Journal of Marine Science and Engineering

18 pages, 14879 KiB

Open AccessArticle

Numerical Analysis of the Sediment Erosion of the Balance Valve in a Buoyancy Regulation System

by Hao Liu, Shenshen Yang, Lei Wang, Yulong Li, Lei Mi, Fangyang Yuan and Cong Ye

J. Mar. Sci. Eng. 2024, 12(8), 1344; https://doi.org/10.3390/jmse12081344 (registering DOI) - 7 Aug 2024

Abstract

Numerical analysis of the sediment erosion of the balance valve in a buoyancy regulation system was performed. A numerical model for the two-phase flow inside the balance valve was constructed based on the discrete phase model. The sediment erosion rate on the balance [...] Read more.

Numerical analysis of the sediment erosion of the balance valve in a buoyancy regulation system was performed. A numerical model for the two-phase flow inside the balance valve was constructed based on the discrete phase model. The sediment erosion rate on the balance valve was discussed, and the effects of five parameters were considered. The effects of the sediment concentration and valve opening were found to be significant, while the effects of the pressure difference, sediment density, and size were found to be moderate. The erosion rate, according to the numerical results, increased linearly with the sediment concentration, so long-term operation of a buoyancy regulation system in high-concentration areas should be avoided. The erosion rate was the highest when the valve opening was 46.3%, so half-open operating conditions are not recommended. The erosion rate was proportional to the square root of the pressure difference. However, adjusting the pressure difference may not be an effective method for regulating the total erosion. The superposition of the secondary flow and the main stream caused particles to spiral along with the fluid, resulting in asymmetric erosion at the working edge. The erosion rate on the working edge decreased with the increase in the sediment size. Conversely, the erosion rate on the valve ball surface increased with the sixth power of the sediment size. Considering that large particles are more likely to cause a blockage, it is recommended to install a seawater pretreatment device at the inlet to prevent large sediments from entering the valve and to improve the working life of the buoyancy regulation system. Full article

(This article belongs to the Section Ocean Engineering)

► Show Figures

Figure 1

23 pages, 5300 KiB

Open AccessArticle

An Automatic Detection and Statistical Method for Underwater Fish Based on Foreground Region Convolution Network (FR-CNN)

by Shenghong Li, Peiliang Li, Shuangyan He, Zhiyan Kuai, Yanzhen Gu, Haoyang Liu, Tao Liu and Yuan Lin

J. Mar. Sci. Eng. 2024, 12(8), 1343; https://doi.org/10.3390/jmse12081343 - 7 Aug 2024

Abstract

Computer vision in marine ranching enables real-time monitoring of underwater resources. Detecting fish presents challenges due to varying water turbidity and lighting, affecting color consistency. We propose a Foreground Region Convolutional Neural Network (FR-CNN) that combines unsupervised and supervised methods. It introduces an [...] Read more.

Computer vision in marine ranching enables real-time monitoring of underwater resources. Detecting fish presents challenges due to varying water turbidity and lighting, affecting color consistency. We propose a Foreground Region Convolutional Neural Network (FR-CNN) that combines unsupervised and supervised methods. It introduces an adaptive multiscale regression Gaussian background model to distinguish fish from noise at different scales. Probability density functions integrate spatiotemporal information for object detection, addressing illumination and water quality shifts. FR-CNN achieves 95% mAP with IoU of 0.5, reducing errors from open-source datasets. It updates anchor boxes automatically on local datasets, enhancing object detection accuracy in long-term monitoring. The results analyze fish species behaviors in relation to environmental conditions, validating the method’s practicality. Full article

(This article belongs to the Section Ocean Engineering)

► Show Figures

Figure 1

15 pages, 4246 KiB

Open AccessArticle

An OOSEM-Based Design Pattern for the Development of AUV Controllers

by Cao Duc Sang, Ngo Van He, Ngo Van Hien and Nguyen Trong Khuyen

J. Mar. Sci. Eng. 2024, 12(8), 1342; https://doi.org/10.3390/jmse12081342 (registering DOI) - 7 Aug 2024

Abstract

This article introduces a new design pattern that provides an optimal solution for the systematic development of AUV controllers. In this study, a hybrid control model is designed on the basis of the OOSEM (Object-Oriented Systems Engineering Method), combined with MDA (Model-Driven Architecture) [...] Read more.

