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Volume 12
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J. Mar. Sci. Eng., Volume 12, Issue 10 (October 2024) – 191 articles

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32 pages, 10733 KiB  
Article
Energy Use and Carbon Footprint Assessment in Retrofitting a Novel Energy Saving Device to a Ship
by Eren Uyan, Mehmet Atlar and Osman Gürsoy
J. Mar. Sci. Eng. 2024, 12(10), 1879; https://doi.org/10.3390/jmse12101879 (registering DOI) - 19 Oct 2024
Abstract
The Gate rudder system (GRS) was recently introduced as an innovative energy-saving device (ESD) for ships, and it is the most attractive ESD currently used in the market, with double figures of fuel savings in full-scale (>10–35%) compared with a ship with a [...] Read more.
The Gate rudder system (GRS) was recently introduced as an innovative energy-saving device (ESD) for ships, and it is the most attractive ESD currently used in the market, with double figures of fuel savings in full-scale (>10–35%) compared with a ship with a conventional rudder system (CRS). Although there are few new ship applications of GRS, the recently completed EC-H2020 GATERS project successfully demonstrated its unique energy-saving and manoeuvrability benefits as a “retrofit” solution for an existing general cargo vessel for the first time. The project results suggested that the GRS holds significant potential for retrofitting existing ships to enhance fuel efficiency (~35%) and improve manoeuvrability. Nevertheless, the application was a comprehensive undertaking requiring various work tasks such as component manufacturing, removing existing systems, and modification and upgrading works, with substantial energy consumption and environmental impacts. Therefore, it was insightful to study energy use and environmental impacts in a GRS retrofit process. This study developed and implemented a comprehensive energy consumption and carbon footprint assessment framework for the GRS retrofit in the GATERS project. A detailed assessment of energy consumption and related carbon emissions was performed during the major stages of manufacturing, system removals, and modifications and assembly in the GRS retrofit. Also, the potential savings in energy use and emissions were addressed. The results demonstrated that the manufacturing stage was the most energy-intensive phase, being responsible for 91.4% of total electricity and 46.7% of fuel-based thermal energy use. The system removals accounted for 53.3% of the fuel-based thermal energy, whereas the modification and assembly work accounted for about 7.7% of the total electricity use. Additionally, various measures such as clean electrification, energy efficiency, mould/tool reuse, and component reuse to reduce the energy consumption and related carbon emissions in future GRS retrofit applications were addressed and discussed together with their reduction potentials. Full article
(This article belongs to the Special Issue Advances in Ships and Marine Structures)
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32 pages, 21139 KiB  
Article
Numerical Simulation on Two-Dimensional Dual-Zone Axisymmetric Consolidation for Marine Soft Soil Improved by PVTD Considering Interfacial Thermal Resistance
by Kejie Tang, Minjie Wen, Yi Tian, Xiaoqiang Gu, Wenbing Wu, Yiming Zhang, Guoxiong Mei, Pan Ding, Yuan Tu, Anyuan Sun and Kaifu Liu
J. Mar. Sci. Eng. 2024, 12(10), 1878; https://doi.org/10.3390/jmse12101878 (registering DOI) - 19 Oct 2024
Abstract
Prefabricated vertical drains combined with heating is a new approach to improving the mechanical properties of soft clay foundations. Rising temperatures cause the formation of concentric and radially aligned soil regions with distinct heterogeneous characteristics. This results in incomplete contact between adjacent soil [...] Read more.
Prefabricated vertical drains combined with heating is a new approach to improving the mechanical properties of soft clay foundations. Rising temperatures cause the formation of concentric and radially aligned soil regions with distinct heterogeneous characteristics. This results in incomplete contact between adjacent soil layers, with the water in the interstices impeding heat transfer and manifesting as a thermal resistance effect. Based on the theory of thermo-hydro-mechanical coupling, a two-dimensional dual-zone axisymmetric marine soft soil model improved by a prefabricated vertical thermo-drain has been established. A generalized incomplete thermal contact model has been proposed to describe the thermal resistance effect at the interface of concentric soil regions. The effectiveness of the numerical solution presented in this paper is verified by comparison with semi-analytical solutions and model experiments. The thermal consolidation characteristics of concentric regions of soil at various depths under different thermal contact models were discussed by comprehensively analyzing the effects of different parameters under various thermal contact models. The outcomes indicate that the generalized incomplete thermal contact model provides a more accurate description of the radial thermal consolidation characteristics of concentric regions of soil. The influence of the thermal conductivity coefficient on the consolidation characteristics of the concentric regions soil is related to the thermal resistance effect. Full article
(This article belongs to the Section Coastal Engineering)
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15 pages, 5474 KiB  
Article
Modulation Classification of Underwater Communication Signals Based on Channel Estimation
by Xiaodan Yang, Zulin Wang, Tongsheng Shen and Dexin Zhao
J. Mar. Sci. Eng. 2024, 12(10), 1877; https://doi.org/10.3390/jmse12101877 (registering DOI) - 19 Oct 2024
Viewed by 117
Abstract
Classifying modulated signals for non-cooperative underwater acoustic communication is challenging due to signal distortion caused by fading and multipath effects in the underwater acoustic channel. Our proposed method utilizes channel estimation parameters to measure and correct signal distortion, thereby enhancing the recognition performance [...] Read more.
Classifying modulated signals for non-cooperative underwater acoustic communication is challenging due to signal distortion caused by fading and multipath effects in the underwater acoustic channel. Our proposed method utilizes channel estimation parameters to measure and correct signal distortion, thereby enhancing the recognition performance of the received signal. Modulation classification experiments were conducted on a public dataset with various modulation schemes, as well as on the same dataset with simulated underwater acoustic channels. The results indicate that our method effectively mitigates the impact of the underwater acoustic channel on modulation signal classification, improves recognition accuracy, and is broadly applicable to a wide range of machine learning classifiers. Finally, we validated these findings using real underwater communication data. Full article
(This article belongs to the Section Physical Oceanography)
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24 pages, 3101 KiB  
Article
Combined Freak Wave, Wind, and Current Effects on the Dynamic Responses of Offshore Triceratops
by Nagavinothini Ravichandran
J. Mar. Sci. Eng. 2024, 12(10), 1876; https://doi.org/10.3390/jmse12101876 (registering DOI) - 18 Oct 2024
Viewed by 225
Abstract
Offshore structures are exposed to various environmental loads, including extreme and abnormal waves, over their operational lifespan. The existence of wind and current can exacerbate the dynamic response of these structures, posing threats to safety and integrity. This study focuses on the dynamic [...] Read more.
