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2026, 40(2)
:231-249.
doi: 10.1007/s13344-026-0019-z
Abstract:
The utilization of marine resources has become a strategic priority of global significance. Offshore platforms and offshore wind turbines are critical components of offshore energy development systems. To address the complexity, randomness, and uncertainty inherent in the marine environment and to ensure the safety of offshore installations during service, structural analysis and optimization of their foundations are essential. Jacket foundations, which provide high rigidity and stability, are suitable for shallow water and have emerged as the preferred foundation type for deepwater offshore installations. This study systematically reviews recent advances in theoretical modeling, numerical simulation, and experimental validation of structural response analyses and optimization methodologies for jacket foundations under complex marine conditions. Driven by diverse engineering requirements, researchers have proposed various structural optimization strategies. Existing efforts have primarily focused on structural topology, lightweight design, and performance-based optimization. Furthermore, this review identifies key technical challenges and outlines future research directions for optimizing offshore jacket foundations in ocean engineering.
The utilization of marine resources has become a strategic priority of global significance. Offshore platforms and offshore wind turbines are critical components of offshore energy development systems. To address the complexity, randomness, and uncertainty inherent in the marine environment and to ensure the safety of offshore installations during service, structural analysis and optimization of their foundations are essential. Jacket foundations, which provide high rigidity and stability, are suitable for shallow water and have emerged as the preferred foundation type for deepwater offshore installations. This study systematically reviews recent advances in theoretical modeling, numerical simulation, and experimental validation of structural response analyses and optimization methodologies for jacket foundations under complex marine conditions. Driven by diverse engineering requirements, researchers have proposed various structural optimization strategies. Existing efforts have primarily focused on structural topology, lightweight design, and performance-based optimization. Furthermore, this review identifies key technical challenges and outlines future research directions for optimizing offshore jacket foundations in ocean engineering.
2026, 40(2)
:250-260.
doi: 10.1007/s13344-026-0020-6
Abstract:
The design of floating wind turbines (FWTs) requires comprehensive consideration of complex marine environments and coupled responses among various components. The efficiency of current time domain simulation methods remains insufficient for design and optimization in the early stages of FWT development. This study validates a proposed frequency domain (FD) modeling method through code-to-experiment comparison. The FD method incorporates fundamental assumptions about the FWT model, including representing the FWT tower as a nonlinear beam and modeling the rotor-nacelle assembly (RNA) and floating platform as rigid bodies positioned at each end of the tower. The method incorporates excitation loads using blade element momentum theory, linear potential flow theory, and quasi-static catenary theory for aerodynamic, hydrodynamic, and mooring dynamics, respectively. Validation involves a code-to-experiment comparison through a basin model test utilizing a 1/50 scaled semi-submersible platform equipped with a 5MW wind turbine. The results demonstrate strong correlation with experimental data regarding mean response and power spectral density of platform and nacelle motions. The overall discrepancy for these physical quantities remains below 10%. Specifically, the mean discrepancy of platform surge and pitch motions under combined wind and wave conditions measures 1.05% and 3.91%, respectively. This validation confirms the viability of the proposed FD method, offering substantial technical support for early-phase analysis and optimization of FWT. The validation results contribute significantly to advancing FWT design and optimization understanding.
The design of floating wind turbines (FWTs) requires comprehensive consideration of complex marine environments and coupled responses among various components. The efficiency of current time domain simulation methods remains insufficient for design and optimization in the early stages of FWT development. This study validates a proposed frequency domain (FD) modeling method through code-to-experiment comparison. The FD method incorporates fundamental assumptions about the FWT model, including representing the FWT tower as a nonlinear beam and modeling the rotor-nacelle assembly (RNA) and floating platform as rigid bodies positioned at each end of the tower. The method incorporates excitation loads using blade element momentum theory, linear potential flow theory, and quasi-static catenary theory for aerodynamic, hydrodynamic, and mooring dynamics, respectively. Validation involves a code-to-experiment comparison through a basin model test utilizing a 1/50 scaled semi-submersible platform equipped with a 5MW wind turbine. The results demonstrate strong correlation with experimental data regarding mean response and power spectral density of platform and nacelle motions. The overall discrepancy for these physical quantities remains below 10%. Specifically, the mean discrepancy of platform surge and pitch motions under combined wind and wave conditions measures 1.05% and 3.91%, respectively. This validation confirms the viability of the proposed FD method, offering substantial technical support for early-phase analysis and optimization of FWT. The validation results contribute significantly to advancing FWT design and optimization understanding.