This article introduces a new design pattern that provides an optimal solution for the systematic development of AUV controllers. In this study, a hybrid control model is designed on the basis of the OOSEM (Object-Oriented Systems Engineering Method), combined with MDA (Model-Driven Architecture) concepts, real-time UML/SysML (Unified Modeling Language/Systems Modeling Language), and the UKF (unscented Kalman filter) algorithm. This hybrid model enables the implementation of the control elements of autonomous underwater vehicles (AUVs), which are considered HDSs (hybrid dynamic systems), and it can be adapted for reuse for most standard AUV platforms. To achieve this goal, a dynamic AUV model is integrated with the specializations of the OOSEM/MDA, in which an analysis model is clarified via a use-case model definition and then combined with HA (hybrid automata) to precisely define the control requirements. Next, the designed model is tailored via real-time UML/SysML to obtain the core control blocks, which describe the behaviors and structures of the control parts in detail. This design model is then transformed into an implementation model with the assistance of round-trip engineering to conveniently realize a controller for AUVs. Based on this new model, a feasible AUV controller for low-cost, turtle-shaped AUVs is implemented, and it is utilized to perform planar trajectory tracking. Full article

(This article belongs to the Section Ocean Engineering)

► Show Figures

Figure 1

18 pages, 13863 KiB

Open AccessArticle

Research on Aerodynamic Characteristics of Three Offshore Wind Turbines Based on Large Eddy Simulation and Actuator Line Model

by Chen Fu, Zhihao Zhang, Meixin Yu, Dai Zhou, Hongbo Zhu, Lei Duan, Jiahuang Tu and Zhaolong Han

J. Mar. Sci. Eng. 2024, 12(8), 1341; https://doi.org/10.3390/jmse12081341 - 7 Aug 2024

Abstract

Investigating the aerodynamic performance and wake characteristics of wind farms under different levels of wake effects is crucial for optimizing wind farm layouts and improving power generation efficiency. The Large Eddy Simulation (LES)–actuator line model (ALM) method is widely used to predict the [...] Read more.

Investigating the aerodynamic performance and wake characteristics of wind farms under different levels of wake effects is crucial for optimizing wind farm layouts and improving power generation efficiency. The Large Eddy Simulation (LES)–actuator line model (ALM) method is widely used to predict the power generation efficiency of wind farms composed of multiple turbines. This study employs the LES-ALM method to numerically investigate the aerodynamic performance and wake characteristics of a single NREL 5 MW horizontal-axis wind turbine and three such turbines under different wake interaction conditions. For the single turbine case, the results obtained using the LES-ALM method were compared with the existing literature, showing good agreement and confirming its reliability for single turbine scenarios. For the three-turbine wake field problem, considering the aerodynamic performance differences under three cases, the results indicate that spacing has a minor impact on the power coefficient and thrust coefficient of the middle turbine but a significant impact on the downstream turbine. For staggered three-turbine arrangements, unilateral turbulent inflow to the downstream turbine causes significant fluctuations in thrust and torque, while bilateral turbulent inflow leads to more stable thrust and torque. The presence of two upstream turbines causes an acceleration effect at the inflow region of the downstream single turbine, significantly increasing its power coefficient. The findings of this study can provide methodological references for reducing wake effects and optimizing the layout of wind farms. Full article

(This article belongs to the Section Ocean Engineering)

► Show Figures

Figure 1

23 pages, 6442 KiB

Open AccessArticle

Numerical Study on Optimization of Combustion Cycle Parameters and Exhaust Gas Emissions in Marine Dual-Fuel Engines by Adjusting Ammonia Injection Phases

by Martynas Drazdauskas and Sergejus Lebedevas

J. Mar. Sci. Eng. 2024, 12(8), 1340; https://doi.org/10.3390/jmse12081340 - 7 Aug 2024

Abstract

Decarbonizing maritime transport hinges on transitioning oil-fueled ships (98.4% of the fleet) to renewable and low-carbon fuel types. This shift is crucial for meeting the greenhouse gas (GHG) reduction targets set by the IMO and the EU, with the aim of achieving climate [...] Read more.