Offshore structures are exposed to various environmental loads, including extreme and abnormal waves, over their operational lifespan. The existence of wind and current can exacerbate the dynamic response of these structures, posing threats to safety and integrity. This study focuses on the dynamic responses of offshore triceratops under different environmental conditions characterized by the superimposition of freak waves, uniform wind, and current. The free surface profile of the freak wave was generated using the dual superposition model. The numerical model of the offshore platform designed for ultra-deep-water applications was developed using the ANSYS AQWA 2023 R2 modeler. Numerical investigations, including the free decay tests and time-domain analysis under random sea states, including freak waves, were initially carried out. Then, the combined effects of freak waves, wind, and current were studied in detail under different loading scenarios. The results revealed the increase in structural response under the freak wave action at the focus time. Wind action resulted in a mean shift in responses, while the inclusion of current led to a pronounced increase in the total response of the platform, encompassing deck and buoyant legs, alongside the tether tension variation. Notably, considerable variations in the response were observed after freak wave exposure under the combined influence of wind, freak wave, and current. The results underscore the profound effects induced by wind and current in the presence of freak waves, providing valuable insights for analyzing similar offshore structures under ultimate design conditions. Full article
(This article belongs to the Special Issue Hydrodynamic Response to the Effect of Current Loads on Floating Offshore Platform)
25 pages, 15710 KiB  
Article
TG-PGAT: An AIS Data-Driven Dynamic Spatiotemporal Prediction Model for Ship Traffic Flow in the Port
by Jianwen Ma, Yue Zhou, Yumiao Chang, Zhaoxin Zhu, Guoxin Liu and Zhaojun Chen
J. Mar. Sci. Eng. 2024, 12(10), 1875; https://doi.org/10.3390/jmse12101875 (registering DOI) - 18 Oct 2024
Viewed by 239
Abstract
Accurate prediction of ship traffic flow is essential for developing intelligent maritime transportation systems. To address the complexity of ship traffic flow data in the port and the challenges of capturing its dynamic spatiotemporal dependencies, a dynamic spatiotemporal model called Temporal convolutional network-bidirectional [...] Read more.
Accurate prediction of ship traffic flow is essential for developing intelligent maritime transportation systems. To address the complexity of ship traffic flow data in the port and the challenges of capturing its dynamic spatiotemporal dependencies, a dynamic spatiotemporal model called Temporal convolutional network-bidirectional Gated recurrent unit-Pearson correlation coefficient-Graph Attention Network (TG-PGAT) is proposed for predicting traffic flow in port waters. This model extracts spatial features of traffic flow by combining the adjacency matrix and spatial dynamic coefficient correlation matrix within the Graph Attention Network (GAT) and captures temporal features through the concatenation of the Temporal Convolutional Network (TCN) and Bidirectional Gated Recurrent Unit (BiGRU). The proposed TG-PGAT model demonstrates higher prediction accuracy and stability than other classic traffic flow prediction methods. The experimental results from multiple angles, such as ablation experiments and robustness tests, further validate the critical role and strong noise resistance of different modules in the TG-PGAT model. The experimental results of visualization demonstrate that this model not only exhibits significant predictive advantages in densely trafficked areas of the port but also outperforms other models in surrounding areas with sparse traffic flow data. Full article
(This article belongs to the Special Issue Management and Control of Ship Traffic Behaviours)
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16 pages, 13038 KiB  
Article
Underwater Gyros Denoising Net (UGDN): A Learning-Based Gyros Denoising Method for Underwater Navigation
by Chun Cao, Can Wang, Shaoping Zhao, Tingfeng Tan, Liang Zhao and Feihu Zhang
J. Mar. Sci. Eng. 2024, 12(10), 1874; https://doi.org/10.3390/jmse12101874 - 18 Oct 2024
Viewed by 194
Abstract
Autonomous Underwater Vehicles (AUVs) are widely used for hydrological monitoring, underwater exploration, and geological surveys. However, AUVs face limitations in underwater navigation due to the high costs associated with Strapdown Inertial Navigation System (SINS) and Doppler Velocity Log (DVL), hindering the development of [...] Read more.
Autonomous Underwater Vehicles (AUVs) are widely used for hydrological monitoring, underwater exploration, and geological surveys. However, AUVs face limitations in underwater navigation due to the high costs associated with Strapdown Inertial Navigation System (SINS) and Doppler Velocity Log (DVL), hindering the development of low-cost vehicles. Micro Electro Mechanical System Inertial Measurement Units (MEMS IMUs) are widely used in industry due to their low cost and can output acceleration and angular velocity, making them suitable as an Attitude Heading Reference System (AHRS) for low-cost vehicles. However, poorly calibrated MEMS IMUs provide an inaccurate angular velocity, leading to rapid drift in orientation. In underwater environments where AUVs cannot use GPS for position correction, this drift can have severe consequences. To address this issue, this paper proposes Underwater Gyros Denoising Net (UGDN), a method based on dilated convolutions and LSTM that learns and extracts the spatiotemporal features of IMU sequences to dynamically compensate for the gyroscope’s angular velocity measurements, reducing attitude and heading errors. In the experimental section of this paper, we deployed this method on a dataset collected from field trials and achieved significant results. The experimental results show that the accuracy of MEMS IMU data denoised by UGDN approaches that of fiber-optic SINS, and when integrated with DVL, it can serve as a low-cost underwater navigation solution. Full article
(This article belongs to the Special Issue Autonomous Marine Vehicle Operations—2nd Edition)
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20 pages, 4544 KiB  
Article
Risk Assessment of Polar Drillship Operations Based on Bayesian Networks
by Qi Wang, Zixin Wang, Hongen Li, Xiaoming Huang, Qianjin Yue, Xiufeng Yue and Yanlin Wang
J. Mar. Sci. Eng. 2024, 12(10), 1873; https://doi.org/10.3390/jmse12101873 - 18 Oct 2024
Viewed by 174
Abstract
In the extreme polar marine environment, safety risks pose a significant threat to drilling vessels. By conducting a safety risk assessment, potential hazards can be predicted and identified, thereby significantly reducing the frequency of accidents and promoting the sustained stability of economic activities. [...] Read more.
In the extreme polar marine environment, safety risks pose a significant threat to drilling vessels. By conducting a safety risk assessment, potential hazards can be predicted and identified, thereby significantly reducing the frequency of accidents and promoting the sustained stability of economic activities. This paper investigates a Bayesian-network-based risk assessment model for polar drilling operations. Grey relational analysis was employed to identify the main risk factors. The model is trained using 525 valid incident sample data and is combined with expert knowledge. The accuracy rate is above 88%. Additionally, corresponding decision-making recommendations are provided through sensitivity analysis. The three most sensitive elements to fire nodes are human error, other causes, and equipment damage, with sensitivity coefficients of 0.046, 0.042, and 0.022, respectively. In terms of deck/handrail collision nodes, the highly sensitive elements are related to lifting (totally more than 0.1). For the events that have already transpired, the probabilities of most related nodes are 0.73 and 0.74, both of which are above 0.5, thereby validating the accuracy of forward and backward reasoning. Risk assessments based on Bayesian networks can offer pertinent decision-making recommendations and preventive measures. Full article
(This article belongs to the Special Issue Monitoring and Evaluation of Marine Engineering Equipment and Structures)
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17 pages, 5741 KiB  
Article
Investigation into Using CFD for Estimation of Ship Specific Parameters for the SPICE Model for Prediction of Sea Spray Icing: Part 1—The Proposal
by Sujay Deshpande and Per-Arne Sundsbø
J. Mar. Sci. Eng. 2024, 12(10), 1872; https://doi.org/10.3390/jmse12101872 - 18 Oct 2024
Viewed by 191
Abstract
A machine learning model for prediction of icing on vessels and offshore structures, Spice, was recently developed by Deshpande 2023. Some variables required for the prediction of icing rates in most prediction models, including Spice, such as the spray flux, cannot be easily [...] Read more.
