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J. Mar. Sci. Eng., Volume 13, Issue 8 (August 2025) – 162 articles

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31 pages, 8943 KiB  
Article
Intelligent Optimization of Waypoints on the Great Ellipse Routes for Arctic Navigation and Segmental Safety Assessment
by Chenchen Jiao, Zhichen Liu, Jiaxin Hou, Jianan Luo and Xiaoxia Wan
J. Mar. Sci. Eng. 2025, 13(8), 1543; https://doi.org/10.3390/jmse13081543 (registering DOI) - 11 Aug 2025
Abstract
A great ellipse route (GER), as one of the fundamental routes for ocean voyages, directly influences the actual voyage distance and the complexity of vessel maneuvering through the location and number of its waypoints. Against the backdrop of global warming, the melting of [...] Read more.
A great ellipse route (GER), as one of the fundamental routes for ocean voyages, directly influences the actual voyage distance and the complexity of vessel maneuvering through the location and number of its waypoints. Against the backdrop of global warming, the melting of Arctic sea ice has accelerated the opening of the Arctic shipping route. This paper addresses the issue of how to reasonably segment and adopt rhumb line routes to approximate the GER in the special navigational environment of the Arctic. Using historical routes, recommended routes, and geospatial data that have passed through the Arctic shipping lane as constraints, this paper proposes a waypoint optimization model based on an adaptive hybrid particle swarm optimization-genetic algorithm (AHPSOGA). Additionally, by integrating Arctic remote sensing ice condition data and the Polar Operational Limit Assessment Risk Indexing System (POLARIS), a safety assessment model tailored for this route has been developed, enabling the quantification of sea ice risks and dynamic evaluation of segment safety. Experimental results indicate that the proposed waypoint optimization model reduces the number of waypoints and voyage distance compared to recommended routes and conventional shipping industry methods. Furthermore, the AHPSOGA algorithm achieves a 16.41% and 19.19% improvement in convergence speed compared to traditional GA and PSO algorithms, respectively. In terms of computational efficiency, the average runtime is improved by approximately 12.00% and 14.53%, respectively. The risk levels of each segment of the optimized route are comparable to those of the recommended Northeast Passage route. This study provides an effective theoretical foundation and technical support for intelligent planning and decision-making for Arctic shipping routes. Full article
(This article belongs to the Special Issue Maritime Transportation Safety and Risk Management)
20 pages, 4410 KiB  
Article
Experimental Investigation on the Hydraulic Characteristics of Self-Rotating Flood Barrier
by Jooyeon Lee, Byoungjoon Na and Sang-Ho Oh
J. Mar. Sci. Eng. 2025, 13(8), 1542; https://doi.org/10.3390/jmse13081542 (registering DOI) - 11 Aug 2025
Abstract
This study investigated the hydraulic characteristics of a self-rotating flood barrier (SRFB) by performing laboratory experiments. The SRFB is proposed as a secure solution to withstand both waves and sudden water level rise, thereby protecting the coastal area behind it. The SRFB is [...] Read more.
This study investigated the hydraulic characteristics of a self-rotating flood barrier (SRFB) by performing laboratory experiments. The SRFB is proposed as a secure solution to withstand both waves and sudden water level rise, thereby protecting the coastal area behind it. The SRFB is designed to rotate and rise automatically by buoyancy when the water level exceeds a certain threshold or waves start to overtop the crest level of the caisson, where the barrier is enclosed. The barrier begins to rise when the chamber is filled with enough water for the buoyancy force to exceed its own weight. The performance of the structure was tested under various regular wave conditions at different water depths. Pressure transducers were placed along the front face of the barrier to measure the wave pressures acting on it. The barrier’s angular displacement was also identified using synchronized video footage during the measurements. The results showed that the overall magnitude of the measured pressures increased with water depth due to the larger volume of water inflow from overtopping waves. During the rise in the barrier, the pressure profiles dynamically varied with the rotation angle as the pattern of water flow into the chamber changed depending on the test cases. Analysis results showed how the pressures are distributed along the barrier at the moment of peak wave force. These findings would provide fundamental information for estimating design wave forces on the structure. Full article
(This article belongs to the Special Issue Advanced Studies in Marine Structures)
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28 pages, 2570 KiB  
Article
Efficient Hydrodynamic Shape Optimization of a Sea-Turtle-Inspired AUH Using an Optuna-Tuned NSGA-II
by Xintong Guo, Hongwu Huang, Chao Yuan, Xiujing Gao, Hao Zhong and Lijiao Wang
J. Mar. Sci. Eng. 2025, 13(8), 1541; https://doi.org/10.3390/jmse13081541 - 11 Aug 2025
Abstract
Disc-shaped Autonomous Underwater Helicopters (AUHs) offer superior maneuverability but suffer from high hydrodynamic drag, which limits their operational endurance. To address this challenge, this study proposes a robust optimization framework for a novel sea-turtle-inspired AUH. A parametric hull, governed by two dimensionless shape [...] Read more.
Disc-shaped Autonomous Underwater Helicopters (AUHs) offer superior maneuverability but suffer from high hydrodynamic drag, which limits their operational endurance. To address this challenge, this study proposes a robust optimization framework for a novel sea-turtle-inspired AUH. A parametric hull, governed by two dimensionless shape factors based on modified Myring equations, was established to facilitate systematic exploration. To reduce the high computational cost of direct CFD evaluations, a high-precision Gaussian Process Regression (GPR) surrogate model was constructed from a small dataset of 24 samples. The core methodological innovation is T-NSGA-II, an algorithm featuring hyperparameters that are systematically optimized by the Optuna framework. In comparative evaluations, the T-NSGA-II-generated Pareto front demonstrated clear superiority over the standard NSGA-II, identifying designs with significantly lower drag for an equivalent vertical force. A key scientific contribution of this research is the identification of a distinct performance gap on the Pareto front. This phenomenon is interpreted not as an algorithmic artifact but as a ‘natural gap’, reflecting a deep physical trade-off, with potential underlying causes including a critical transition in flow physics or a topological shift in the optimal hull geometries. This work not only delivers a suite of optimized, practical AUH designs but also presents a powerful, intelligent optimization methodology that is capable of revealing fundamental physical trade-offs in complex engineering problems. Full article
(This article belongs to the Section Ocean Engineering)
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20 pages, 10557 KiB  
Article
HAUV-USV Collaborative Operation System for Hydrological Monitoring
by Qiusheng Wang, Shuibo Hu, Zhou Yang and Guofeng Wu
J. Mar. Sci. Eng. 2025, 13(8), 1540; https://doi.org/10.3390/jmse13081540 - 11 Aug 2025
Abstract
Research in marine hydrographic environmental monitoring continues to deepen, necessitating a hardware platform capable of traversing air–water interfaces to collect vertical gradient parameters across oceanographic profiles. This paper proposes a deeply integrated heterogeneous monitoring platform for marine hydrological vertical profiling, addressing the functional [...] Read more.