Decarbonizing maritime transport hinges on transitioning oil-fueled ships (98.4% of the fleet) to renewable and low-carbon fuel types. This shift is crucial for meeting the greenhouse gas (GHG) reduction targets set by the IMO and the EU, with the aim of achieving climate neutrality by 2050. Ammonia, which does not contain carbon atoms that generate CO₂, is considered one of the effective solutions for decarbonization in the medium and long term. However, the concurrent increase in nitrogen oxide (NO_x) emissions during the ammonia combustion cycle, subject to strict regulation by the MARPOL 73/78 convention, necessitates implementing solutions to reduce them through optimizing the combustion cycle. This publication presents a numerical study on the optimization of diesel and ammonia injection phases in a ship’s medium-speed engine, Wartsila 6L46. The study investigates the exhaust gas emissions and combustion cycle parameters through a high-pressure injection strategy. At an identified 7° CAD injection phase distance between diesel and ammonia, along with an optimal dual-fuel start of injection 10° CAD before TDC, a reduction of 47% in greenhouse gas emissions (GHG = CO₂ + CH₄ + N₂O) was achieved compared to the diesel combustion cycle. This result aligns with the GHG reduction target set by both the IMO and the EU for 2030. Additionally, during the investigation of the thermodynamic combustion characteristics of the cycle, a comparative reduction in NO_x of 4.6% was realized. This reduction is linked to the DeNO_x process, where the decrease in NO_x is offset by an increase in N₂O. However, the optimized ammonia combustion cycle results in significant emissions of unburnt NH₃, reaching 1.5 g/kWh. In summary, optimizing the combustion cycle of dual ammonia and diesel fuel is essential for achieving efficient and reliable engine performance. Balancing combustion efficiency with emission levels of greenhouse gases, unburned NH₃, and NO_x is crucial. For the Wartsila 6L46 marine diesel engine, the recommended injection phasing is A710/D717, with a 7° CAD between injection phases. Full article

(This article belongs to the Special Issue Advanced Technologies of Ship Power Plants and Infrastructure of Seaports)

► Show Figures

Figure 1

15 pages, 2698 KiB

Open AccessArticle

Salinity Prediction Based on Improved LSTM Model in the Qiantang Estuary, China

by Rong Zheng, Zhilin Sun, Jiange Jiao, Qianqian Ma and Liqin Zhao

J. Mar. Sci. Eng. 2024, 12(8), 1339; https://doi.org/10.3390/jmse12081339 - 7 Aug 2024

Abstract

Accurate prediction of estuarine salinity can effectively mitigate the adverse effects of saltwater intrusion and help ensure the safety of water resources in estuarine regions. Presently, diverse data-driven models, mainly neural network models, have been employed to predict tidal estuarine salinity and obtained [...] Read more.

Accurate prediction of estuarine salinity can effectively mitigate the adverse effects of saltwater intrusion and help ensure the safety of water resources in estuarine regions. Presently, diverse data-driven models, mainly neural network models, have been employed to predict tidal estuarine salinity and obtained considerable achievements. Due to the nonlinear and nonstationary features of estuarine salinity sequences, this paper proposed a multi-factor salinity prediction model using an enhanced Long Short-Term Memory (LSTM) network. To improve prediction accuracy, input variables of the model were determined through Grey Relational Analysis (GRA) combined with estuarine dynamic analysis, and hyperparameters for the LSTM model were optimized using a multi-strategy Improved Sparrow Search Algorithm (ISSA). The proposed ISSA-LSTM model was applied to predict salinity at the Cangqian and Qibao stations in the Qiantang Estuary of China, based on measured data from 2011–2012. The model performance is evaluated by mean absolute error (MAE), mean absolute percentage error (MAPE), root mean square error (RMSE), and Nash-Sutcliffe efficiency (NSE). The results show that compared to other models including Back Propagation neural network (BP), Gate Recurrent Unit (GRU), and LSTM model, the new model has smaller errors and higher prediction accuracy, with NSE improved by 8–32% and other metrics (MAP, MAPE, RMSE) improved by 15–67%. Meanwhile, compared with LSTM optimized with the original SSA (SSA-LSTM), MAE, MAPE, and RMSE values of the new model decreased by 13–16%, 15–16%, and 11–13%, and NSE value increased by 5–6%, indicating that the ISSA has a better hyperparameter optimization ability than the original SSA. Thus, the model provides a practical solution for the rapid and precise prediction of estuarine salinity. Full article