A machine learning model for prediction of icing on vessels and offshore structures, Spice, was recently developed by Deshpande 2023. Some variables required for the prediction of icing rates in most prediction models, including Spice, such as the spray flux, cannot be easily measured. Existing models estimate these using empirical formulations that have been heavily criticized. Most existing models are also incapable of providing the distribution of icing on the structure. The current study demonstrates a method to estimate the local wind speeds, along with spray duration, spray period, and spray flux at different locations on the surface of a moving vessel. These, along with other easily measurable values of air temperature, water temperature, and salinity, are used to predict the icing rates. The result is a model, dubbed Spice2—an upgrade of the existing Spice model—that is able to provide the icing rates and the distribution of icing on the surface of vessels and other offshore structures. The model was demonstrated with a case study of a totally enclosed lifeboat where icing rates were predicted at different locations on its surface. Successful implementation of a two-phase simulation with a coupled wind–wave domain and a moving vessel was demonstrated. Research into simplification of the currently computationally expensive method is suggested. Validation of the proposed Spice2 model against a full-scale measurement is covered in part 2 of the study. Full article
(This article belongs to the Special Issue Novel Maritime Techniques and Technologies, and Their Safety)
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19 pages, 14529 KiB  
Article
Morphology and Effect of Load on Bridge Piers Impacted by Continuous Sea Ice
by Li Gong, Yue Cui, Yunfei Du, Long Qin and Xinyuan Zhao
J. Mar. Sci. Eng. 2024, 12(10), 1871; https://doi.org/10.3390/jmse12101871 - 18 Oct 2024
Viewed by 217
Abstract
In order to study the collision of sea ice on bridge piers of a sea-crossing bridge, this study establishes a finite element model of the impact of sea ice on bridge piers in aqueous media based on explicit dynamics analysis software and programming [...] Read more.
In order to study the collision of sea ice on bridge piers of a sea-crossing bridge, this study establishes a finite element model of the impact of sea ice on bridge piers in aqueous media based on explicit dynamics analysis software and programming software using the arbitrary Lagrangian Eulerian (ALE) method. The results show that, when the sea-ice spacing is larger than the sea-ice edge length, the increase in sea-ice spacing leads to a decrease in the collision force and a significant increase in the probability of climbing and overturning. The increase in sea-ice mass significantly increases the impact force on the bridge abutment, and the peak value increases linearly with the increase in mass, and the sea-ice climbing and overturning phenomena are obvious. Different shapes of sea ice are obtained by cutting the sea-ice field with the two-dimensional Voronoi method, and the maximum impact force increases significantly with the increase in the average area. Irregularly shaped sea ice leads to a larger impact force and triggers the accumulation climbing phenomenon, which is verified by experiments, and the experimental values are in good agreement with the simulated values. In conclusion, this study reveals the significant effects of the spacing, mass, and shape of sea ice on the impact force of bridge piers, which provides an important reference for the design of bridge structures. Full article
(This article belongs to the Special Issue Numerical Analysis and Modeling of Floating Structures)
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23 pages, 6148 KiB  
Article
An Analysis of the Flexural Stiffness and Horizontal Bearing Capacity of CFRP Composite Pipe Piles in Marine Environments
by Wei Zhang, Wei Shao and Yinghui Nie
J. Mar. Sci. Eng. 2024, 12(10), 1870; https://doi.org/10.3390/jmse12101870 - 18 Oct 2024
Viewed by 200
Abstract
Carbon-fiber-reinforced polymer (CFRP) is a composite material consisting of a resin matrix reinforced with carbon fibers. This study focuses on CFRP composite pipe piles as the subject of investigation, exploring the impact of substituting steel bars with CFRP bars on the bending performance [...] Read more.
Carbon-fiber-reinforced polymer (CFRP) is a composite material consisting of a resin matrix reinforced with carbon fibers. This study focuses on CFRP composite pipe piles as the subject of investigation, exploring the impact of substituting steel bars with CFRP bars on the bending performance of pipe piles through rigorous three-point bending tests. The attenuation of flexural stiffness in CFRP pipe piles under a chloride salt environment was anticipated. The lateral bearing capacity of CFRP pipe piles was calculated by introducing a stiffness degradation coefficient for the piles and utilizing the finite difference method. The findings of the analysis suggest that as the CFRP reinforcement replacement rate increases, the initial bending stiffness of the composite pipe pile experiences a corresponding decrease. After serving for 28.15 years, the steel reinforcement within the pipe pile commences rusting, resulting in a nonlinear decline in the bending stiffness of the composite pipe pile. As the service time of pipe piles increases, a higher replacement rate of CFRP reinforcement results in a slower attenuation of pile stiffness. Consequently, both the horizontal displacement at the top of the pile and the bending moment along the body of the composite pipe pile gradually increase over time. During the same service period, the higher the rate of CFRP reinforcement, the less noticeable the attenuation in the horizontal bearing capacity of the pile shaft. Full article
(This article belongs to the Section Ocean Engineering)
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18 pages, 6752 KiB  
Article
Study on the Prediction of Motion Response of Offshore Platforms Based on ResCNN-LSTM
by Feng Diao, Tianyu Liu, Franck Aurel Likeufack Mdemaya and Gang Xu
J. Mar. Sci. Eng. 2024, 12(10), 1869; https://doi.org/10.3390/jmse12101869 - 18 Oct 2024
Viewed by 211
Abstract
In the random sea environment, offshore platforms are influenced by factors such as wind, waves, and currents, as well as their interactions, leading to complex motion phenomena that affect the safety of offshore platform operations. Consequently, accurately predicting the motion response of offshore [...] Read more.
In the random sea environment, offshore platforms are influenced by factors such as wind, waves, and currents, as well as their interactions, leading to complex motion phenomena that affect the safety of offshore platform operations. Consequently, accurately predicting the motion response of offshore platforms has long been a key focus in the fields of naval architecture and ocean engineering. This paper utilizes STAR-CCM+ to simulate time-history data of offshore platform motion responses under both regular and irregular waves. Furthermore, a predictive model combining residual convolutional neural networks and long short-term memory neural networks using neural network technology is also studied. This model utilizes an autoregressive approach to predict the motion responses of offshore platforms, with its predictive accuracy validated through comprehensive evaluations. Under regular wave conditions, the coefficient of determination (R2) for the platform’s heave and pitch responses consistently exceeds 0.99. Meanwhile, under irregular wave conditions, the R2 values remain generally above 0.4. Additionally, the model exhibits commendable performance in terms of Mean Squared Error (MSE) and Mean Absolute Percentage Error (MAPE) metrics. The aim of this study is to present a novel approach to predicting offshore platform motion responses, while providing a more scientific basis for decision-making in offshore platform operations. Full article
(This article belongs to the Section Ocean Engineering)
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28 pages, 9539 KiB  
Article
Improved Fracture Permeability Evaluation Model for Granite Reservoirs in Marine Environments: A Case Study from the South China Sea
by Jianhong Guo, Baoxiang Gu, Hengyang Lv, Zuomin Zhu and Zhansong Zhang
J. Mar. Sci. Eng. 2024, 12(10), 1868; https://doi.org/10.3390/jmse12101868 - 18 Oct 2024
Viewed by 212
Abstract
Permeability is a crucial parameter in the exploration and development of oil and gas reservoirs, particularly in unconventional ones, where fractures significantly influence storage capacity and fluid flow. This study investigates the fracture permeability of granite reservoirs in the South China Sea, introducing [...] Read more.