Research in marine hydrographic environmental monitoring continues to deepen, necessitating a hardware platform capable of traversing air–water interfaces to collect vertical gradient parameters across oceanographic profiles. This paper proposes a deeply integrated heterogeneous monitoring platform for marine hydrological vertical profiling, addressing the functional limitations of conventional unmanned surface vehicles (USVs) and unmanned aerial vehicles (UAVs) in subsurface monitoring. By co-designing a hybrid aerial underwater vehicle (HAUV) with cross-domain capabilities and a USV, the system leverages USVs for long-endurance surface operations and HAUVs for high-speed vertical column monitoring. Key innovations include (1) a distributed collaborative architecture enabling “Air–Sea–Air” cyclic operations; (2) dynamic modeling of HAUV-USV interactions incorporating aerodynamic and hydrodynamic coupling; (3) an MPC-based collaborative tracking algorithm for real-time USV pursuit under marine disturbances; and (4) a vision-guided synchronous landing strategy achieving decimeter-level docking accuracy in bad conditions. Simulation experiments validate the system’s efficacy in trajectory tracking and precision landing. This work bridges the critical gap in marine vertical profile monitoring while demonstrating robust cross-domain coordination. Full article
(This article belongs to the Section Ocean Engineering)
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24 pages, 4158 KiB  
Article
Land Subsidence and Coastal Flood Impact Scenarios Based on Remote Sensing in Selangor, Malaysia
by Navakanesh M. Batmanathan, Joy Jacqueline Pereira, Afroz Ahmad Shah, Nurfashareena Muhamad and Lim Choun Sian
J. Mar. Sci. Eng. 2025, 13(8), 1539; https://doi.org/10.3390/jmse13081539 - 11 Aug 2025
Abstract
This study uses remote sensing data to assess susceptibility to hazards, which are then validated to model impact scenarios for land subsidence and coastal flooding in the Integrated Coastal Zone Management (ICZM) of Selangor, Malaysia, to support decision-making in urban planning and land [...] Read more.
This study uses remote sensing data to assess susceptibility to hazards, which are then validated to model impact scenarios for land subsidence and coastal flooding in the Integrated Coastal Zone Management (ICZM) of Selangor, Malaysia, to support decision-making in urban planning and land management. Land subsidence and coastal floods affect a major proportion of the population in the ICZM, with subsidence being significant contributing factors, but information on the extent of susceptible areas, monitoring, and wide-area coverage is limited. Land subsidence distribution is demarcated using Interferometric Synthetic Aperture Radar (InSAR) time-series data (2015–2022), and integrated with coastal flood susceptibility derived from Analytic Hierarchy Process (AHP)-based weights to model impacts on land cover. Results indicate maximum subsidence rates of 46 mm/year (descending orbit) and 61 mm/year (ascending orbit); reflecting a gradual increase in subsidence trends with an average rate of 13 mm/year. In the worst-case scenario, within the ICZM area of 2262 km2, nearly 12% of the total built-up land cover with the highest population density is exposed to land subsidence, while exposure to coastal floods is relatively larger, covering nearly 34% of the built-up area. Almost 27% of the built-up area is exposed to the combined effects of both land subsidence and coastal floods, under present sea level conditions, with increasing risks of coastal floods over 2040, 2050 and 2100, due to both combinations. This research prioritizes areas for further study and provides a scientific foundation for resilience strategies aimed at ensuring sustainable coastal development within the ICZM. Full article
(This article belongs to the Section Coastal Engineering)
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25 pages, 4591 KiB  
Article
Dynamic Response Analysis of a New Combined Concept of a Spar Wind Turbine and Multi-Section Wave Energy Converter Under Operational Conditions
by Jiahao Xu, Ling Wan, Guochun Xu, Jianjian Xin, Wei Shi, Kai Wang and Constantine Michalides
J. Mar. Sci. Eng. 2025, 13(8), 1538; https://doi.org/10.3390/jmse13081538 - 11 Aug 2025
Abstract
To achieve the ‘zero carbon’ target, offshore renewable energy exploration plays a key role in many countries. Offshore wind energy and wave energy are both important offshore renewable energies. With the target to reduce the cost of energy, a new combined wind and [...] Read more.
To achieve the ‘zero carbon’ target, offshore renewable energy exploration plays a key role in many countries. Offshore wind energy and wave energy are both important offshore renewable energies. With the target to reduce the cost of energy, a new combined wind and wave energy converter is proposed in this work. The new concept consists of a spar-type floating wind turbine and a multi-section pitch-type wave energy converter (WEC). The WEC is attached to the spar column and consists of multiple sections with different lengths to absorb wave energy at different wave frequencies, i.e., multi-band absorption. Through multi-band wave energy absorption, the total power is expected to increase. In addition, through synergetic design, the dynamic motions of the platform are expected to decrease. In this paper, a fully coupled numerical model of the concept is established, based on the hybrid time–frequency-domain simulation framework. The frequency-domain hydrodynamic properties were transferred to the time domain. Then, the dynamic performance of the combined concept under wind–wave conditions was studied, especially under operational conditions. Mechanical couplings among multiple floating bodies were taken into account. To demonstrate the WEC effects on the floating wind turbine, the dynamic performance of the combined wind–wave energy converter concept was compared with the segregated floating wind turbine, with a focus on motions and output power. It was expected that the average overall output power of the multi-section WEC could be above 160 kW. The advantages of the combined concept are demonstrated. Full article
(This article belongs to the Special Issue Optimized Design of Offshore Wind Turbines)
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31 pages, 4909 KiB  
Article
A Study on UAV Path Planning for Navigation Mark Inspection Using Two Improved SOM Algorithms
by Liangkun Xu, Zaiwei Zhu, Zhihui Hu, Liyan Cai, Xinqiang Chen and Xiaomeng Wang
J. Mar. Sci. Eng. 2025, 13(8), 1537; https://doi.org/10.3390/jmse13081537 - 10 Aug 2025
Abstract
With the widespread application of unmanned aerial vehicle technology in navigation mark inspection, path planning algorithm efficiency has become crucial to improve inspection effectiveness. The traditional self-organizing mapping (SOM) algorithm suffers from dual limitations in UAV inspection path optimization, including insufficient global exploration [...] Read more.
With the widespread application of unmanned aerial vehicle technology in navigation mark inspection, path planning algorithm efficiency has become crucial to improve inspection effectiveness. The traditional self-organizing mapping (SOM) algorithm suffers from dual limitations in UAV inspection path optimization, including insufficient global exploration during early training stages and susceptibility to local optima entrapment in later stages, resulting in limited inspection efficiency and increased operational costs. For this reason, this study proposes two improved self-organizing mapping algorithms. First, the ORC_SOM algorithm incorporating a generalized competition mechanism and local infiltration strategy is developed. Second, the ORCTS_SOM hybrid optimization model is constructed by integrating the Tabu Search algorithm. Validation using two different scale navigation mark datasets shows that compared with traditional methods, the proposed improved methods achieve significantly enhanced path planning optimization. This study provides effective path planning methods for unmanned aerial vehicle navigation mark inspection, offering algorithmic support for intelligent maritime supervision system construction. Full article
(This article belongs to the Section Ocean Engineering)
27 pages, 3451 KiB  
Article
Climate Variability and Atlantic Surface Gravity Wave Variability Based on Reanalysis Data
by Yuri Onça Prestes, Alex Costa da Silva, André Lanfer Marquez, Gabriel D’annunzio Gomes and Fabrice Hernandez
J. Mar. Sci. Eng. 2025, 13(8), 1536; https://doi.org/10.3390/jmse13081536 - 10 Aug 2025
Abstract
Wave climate variability, including seasonal cycles, long-term trends, and interannual anomalies of wave parameters, was investigated across five latitudinal sectors using ERA5 reanalysis data from 1980 to 2023. Pronounced seasonal cycles were observed in both Northern and Southern Hemisphere sectors, although the variability [...] Read more.