(This article belongs to the Topic Sustainable River and Lake Restoration: From Challenges to Solutions)

► Show Figures

Figure 1

20 pages, 7125 KiB

Open AccessArticle

Research on Hydrodynamics of Trans-Media Vehicles Considering Underwater Time-Varying Attitudes

by Shuo Liu, Chihao Du, Yijie Han, Yu Zhang, Wanglin Lin, Yong Cai and Tao Wang

J. Mar. Sci. Eng. 2024, 12(8), 1338; https://doi.org/10.3390/jmse12081338 - 6 Aug 2024

Viewed by 210

Abstract

A trans-media vehicle is a new type of equipment that can adapt to two environments, water and air, to maintain optimal hydrodynamic and aerodynamic performance. However, no matter what kind of trans-media vehicle, its dynamics are much more complicated when traversing the interface [...] Read more.

A trans-media vehicle is a new type of equipment that can adapt to two environments, water and air, to maintain optimal hydrodynamic and aerodynamic performance. However, no matter what kind of trans-media vehicle, its dynamics are much more complicated when traversing the interface of the medium, as the parameters are time-varying due to the change in ambient medium and vehicle attitudes. In order to improve the stability and performance of the trans-media vehicle in complex environments, an accurate mathematical model is established to characterize the dynamics of the trans-media vehicle in this process in this study. The time-varying hydrodynamic coefficients with different attitudes or depths are obtained using computational fluid dynamics software. The mathematical model is solved iteratively using a Runge–Kutta solver to calculate the dynamic response. A prototype of trans-media vehicle is fabricated, and motion experiments are performed in the pool. The experimental results confirm the effectiveness of the established model and lay the foundation for further controller design, providing a reference for the dynamic modeling of other similar equipment operating in complex environments. The primary novelty of this study lies in the fact that the established dynamic model considers the complex interaction between the attitude of the trans-media vehicle and the inherent different properties of water and air and utilizes computational fluid dynamics software to accurately obtain time-varying coefficients under different attitudes and depths. This approach not only recognizes the criticality of orientation-dependent hydrodynamic coefficients but also incorporates their temporal variations, which were often overlooked in previous studies. Full article

(This article belongs to the Section Ocean Engineering)

► Show Figures

Figure 1

33 pages, 18116 KiB

Open AccessArticle

Investigation on Calm Water Resistance of Wind Turbine Installation Vessels with a Type of T-BOW

by Mingsheng Xiahou, Deqing Yang, Hengxu Liu and Yuanhe Shi

J. Mar. Sci. Eng. 2024, 12(8), 1337; https://doi.org/10.3390/jmse12081337 - 6 Aug 2024

Viewed by 229

Abstract

Given the typical characteristics of self-propulsion and jack-up wind turbine installation vessels (WTIVs), including their full and blunt hull form and complex appendages, this paper combines the model test method with the RANS-based CFD numerical prediction method to experimentally and numerically study the [...] Read more.

Given the typical characteristics of self-propulsion and jack-up wind turbine installation vessels (WTIVs), including their full and blunt hull form and complex appendages, this paper combines the model test method with the RANS-based CFD numerical prediction method to experimentally and numerically study the resistance of the optimized hull at different spudcan retraction positions. The calm water resistance components and their mechanisms of WTIVs based on T-BOW were obtained. Furthermore, using the multivariate nonlinear least squares method, an empirical formula for rapid resistance estimation based on the Holtrop method was derived, and its prediction accuracy and applicability were validated with a full-scale ship case. This study indicates that the primary resistance components of such low-speed vessels are viscous pressure resistance, followed by frictional resistance and wave-making resistance. Notably, the spudcan retraction well area, as a unique appendage of WTIVs, exhibits a significant “moonpool additional resistance” effect. Different spudcan retraction positions affect the total calm water resistance by approximately 20% to 30%. Therefore, in the resistance optimization design of WTIVs, special attention should be paid to the matching design of the spudcan structure and the hull shell plate lines in the spudcan retraction well area. Full article