Permeability is a crucial parameter in the exploration and development of oil and gas reservoirs, particularly in unconventional ones, where fractures significantly influence storage capacity and fluid flow. This study investigates the fracture permeability of granite reservoirs in the South China Sea, introducing an enhanced evaluation model for planar fracture permeability based on Darcy’s law and Poiseuille’s law. The model incorporates factors such as fracture heterogeneity, tortuosity, angle, and aperture to improve permeability assessments. Building on a single-fracture model, this research integrates mass transfer equations and trigonometric functions to assess intersecting fractures’ permeability. Numerical simulations explore how tortuosity, angle, and aperture affect individual fracture permeability and the influence of relative positioning in intersecting fractures. The model makes key assumptions, including minimal consideration of horizontal stress and the assumption of unidirectional laminar flow in cross-fractures. Granite outcrop samples were systematically collected, followed by full-diameter core drilling. A range of planar models with varying fracture apertures were designed, and permeability measurements were conducted using the AU-TOSCAN-II multifunctional core scanner with a steady-state gas injection method. The results showed consistency between the improved model and experimental findings regarding the effects of fracture aperture and angle on permeability, confirming the model’s accuracy in reflecting the fractures’ influence on reservoir flow capacity. For intersecting fractures, a comparative analysis of core X-ray computed tomography (X-CT) scanning results and experimental outcomes highlighted discrepancies between actual permeability measurements and theoretical simulations based on tortuosity and aperture variations. Limitations exist, particularly for cross-fractures, where quantifying complexity is challenging, leading to potential discrepancies between simulation and experimental results. Further comparisons between core experiments and logging responses are necessary for model refinement. In response to the challenges associated with evaluating absolute permeability in fractured reservoirs, this study presents a novel theoretical assessment model that considers both single and intersecting fractures. The model’s validity is demonstrated through actual core experiments, confirming the effectiveness of the single-fracture model while highlighting the need for further refinement of the dual-fracture model. The findings provide scientific support for the exploration and development of granite reservoirs in the South China Sea and establish a foundation for permeability predictions in other complex fractured reservoir systems, thereby advancing the field of fracture permeability assessment. Full article
(This article belongs to the Special Issue High-Efficient Exploration and Development of Oil & Gas from Ocean—2nd Edition)
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13 pages, 752 KiB  
Article
Contribution of Lab Radon Flux Measurements for Evaluating Submarine Groundwater Discharge in Coastal Areas
by Daniel M. Bonotto, José R. C. Nery, Tatiani P. P. Sabaris, Luis H. Mancini, Marina Lunardi, Cristiano Cigagna, Lucas P. Fontanetti and Gabrielle R. Ceccato
J. Mar. Sci. Eng. 2024, 12(10), 1867; https://doi.org/10.3390/jmse12101867 - 18 Oct 2024
Viewed by 246
Abstract
Laboratory-scale experiments were conducted on Carboniferous Limestone gravels from the Mendip Hills area, England; sandstones from the Pirambóia and Botucatu formations, Paraná sedimentary basin, Brazil; samples of schist and quartzite from Caldas Novas Hydrothermal Complex, Brazil; and the minerals tantalite, cassiterite, and columbite [...] Read more.
Laboratory-scale experiments were conducted on Carboniferous Limestone gravels from the Mendip Hills area, England; sandstones from the Pirambóia and Botucatu formations, Paraná sedimentary basin, Brazil; samples of schist and quartzite from Caldas Novas Hydrothermal Complex, Brazil; and the minerals tantalite, cassiterite, and columbite from mining areas at Rio Grande do Norte State, Brazil, with the purpose of evaluating the release of 222Rn to the water phase. The specific surface area of the samples corresponded to 1.69–81.36 cm2g−1, which provided values of 0.001–1.68 dpm/g and 3.18 × 10−6 to 0.59 for the radon released and radon emanation coefficient, respectively. These results allowed us to calculate the radon flux with respect to the radon leakage, which corresponded to values of 0.00016–0.00158 Bq/m2/d for the denser materials and 0.018–0.43 Bq/m2/d for limestones and sandstones. They also permitted us to find an inverse, significant relationship between the radon generated by the minerals/rocks and the radon flux into the water phase, which was tested for sediments in coastal and inland Brazilian areas, demonstrating utility for evaluating the diffusive radon flux from the sediments, which is an important parameter to monitor submarine groundwater discharge (SGD) by means of radon as a natural tracer. Full article
(This article belongs to the Special Issue Distribution and Content of Trace Elements in Seawater and Sediments)
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10 pages, 2049 KiB  
Article
An Investigation into Using CFD for the Estimation of Ship Specific Parameters for the SPICE Model for the Prediction of Sea Spray Icing: Part 2—The Verification of SPICE2 with a Full-Scale Test
by Per-Arne Sundsbø and Sujay Deshpande
J. Mar. Sci. Eng. 2024, 12(10), 1866; https://doi.org/10.3390/jmse12101866 - 18 Oct 2024
Viewed by 238
Abstract
A hybrid CFD–ML model for the prediction of sea spray icing, SPICE2, was developed in Part 1 of this study in Deshpande et al., 2024. The SPICE2 model is an extension of the ML model, SPICE, where some of the variables required for [...] Read more.
A hybrid CFD–ML model for the prediction of sea spray icing, SPICE2, was developed in Part 1 of this study in Deshpande et al., 2024. The SPICE2 model is an extension of the ML model, SPICE, where some of the variables required for icing rate predictions: local wind speed, spray duration, spray period, and spray flux, are computed from CFD simulations. These, along with the air and water temperatures, and the salinity from the metocean data are used for the prediction of icing rates at different locations on a moving vessel. The existing full-scale icing measurements proved to be not detailed enough for the purpose of the verification of sea spray icing prediction models and the verification of the SPICE2 required distribution of sea spray icing data on the vessel surface in addition to the vessel design for simulation. A full-scale sea spray icing test was conducted in 2018 by Sundsbø et al. on a fully enclosed lifeboat equipped for the Goliat field in the Barents Sea. The 3D design of the same lifeboat, together with the corresponding metocean conditions and ship characteristics was used for the simulation of the vessel-specific parameters required for the verification of the icing rate and distribution prediction from the SPICE2 model against the measured distribution of sea spray icing rates on the lifeboat surface. The availability of the 3D model of this lifeboat, in addition to the fact that the icing measurements from this test were detailed enough to attempt a model verification served the purpose of validating the SPICE2 model. The icing rates measured on this lifeboat are used for the full-scale validation of the SPICE2 model that is proposed in Part 1 of this study. It was seen that the icing rates predicted by SPICE2 concurred with 9 of 13 selected locations on the lifeboat. The ones which did not showed very little deviation from the measurements. The icing rate and distribution prediction with SPICE2 were satisfactorily validated against full-scale icing measurements. This is a first attempt in modelling sea spray generation using CFD and further research into CFD for the estimation of spray flux is suggested. Full article
(This article belongs to the Special Issue Novel Maritime Techniques and Technologies, and Their Safety)
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20 pages, 6186 KiB  
Article
Optimizing Ship Draft Observation with Wave Energy Attenuation and PaddlePaddle-OCR in an Anti-Fluctuation Device
by Yaoming Wei, Huan Du, Qinyou Hu and Hu Wang
J. Mar. Sci. Eng. 2024, 12(10), 1865; https://doi.org/10.3390/jmse12101865 - 18 Oct 2024
Viewed by 258
Abstract
With the development and application of artificial intelligence (AI) in the shipping industry, using AI to replace traditional draft survey methods in bulk carriers can significantly reduce manpower, lower the risks associated with visual observations, improve measurement accuracy, and minimize the impact of [...] Read more.