Wave climate variability, including seasonal cycles, long-term trends, and interannual anomalies of wave parameters, was investigated across five latitudinal sectors using ERA5 reanalysis data from 1980 to 2023. Pronounced seasonal cycles were observed in both Northern and Southern Hemisphere sectors, although the variability was more marked in the Northern Hemisphere. In contrast, the tropical region exhibited comparatively stable conditions throughout the year. Long-term trends revealed increases in both significant wave height and peak period across most sectors. The tropical region exhibited a trimodal regime driven by wind waves at low latitudes and remotely generated swells from both hemispheres. Teleconnections associated with the North Atlantic Oscillation (NAO) explained interannual variability in wind-wave direction in the tropics with an r2 of 0.74 and wind-wave height variability in the Northern Hemisphere with an r2 of 0.81. Additional indices, such as the Arctic Oscillation (AO), the Tropical North Atlantic (TNA) index, and the Northern Annular Mode (NAM), explained 30 to 60 percent of the directional variability. These results underscore the need to account for climate-driven variability in wave modeling frameworks to improve forecast accuracy and representation of directional trends. Full article
(This article belongs to the Section Physical Oceanography)
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28 pages, 3360 KiB  
Article
Dynamic Surrogate Model-Driven Multi-Objective Shape Optimization for Photovoltaic-Powered Underwater Vehicle
by Chenyu Wang, Likun Peng, Jiabao Chen, Wei Pan, Jia Chen and Huarui Wang
J. Mar. Sci. Eng. 2025, 13(8), 1535; https://doi.org/10.3390/jmse13081535 - 10 Aug 2025
Abstract
In this study, a multi-objective shape optimization framework was established for photovoltaic-powered underwater vehicles (PUVs) to systematically investigate multidisciplinary coupled design methodologies. Specifically, a global sensitivity analysis was conducted to identify four critical design parameters with 24 h energy consumption and cabin volume [...] Read more.
In this study, a multi-objective shape optimization framework was established for photovoltaic-powered underwater vehicles (PUVs) to systematically investigate multidisciplinary coupled design methodologies. Specifically, a global sensitivity analysis was conducted to identify four critical design parameters with 24 h energy consumption and cabin volume serving as dual optimization objectives. An integrated automated optimization workflow was constructed by incorporating parametric modeling, computational fluid dynamics (CFD) simulations, and dynamic surrogate models. Additionally, a new phased hybrid adaptive lower confidence bound (PHA-LCB) infill criterion was designed under the consideration of error-driven mechanisms, improvement feedback loops, and iterative attenuation factors to develop high-precision dynamic surrogate models. Coupled with the NSGA-II multi-objective genetic algorithm, this framework generated Pareto-optimal front solutions possessing significant engineering value. Furthermore, an optimal design configuration was ultimately determined through multi-criteria decision analysis. Compared to the initial form, it generates an additional 1148.12 Wh of electrical energy within 24 h, with an 22.36% increase in sailing range and a 2.77% improvement in cabin volume capacity. The proposed closed-loop “modeling–simulation–optimization” framework realized multi-objective optimization of PUV shape parameters, providing methodological paradigms and technical foundations for the engineering design of next-generation autonomous underwater vehicles. Full article
(This article belongs to the Section Ocean Engineering)
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16 pages, 3772 KiB  
Article
Morphological and Immunohistochemical Study of Ventral Photophores of Ichthyococcus ovatus (Cocco, 1838) (Fam: Stomiidae)
by Mauro Cavallaro, Lidia Pansera, Kamel Mhalhel, Rosaria Laurà, Maria Levanti, Giuseppe Montalbano, Francesco Abbate, Marialuisa Aragona and Maria Cristina Guerrera
J. Mar. Sci. Eng. 2025, 13(8), 1534; https://doi.org/10.3390/jmse13081534 - 10 Aug 2025
Abstract
Photophores are light-producing organs found in many fish species living in the mesopelagic, bathypelagic, and abyssal layers of the ocean. They function to attract prey, confuse predators, and communicate with other individuals of the same species. Understanding the structure and function of photophores [...] Read more.
Photophores are light-producing organs found in many fish species living in the mesopelagic, bathypelagic, and abyssal layers of the ocean. They function to attract prey, confuse predators, and communicate with other individuals of the same species. Understanding the structure and function of photophores is crucial to exploring bioluminescence and the ecological adaptations of marine life in deep-sea environments. The present study is the first to investigate the photophore anatomy of the mesopelagic fish Ichthyococcus ovatus (Cocco, 1838), using specimens naturally stranded along the coast of the Strait of Messina. The morphology of the ventral photophores of I. ovatus includes four functional parts: a tank containing photogenic cells, a lens filter, a reflector surrounding the entire organ, and a pigmented layer. An immunohistochemical assay was conducted using anti-nNOS and anti-S100p antibodies. The presence of nNOS/NOS type I immunolabeling the pigmented layer surrounding the photophores and the nerve fibers reaching the lens suggests a potential role of neuronal nitric oxide signaling in modulating light shielding by the pigment sheath, controlling light exposure, and adjusting light focusing though the lens-associated nerves. S100p immunostaining was observed in the nerve fibers reaching the photophores, highlighting its potential involvement in regulating neuronal calcium levels and, consequently, influencing signal transmission to control bioluminescence output. A sensory feedback pathway from the photophore to the CNS is suggested. Within the lens and in the irregularly shaped cells located in the photophore’s lens, S100p immunolabeling could indicate active signaling and differentiation processes. These findings expand our understanding of light-emitting systems in mesopelagic fishes and offer a valuable foundation for future studies on the functional and evolutionary significance of photophores. Full article
(This article belongs to the Section Marine Biology)
21 pages, 17766 KiB  
Article
Contrastive Analysis of Deep-Water Sedimentary Architectures in Central West African Passive Margin Basins During Late-Stage Continental Drift
by Futao Qu, Xianzhi Gao, Lei Gong and Jinyin Yin
J. Mar. Sci. Eng. 2025, 13(8), 1533; https://doi.org/10.3390/jmse13081533 - 10 Aug 2025
Abstract
The Lower Congo Basin (LCB) and the Niger Delta Basin (NDB), two end-member deep-water systems along the West African passive margin, exhibit contrasting sedimentary architectures despite shared geodynamic settings. The research comprehensively utilizes seismic reflection structure, root mean square amplitude slices, drilling lithology, [...] Read more.
The Lower Congo Basin (LCB) and the Niger Delta Basin (NDB), two end-member deep-water systems along the West African passive margin, exhibit contrasting sedimentary architectures despite shared geodynamic settings. The research comprehensively utilizes seismic reflection structure, root mean square amplitude slices, drilling lithology, changes in logging curves, and previous research achievements to elucidate the controlling mechanisms behind these differences. Key findings include: (1) Stark depositional contrast: Since the Eocene, the LCB developed retrogradational narrow-shelf systems dominated by erosional channels and terminal lobes, whereas the NDB formed progradational broad-shelf complexes with fan lobes and delta-fed turbidites. (2) Primary controls: Diapir-driven topographic features and basement uplift govern architectural variability, whereas shelf-slope break configuration and oceanic relief constitute subordinate controls. (3) Novel mechanism: First quantification of how diapir-induced seafloor relief redirects sediment pathways and amplifies facies heterogeneity. These insights establish a tectono-sedimentary framework for predicting deep-water reservoirs in diapir-affected passive margins, refine the conventional “source-to-sink” model by emphasizing salt-geomorphic features coupling as the primary driver. By analyzing the differences in lithofacies assemblages and sedimentary configurations among the above-mentioned different basins, this study can provide beneficial insights for the research on related deep-water turbidity current systems and also offer guidance for deep-water oil and gas exploration and development in the West African region and other similar areas. Full article
(This article belongs to the Special Issue Advances in Marine Engineering: Geological Environment and Hazards—3rd Edition)
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19 pages, 4183 KiB  
Article
Centrifuge and Numerical Investigations on Responses of Monopile-Supported Offshore Wind Turbines with Riprap Scour Protection Under Earthquakes
by Hao Zhang, Xiaojing Jia, Fayun Liang and Zhouchi Yuan
J. Mar. Sci. Eng. 2025, 13(8), 1532; https://doi.org/10.3390/jmse13081532 - 10 Aug 2025
Abstract
Riprap scour protection is commonly employed to protect against local scour around large-diameter monopile foundations for offshore wind turbines (OWTs), and considering its influence on the static and dynamic behavior of monopiles may also provide the opportunity for further optimization of monopile design. [...] Read more.