(This article belongs to the Special Issue Advanced Technologies of Ship Power Plants and Infrastructure of Seaports)

► Show Figures

Figure 1

17 pages, 6557 KiB

Open AccessArticle

A Novel Hill Climbing-Golden Section Search Maximum Energy Efficiency Tracking Method for Wireless Power Transfer Systems in Unmanned Underwater Vehicles

by Yayu Ma, Bo Liang, Jiale Wang, Bo Cheng, Zhengchao Yan, Moyan Dong and Zhaoyong Mao

J. Mar. Sci. Eng. 2024, 12(8), 1336; https://doi.org/10.3390/jmse12081336 - 6 Aug 2024

Viewed by 234

Abstract

Efficiency has always been one of the most critical indicators for evaluating wireless power transfer (WPT) systems. To achieve fast maximum energy efficiency tracking (MEET), this paper provides an innovative control method utilizing the hill climbing-golden section search (HC-GSS) method of an LCC-S [...] Read more.

Efficiency has always been one of the most critical indicators for evaluating wireless power transfer (WPT) systems. To achieve fast maximum energy efficiency tracking (MEET), this paper provides an innovative control method utilizing the hill climbing-golden section search (HC-GSS) method of an LCC-S compensated WPT system. The receiver side includes a buck-boost converter that regulates the output current or voltage to meet output requirements. In the meantime, the buck-boost converter on the transmitter side is managed by the HC-GSS approach for MEET by minimizing the input power under the premise of output stability. Compared with the conventional P&O method, the HC-GSS method can eliminate the trade-off between the oscillation and convergence rate because it is designed for different system stages. In this WPT system, there is no need for direct communication between the transmitter and receiver. Therefore, the system is potentially cheaper to implement and does not suffer from annoying communication delays, which are prevalent in underwater environments for unmanned underwater vehicles’ (UUV) WPT systems. Both the simulation and experiment results show that this method can improve the efficiency of the WPT system without communication. The proposed method remains valid with coupler displacement as it does not include the mutual inductance of the system. Full article

(This article belongs to the Special Issue Advancements in New Concepts of Underwater Robotics)

► Show Figures

Figure 1

18 pages, 1984 KiB

Open AccessArticle

Feeding Habits of Scomber japonicus Inferred by Stable Isotope and Fatty Acid Analyses

by Yingcong Chen, Guanyu Hu, Zhenfang Zhao, Xinjun Chen and Bilin Liu

J. Mar. Sci. Eng. 2024, 12(8), 1335; https://doi.org/10.3390/jmse12081335 - 6 Aug 2024

Viewed by 230

Abstract

Scomber japonicus is widely distributed off the coast of Japan and in the northwestern Pacific. It is an important target for fisheries. To reveal the differences in diet shifts and niche changes of S. japonicus, we collected samples in the high seas [...] Read more.

Scomber japonicus is widely distributed off the coast of Japan and in the northwestern Pacific. It is an important target for fisheries. To reveal the differences in diet shifts and niche changes of S. japonicus, we collected samples in the high seas of the northwest Pacific (38°59′ N–43°00′ N, 150°30′ E–161°48′ E) from June to August 2021. We utilized stable isotope and fatty acid analyses to study the differences in body length and sex of S. japonicus. The results showed no significant differences in stable isotope values and fatty acid composition between male and female individuals (p > 0.05). Differences in δ¹³C and δ¹⁵N values among different body length groups were also not significant (p > 0.05). Both δ¹³C and δ¹⁵N values showed a trend of increasing and then decreasing across different body length groups. The niche width of S. japonicus in different body length groups first increased and then decreased, with niche overlap among the groups exceeding 60%. Principal component analysis (PCA) results showed that the main fatty acids in S. japonicus were C14:0, C16:0, C18:0, C16:1n-7, C18:1n-9, C18:3n-6, C20:5n-3, C20:4n-6 and 22:6n-3. Except for C18:0 and C20:4n-6, the content of the other fatty acids showed significant differences among different body length groups (p < 0.05). The results of the similarity analysis (ANOSIM) indicated that the fatty acid compositions of the 100–130 mm length group were significantly different from those of the 131–160 mm and 161–190 mm length groups (p < 0.05). However, there were no significant differences among the other size groups (p > 0.05). During the growth and development of S. japonicus, the proportion of krill in their diet gradually decreased. Meanwhile, their consumption of zooplankton, diatoms and fish significantly increased. Additionally, S. japonicus also consumed crustaceans, but their intakes of planktonic bacteria and green algae were relatively low. We suggested that there were no significant differences between male and female individuals of S. japonicus. As they grew and developed, the ecological niche and feeding habits of S. japonicus continuously changed. Full article