2026, 40(2)
:261-274.
doi: 10.1007/s13344-026-0021-5
Abstract:
Floating offshore wind turbines (FOWTs) are extensively utilized in offshore energy development. However, FOWTs are vulnerable to pitch motion, and high-frequency pitch motion may result in structural damage, equipment failure, and associated hazards. To suppress the undesired pitch motion of FOWTs, this paper presents an innovative Rotating Plates Tuned Mass Damper (RPTMD) system designed according to the natural frequency characteristics and spatial features of FOWTs. The motion equations of the RPTMD-FOWT system are established based on the TMD similarity principle. Through numerical modeling, parameters including rotating plate size, tuning ratio, and damping ratio are systematically examined. Furthermore, a comprehensive three-dimensional motion response model of floating body-wave-mooring interaction is developed to assess the RPTMD system’s effectiveness in FOWT motion control under extreme loading conditions. The motion suppression effect is evaluated using displacement peaks and displacement mean-square responses of the main mass. The energy dissipation characteristics of RPTMD are quantitatively analyzed through damping moments. Results indicate that the RPTMD exhibits optimal damping capability under resonant excitation, with a rotational inertia ratio of 0.7% achieving pitch suppression efficiency of 38.92% and heave suppression efficiency of 31.12%.
Floating offshore wind turbines (FOWTs) are extensively utilized in offshore energy development. However, FOWTs are vulnerable to pitch motion, and high-frequency pitch motion may result in structural damage, equipment failure, and associated hazards. To suppress the undesired pitch motion of FOWTs, this paper presents an innovative Rotating Plates Tuned Mass Damper (RPTMD) system designed according to the natural frequency characteristics and spatial features of FOWTs. The motion equations of the RPTMD-FOWT system are established based on the TMD similarity principle. Through numerical modeling, parameters including rotating plate size, tuning ratio, and damping ratio are systematically examined. Furthermore, a comprehensive three-dimensional motion response model of floating body-wave-mooring interaction is developed to assess the RPTMD system’s effectiveness in FOWT motion control under extreme loading conditions. The motion suppression effect is evaluated using displacement peaks and displacement mean-square responses of the main mass. The energy dissipation characteristics of RPTMD are quantitatively analyzed through damping moments. Results indicate that the RPTMD exhibits optimal damping capability under resonant excitation, with a rotational inertia ratio of 0.7% achieving pitch suppression efficiency of 38.92% and heave suppression efficiency of 31.12%.
2026, 40(2)
:275-288.
doi: 10.1007/s13344-026-0022-4
Abstract:
Contemporary research on near-surface explosions predominantly examines shock waves and bubbles, while investigations into explosion-generated waves remain limited. In naval combat scenarios, explosion-generated waves present a substantial threat to vessels, potentially resulting in catastrophic outcomes. This paper examines the characteristics of waves generated by near-surface explosions, specifically focusing on wave propagation patterns under varying explosive configurations and marine conditions. The Structured Arbitrary Lagrangian-Eulerian (S-ALE) method is employed to simulate and analyze wave characteristics resulting from near-surface explosions, seeking to understand surface movement behavior under diverse conditions. The research demonstrates that dual explosion charges produce more intense waves compared to single explosion charges of equivalent explosive force. Within the wave field, explosion-generated waves can enhance the roll and pitch movements of structures by 50% to 150%.
Contemporary research on near-surface explosions predominantly examines shock waves and bubbles, while investigations into explosion-generated waves remain limited. In naval combat scenarios, explosion-generated waves present a substantial threat to vessels, potentially resulting in catastrophic outcomes. This paper examines the characteristics of waves generated by near-surface explosions, specifically focusing on wave propagation patterns under varying explosive configurations and marine conditions. The Structured Arbitrary Lagrangian-Eulerian (S-ALE) method is employed to simulate and analyze wave characteristics resulting from near-surface explosions, seeking to understand surface movement behavior under diverse conditions. The research demonstrates that dual explosion charges produce more intense waves compared to single explosion charges of equivalent explosive force. Within the wave field, explosion-generated waves can enhance the roll and pitch movements of structures by 50% to 150%.
2026, 40(2)
:289-304.
doi: 10.1007/s13344-026-0023-3
Abstract:
This study experimentally investigates Slug flow-induced vibration (SIV) of an S-shaped flexible riser in a small-scale gas-liquid two-phase test loop. The investigation examines slug flow across gas-liquid ratios ranging from 1.0 to 4.0 with a constant superficial mixture velocity. Non-intrusive high-speed cameras simultaneously capture the internal unsteady slug flow characteristics and dynamic responses of the riser. The analysis encompasses slug flow properties, spatial-temporal evolution of vibration displacements, vibration frequency, mode response, and the buoyancy module’s influence on riser response. Results indicate that translational velocity, liquid slug length, and gas plug length increase with rising gas-liquid ratios at constant superficial mixture velocity. The translational velocity shows modest increases, while liquid holdup and slug flow recurrence frequency decrease. Unsteady slug flow induces both in-plane and out-of-plane responses across all experimental cases. At fixed superficial mixture velocity, amplitude increases with higher gas-liquid ratios. The out-of-plane direction exhibits first three order mode responses, while in-plane vibration primarily demonstrates fundamental mode response, despite higher-order frequency presence at both ends. The buoyancy module affects both in-plane and out-of-plane responses, with in-plane vibration showing larger amplitude at lower frequency. The buoyancy module’s influence intensifies with increasing gas-liquid ratios.