With the development and application of artificial intelligence (AI) in the shipping industry, using AI to replace traditional draft survey methods in bulk carriers can significantly reduce manpower, lower the risks associated with visual observations, improve measurement accuracy, and minimize the impact of human subjective factors. Ultimately, the integration of software and hardware technologies will replace human visual observations with automated draft measurement calculations. A similar anti-fluctuation device described in this article has been used in ship draft observation based on AI-assisted proving, which can ease the fluctuation of the wave inside the pipe. Observers can directly read the water surface inside the pipe and compare it to the ship’s draft mark to obtain the final draft, effectively improving draft observation accuracy. However, some surveyors refuse to accept the readings obtained from this device, citing a lack of theoretical basis or the absence of accreditation from relevant technical authorities, leading to the rejection of results. To address these issues, this paper integrates wave energy attenuation theory with PaddlePaddle-OCR recognition to further validate the anti-fluctuation device for accurate ship draft observation. The experimental results are as follows: first, the pipe effectively suppresses the amplitude of external water surface fluctuations by 75%, explaining the fundamental theory that wave heights within the anti-fluctuation device are consistent with external swell heights. When taking a draft measurement, the system dynamically adjusts the position of the main tube in response to the ship’s movements, maintaining the stability of the measurement section and significantly reducing the difficulty of observations. Due to the reduction in fluctuation amplitude, there is a noticeable improvement in observation accuracy. Full article
(This article belongs to the Special Issue Smart and Low Carbon Emission-Oriented Maritime Traffic Management and Controlling)
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17 pages, 1379 KiB  
Article
Range-Domain Subspace Detector in the Presence of Direct Blast for Forward Scattering Detection in Shallow-Water Environments
by Jiahui Luo, Chao Sun and Mingyang Li
J. Mar. Sci. Eng. 2024, 12(10), 1864; https://doi.org/10.3390/jmse12101864 - 17 Oct 2024
Viewed by 221
Abstract
This paper aims to detect a target that crosses the baseline connecting the source and the receiver in shallow-water environments, which is a special scenario for a bistatic sonar system. In such a detection scenario, an intense sound wave, known as the direct [...] Read more.
This paper aims to detect a target that crosses the baseline connecting the source and the receiver in shallow-water environments, which is a special scenario for a bistatic sonar system. In such a detection scenario, an intense sound wave, known as the direct blast, propagates directly from the source to the receiver without target scattering. This direct blast usually arrives at the receiver simultaneously with the forward scattering signal and exhibits a larger intensity than the signal, posing a significant challenge for target detection. In this paper, a range-domain subspace is constructed by the horizontal distance between the source/target and each element of a horizontal linear array (HLA) when the ranges of environmental parameters are known a priori. Meanwhile, a range-domain subspace detector based on direct blast suppression (RSD-DS) is proposed for forward scattering detection. The source and the target are located at different positions, so the direct blast and the scattered signal are in different range-domain subspaces. By projecting the received data onto the orthogonal complement subspace of the direct blast subspace, the direct blast can be suppressed and the signal that lies outside the direct blast subspace is used for target detection. The simulation results indicate that the proposed RSD-DS exhibits a performance close to the generalized likelihood ratio detector (GLRD) while requiring less prior knowledge of environments (only known are the ranges of the sediment sound speed and the bottom sound speed), and its robustness to environmental uncertainties is better than that of the latter. Moreover, the proposed RSD-DS exhibits better immunity against the direct blast than the GLRD, since it can still work effectively at a signal-to-direct blast ratio (SDR) of −30 dB, while the GLRD stops working in this case. Full article
(This article belongs to the Special Issue Applications of Underwater Acoustics in Ocean Engineering)
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25 pages, 27177 KiB  
Article
Bollard Pull and Self-Propulsion Performance of a Waterjet Propelled Tracked Amphibian
by Taehyung Kim, Donghyeon Yoon, Jeongil Seo and Jihyeun Wang
J. Mar. Sci. Eng. 2024, 12(10), 1863; https://doi.org/10.3390/jmse12101863 - 17 Oct 2024
Viewed by 348
Abstract
This paper describes the unique full-scale bollard pull and self-propulsion tests of a large amphibious tracked military vehicle with two waterjet propulsors. To provide a reference for the self-propulsion and cavitation performance, a series of sea trials and bollard pull tests were performed [...] Read more.
This paper describes the unique full-scale bollard pull and self-propulsion tests of a large amphibious tracked military vehicle with two waterjet propulsors. To provide a reference for the self-propulsion and cavitation performance, a series of sea trials and bollard pull tests were performed in a military sea bay and in a large test basin, respectively. Good overall agreement between the sea trial and the computation was observed in the speed–power relationship. The cavitation-induced breakdown phenomenon was further explored via numerical simulations. The results indicated that the uncertainties in the numerical results were dominated by the scales of vapor bubbles. The analysis showed that the selection of the vapor bubble scale factors of 1.0 for growth and 0.05 for collapse were in good agreement with the experimental results. Rapid performance breakdown occurred when sufficient suction side-attached cavities were extended into the blade mid-chord and tip-board regions. Full article
(This article belongs to the Special Issue Ship Performance in Actual Seas)
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16 pages, 4906 KiB  
Article
SC-DiatomNet: An Efficient and Accurate Algorithm for Diatom Classification
by Jiongwei Li, Chengshuo Jiang, Lishuang Yao and Shiyuan Zhang
J. Mar. Sci. Eng. 2024, 12(10), 1862; https://doi.org/10.3390/jmse12101862 - 17 Oct 2024
Viewed by 290
Abstract
Detecting the quantity and diversity of diatoms is of great significance in areas such as climate change, water quality assessment, and oil exploration. Here, an efficient and accurate object detection model, named SC-DiatomNet, is proposed for diatom detection in complex environments. This model [...] Read more.