Riprap scour protection is commonly employed to protect against local scour around large-diameter monopile foundations for offshore wind turbines (OWTs), and considering its influence on the static and dynamic behavior of monopiles may also provide the opportunity for further optimization of monopile design. However, only limited studies have gradually begun to investigate the contribution of scour protection to monopile bearing capacity, while its effects on the seismic responses of monopile-supported OWTs deployed in seismic zones have attracted even less attention. In this study, a series of centrifuge shaking table tests were conducted on large-diameter monopile foundations under both initial and scour protection conditions. Then, to further investigate the effects of scour protection parameters on the seismic response of offshore wind turbines, a three-dimensional finite element model was developed and validated based on experimental results. The results demonstrate that the presence of scour protection not only slightly increases the first natural frequency but also alters seismic responses of the OWT. Lower peak responses at the lumped mass are observed under Chi-Chi excitation, while lower peak bending moments of the pile occur under Kobe excitation. Additionally, seismic responses are more sensitive to variations in the scour protection length than its elastic modulus. Therefore, compared to material selection, greater emphasis should be placed on optimizing the scour protection length by comprehensively considering environmental loads, site conditions, and turbine dynamic characteristics. This study quantifies the effects of scour protection on the seismic responses of monopile-supported offshore wind turbines, which can provide new insights into seismic design optimization of offshore wind turbines with riprap scour protection. Full article
(This article belongs to the Section Coastal Engineering)
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19 pages, 4425 KiB  
Article
A Multi-Scale Contextual Fusion Residual Network for Underwater Image Enhancement
by Chenye Lu, Li Hong, Yan Fan and Xin Shu
J. Mar. Sci. Eng. 2025, 13(8), 1531; https://doi.org/10.3390/jmse13081531 - 9 Aug 2025
Abstract
Underwater image enhancement (UIE) is a key technology in the fields of underwater robot navigation, marine resources development, and ecological environment monitoring. Due to the absorption and scattering of different wavelengths of light in water, the quality of the original underwater images usually [...] Read more.
Underwater image enhancement (UIE) is a key technology in the fields of underwater robot navigation, marine resources development, and ecological environment monitoring. Due to the absorption and scattering of different wavelengths of light in water, the quality of the original underwater images usually deteriorates. In recent years, UIE methods based on deep neural networks have made significant progress, but there still exist some problems, such as insufficient local detail recovery and difficulty in effectively capturing multi-scale contextual information. To solve the above problems, a Multi-Scale Contextual Fusion Residual Network (MCFR-Net) for underwater image enhancement is proposed in this paper. Firstly, we propose an Adaptive Feature Aggregation Enhancement (AFAE) module, which adaptively strengthens the key regions in the input images and improves the feature expression ability by fusing multi-scale convolutional features and a self-attention mechanism. Secondly, we design a Residual Dual Attention Module (RDAM), which captures and strengthens features in key regions through twice self-attention calculation and residual connection, while effectively retaining the original information. Thirdly, a Multi-Scale Feature Fusion Decoding (MFFD) module is designed to obtain rich contexts at multiple scales, improving the model’s understanding of details and global features. We conducted extensive experiments on four datasets, and the results show that MCFR-Net effectively improves the visual quality of underwater images and outperforms many existing methods in both full-reference and no-reference metrics. Compared with the existing methods, the proposed MCFR-Net can not only capture the local details and global contexts more comprehensively, but also show obvious advantages in visual quality and generalization performance. It provides a new technical route and benchmark for subsequent research in the field of underwater vision processing, which has important academic and application values. Full article
(This article belongs to the Section Ocean Engineering)
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18 pages, 4008 KiB  
Article
Numerical Study of the Negative Skin Friction (NSF) of Large-Diameter Rock-Socketed Monopiles for Offshore Wind Turbines Incorporating Lateral Loading Effects
by Yuanyuan Ren, Zhiwei Chen and Wenbo Zhu
J. Mar. Sci. Eng. 2025, 13(8), 1530; https://doi.org/10.3390/jmse13081530 - 9 Aug 2025
Viewed by 35
Abstract
Large-diameter rock-socketed monopiles supporting offshore wind turbines in soft clay strata face significant geotechnical risks from negative skin friction (NFS) induced by construction surcharges. While the effects of NFS on axial drag loads are documented, the critical interaction between horizontal pile loading and [...] Read more.
Large-diameter rock-socketed monopiles supporting offshore wind turbines in soft clay strata face significant geotechnical risks from negative skin friction (NFS) induced by construction surcharges. While the effects of NFS on axial drag loads are documented, the critical interaction between horizontal pile loading and NFS development remains poorly understood. This research bridges this gap using a rigorously validated 3D finite element model that simulates the complex coupling of vertical substructure loads (5 MN), horizontal loading, and surcharge-induced consolidation. The model’s accuracy was confirmed through comprehensive verification against field data for both NFS evolution under surcharge and horizontal load–displacement behavior. The initial analysis under representative conditions (10 MN horizontal load, 100 kPa surcharge, 3600 days consolidation) revealed that horizontal loading fundamentally distorts NFS distribution in the upper pile segment (0 to −24 m), transforming smooth profiles into distinct dual-peak morphologies while increasing the maximum NFS magnitude by 57% (from −45.4 kPa to −71.5 kPa) and relocating its position 21 m upward. This redistribution was mechanistically linked to horizontal soil displacement patterns. Crucially, the NFS neutral plane remained invariant at the clay–rock interface (−39 m), demonstrating complete independence from horizontal loading effects. A systematic parametric study evaluated key operational factors: (1) consolidation time progressively increased NFS magnitude throughout the clay layer, evolving from near-linear to dual-peaked distributions in the upper clay (0 to −18 m); NFS stabilized in the upper clay after 720 days while continuing to increase in the lower clay (−18 to −39 m) due to downward surcharge transfer, accompanied by neutral plane deepening (from −36.5 m to −39.5 m) and 84% maximum axial force escalation (12.5 MN to 23 MN); (2) horizontal load magnitude amplified upper clay NFS peaks at −3.2 m and −9.3 m, with the shallow peak magnitude increasing linearly with load intensity, though it neither altered lower clay NFS nor neutral plane position; (3) surcharge magnitude increased overall NFS, but upper clay NFS (0 to −18 m) stabilized beyond 100 kPa, while lower clay NFS continued rising with higher surcharges, and the neutral plane descended progressively (from −38 m to −39.5 m). These findings demonstrate that horizontal loading critically exacerbates peak NFS values and redistributes friction in upper pile segments without influencing the neutral plane, whereas surcharge magnitude and consolidation time govern neutral plane depth, total NFS magnitude, and maximum drag load. This research delivers essential theoretical insights and practical guidelines for predicting NFS-induced drag loads and ensuring the long-term safety of offshore wind foundations in soft clays under complex multi-directional loading scenarios. Full article
(This article belongs to the Section Ocean Engineering)
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20 pages, 2261 KiB  
Article
Assessing the Changes in Precipitation Patterns and Aridity in the Danube Delta (Romania)
by Alina Bărbulescu and Cristian Ștefan Dumitriu
J. Mar. Sci. Eng. 2025, 13(8), 1529; https://doi.org/10.3390/jmse13081529 - 9 Aug 2025
Viewed by 47
Abstract
Understanding long-term precipitation variability is essential for assessing the climate’s impact on sensitive ecosystems, particularly in regions of high environmental value, such as the Danube Delta Biosphere Reserve (DDBR). This study examines the temporal dynamics of monthly precipitation in the Danube Delta, Romania, [...] Read more.