This study experimentally investigates Slug flow-induced vibration (SIV) of an S-shaped flexible riser in a small-scale gas-liquid two-phase test loop. The investigation examines slug flow across gas-liquid ratios ranging from 1.0 to 4.0 with a constant superficial mixture velocity. Non-intrusive high-speed cameras simultaneously capture the internal unsteady slug flow characteristics and dynamic responses of the riser. The analysis encompasses slug flow properties, spatial-temporal evolution of vibration displacements, vibration frequency, mode response, and the buoyancy module’s influence on riser response. Results indicate that translational velocity, liquid slug length, and gas plug length increase with rising gas-liquid ratios at constant superficial mixture velocity. The translational velocity shows modest increases, while liquid holdup and slug flow recurrence frequency decrease. Unsteady slug flow induces both in-plane and out-of-plane responses across all experimental cases. At fixed superficial mixture velocity, amplitude increases with higher gas-liquid ratios. The out-of-plane direction exhibits first three order mode responses, while in-plane vibration primarily demonstrates fundamental mode response, despite higher-order frequency presence at both ends. The buoyancy module affects both in-plane and out-of-plane responses, with in-plane vibration showing larger amplitude at lower frequency. The buoyancy module’s influence intensifies with increasing gas-liquid ratios.
2026, 40(2)
:305-316.
doi: 10.1007/s13344-026-0024-2
Abstract:
This study presents a model incorporating structure and wake oscillators to predict coupled in-line and cross-flow vortex-induced vibration (VIV) of a near-wall cylinder capable of wall collision. To evaluate wall proximity effects, the model employs hydrodynamic parameters, including vortex shedding frequency and time-varying/time-averaged lift/drag coefficients, in relation to the Reynolds number, boundary layer thickness, and cylinder-wall gap. While the general VIV model effectively predicts wall proximity effects, it proves inadequate for collision prediction. Through analysis and comparison of three impact models, the study determines that resetting cross-flow velocity after collision using a restitution coefficient of 1, assuming elastic impact, optimally predicts collision while preventing penetration. The validated VIV model accurately reflects wall effects and collision impacts on vibrations. Collisions manifest in both streamwise-transverse 1:1 and 2:1 resonance, as well as multi-frequency vibrations in pre- and de-synchronization regimes, introducing additional nonlinear characteristics. Quasi-symmetric tips appear in lower sections of irregular trajectories due to elastic impact assumptions and subsequent fluid-structure interaction. The research reveals that small gaps and collision can independently or jointly induce oval trajectories, indicating reduced vortex shedding from the wall-side of the cylinder. Additionally, increased mass and damping ratios diminish vibrations and collision regions. With continued research to enhance accuracy and practicability, this model shows potential application to submarine pipelines with multi-spans and internal multiphase flow.
This study presents a model incorporating structure and wake oscillators to predict coupled in-line and cross-flow vortex-induced vibration (VIV) of a near-wall cylinder capable of wall collision. To evaluate wall proximity effects, the model employs hydrodynamic parameters, including vortex shedding frequency and time-varying/time-averaged lift/drag coefficients, in relation to the Reynolds number, boundary layer thickness, and cylinder-wall gap. While the general VIV model effectively predicts wall proximity effects, it proves inadequate for collision prediction. Through analysis and comparison of three impact models, the study determines that resetting cross-flow velocity after collision using a restitution coefficient of 1, assuming elastic impact, optimally predicts collision while preventing penetration. The validated VIV model accurately reflects wall effects and collision impacts on vibrations. Collisions manifest in both streamwise-transverse 1:1 and 2:1 resonance, as well as multi-frequency vibrations in pre- and de-synchronization regimes, introducing additional nonlinear characteristics. Quasi-symmetric tips appear in lower sections of irregular trajectories due to elastic impact assumptions and subsequent fluid-structure interaction. The research reveals that small gaps and collision can independently or jointly induce oval trajectories, indicating reduced vortex shedding from the wall-side of the cylinder. Additionally, increased mass and damping ratios diminish vibrations and collision regions. With continued research to enhance accuracy and practicability, this model shows potential application to submarine pipelines with multi-spans and internal multiphase flow.
Theoretical Investigation of Double Carcass Hoses Under Combined Internal Pressure and Axial Loading
2026, 40(2)
:317-332.
doi: 10.1007/s13344-026-0025-1
Abstract:
As offshore oil and gas exploration advances into deeper waters, double carcass hoses (DCHs) are subjected to increasingly complex combined loading conditions, necessitating enhanced reliability and durability in extreme environments. This paper presents a theoretical analysis methodology for evaluating the stress and deformation of DCHs under concurrent internal pressure and axial tensile forces. The approach, based on the laminated plate theory and Mooney-Rivlin model, incorporates the nonlinear characteristics of the rubber matrix and geometric nonlinearity within reinforcement layers. Through iterative loading processes, material parameters and reinforcement layer winding angles are systematically updated. The failure criteria are established using the maximum tensile strength of the cord and Von Mises criterion for helical steel wires. The model’s validity was verified through axial tensile tests on a DCH with a 500 mm inner diameter. The analysis reveals distinct variations in load-bearing contributions between helical steel wire and cord layers at different internal pressure levels. The hose demonstrates complex nonlinear behavior under combined loading conditions. Comprehensive sensitivity analyses examined the influence of critical parameters, including cord winding angle, layer count, hose diameter, helical steel wire pitch, and wire diameter, on hose failure characteristics. A failure envelope for DCHs under various parameter conditions was developed, providing a theoretical framework for optimizing DCH structural design.