Detecting the quantity and diversity of diatoms is of great significance in areas such as climate change, water quality assessment, and oil exploration. Here, an efficient and accurate object detection model, named SC-DiatomNet, is proposed for diatom detection in complex environments. This model is based on the YOLOv3 architecture and uses the K-means++ algorithm for anchor box clustering on the diatom dataset. A convolutional block attention module is incorporated in the feature extraction network to enhance the model’s ability to recognize important regions. A spatial pyramid pooling module and adaptive anchor boxes are added to the encoder to improve detection accuracy for diatoms of different sizes. Experimental results show that SC-DiatomNet can successfully detect and classify diatoms accurately without reducing detection speed. The recall, precision, and F1 score were 94.96%, 94.21%, and 0.94, respectively. It further improved the mean average precision (mAP) of YOLOv3 by 9.52% on the diatom dataset. Meanwhile, the detection accuracy was improved compared with those of other advanced deep learning algorithms. SC-DiatomNet has potential applications in water quality analysis and monitoring of harmful algal blooms. Full article
(This article belongs to the Section Ocean Engineering)
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10 pages, 2462 KiB  
Article
Effect of CO2 Thickeners on CH4-CO2 Replacement in Hydrate-Bearing Sediment
by Xuebing Zhou, Jiahong Zhou, Zhen Long, Huiyun Wen, Shuanshi Fan and Deqing Liang
J. Mar. Sci. Eng. 2024, 12(10), 1861; https://doi.org/10.3390/jmse12101861 - 17 Oct 2024
Viewed by 244
Abstract
CO2 fracturing is known as the best solution to improve the efficiency of the CO2 replacement of natural gas hydrates, but the effect of CO2 thickeners on CH4-CO2 replacement are barely noticed. In this work, the effect [...] Read more.
CO2 fracturing is known as the best solution to improve the efficiency of the CO2 replacement of natural gas hydrates, but the effect of CO2 thickeners on CH4-CO2 replacement are barely noticed. In this work, the effect of four kinds of CO2 thickener—including DL-Lactic acid, polyvinyl acetate, ethyl trifluoroacetate and octamethyl trisiloxane—on the CH4-CO2 replacement in quartz sand was measured thermodynamically and kinetically. The results show that the majority of the CO2 thickeners had no effect on the equilibria of the CH4 and CO2 hydrates, except for DL-Lactic acid, where the temperature depression caused by the addition of 5.5 wt% DL-Lactic acid was about 0.52 and 0.48 K for the CH4 and CO2 hydrates, respectively. In the kinetic measurements, the CH4-CO2 replacement was promoted via the addition of the CO2 thickeners, except DL-Lactic acid. The CO2 thickeners were suggested to strengthen the CH4-CO2 replacement by enhancing the gas exchange in the pore space. Octamethyl trisiloxane, which could promote CH4 recovery and CO2 capture at a low concentration, was suggested to be an ideal CO2 thickener for CH4-CO2 replacement. Full article
(This article belongs to the Special Issue Analytical and Experimental Technology for Marine Gas Hydrate)
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33 pages, 5435 KiB  
Article
Scheduling of Mixed Fleet Passing Through River Bottleneck in Multiple Ways
by De-Chang Li and Hua-Long Yang
J. Mar. Sci. Eng. 2024, 12(10), 1860; https://doi.org/10.3390/jmse12101860 - 17 Oct 2024
Viewed by 280
Abstract
This paper addresses the scheduling problem of a mixed fleet passing through a river bottleneck in multiple ways, considering the impact of streamflow velocity, the fuel cost with different sailing speeds, and the potential opportunity cost of various types and sizes of vessels. [...] Read more.
This paper addresses the scheduling problem of a mixed fleet passing through a river bottleneck in multiple ways, considering the impact of streamflow velocity, the fuel cost with different sailing speeds, and the potential opportunity cost of various types and sizes of vessels. From the perspective of centralized management by river bottleneck authorities, a unified scheduling approach is proposed, and a nonlinear model is constructed, where the total fuel cost and potential opportunity cost of the fleet are minimized. To handle the nonlinear terms in the model, an outer approximation technique is applied to linearize the model while ensuring the approximation error remains controlled. The optimal value range of the nonlinear variables is also proven to ensure solution speed. Furthermore, the applicability and effectiveness of the model and solution method are validated through a real-world case study on the Yangtze River. The results show the following: (1) Unified collaborative scheduling by bottleneck authorities can ensure the optimal total cost of the fleet is effectively met and that the vessels passing through the river bottleneck are arranged under rational ways. (2) When fuel consumption is the same as that of traditional oil-fuelled vessels, giving priority to liquefied natural gas (LNG)-fuelled vessels to pass through the river bottleneck can reduce the potential opportunity cost and the total cost of the fleet reasonably. (3) In accordance with changes in the fuel price, streamflow velocity, and proportion of LNG-fuelled vessels, timely adjusting the opportunity cost expectations, vessel arrival time, and service times of bottleneck passing ways is crucial for shipowners and authorities to reduce fleet waiting times at the bottleneck, delay time, and the total cost. Full article
(This article belongs to the Section Ocean Engineering)
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24 pages, 5896 KiB  
Article
Graph Matching for Underwater Simultaneous Localization and Mapping Using Multibeam Sonar Imaging
by Lingfei Zhuang, Xiaofeng Chen, Wenjie Lu and Yiting Yan
J. Mar. Sci. Eng. 2024, 12(10), 1859; https://doi.org/10.3390/jmse12101859 - 17 Oct 2024
Viewed by 270
Abstract
This paper addresses the challenges of underwater Simultaneous Localization and Mapping (SLAM) using multibeam sonar imaging. The widely used Iterative Closest Point (ICP) often falls into local optima due to non-convexity and the lack of features for correct registration. To overcome this, we [...] Read more.
This paper addresses the challenges of underwater Simultaneous Localization and Mapping (SLAM) using multibeam sonar imaging. The widely used Iterative Closest Point (ICP) often falls into local optima due to non-convexity and the lack of features for correct registration. To overcome this, we propose a novel registration algorithm based on Gaussian clustering and Graph Matching with maximal cliques. The proposed approach enhances feature-matching accuracy and robustness in complex underwater environments. Inertial measurements and velocity estimates are also fused for global state estimation. Comprehensive tests in simulated and real-world underwater environments have demonstrated that the proposed registration method effectively addresses the issue of the ICP algorithm easily falling into local optima while also exhibiting excellent inter-frame registration performance and robustness. Full article
(This article belongs to the Special Issue Autonomous Marine Vehicle Operations—2nd Edition)
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21 pages, 15651 KiB  
Article
Numerical Analysis of the Influence of Runoff Input on Salinity Distribution and Its Mechanisms in Laizhou Bay
by Kaixuan Ju, Lehang Xiong, Tao Liu, Zilong Li and Minxia Zhang
J. Mar. Sci. Eng. 2024, 12(10), 1858; https://doi.org/10.3390/jmse12101858 - 17 Oct 2024
Viewed by 258
Abstract
This study employs the MIKE 3 Flow Model, incorporating forcing conditions such as inflow from 18 major rivers along the Bohai coast, wind, precipitation, evaporation, and solar radiation, to develop a hydrodynamic and temperature-salinity model for the Bohai Sea, using a finer mesh [...] Read more.