Understanding long-term precipitation variability is essential for assessing the climate’s impact on sensitive ecosystems, particularly in regions of high environmental value, such as the Danube Delta Biosphere Reserve (DDBR). This study examines the temporal dynamics of monthly precipitation in the Danube Delta, Romania, spanning the period from 1965 to 2019. Three approaches were used to analyze climatic variability: Change Point detection (CPD) to identify shifts in precipitation regimes, the De Martonne Index (IM) to assess aridity trends, and the Standardized Precipitation Index (SPI) to evaluate drought conditions across annual and monthly scales. Using robust monthly precipitation and temperature datasets from the Sulina meteorological station, CPD analysis revealed statistically significant structural breaks in precipitation trends, suggesting periods of altered climate behavior likely associated with broader regional or global climate changes. IM values indicated mostly hyper-aridity and aridity at monthly and annual scales, respectively. No monotonic trend was found in this index during the analyzed segments, as emphasized by the Mann–Kendall (MK) test. SPI values provided further evidence of variability in the precipitation regime, highlighting a transition toward more extreme hydrological conditions in the region. The combined use of these indices offers a comprehensive view of the evolution of climatic conditions in the Danube Delta. The findings underscore the growing vulnerability of this unique wetland ecosystem to climatic variability, supporting the need for adaptive water management strategies in the face of anticipated future changes. Full article
(This article belongs to the Special Issue Marine Modelling and Environmental Statistics in Honor of Professor Keith Thompson)
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27 pages, 33921 KiB  
Article
Seeing Through Turbid Waters: A Lightweight and Frequency-Sensitive Detector with an Attention Mechanism for Underwater Objects
by Shibo Song and Bing Sun
J. Mar. Sci. Eng. 2025, 13(8), 1528; https://doi.org/10.3390/jmse13081528 - 9 Aug 2025
Viewed by 49
Abstract
Precise underwater object detectors can provide Autonomous Underwater Vehicles (AUVs) with good situational awareness in underwater environments, supporting a wide range of unmanned exploration missions. However, the quality of optical imaging is often insufficient to support high detector accuracy due to poor lighting [...] Read more.
Precise underwater object detectors can provide Autonomous Underwater Vehicles (AUVs) with good situational awareness in underwater environments, supporting a wide range of unmanned exploration missions. However, the quality of optical imaging is often insufficient to support high detector accuracy due to poor lighting and the complexity of underwater environments. Therefore, this paper develops an efficient and precise object detector that maintains high recognition accuracy on degraded underwater images. We design a Cross Spatial Global Perceptual Attention (CSGPA) mechanism to achieve accurate recognition of target and background information. We then construct an Efficient Multi-Scale Weighting Feature Pyramid Network (EMWFPN) to eliminate computational redundancy and increase the model’s feature-representation ability. The proposed Occlusion-Robust Wavelet Network (ORWNet) enables the model to handle fine-grained frequency-domain information, enhancing robustness to occluded objects. Finally, EMASlideloss is introduced to alleviate sample-distribution imbalance in underwater datasets. Our architecture achieves 81.8% and 83.8% mAP on the DUO and UW6C datasets, respectively, with only 7.2 GFLOPs, outperforming baseline models and balancing detection precision with computational efficiency. Full article
(This article belongs to the Section Ocean Engineering)
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38 pages, 9302 KiB  
Article
Numerical and Experimental Investigation of a Ducky Wave Energy Converter and Its Impact on Floating Ocean Wind Turbines
by Tao Tao, Yu Dong, Xinran Guo, Shi Liu, Yichen Jiang and Zhiming Yuan
J. Mar. Sci. Eng. 2025, 13(8), 1527; https://doi.org/10.3390/jmse13081527 - 8 Aug 2025
Viewed by 80
Abstract
The ocean represents a vast reservoir of energy. To address the issue of wave-induced motion in floating wind farms—particularly pitch motion—while harnessing the otherwise dissipated wave energy for power generation, this study proposes an integrated solution. Specifically, a duck-shaped wave energy converter incorporating [...] Read more.
The ocean represents a vast reservoir of energy. To address the issue of wave-induced motion in floating wind farms—particularly pitch motion—while harnessing the otherwise dissipated wave energy for power generation, this study proposes an integrated solution. Specifically, a duck-shaped wave energy converter incorporating mooring and power take-off systems is introduced. By combining computational fluid dynamics with experimental fluid dynamics methodologies, the performance of the device was systematically evaluated and its key parameters—including floating attitude, power take-off damping, and mooring configuration—were optimized. Furthermore, results indicate that deploying the duck-shaped converter around the periphery of a wind farm can reduce the wave-induced motion amplitude of the floating wind turbine platform by more than 70%, especially in terms of pitch motion, thereby significantly improving the operational efficiency and structural stability of the wind turbines. Full article
(This article belongs to the Section Marine Energy)
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27 pages, 3537 KiB  
Article
Battery-Powered AGV Scheduling and Routing Optimization with Flexible Dual-Threshold Charging Strategy in Automated Container Terminals
by Wenwen Guo, Huapeng Hu, Mei Sha, Jiarong Lian and Xiongfei Yang
J. Mar. Sci. Eng. 2025, 13(8), 1526; https://doi.org/10.3390/jmse13081526 - 8 Aug 2025
Viewed by 187
Abstract
Battery-powered automatic guided vehicles (B-AGVs) serve as crucial horizontal transportation equipment in terminals and significantly impact the terminal transportation efficiency. Imbalanced B-AGV availability during terminal peak and off-peak periods is driven by dynamic vessel arrivals. We propose a flexible dual-threshold charging (FDTC) strategy [...] Read more.
Battery-powered automatic guided vehicles (B-AGVs) serve as crucial horizontal transportation equipment in terminals and significantly impact the terminal transportation efficiency. Imbalanced B-AGV availability during terminal peak and off-peak periods is driven by dynamic vessel arrivals. We propose a flexible dual-threshold charging (FDTC) strategy synchronized with vessel dynamics. Unlike the static threshold charging (STC) strategy, FDTC dynamically adjusts its charging thresholds based on terminal workload intensity. And we develop a collaborative B-AGV scheduling and routing optimization model incorporating FDTC. A tailored Dijkstra-Partition neighborhood search (Dijkstra-Pns) algorithm is designed to resolve the problem in alignment with practical scenarios. Compared to the STC strategy, FDTC strategy significantly reduces the maximum B-AGV running time and decreases conflict waiting delays and charging times by 25.04% and 24.41%, respectively. Moreover, FDTC slashes quay crane (QC) waiting time by 40.78%, substantially boosting overall terminal operational efficiency. Full article
(This article belongs to the Section Ocean Engineering)
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40 pages, 824 KiB  
Article
An Extended VIKOR-Based Marine Equipment Reliability Assessment Method with Picture Fuzzy Information
by Chenlin Li and Baozhu Jia
J. Mar. Sci. Eng. 2025, 13(8), 1525; https://doi.org/10.3390/jmse13081525 - 8 Aug 2025
Viewed by 72
Abstract
Reliable operation of marine equipment is crucial for ensuring vessel performance and safeguarding the safety of personnel and the marine environment. However, the complexity of evaluation criteria and the subjectivity inherent in expert judgments pose significant challenges for effective reliability assessment. To address [...] Read more.