As offshore oil and gas exploration advances into deeper waters, double carcass hoses (DCHs) are subjected to increasingly complex combined loading conditions, necessitating enhanced reliability and durability in extreme environments. This paper presents a theoretical analysis methodology for evaluating the stress and deformation of DCHs under concurrent internal pressure and axial tensile forces. The approach, based on the laminated plate theory and Mooney-Rivlin model, incorporates the nonlinear characteristics of the rubber matrix and geometric nonlinearity within reinforcement layers. Through iterative loading processes, material parameters and reinforcement layer winding angles are systematically updated. The failure criteria are established using the maximum tensile strength of the cord and Von Mises criterion for helical steel wires. The model’s validity was verified through axial tensile tests on a DCH with a 500 mm inner diameter. The analysis reveals distinct variations in load-bearing contributions between helical steel wire and cord layers at different internal pressure levels. The hose demonstrates complex nonlinear behavior under combined loading conditions. Comprehensive sensitivity analyses examined the influence of critical parameters, including cord winding angle, layer count, hose diameter, helical steel wire pitch, and wire diameter, on hose failure characteristics. A failure envelope for DCHs under various parameter conditions was developed, providing a theoretical framework for optimizing DCH structural design.
2026, 40(2)
:333-340.
doi: 10.1007/s13344-026-0026-0
Abstract:
Subsea pipelines with egg-shaped profiles may develop cracks during extended operational periods. A cost-effective trenchless rehabilitation method involves installing a thin-walled liner adjacent to the cracked pipeline’s inner surface. This rehabilitation enables the pipeline-liner system to maintain normal liquid/gas transportation functions. The liner can be heated to decrease transportation viscosity and enhance flow rates. However, thermal instability frequently occurs when thin-walled liners are exposed to elevated temperatures. This research presents a computational scheme to analyze the thermal properties of an installed liner with an egg-shaped profile. A modified sine function describes the radial inward deflection, considering the liner’s rigid and tight encasement within the pipeline. Response formulae are derived by combining classic shell principle with the principle of minimum potential energy. These formulae are then solved to determine equilibrium curves and buckling temperature variations. A rigorous verification process validates the computational scheme, demonstrating that the calculated equilibrium curves align well with previous research findings. The study examines the effects of various thickness-to-radius ratios on the egg-shaped liner’s thermostability and compares the thermal buckling resistance between egg-shaped and circular liners. Results indicate superior thermostability in egg-shaped liners compared to circular configurations.
Subsea pipelines with egg-shaped profiles may develop cracks during extended operational periods. A cost-effective trenchless rehabilitation method involves installing a thin-walled liner adjacent to the cracked pipeline’s inner surface. This rehabilitation enables the pipeline-liner system to maintain normal liquid/gas transportation functions. The liner can be heated to decrease transportation viscosity and enhance flow rates. However, thermal instability frequently occurs when thin-walled liners are exposed to elevated temperatures. This research presents a computational scheme to analyze the thermal properties of an installed liner with an egg-shaped profile. A modified sine function describes the radial inward deflection, considering the liner’s rigid and tight encasement within the pipeline. Response formulae are derived by combining classic shell principle with the principle of minimum potential energy. These formulae are then solved to determine equilibrium curves and buckling temperature variations. A rigorous verification process validates the computational scheme, demonstrating that the calculated equilibrium curves align well with previous research findings. The study examines the effects of various thickness-to-radius ratios on the egg-shaped liner’s thermostability and compares the thermal buckling resistance between egg-shaped and circular liners. Results indicate superior thermostability in egg-shaped liners compared to circular configurations.
2026, 40(2)
:341-356.
doi: 10.1007/s13344-026-0027-z
Abstract:
A fully nonlinear potential flow (FNPF) solver has been developed using the Finite Element Method (FEM) to simulate time-domain interactions between free-surface waves and marine structures. The ALE framework is implemented alongside a segment spring analogy-based moving mesh strategy to accurately track evolving free surfaces and moving boundaries of floating bodies. The solver employs a preconditioned conjugate gradient method to efficiently resolve the resulting sparse, symmetric linear system at each time step. Temporal evolution is managed through a standard fourth-order Runge-Kutta scheme, while Chebyshev 5-point smoothing suppresses non-physical saw-tooth instabilities. The solver’s performance and reliability are verified through comprehensive benchmark tests, including free-surface sloshing, nonlinear wave propagation, and wave-structure interactions with submerged or floating bodies. Furthermore, the study explores a modified potential flow model incorporating a quadratic damping term to address viscous effects in gap/moonpool resonance problems.