This study employs the MIKE 3 Flow Model, incorporating forcing conditions such as inflow from 18 major rivers along the Bohai coast, wind, precipitation, evaporation, and solar radiation, to develop a hydrodynamic and temperature-salinity model for the Bohai Sea, using a finer mesh for more detailed simulation in Laizhou Bay. The residual current in the surface layer primarily flowed eastward, exhibiting coastal transport characteristics in the southern region, leading to the formation of a large low-salinity region. The bottom salinity distribution closely mirrored that of the surface, with the isohaline shifting shoreward due to the high-salinity Bohai Sea water transported by the residual current. By grouping major runoff sources according to river outlet locations and residual current patterns, the study analyzed the impact of freshwater plumes formed by runoff from different directions on the salinity distribution in Laizhou Bay. The results indicate that the influence of freshwater inputs on both the mean salinity and the area of low-salinity zones in Laizhou Bay, ranked from greatest to least, is as follows: the Yellow River, the southwest, and the southeast. The variation in the area of low-salinity regions is closely related to factors such as runoff volume, residual currents, and the selection of boundaries for the low-salinity regions. Full article
(This article belongs to the Section Marine Environmental Science)
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16 pages, 12873 KiB  
Article
A Hybrid Approach Based on the SR-HWPT-PDF for Identifying Early Fault Signals in Rolling Bearings
by Zhaoyang Feng, Pengfei Xing, Guobin Li, Lu Zhang, Lixun Lu, Xiaoliang He and Hongpeng Zhang
J. Mar. Sci. Eng. 2024, 12(10), 1857; https://doi.org/10.3390/jmse12101857 - 17 Oct 2024
Viewed by 228
Abstract
An approach combining the stochastic resonance, the harmonic wavelet packet transforms and the probability density function was proposed to obtain the early fault signal of a rolling bearing. Firstly, an adaptive variable-scale stochastic resonance was employed to detect the frequency range of the [...] Read more.
An approach combining the stochastic resonance, the harmonic wavelet packet transforms and the probability density function was proposed to obtain the early fault signal of a rolling bearing. Firstly, an adaptive variable-scale stochastic resonance was employed to detect the frequency range of the rolling bearing’s fault signal based on the improved signal-to-noise ratio, and then the harmonic wavelet packet transforms and the probability density function were utilized to extract and identify the fault signal of the rolling bearings from the detected signals. The case studies show that the proposed method can effectively obtain the early fault signals of the outer race, inner race and rolling element in the rolling bearings despite not knowing the frequency band distribution, and that the early fault diagnosis of the rolling bearings can be achieved. Full article
(This article belongs to the Section Ocean Engineering)
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23 pages, 12281 KiB  
Article
Research on the Hydrodynamic Characteristics of a Rectangular Otter Board in Different Work Postures Based on a Dynamic Model
by Wenhua Chu, Minghao Zhai, Senqi Cui, Yu Cao, Xinyang Zhang and Qiaoli Zhou
J. Mar. Sci. Eng. 2024, 12(10), 1856; https://doi.org/10.3390/jmse12101856 - 17 Oct 2024
Viewed by 217
Abstract
This paper investigates the hydrodynamic characteristics of a rectangular otter board in different working postures by using a dynamic model. Dynamic models are mainly based on dynamic mesh techniques. The results of the dynamic model are, compared to the model test, carried out [...] Read more.
This paper investigates the hydrodynamic characteristics of a rectangular otter board in different working postures by using a dynamic model. Dynamic models are mainly based on dynamic mesh techniques. The results of the dynamic model are, compared to the model test, carried out in a flume tank. Furthermore, different rotation speeds of dynamic model were analyzed. The research results are as follows: compared to flume tank results, the maximum error of the dynamic model is 23.77%. Moreover, the influence of rotation speed on the hydrodynamic board is not obvious, and 2 deg./s was chosen as the rotation speed. When the board is tilted slightly (including four working postures), its lift-to-drag ratio first increases slightly and then gradually decreases. Compared with the other three working postures, the pressure center coefficient of the board does not change significantly when it is tilted inward. When studying different working angles (including AOA and tilt angle) of the otter board, the numerical dynamic model significantly reduces repetitive setup work, making simulations more efficient. Its ability to provide continuous curves and a large volume of results offers researchers a more detailed and comprehensive understanding of the board’s hydrodynamics. Additionally, the dynamic model supports innovative fishery equipment development by allowing more accurate and continuous numerical simulations. Full article
(This article belongs to the Special Issue Next-Generation Sustainable Marine Fisheries and Aquaculture Engineering)
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10 pages, 255 KiB  
Article
Mitigating Genotype–Environment Interaction Effects in a Genetic Improvement Program for Liptopenaeus vannamei
by Tran Thi Mai Huong, Nguyen Huu Hung, Vu Dinh Ty, Dinh Cong Tri and Nguyen Hong Nguyen
J. Mar. Sci. Eng. 2024, 12(10), 1855; https://doi.org/10.3390/jmse12101855 - 17 Oct 2024
Viewed by 251
Abstract
The genotype-by-environment interaction (G × E) might have crucial impacts on the performance and fitness of agricultural species, such as Pacific whiteleg shrimp (Litopenaeus vannamei). This study explores how enhancements in management practices can counteract G × E effects on growth [...] Read more.
The genotype-by-environment interaction (G × E) might have crucial impacts on the performance and fitness of agricultural species, such as Pacific whiteleg shrimp (Litopenaeus vannamei). This study explores how enhancements in management practices can counteract G × E effects on growth traits. We analyzed a selectively bred population of whiteleg shrimp spanning the latest two generations, encompassing 259 full-sib and half-sib families with 40,862 individual shrimp, measured for body weight and total length. Our analysis revealed moderate genetic correlations (0.60–0.65) between trait expressions in pond and tank environments, a significant improvement compared to earlier generations. Employing the average information-restricted maximum likelihood (REML) approach in mixed model analysis showed significant differences in heritability (h2) estimates between the two environments; however, the extent of these differences varied by trait (h2 = 0.68 in pond vs. 0.37 in tank for weight, and 0.41 vs. 0.67 for length). Our results indicate that G × E effects on growth traits in this population of L. vannamei were moderate but biologically significant. Consistent with our previous estimates in this population, genetic correlations between body weight and total length remained high (close to one) in pond and tank environments. The present findings collectively demonstrate that management improvements targeting stocking density, aeration, water quality, feeds, and feeding regimes mitigated the G × E effects on two economically significant traits in this population of whiteleg shrimp. Full article
(This article belongs to the Section Marine Biology)
19 pages, 14046 KiB  
Article
Global Responses Analysis of Submerged Floating Tunnel Considering Hydroelasticity Effects
by Xiangji Ye, Xiangbo Zhou, Ming Wang, Dongsheng Qiao, Xin Zhao and Li Wang
J. Mar. Sci. Eng. 2024, 12(10), 1854; https://doi.org/10.3390/jmse12101854 - 17 Oct 2024
Viewed by 285
Abstract
To investigate the applicability and differences in wave loads and the dynamic response calculation principles for SFT on an entire-length scale, two numerical models of entire-length SFT with identical dimensions and parameters were established. These models are employed by a 3D diffraction method [...] Read more.
To investigate the applicability and differences in wave loads and the dynamic response calculation principles for SFT on an entire-length scale, two numerical models of entire-length SFT with identical dimensions and parameters were established. These models are employed by a 3D diffraction method based on rigid-body assumptions, the potential flow theory and the Dummy-Connection-Mass (DCM) method based on the lumped mass method and Morison equation while considering hydroelasticity effects. The applicability of the potential flow theory and Morison equation for wave load calculation of SFT is presented along with the differences in their dynamic response calculation, which aim to explore the impact on SFT dynamic responses considering hydroelasticity by comparing the numerical calculation results. Furthermore, a comparison between free-end boundary and fixed-end boundary models, established using the DCM method, is conducted to examine the reasonableness of the commonly adopted free-end boundary condition. Full article
(This article belongs to the Special Issue Wave Loads on Offshore Structure)
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21 pages, 7592 KiB  
Article
Multi-Objective Optimization Design of a Mooring System Based on the Surrogate Model
by Xiangji Ye, Peizi Zheng, Dongsheng Qiao, Xin Zhao, Yichen Zhou and Li Wang
J. Mar. Sci. Eng. 2024, 12(10), 1853; https://doi.org/10.3390/jmse12101853 - 17 Oct 2024
Viewed by 253
Abstract
As the development of floating offshore wind turbines (FOWTs) progresses from offshore to deeper sea, the demands on mooring systems to ensure the safety of the structure have become increasingly stringent, leading to a concomitant rise in costs. A parameter optimization method for [...] Read more.