Reliable operation of marine equipment is crucial for ensuring vessel performance and safeguarding the safety of personnel and the marine environment. However, the complexity of evaluation criteria and the subjectivity inherent in expert judgments pose significant challenges for effective reliability assessment. To address these challenges, this study proposes an extended VIKOR method within a group decision-making (GDM) framework based on picture fuzzy numbers. The method first collects expert evaluations through questionnaires and voting to construct individual decision matrices, and then it applies a newly developed entropy-based approach to determine attribute weights, resulting in a group-weighted decision matrix. Subsequently, an extended VIKOR model is introduced, where the group utility measure is derived from one positive reference matrix and two negative reference matrices, while the group regret measure is based on two negative reference matrices. To improve assessment precision, this study also introduces a novel normalized projection measure to evaluate the closeness between decision matrices. Finally, two ranking strategies are developed, for static and dynamic environments, respectively. The proposed method is validated through a case study on marine equipment reliability assessment, confirming its effectiveness and feasibility. This study provides valuable insights for both theoretical research and practical applications in maritime engineering. Full article
(This article belongs to the Section Ocean Engineering)
23 pages, 7920 KiB  
Article
Dynamic Behavior of a Rotationally Restrained Pipe Conveying Gas-Liquid Two-Phase Flow
by Guangming Fu, Huilin Jiao, Aixia Zhang, Xiao Wang, Boying Wang, Baojiang Sun and Jian Su
J. Mar. Sci. Eng. 2025, 13(8), 1524; https://doi.org/10.3390/jmse13081524 - 8 Aug 2025
Viewed by 94
Abstract
This study explores the dynamic behavior of a vertical pipe conveying gas-liquid two-phase flow with rotationally restrained boundaries, employing the generalized integral transform technique (GITT). The rotationally restrained boundary conditions are more realistic for practical engineering applications in comparison to the classical simply-supported [...] Read more.
This study explores the dynamic behavior of a vertical pipe conveying gas-liquid two-phase flow with rotationally restrained boundaries, employing the generalized integral transform technique (GITT). The rotationally restrained boundary conditions are more realistic for practical engineering applications in comparison to the classical simply-supported and clamped boundary conditions, which can be viewed as limiting scenarios of the rotationally restrained boundary conditions when rotational stiffness approaches zero and infinity, respectively. Utilizing the small-deflection Euler-Bernoulli beam theory, the governing equation of motion for the deflection of the pipe is transformed into an infinite set of coupled ordinary differential equations, which is then numerically solved following truncation at a finite order NW. The proposed integral transform solution was initially validated against extant literature results. Numerical findings demonstrate that as the gas volume fraction increases, there is a reduction in both the first-order critical flow velocity and the vibration frequency of the pipe conveying two-phase flow. Conversely, as the rotational stiffness factor enhances, both the first-order critical velocity and vibration frequency increase, resulting in improved stability of the pipe. The impact of the bottom-end rotational stiffness factor r2 on the dynamic stability of the pipe is more pronounced compared to the top-end rotational factor r1. The variation in two-phase flow parameters is closely associated with the damping and stiffness matrices. Modifying the gas volume fraction in the two-phase flow alters the distribution of centrifugal and Coriolis forces within the pipeline system, thereby affecting the pipeline’s natural frequency. The results illustrate that an increase in the gas volume fraction leads to a decrease in both the pipeline’s critical velocity and vibration frequency, culminating in reduced stability. The findings suggest that both the gas volume fraction and boundary rotational stiffness exert a significant influence on the dynamic behavior and stability of the pipe conveying gas-liquid two-phase flow. Full article
(This article belongs to the Special Issue Theory, Method and Engineering Application of Computational Mechanics in Offshore Structures II)
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32 pages, 10173 KiB  
Article
Field-Calibrated Nonlinear Finite Element Diagnosis of Localized Stern Damage from Tugboat Collision: A Measurement-Driven Forensic Approach
by Myung-Su Yi and Joo-Shin Park
J. Mar. Sci. Eng. 2025, 13(8), 1523; https://doi.org/10.3390/jmse13081523 - 8 Aug 2025
Viewed by 107
Abstract
This study conducts a high-resolution forensic evaluation of stern structural damage resulting from a tugboat collision during berthing, integrating real-world measurement data with calibrated nonlinear finite element analysis. Based on field-acquired deformation geometry and residual dent profiles at Frame 76, five distinct collision [...] Read more.
This study conducts a high-resolution forensic evaluation of stern structural damage resulting from a tugboat collision during berthing, integrating real-world measurement data with calibrated nonlinear finite element analysis. Based on field-acquired deformation geometry and residual dent profiles at Frame 76, five distinct collision scenarios varying in impact orientation, contact area, and load path were simulated using shell-based nonlinear plastic analysis. Particular attention is given to comparing the plastic equivalent strain (PEEQ), von-Mises stress fields, and residual deformation contours at Point A—the critical zone identified from damage surveys. Among the five cases, Case-2, defined by a vertically eccentric external impact, demonstrated the highest plastic strain intensity (PEEQ > 2.0%), the sharpest post-yield drops in stiffness, and the closest match to the residual dent profile observed in the actual structure. The integrated correlation between field damage and some of the results (strain, stress, and deformed shape) enabled clear identification of the most probable accident mechanism with engineering accuracy. This study proposes a validated, measurement-calibrated nonlinear finite element analysis framework to diagnose stern damage from tugboat collisions, enhancing repair decision-making and structural safety assessment. Such a calibrated forensic strategy enhances the reliability of structural safety predictions in marine collision incidents and supports eco-friendly rescue engineering by minimizing unnecessary structural renewal through precise damage localization. The proposed approach establishes a new benchmark for scenario-driven collision assessment, particularly relevant to sustainable, automation-compatible, and damage-tolerant ship design practices. Full article
(This article belongs to the Special Issue Advanced Studies in Marine Mechanical and Naval Engineering)
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18 pages, 4602 KiB  
Article
Impact of Kara Sea Shelf Water on Seawater Parameters in Subsurface Layer of Laptev Sea
by Andrey Andreev, Irina Pipko, Svetlana Pugach and Igor Semiletov
J. Mar. Sci. Eng. 2025, 13(8), 1522; https://doi.org/10.3390/jmse13081522 - 8 Aug 2025
Viewed by 112
Abstract
Global climate changes impact the Arctic seas by decreasing the sea ice area and changing the inorganic and organic matter supply via rivers and coastal permafrost thawing. Therefore, climate change may affect biogeochemical processes in the Kara Sea (KS) and Laptev Sea (LS), [...] Read more.