(This article belongs to the Section Marine Biology)

► Show Figures

Figure 1

20 pages, 9503 KiB

Open AccessArticle

Manipulation-Compliant Artificial Potential Field and Deep Q-Network: Large Ships Path Planning Based on Deep Reinforcement Learning and Artificial Potential Field

by Weifeng Xu, Xiang Zhu, Xiaori Gao, Xiaoyong Li, Jianping Cao, Xiaoli Ren and Chengcheng Shao

J. Mar. Sci. Eng. 2024, 12(8), 1334; https://doi.org/10.3390/jmse12081334 - 6 Aug 2024

Viewed by 281

Abstract

Enhancing the path planning capabilities of ships is crucial for ensuring navigation safety, saving time, and reducing energy consumption in complex maritime environments. Traditional methods, reliant on static algorithms and singular models, are frequently limited by the physical constraints of ships, such as [...] Read more.

Enhancing the path planning capabilities of ships is crucial for ensuring navigation safety, saving time, and reducing energy consumption in complex maritime environments. Traditional methods, reliant on static algorithms and singular models, are frequently limited by the physical constraints of ships, such as turning radius, and struggle to adapt to the maritime environment’s variability and emergencies. The development of reinforcement learning has introduced new methods and perspectives to path planning by addressing complex environments, achieving multi-objective optimization, and enhancing autonomous learning and adaptability, significantly improving the performance and application scope. In this study, we introduce a two-stage path planning approach for large ships named MAPF–DQN, combining Manipulation-Compliant Artificial Potential Field (MAPF) with Deep Q-Network (DQN). In the first stage, we improve the reward function in DQN by integrating the artificial potential field method and use a time-varying greedy algorithm to search for paths. In the second stage, we use the nonlinear Nomoto model for path smoothing to enhance maneuverability. To validate the performance and effectiveness of the algorithm, we conducted extensive experiments using the model of “Yupeng” ship. Case studies and experimental results demonstrate that the MAPF–DQN algorithm can find paths that closely match the actual trajectory under normal environmental conditions and U-shaped obstacles. In summary, the MAPF–DQN algorithm not only enhances the efficiency of path planning for large ships, but also finds relatively safe and maneuverable routes, which are of great significance for maritime activities. Full article

(This article belongs to the Special Issue Maritime Security and Risk Assessments—2nd Edition)

► Show Figures

Figure 1

11 pages, 482 KiB

Open AccessArticle

Detecting Gaps in Knowledge: The Case of the Anisakis in Northwestern Spain

by Beatriz Garcia-Sanchez, Paula Masiá, Eva Garcia-Vazquez, Alba Ardura and Eduardo Dopico

J. Mar. Sci. Eng. 2024, 12(8), 1333; https://doi.org/10.3390/jmse12081333 - 6 Aug 2024

Viewed by 193

Abstract

In the marine environment, fish parasites are present in most seafood species. The most common are nematodes of the genus Anisakis, which can parasitize human tissues, causing anisakiasis and allergies—in some cases with a strong reaction, such as anaphylactic shock. This happens [...] Read more.