A fully nonlinear potential flow (FNPF) solver has been developed using the Finite Element Method (FEM) to simulate time-domain interactions between free-surface waves and marine structures. The ALE framework is implemented alongside a segment spring analogy-based moving mesh strategy to accurately track evolving free surfaces and moving boundaries of floating bodies. The solver employs a preconditioned conjugate gradient method to efficiently resolve the resulting sparse, symmetric linear system at each time step. Temporal evolution is managed through a standard fourth-order Runge-Kutta scheme, while Chebyshev 5-point smoothing suppresses non-physical saw-tooth instabilities. The solver’s performance and reliability are verified through comprehensive benchmark tests, including free-surface sloshing, nonlinear wave propagation, and wave-structure interactions with submerged or floating bodies. Furthermore, the study explores a modified potential flow model incorporating a quadratic damping term to address viscous effects in gap/moonpool resonance problems.
2026, 40(2)
:357-368.
doi: 10.1007/s13344-026-0028-y
Abstract:
This paper presents a novel fast prediction method for ship waves through the development of a neural network model called Ship Wave Residual Network (SWRN). The study employs a Wigley hull model for analysis, with datasets generated through Computational Fluid Dynamics (CFD) simulations. A comprehensive validation study addresses simulation uncertainties through the grid convergence index (GCI), Monte Carlo method, and Chebyshev inequality. The SWRN framework is applied to datasets encompassing various ship form parameters and Froude numbers. The accuracy of the neural network is evaluated by comparing ship-generated wave field and total resistance predictions from SWRN and CFD for hull forms and Froude numbers beyond the training datasets. Results demonstrate that SWRN training requires only 40% of the computational resources needed for a single CFD simulation. The trained model generates predictions for ship wave fields and total resistance under calm water conditions within seconds, maintaining acceptable accuracy levels. This prediction technology establishes a foundation for AI-accelerated solutions in ship-generated flow field analysis.
This paper presents a novel fast prediction method for ship waves through the development of a neural network model called Ship Wave Residual Network (SWRN). The study employs a Wigley hull model for analysis, with datasets generated through Computational Fluid Dynamics (CFD) simulations. A comprehensive validation study addresses simulation uncertainties through the grid convergence index (GCI), Monte Carlo method, and Chebyshev inequality. The SWRN framework is applied to datasets encompassing various ship form parameters and Froude numbers. The accuracy of the neural network is evaluated by comparing ship-generated wave field and total resistance predictions from SWRN and CFD for hull forms and Froude numbers beyond the training datasets. Results demonstrate that SWRN training requires only 40% of the computational resources needed for a single CFD simulation. The trained model generates predictions for ship wave fields and total resistance under calm water conditions within seconds, maintaining acceptable accuracy levels. This prediction technology establishes a foundation for AI-accelerated solutions in ship-generated flow field analysis.
2026, 40(2)
:369-381.
doi: 10.1007/s13344-026-0029-x
Abstract:
Water jet propulsor (WJP) is an integrated propulsion system comprising a stator, rotor, and duct. Limited research exists on characterizing the flow and acoustic properties of individual components. This study employs improved delayed detached-eddy simulation with the Ffowcs Williams and Hawkings method to analyze flow patterns and noise generation around a WJP. The numerical results demonstrate strong correlation with experimental data, enabling detailed analysis of both internal and wake flow fields. Findings indicate that the WJP wake exhibits an axisymmetric conical flow field without a distinct stable region in its trajectory. The vortex passing through the nozzle rapidly transitions to an unstable state. Increased rotation speed results in greater wake wave height, decreased trailing angle, and pronounced secondary vortex formation in the unstable region. The study examines WJP flow noise characteristics and component acoustic contributions using energy method analysis. Directional variation in WJP flow noise reveals distinct component contributions: maximum overall sound pressure level occurs at the rear, where the rotor set contributes 90%, while at the sides and bottom, the rotor set accounts for 77% of acoustic output.
Water jet propulsor (WJP) is an integrated propulsion system comprising a stator, rotor, and duct. Limited research exists on characterizing the flow and acoustic properties of individual components. This study employs improved delayed detached-eddy simulation with the Ffowcs Williams and Hawkings method to analyze flow patterns and noise generation around a WJP. The numerical results demonstrate strong correlation with experimental data, enabling detailed analysis of both internal and wake flow fields. Findings indicate that the WJP wake exhibits an axisymmetric conical flow field without a distinct stable region in its trajectory. The vortex passing through the nozzle rapidly transitions to an unstable state. Increased rotation speed results in greater wake wave height, decreased trailing angle, and pronounced secondary vortex formation in the unstable region. The study examines WJP flow noise characteristics and component acoustic contributions using energy method analysis. Directional variation in WJP flow noise reveals distinct component contributions: maximum overall sound pressure level occurs at the rear, where the rotor set contributes 90%, while at the sides and bottom, the rotor set accounts for 77% of acoustic output.