Global climate changes impact the Arctic seas by decreasing the sea ice area and changing the inorganic and organic matter supply via rivers and coastal permafrost thawing. Therefore, climate change may affect biogeochemical processes in the Kara Sea (KS) and Laptev Sea (LS), which form the Arctic Transpolar Drift. This study explores the effect of the KS shelf water supply on seawater parameters in the LS in late summer and early fall 2007, 2008, 2018, 2019, and 2024 using ship-borne (temperature, salinity, dissolved oxygen, nutrients, and pH), satellite-derived (sea surface heights, geostrophic current velocities), and model (current velocities) data. The results demonstrate that an inflow of KS shelf water with salinity of 33.0–34.5, high Apparent Oxygen Utilization values (50–110 µM), and increased concentrations of the dissolved inorganic phosphorus (DIP~ 0.7–1.2 µM), dissolved inorganic nitrogen (DIN~ 4–12 µM) and silicic acid (DSi~ 10–18 µM) enriches the subsurface layer of the LS with nutrients. The distributions of Atlantic—derived water (ADW) and KS shelf water in the LS from August to October depend on water dynamics caused by wind and river discharge. High Lena River discharge and westerly (downwelling favorable) winds promoted the supply of the KS shelf water to the LS through Vilkitsky Strait. In the area of the central trough of the LS, the KS shelf water can be modified by mixing with ADW. Mixing ADW with high DIN/DIP ratios (DIN~ 10 µM at DIP of 0.80 µM) and KS shelf water with low DIN/DIP ratios (DIN~ 8 µM at DIP of 0.80 µM) leads to changes in the DIN vs. DIP ratio in the subsurface layer of the LS. Full article
(This article belongs to the Section Marine Environmental Science)
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23 pages, 18956 KiB  
Article
Offshore Site Investigation of Sandy Sediments for Anchoring and Foundation Design of Renewable Energy Applications—NW Center of Portugal
by Joaquim Pombo, Aurora Rodrigues and Paula F. da Silva
J. Mar. Sci. Eng. 2025, 13(8), 1521; https://doi.org/10.3390/jmse13081521 - 8 Aug 2025
Viewed by 191
Abstract
The expansion of offshore renewable energy development in Portugal necessitates accurate geological and geotechnical site characterization, especially in regions with limited baseline information. This study focuses on the S. Pedro de Moel area (NW central Portugal), which is characterized by sandy sediments, with [...] Read more.
The expansion of offshore renewable energy development in Portugal necessitates accurate geological and geotechnical site characterization, especially in regions with limited baseline information. This study focuses on the S. Pedro de Moel area (NW central Portugal), which is characterized by sandy sediments, with the aim of supporting the preliminary design of anchoring and foundation systems for renewable energy structures. An integrated methodology was applied, combining multibeam bathymetry, acoustic backscatter data, high-resolution seismic reflection profiling, sediment sampling, and onshore laboratory testing. Seismic interpretation identified three subsurface units: (1) a deformed carbonated sandstone serving as the acoustic basement; (2) a well-graded sandy gravel layer, up to 8 m thick, interpreted as a marginal marine deposit; and (3) a modern sandy deposit, up to 7 m thick, with variable silt content. Geotechnical analyses yielded effective friction angles for sandy sediments ranging from 39 to 44°, and deformation moduli between 22 MPa and 54 MPa. The sedimentary succession exhibits marked lateral and vertical heterogeneity, which must be considered in engineering design. This cost-effective methodology offers a viable alternative to offshore in situ testing, enabling medium-scale site characterization and providing essential information to support the development of offshore renewable energy infrastructure. Full article
(This article belongs to the Section Coastal Engineering)
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29 pages, 6429 KiB  
Article
Effects of Wave–Current Interaction on Hydrodynamic Performance and Motion Response of a Floating Tidal Stream Turbine
by Ming Kong, Xiaojie Zhang, Renwei Ji, He Wu, Minwei Yin, Hongzang Liu, Ke Sun and Ratthakrit Reabroy
J. Mar. Sci. Eng. 2025, 13(8), 1520; https://doi.org/10.3390/jmse13081520 - 8 Aug 2025
Viewed by 185
Abstract
Within real-world marine settings, the operational performance of floating tidal stream turbines is impacted by wave–current interaction effects and platform motion responses. Leveraging the improved delayed detached eddy simulation (IDDES) method, this research constructs a computational fluid dynamics (CFD) numerical analysis framework for [...] Read more.
Within real-world marine settings, the operational performance of floating tidal stream turbines is impacted by wave–current interaction effects and platform motion responses. Leveraging the improved delayed detached eddy simulation (IDDES) method, this research constructs a computational fluid dynamics (CFD) numerical analysis framework for floating turbines in wave–current environments. It further investigates the hydrodynamic behaviors and motion response features of the turbine under wave–current interactions. The results show that under the combined action of regular waves and steady currents, the fluctuation amplitudes of the power coefficient and thrust coefficient of the floating turbine exhibit a positive correlation with wave height, whereas the mean values of these coefficients remain relatively stable; in contrast, the mean values of the Cp and Ct are proportional to the wave period. Additionally, the motion amplitude of the platform shows a proportional relationship with both wave height and wave period. Flow field analysis demonstrates that elevations in wave height and period result in enhanced flow turbulence, disrupted wake vortex shedding patterns, non-uniform pressure distributions across the blades, and a larger pressure differential in the blade tip area. Such conditions may potentially induce cavitation erosion and fatigue loads. The results of the research have certain academic significance and value to the development and engineering of floating tidal current energy devices. Full article
(This article belongs to the Special Issue Floating Wave–Wind Energy Converter Plants)
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31 pages, 2334 KiB  
Article
Weak Fault Feature Extraction for AUV Thrusters with Multi-Input Signals
by Dacheng Yu, Feng Yao, Yan Gao, Xing Liu and Mingjun Zhang
J. Mar. Sci. Eng. 2025, 13(8), 1519; https://doi.org/10.3390/jmse13081519 - 7 Aug 2025
Viewed by 89
Abstract
This paper investigates weak fault feature extraction in AUV thrusters under multi-input signal conditions. Conventional methods often rely on insufficient input signals, leading to a non-monotonic mapping between fault features and fault severity. This, in turn, makes accurate fault severity identification infeasible. To [...] Read more.
This paper investigates weak fault feature extraction in AUV thrusters under multi-input signal conditions. Conventional methods often rely on insufficient input signals, leading to a non-monotonic mapping between fault features and fault severity. This, in turn, makes accurate fault severity identification infeasible. To overcome this limitation, this paper increases the number of input signals by utilizing all available measurable signals. To address the problems arising from the expanded signal set, a signal denoising method that combines Feature Mode Decomposition and wavelet denoising is proposed. Furthermore, a signal enhancement technique that integrates energy operators and the Modified Bayes method. Additionally, distinct technical approaches for noise reduction and enhancement are specifically designed for different input signals. Unlike conventional methods that extract features directly from raw input signals, for fault feature extraction and fusion, this study transforms the signals into the time, frequency, and time–frequency domains, extracting diverse fault features across these domains. A sensitivity factor selection method is then employed to identify the sensitive features. These selected features are subsequently fused using Dempster–Shafer evidence theory to construct the final fault feature. Finally, fault severity identification is carried out using the classical grey relational analysis. Pool experiments using the “Beaver II” AUV prototype validate the effectiveness of the proposed method. Full article
(This article belongs to the Special Issue Intelligent Measurement and Control System of Marine Robots)
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32 pages, 4635 KiB  
Article
Maritime Rescue Task Allocation and Sequencing Using MOEA/D with Adaptive Operators and Idle-Time-Aware Decoding Strategy
by Jianhua Sun, Suihuai Yu, Jianjie Chu and Ruisi Liu
J. Mar. Sci. Eng. 2025, 13(8), 1518; https://doi.org/10.3390/jmse13081518 - 7 Aug 2025
Viewed by 109
Abstract
The timeliness of maritime rescue critically depends on the efficient generation of solutions and the execution of missions. Therefore, this study aims to implement maritime rescue task allocation and sequencing (MRTAS) while ensuring solution generation and mission execution efficiencies. First, a mathematical model [...] Read more.