As the development of floating offshore wind turbines (FOWTs) progresses from offshore to deeper sea, the demands on mooring systems to ensure the safety of the structure have become increasingly stringent, leading to a concomitant rise in costs. A parameter optimization method for the mooring system of FOWTs is proposed, with the mooring line length and anchor radial spacing as the optimization variables, and the minimization of surge, yaw, and nacelle acceleration as the objectives. A series of mooring system configuration samples are generated by the fully analytical factorial design method, and the open source program OpenFAST is employed to simulate the global responses in the time domain. To enhance the efficiency of the optimization process, a multi-objective evolutionary algorithm, Non-dominated Sorting Genetic Algorithm II (NSGA-II), is utilized to find the Pareto-optimal solutions, alongside a Kriging model, which serves as a surrogate model for the FOWTs. This approach was applied to an IEC 15MW FOWT to demonstrate the optimization procedure. The results indicate that the integration of the genetic algorithm and the surrogate model achieved rapid convergence and high accuracy. Through this optimization process, the longitudinal motion response of FOWTs is reduced by a maximum of 6.46%, the yaw motion by 2.87%, and the nacelle acceleration by 11.55%. Full article
(This article belongs to the Special Issue Design and Analysis of Mooring System for Floating Offshore Structures)
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17 pages, 4788 KiB  
Article
Benchmark Dataset for Offshore Platform Motion Prediction and Its Applications
by Wenyin Pan, Xiaoxian Guo and Xin Li
J. Mar. Sci. Eng. 2024, 12(10), 1852; https://doi.org/10.3390/jmse12101852 - 17 Oct 2024
Viewed by 280
Abstract
The accurate prediction of offshore platform and ship motion is crucial for motion compensation devices and for helping the crew make informed decisions. Traditional time series and physical models are being replaced by machine learning models due to their simplicity and lower training [...] Read more.
The accurate prediction of offshore platform and ship motion is crucial for motion compensation devices and for helping the crew make informed decisions. Traditional time series and physical models are being replaced by machine learning models due to their simplicity and lower training cost. However, insufficient data has hindered model training, making evaluating and comparing different models difficult. This paper introduces a comprehensive motion dataset containing data of more than 400 pieces from tens of offshore platform tests conducted at the State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University. The dataset is divided into subsets tailored for four application scenarios, including specific types of offshore platforms, wave conditions, noise addition data, and transfer learning. A Convolutional Attention-based LSTM model that combines convolution and self-attention mechanisms is proposed to validate the dataset and improve the accuracy of motion prediction. The proposed model is compared with classical models using our introduced dataset, achieving 5–10% improvement and confirming the dataset’s high reliability and applicability, as well as the effectiveness of the Conv-Att-LSTM model. This development sets a new standard for motion prediction and furthers the application of machine learning in ocean engineering. Full article
(This article belongs to the Section Ocean Engineering)
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18 pages, 1949 KiB  
Review
Geochemical and Physical Methods for Estimating the Saturation of Natural Gas Hydrates in Sediments: A Review
by Yuan Xue, Hailong Lu, Hailin Yang, Wenjiu Cai and Linsen Zhan
J. Mar. Sci. Eng. 2024, 12(10), 1851; https://doi.org/10.3390/jmse12101851 - 16 Oct 2024
Viewed by 499
Abstract
The saturation of natural gas hydrates is a key parameter for characterizing hydrate reservoirs, estimating hydrate reserves, and developing hydrate as an energy resource. Several methods have been proposed to estimate hydrate saturation, although most of these studies rely on logging and seismic [...] Read more.
The saturation of natural gas hydrates is a key parameter for characterizing hydrate reservoirs, estimating hydrate reserves, and developing hydrate as an energy resource. Several methods have been proposed to estimate hydrate saturation, although most of these studies rely on logging and seismic data. However, the methods for estimating hydrate saturation from recovered core sediments have not been thoroughly reviewed, which hinders a deeper understanding, proper application, and the use of these experimental data to integrate geophysical and numerical model results with the actual geological conditions. In this paper, the methods widely used for estimating natural gas hydrate saturation from core sediments, including those based on pore water chemistry (Cl− concentration, δD, and δ18O values), gas volumetric analysis, and temperature anomaly, have been summarized in terms of the principle, estimation strategy, and issues to be considered of each method. The applicability, advantages and disadvantages, and scope of application of each method are also compared and discussed. All methods for estimating gas hydrate saturation have certain limitations. A comprehensive application of results from multiple methods could lead to a better understanding of the amount of gas hydrate in sediments, although the chlorinity of pore water is the most commonly used method of estimation. Full article
(This article belongs to the Special Issue Advances in Marine Gas Hydrates)
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27 pages, 4733 KiB  
Article
Simultaneous Optimization of Exergy and Economy and Environment (3E) for a Multistage Nested LNG Power Generation System
by Zhenzhen Chen, Xinglin Yang, Junhu Zou, Qiang Lei and Bin Yan
J. Mar. Sci. Eng. 2024, 12(10), 1850; https://doi.org/10.3390/jmse12101850 - 16 Oct 2024
Viewed by 277
Abstract
The study introduces an innovative three-stage nested power generation system that enables the cascading utilization of LNG cold energy. It makes the most of wasted energy by using ship jacket cooling water (JCW) and exhaust gas (EG) as heat sources, a trans-critical carbon [...] Read more.
The study introduces an innovative three-stage nested power generation system that enables the cascading utilization of LNG cold energy. It makes the most of wasted energy by using ship jacket cooling water (JCW) and exhaust gas (EG) as heat sources, a trans-critical carbon dioxide cycle as internal circulation, and utilizing the pressure exergy of LNG. We choose two azeotrope mixing fluids that match the requirements and create four cases for the outer and middle cycle working fluids in the three-stage nested system. To discover the ideal system performance from the perspectives of exergy (E), economy (E), and environment (E), four cases were subjected to multi-objective optimization using the multi-objective particle swarm optimization technique (MOPSO). Finally, the optimal solution was found by applying the TOPSIS decision-making method. Through comparative analysis, the optimal system is selected among the four optimization results. R170 (22.66%) and R1150 (77.34%) are used as the outer circulating working medium, while R170 (90.86%) and R1270 (9.14%) are utilized as the inter-cycle working fluid. The net output work is 575.75 kW, the optimal exergy efficiency is 46.09%, the optimal electricity production cost is $0.04009 per kWh, the carbon dioxide emissions can be reduced by 36,910 tons, and the payback period is 2.548 years. After optimization, a more energy-efficient and environmentally friendly power generation system is obtained. Full article
(This article belongs to the Section Ocean Engineering)
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