2026, 40(2)
:382-396.
doi: 10.1007/s13344-026-0030-4
Abstract:
The Autonomous Underwater Glider (AUG), driven by gravity and buoyancy forces, plays a vital role in ocean observation networks because of its cost efficiency, low noise, and energy-efficient operation. This study investigates the motion parameters and energy consumption of AUGs during spiral motion. Dynamic and energy consumption models for three-dimensional movement are established, incorporating variations in seawater density and AUG volume. The performance of AUGs is evaluated across various spiral motion scenarios in terms of spatial, temporal, and energy metrics. For example, during descent, the turning radius ranges from 73.6 m to 457.5 m, the turning angular velocity varies from 1.8°/min to 8.2°/min, and the energy consumption rate spans from 0.86 kJ/rad to 4.29 kJ/rad. Additionally, an optimization boundary surface targeting minimum energy consumption is presented for parameter selection. Considering ocean currents, a multi-objective optimization of control parameters reveals that c1 frequently serves as the critical parameter affecting AUG performance. Both the nondominated sorting genetic algorithm II (NSGA-II) and nondominated particle swarm optimization (NSPSO) methods are employed, yielding similar Pareto sets. Specific control parameter selections and simulation results for various task requirements demonstrate the achievement of both minimum energy consumption and maximum turning speed. For example, with a turning angle of 0.5π, the optimized maximum angular velocity reaches 8.18°/min, while the minimum energy consumption is 1.708 kJ. These findings offer valuable insights for optimizing control strategies in AUGs’ three-dimensional spiral motion, enhancing ocean observation technologies.
The Autonomous Underwater Glider (AUG), driven by gravity and buoyancy forces, plays a vital role in ocean observation networks because of its cost efficiency, low noise, and energy-efficient operation. This study investigates the motion parameters and energy consumption of AUGs during spiral motion. Dynamic and energy consumption models for three-dimensional movement are established, incorporating variations in seawater density and AUG volume. The performance of AUGs is evaluated across various spiral motion scenarios in terms of spatial, temporal, and energy metrics. For example, during descent, the turning radius ranges from 73.6 m to 457.5 m, the turning angular velocity varies from 1.8°/min to 8.2°/min, and the energy consumption rate spans from 0.86 kJ/rad to 4.29 kJ/rad. Additionally, an optimization boundary surface targeting minimum energy consumption is presented for parameter selection. Considering ocean currents, a multi-objective optimization of control parameters reveals that c1 frequently serves as the critical parameter affecting AUG performance. Both the nondominated sorting genetic algorithm II (NSGA-II) and nondominated particle swarm optimization (NSPSO) methods are employed, yielding similar Pareto sets. Specific control parameter selections and simulation results for various task requirements demonstrate the achievement of both minimum energy consumption and maximum turning speed. For example, with a turning angle of 0.5π, the optimized maximum angular velocity reaches 8.18°/min, while the minimum energy consumption is 1.708 kJ. These findings offer valuable insights for optimizing control strategies in AUGs’ three-dimensional spiral motion, enhancing ocean observation technologies.
2026, 40(2)
:397-413.
doi: 10.1007/s13344-026-0031-3
Abstract:
Sediment siltation in the Deepwater Navigational Channel (DNC) of the Changjiang River Estuary (CRE) remains a persistent critical challenge. A numerical model was developed to investigate the near-bottom transport of sediment-laden gravity currents in the CRE and their potential contribution to siltation. The model successfully reproduces the gravity current process of near-bottom high-concentration sediment through the integration of the three-dimensional Herschel-Bulkley rheological model, incorporating combined stratification of salinity and sediment. The model was validated through simulations of idealized estuarine sediment stratification and flume slope flow experiments with fluid mud, followed by application to the CRE with verification against field-observed data. The simulation results demonstrate that stratification promotes the formation of high sediment concentrations near the bottom. During tidal transitions, the reduction in longitudinal tidal forcing along the North Passage (NP) enhances sediment retention, resulting in accumulated high sediment concentrations along the DNC sides in the middle–lower sections. Gravity currents predominantly occur during the flood-to-ebb tide transition and significantly influence lateral bottom sediment transport beyond typical tidal dynamics. Quantitative assessment indicates that lateral gravity currents may contribute up to 68% of DNC siltation, suggesting that near-bottom high sediment concentration gravity currents substantially impact siltation in the mid-lower section of the DNC.
Sediment siltation in the Deepwater Navigational Channel (DNC) of the Changjiang River Estuary (CRE) remains a persistent critical challenge. A numerical model was developed to investigate the near-bottom transport of sediment-laden gravity currents in the CRE and their potential contribution to siltation. The model successfully reproduces the gravity current process of near-bottom high-concentration sediment through the integration of the three-dimensional Herschel-Bulkley rheological model, incorporating combined stratification of salinity and sediment. The model was validated through simulations of idealized estuarine sediment stratification and flume slope flow experiments with fluid mud, followed by application to the CRE with verification against field-observed data. The simulation results demonstrate that stratification promotes the formation of high sediment concentrations near the bottom. During tidal transitions, the reduction in longitudinal tidal forcing along the North Passage (NP) enhances sediment retention, resulting in accumulated high sediment concentrations along the DNC sides in the middle–lower sections. Gravity currents predominantly occur during the flood-to-ebb tide transition and significantly influence lateral bottom sediment transport beyond typical tidal dynamics. Quantitative assessment indicates that lateral gravity currents may contribute up to 68% of DNC siltation, suggesting that near-bottom high sediment concentration gravity currents substantially impact siltation in the mid-lower section of the DNC.