The timeliness of maritime rescue critically depends on the efficient generation of solutions and the execution of missions. Therefore, this study aims to implement maritime rescue task allocation and sequencing (MRTAS) while ensuring solution generation and mission execution efficiencies. First, a mathematical model minimizing mission completion time and resource consumption for MRTAS is established. Second, adaptive operators considering iteration progress and population objective distribution status and an idle-time-aware decoding strategy based on an in-degree embedded gap insertion are proposed. The adaptive operators and idle-time-aware decoding strategy are employed to enhance the multi-objective evolutionary algorithm based on decomposition (MOEA/D) for efficiency improvement in both solution generation and mission execution. The enhanced MOEA/D is then employed to identify Pareto-optimal MRTAS schemes. Validation using two case studies (Case 1–18 task, Case 2–100 task) confirms the practicality and feasibility of the enhanced MOEA/D. Furthermore, ablation studies, sensitivity analyses, and comprehensive comparisons against fixed operators, state-of-the-art algorithms, and traditional decoding strategies all demonstrate that the enhanced MOEA/D can accelerate convergence while maintaining converged solution quality and reduce mission completion time. Full article
(This article belongs to the Section Ocean Engineering)
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16 pages, 17061 KiB  
Article
Numerical Analysis of Cavitation Suppression on a NACA 0018 Hydrofoil Using a Surface Cavity
by Pankaj Kumar, Ebrahim Kadivar and Ould el Moctar
J. Mar. Sci. Eng. 2025, 13(8), 1517; https://doi.org/10.3390/jmse13081517 - 6 Aug 2025
Viewed by 155
Abstract
This study examines the hydrodynamic and acoustic performance of plain NACA0018 hydrofoil and modified NACA0018 hydrofoils (foil with a cavity on suction surface) at a Reynolds number (Re) of 40,000, which is indicative of small-scale turbines and [...] Read more.
This study examines the hydrodynamic and acoustic performance of plain NACA0018 hydrofoil and modified NACA0018 hydrofoils (foil with a cavity on suction surface) at a Reynolds number (Re) of 40,000, which is indicative of small-scale turbines and marine applications. A cavity was created on suction side surface at 40–50% of the chord length, which is chosen for its efficacy in cavitation control. The present analysis examines the impact of the cavity on lift-to-drag-ratio (L/D) and cavity length at three cavitation numbers (1.7, 1.2, and 0.93) for plain and modified hydrofoils. Simulations demonstrate a significant enhancement of 7% in the lift-to-drag ratio relative to traditional designed foils. Contrary to earlier observations, the cavity length increases instead of decreasing for the modified hydrofoil. Both periodic steady and turbulent inflow conditions are captured that simulate the complex cavity dynamics and flow–acoustic interactions. It is found that a reduction in RMS velocity with modified blade suggests flow stabilization. Spectral analysis using Mel-frequency techniques confirms the cavity’s potential to reduce low-frequency flow-induced noise. These findings offer new insights for designing quieter and more efficient hydrofoils and turbine blades. Full article
(This article belongs to the Section Ocean Engineering)
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20 pages, 7928 KiB  
Article
Nonlinear Effects on the Formation of Large Random Wave Events
by George Spiliotopoulos and Vanessa Katsardi
J. Mar. Sci. Eng. 2025, 13(8), 1516; https://doi.org/10.3390/jmse13081516 - 6 Aug 2025
Viewed by 153
Abstract
This work aims to highlight the effects of nonlinearity on the crest shape of large directional water wave events. To simulate such events, we chose to focus frequencies on a pre-determined time step over a wavefield with randomised phases, running the simulations with [...] Read more.
This work aims to highlight the effects of nonlinearity on the crest shape of large directional water wave events. To simulate such events, we chose to focus frequencies on a pre-determined time step over a wavefield with randomised phases, running the simulations with HOS-ocean, a fully nonlinear potential flow solver. By also applying a phase separation scheme, we were able to identify the contributions of the various orders of nonlinearity to the formation of these large wave events. The findings show a significant change in the shape of these large water waves compared to linear theory, particularly in shallower water depth. In addition, the phase separation reveals the increased significance of high-order harmonics in finite water depths compared to deep water. Full article
(This article belongs to the Section Ocean Engineering)
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22 pages, 5041 KiB  
Article
Dynamic Characteristic (Axial Impedances) of a Novel Sandwich Flexible Insert with Fluid
by Leipeng Song, Lulu Chang, Feng Li, Xinjian Xiang, Zhiyong Yin, Xichen Hou, Yongping Zheng, Xiaozhou Xu, Yang Li and Zhihua Huang
J. Mar. Sci. Eng. 2025, 13(8), 1515; https://doi.org/10.3390/jmse13081515 - 6 Aug 2025
Viewed by 143
Abstract
Piping systems can be analogized to the “vascular systems” of vessels, but their transmission characteristics often result in loud noises and large vibrations. The integration of flexible inserts within these piping systems has been shown to isolate and/or mitigate such vibrations and noise. [...] Read more.
Piping systems can be analogized to the “vascular systems” of vessels, but their transmission characteristics often result in loud noises and large vibrations. The integration of flexible inserts within these piping systems has been shown to isolate and/or mitigate such vibrations and noise. In this work, a novel sandwich flexible insert (NSFI) was presented specifically to reduce the vibrations and noise associated with piping systems on vessels. In contrast to conventional flexible inserts, the NSFI features a distinctive three-layer configuration, comprising elastic inner and outer layers, along with a honeycomb core exhibiting a zero Poisson’s ratio. The dynamic characteristics, specifically axial impedance, of the fluid-filled NSFI are examined utilizing a fluid–structure interaction (FSI) four-equation model. The validity of the theoretical predictions is corroborated through finite element analysis, experimental results, and comparisons with existing literature. Furthermore, the study provides a comprehensive evaluation of the effects of geometric and structural parameters on the dynamic characteristics of the NSFI. It is worth noting that axial impedance is significantly affected by these parameters, which suggests that the dynamic characteristics of the NSFI can be customized by parameter adjustments. Full article
(This article belongs to the Section Ocean Engineering)
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13 pages, 3237 KiB  
Article
Evaluating the Trophic Structure of an Artificial Macroalgal Bed of Eisenia bicyclis Using C and N Stable Isotopes
by Dong-Young Lee, Dongyoung Kim, Chan-Kil Chun, Youngkweon Lee, Kyu-Sam Han, Hyun Kyum Kim, Tae Hee Park and Hyun Je Park
J. Mar. Sci. Eng. 2025, 13(8), 1514; https://doi.org/10.3390/jmse13081514 - 6 Aug 2025
Viewed by 171
Abstract
In this study, we applied a new technique for vegetatively transplanting kelp Eisenia bicyclis to restore macroalgal habitats. We aimed to assess the restoration success of the E. bicyclis bed by comparing the carbon and nitrogen stable isotope ratios of macrobenthic consumers and [...] Read more.
In this study, we applied a new technique for vegetatively transplanting kelp Eisenia bicyclis to restore macroalgal habitats. We aimed to assess the restoration success of the E. bicyclis bed by comparing the carbon and nitrogen stable isotope ratios of macrobenthic consumers and their isotopic niches in artificial and control (barren ground) habitats. Except for the deposit feeding group, no significant differences were observed in isotopic values of the other feeding groups (suspension feeders, herbivores, omnivores, and carnivores) between the two sites. In contrast, our results showed wider isotopic niche indices for all feeding groups at the transplantation site compared to those at the control site, suggesting increased trophic diversity in the artificial habitat. Overall, these results indicate that the macroalgal bed created using the new method can play an ecological role in restoring functional properties of food web structures via trophic support of degraded coastal ecosystems. Full article
(This article belongs to the Section Ocean Engineering)
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