect evaluation of reactive fragments.
2026, 46(1): 014101.
doi: 10.11883/bzycj-2025-0037
Abstract:
Shock initiation and ignition techniques driven by electrically exploded metallic bridge foils with insulating flyers have been widely implemented in initiation and ignition system of weapon. To address the deficiency in existing research regarding the description of the flow field evolution during the motion of flyer and promote the development of this technology towards efficient energy utilization and miniaturization, a double-pulse laser schlieren transient observation system was constructed. This system enables the acquisition of density distributions of the flow field and the motion distance of the flyer at different time. Additionally, a two-dimensional axisymmetric fluid dynamics calculation model and calculation method for the motion process of flyer driven by the electric explosion of metal foil were established, and corresponding numerical simulation calculations were performed in consideration of the evolution laws of the flow field inside and outside the acceleration chamber under the effects of the motion of flyer, the compression of shock wave, and the expansion of high-temperature and high-pressure plasma. The phase transition of bridge foil from solid phase to plasma phase was described by phase transition fraction, the state of plasma with high temperature and pressure was described by the state equation of plasma which consider the changes in particle number and coulomb interaction between particles, and the motion of flyer was described by dynamic grid model. The calculated flow field density distribution closely matches the experimental results, and the maximum errors in flyer motion distance and velocity are 6.1% and 8.1%, respectively, validating the accuracy of the calculation model and calculation method. The research results indicate that when the capacitance is 0.33 μF and the initiation voltage is2800 V, within the research range, the maximum pressure in the flow field remains approximately 1×107 Pa; the temperature in the flow field gradually decreases from 9950 K at 516 ns to 3100 K at 2310 ns; and the plasma phase distribution in the flow field gradually evolves from a flat shape to a long strip shape, with the maximum diffusion distance of plasma in the direction perpendicular to the motion of the flyer being 0.8 mm. At 1360 ns, upon th flyer's breakthrough of the shock-wave front, a distinct bulge-shaped profile emerges in the leading edge of both pressure and temperature distributions within the flow field.
Shock initiation and ignition techniques driven by electrically exploded metallic bridge foils with insulating flyers have been widely implemented in initiation and ignition system of weapon. To address the deficiency in existing research regarding the description of the flow field evolution during the motion of flyer and promote the development of this technology towards efficient energy utilization and miniaturization, a double-pulse laser schlieren transient observation system was constructed. This system enables the acquisition of density distributions of the flow field and the motion distance of the flyer at different time. Additionally, a two-dimensional axisymmetric fluid dynamics calculation model and calculation method for the motion process of flyer driven by the electric explosion of metal foil were established, and corresponding numerical simulation calculations were performed in consideration of the evolution laws of the flow field inside and outside the acceleration chamber under the effects of the motion of flyer, the compression of shock wave, and the expansion of high-temperature and high-pressure plasma. The phase transition of bridge foil from solid phase to plasma phase was described by phase transition fraction, the state of plasma with high temperature and pressure was described by the state equation of plasma which consider the changes in particle number and coulomb interaction between particles, and the motion of flyer was described by dynamic grid model. The calculated flow field density distribution closely matches the experimental results, and the maximum errors in flyer motion distance and velocity are 6.1% and 8.1%, respectively, validating the accuracy of the calculation model and calculation method. The research results indicate that when the capacitance is 0.33 μF and the initiation voltage is