2026, 40(2)
:414-427.
doi: 10.1007/s13344-026-0032-2
Abstract:
The analysis of suction-assisted penetration resistance necessitates consideration of inherent variability in sand properties within suction foundations must be considered during the analysis of suction-assisted penetration resistance. This paper derives the critical particle size for particle initiation on the soil surface based on the upward seepage effect on soil particles. An exponential decay function is introduced to explain the erosion mechanism of soil particles during transport and blockage. The study analyzes penetration depth during suction and establishes a database of 66 measured data points on sand erosion, enabling optimization analysis of the particle activation distribution coefficient A in the exponential decay function. The research yields a highly accurate and moderately dispersed soil particle transport mathematical model. This model enables precise calculation of soil particle erosion during suction-assisted penetration processes in suction foundations, facilitating inference of changes in internal porosity and permeability coefficient. The enhanced understanding significantly improves suction foundation penetration design, particularly regarding permeability impacts on both sides of the foundation.
The analysis of suction-assisted penetration resistance necessitates consideration of inherent variability in sand properties within suction foundations must be considered during the analysis of suction-assisted penetration resistance. This paper derives the critical particle size for particle initiation on the soil surface based on the upward seepage effect on soil particles. An exponential decay function is introduced to explain the erosion mechanism of soil particles during transport and blockage. The study analyzes penetration depth during suction and establishes a database of 66 measured data points on sand erosion, enabling optimization analysis of the particle activation distribution coefficient A in the exponential decay function. The research yields a highly accurate and moderately dispersed soil particle transport mathematical model. This model enables precise calculation of soil particle erosion during suction-assisted penetration processes in suction foundations, facilitating inference of changes in internal porosity and permeability coefficient. The enhanced understanding significantly improves suction foundation penetration design, particularly regarding permeability impacts on both sides of the foundation.
2026, 40(2)
:428-442.
doi: 10.1007/s13344-026-0033-1
Abstract:
Motivated by a real-world engineering project, this study explores the temporal development of scour depth and the morphology of scour pits around suction bucket foundations in silty clay subjected to unidirectional currents, through controlled laboratory flume experiments. The findings indicate that: (1) the maximum scour depth of the triple suction bucket foundation demonstrates substantial variation around the threshold flow velocity for silty clay\begin{document}${U_{\text{c}}} = 0.4{\text{ m/s}}$\end{document}
Motivated by a real-world engineering project, this study explores the temporal development of scour depth and the morphology of scour pits around suction bucket foundations in silty clay subjected to unidirectional currents, through controlled laboratory flume experiments. The findings indicate that: (1) the maximum scour depth of the triple suction bucket foundation demonstrates substantial variation around the threshold flow velocity for silty clay
2026, 40(2)
:443-451.
doi: 10.1007/s13344-026-0034-0
Abstract:
This study investigates the complex processes of tsunami wave propagation in the waters of Xuande Atoll to assess tsunami hazards from potential earthquakes in the Manila subduction zone. The investigation employs numerical simulations of tsunami wave generation and propagation using locally refined grids for the atoll topography. Analysis reveals that tsunami waves oscillating on the reef flat can generate a higher secondary wave that exceeds the leading wave amplitude. The study identifies high-risk areas primarily concentrated on the eastern reef facing the source area, with local high tsunami hazard points typically resulting from wave oscillations on the reef. For magnitude 8.9 earthquake tsunamis, the maximum wave height on the atoll may exceed 4 m. The research demonstrates that heterogeneous slip and epicenter position significantly influence wave size and spatial distribution, with epicenter location particularly affecting incident wave direction and subsequent tsunami hazard distribution across Xuande Atoll.
This study investigates the complex processes of tsunami wave propagation in the waters of Xuande Atoll to assess tsunami hazards from potential earthquakes in the Manila subduction zone. The investigation employs numerical simulations of tsunami wave generation and propagation using locally refined grids for the atoll topography. Analysis reveals that tsunami waves oscillating on the reef flat can generate a higher secondary wave that exceeds the leading wave amplitude. The study identifies high-risk areas primarily concentrated on the eastern reef facing the source area, with local high tsunami hazard points typically resulting from wave oscillations on the reef. For magnitude 8.9 earthquake tsunamis, the maximum wave height on the atoll may exceed 4 m. The research demonstrates that heterogeneous slip and epicenter position significantly influence wave size and spatial distribution, with epicenter location particularly affecting incident wave direction and subsequent tsunami hazard distribution across Xuande Atoll.
2026, 40(2)
:452-465.
doi: 10.1007/s13344-026-0035-z
Abstract:
This study examines the interaction between internal solitary waves (ISWs) and an elliptical submersible based on the eKdV theory. The numerical model’s accuracy is validated through comparison of force calculations on a single cylinder with experimental data. Analysis reveals significant hydrodynamic characteristics around the elliptical submersible. The findings demonstrate that vertical positioning and elevation angle substantially influence wave loads on the submersible. At various vertical positions, uniform distribution of elevated hydrodynamic pressure may result in submersible disintegration. Submersibles with ±30° elevation angles experience greater total moments, increasing their susceptibility to capsizing. The maximum horizontal force increases by factors ranging from 1.46 to 8.81 when the submersible is inclined between −30° and 30°. The interface exhibits negative vorticity accumulation due to shear effects between upper and lower fluids. Submersible inclination leads to increased surrounding velocity and vorticity.
This study examines the interaction between internal solitary waves (ISWs) and an elliptical submersible based on the eKdV theory. The numerical model’s accuracy is validated through comparison of force calculations on a single cylinder with experimental data. Analysis reveals significant hydrodynamic characteristics around the elliptical submersible. The findings demonstrate that vertical positioning and elevation angle substantially influence wave loads on the submersible. At various vertical positions, uniform distribution of elevated hydrodynamic pressure may result in submersible disintegration. Submersibles with ±30° elevation angles experience greater total moments, increasing their susceptibility to capsizing. The maximum horizontal force increases by factors ranging from 1.46 to 8.81 when the submersible is inclined between −30° and 30°. The interface exhibits negative vorticity accumulation due to shear effects between upper and lower fluids. Submersible inclination leads to increased surrounding velocity and vorticity.
2026, 40(2)
:466-477.
doi: 10.1007/s13344-026-0036-y
Abstract:
The accurate detection of submarine pipelines and cables is essential for marine energy transmission. Current object detection algorithms exhibit limitations due to poor underwater visibility, complex seabed terrain, and dense occlusions, resulting in high false positive rates and missed detections. This study presents SPC-YOLO (Submarine Pipeline and Cable-YOLO), an enhanced object detection framework that combines YOLOv8 with the ByteTrack tracking algorithm. The framework introduces three key innovations: (1) Enhanced Feature Extraction: Integration of a Diverse Branch Block (DBB) into the backbone network to enhance multi-scale feature representation. (2) Adaptive Feature Learning: Replacement of the original C2f module with an Inverted Residual Mobile Block (iRMB) in the neck section, and implementation of a novel Dual Multi-Scale Attention (DMSA) mechanism for adaptive spatial-contextual feature fusion. (3) Training Optimization: Implementation of a Soft Intersection over Union (SIoU) loss function to improve bounding box regression accuracy. Additionally, the ByteTrack algorithm enables pipeline and cable tracking in video sequences. Extensive experiments on a real-world dataset from side-scan sonar videos in Bohai Bay demonstrate that SPC-YOLO achieves a precision of 93.3%, recall of 89.1%, and mean Average Precision (mAP) of 94.9% and 59.2% at IoU thresholds of 0.50 and 0.50:0.95, respectively. These results represent improvements of 6.9%, 4.1%, 4.6%, and 6.1% compared with YOLOv8, validating SPC-YOLO’s superior detection accuracy and robustness in challenging underwater environments and establishing a framework for surveillance and maintenance of critical seabed infrastructure.
The accurate detection of submarine pipelines and cables is essential for marine energy transmission. Current object detection algorithms exhibit limitations due to poor underwater visibility, complex seabed terrain, and dense occlusions, resulting in high false positive rates and missed detections. This study presents SPC-YOLO (Submarine Pipeline and Cable-YOLO), an enhanced object detection framework that combines YOLOv8 with the ByteTrack tracking algorithm. The framework introduces three key innovations: (1) Enhanced Feature Extraction: Integration of a Diverse Branch Block (DBB) into the backbone network to enhance multi-scale feature representation. (2) Adaptive Feature Learning: Replacement of the original C2f module with an Inverted Residual Mobile Block (iRMB) in the neck section, and implementation of a novel Dual Multi-Scale Attention (DMSA) mechanism for adaptive spatial-contextual feature fusion. (3) Training Optimization: Implementation of a Soft Intersection over Union (SIoU) loss function to improve bounding box regression accuracy. Additionally, the ByteTrack algorithm enables pipeline and cable tracking in video sequences. Extensive experiments on a real-world dataset from side-scan sonar videos in Bohai Bay demonstrate that SPC-YOLO achieves a precision of 93.3%, recall of 89.1%, and mean Average Precision (mAP) of 94.9% and 59.2% at IoU thresholds of 0.50 and 0.50:0.95, respectively. These results represent improvements of 6.9%, 4.1%, 4.6%, and 6.1% compared with YOLOv8, validating SPC-YOLO’s superior detection accuracy and robustness in challenging underwater environments and establishing a framework for surveillance and maintenance of critical seabed infrastructure.
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