In the marine environment, fish parasites are present in most seafood species. The most common are nematodes of the genus Anisakis, which can parasitize human tissues, causing anisakiasis and allergies—in some cases with a strong reaction, such as anaphylactic shock. This happens when people ingest live or dead larvae present in the muscles or viscera of a wide range of fish and cephalopods. Consumer education has been positioned as one of the most effective alternatives for its prevention. This study, carried out in Asturias (northwest Spain), sought to identify the seafood products that present the greatest risk of anisakiasis for consumers, taking into account their consumption, the prevalence of Anisakis, and consumer knowledge about this parasitosis. In the results, hake (Merluccius merluccius) and cod (Gadus morhua), frequently consumed in the region and with high parasite prevalence, do not pose a great risk because they are consumed when well cooked. Instead, sardine (Sardina pilchardus), highly consumed and less parasitized, and anchovy (Engraulis encrasicolus), highly parasitized and less consumed, would exhibit a medium risk. Young participants know more about the risks of anisakiasis from raw seafood. The gaps detected in the knowledge about the ability of temperature treatments to eliminate parasites, especially in allergic people, must be addressed for better prevention. We suggest campaigns adapted to the population sectors. Full article

(This article belongs to the Section Marine Biology)

► Show Figures

Figure 1

24 pages, 5638 KiB

Open AccessArticle

Consensus Control of Heterogeneous Uncertain Multiple Autonomous Underwater Vehicle Recovery Systems in Scenarios of Implicit Reduced Visibility

by Zixuan Li, Wei Zhang, Wenhua Wu and Yefan Shi

J. Mar. Sci. Eng. 2024, 12(8), 1332; https://doi.org/10.3390/jmse12081332 - 6 Aug 2024

Viewed by 189

Abstract

This paper investigates consensus control in heterogeneous and uncertain multiple autonomous underwater vehicle (AUV) systems under implicit reduced visibility conditions. We address challenges such as environmental uncertainties and system nonlinearity by utilizing a unified connectivity approach to model low-visibility interactions and heterogeneous multi-AUV [...] Read more.

This paper investigates consensus control in heterogeneous and uncertain multiple autonomous underwater vehicle (AUV) systems under implicit reduced visibility conditions. We address challenges such as environmental uncertainties and system nonlinearity by utilizing a unified connectivity approach to model low-visibility interactions and heterogeneous multi-AUV dynamics. Our main contributions include developing a feedback linearization model for heterogeneous multi-AUV systems that accounts for uncertainties, introducing an adaptive consensus controller based on relative positioning that effectively manages implicit visual interaction limitations and validating our strategies through stability analysis and numerical simulations. Our simulations demonstrate approximately a 60% improvement in accuracy compared to previous algorithms, highlighting the practical value of our approach in AUV recovery operations. These advancements provide a robust solution for consensus control in complex underwater environments. Full article

(This article belongs to the Special Issue Optimal Maneuvering and Control of Ships—2nd Edition)

► Show Figures

Figure 1

24 pages, 9556 KiB

Open AccessArticle

Field Redevelopment and Weight Shedding for Decommissioning of Offshore Facilities

by Ahmed Reda, Chiemela Victor Amaechi, Mohamed A. Shahin and Kristoffer K. McKee

J. Mar. Sci. Eng. 2024, 12(8), 1331; https://doi.org/10.3390/jmse12081331 - 6 Aug 2024

Viewed by 241

Abstract

There is currently a rising interest in reusing and repurposing offshore facilities through decommissioning; however, major challenges arise, such as size, weight, sea depth, planned use, and location. This article aims to discuss the philosophy that needs to be adopted for field redevelopment, [...] Read more.

There is currently a rising interest in reusing and repurposing offshore facilities through decommissioning; however, major challenges arise, such as size, weight, sea depth, planned use, and location. This article aims to discuss the philosophy that needs to be adopted for field redevelopment, particularly when existing platforms must be preserved and integrated into new greenfield facilities. The article also discusses the concept of weight shedding during the decommissioning of offshore facilities to either extend the life of existing platforms or provide clear space for new equipment to be installed by removing unnecessary components and structures. The above aspects of decommissioning are investigated through the redevelopment of a case study of a mature offshore oil field located in shallow water. The study indicated that weight shedding presents a favourable method for decommissioning offshore installations and can effectively lower expenses, minimise environmental consequences, and optimise the use of resources. Full article

(This article belongs to the Section Marine Energy)

► Show Figures

Figure 1

18 pages, 11487 KiB

Open AccessArticle

Wideband Vibro-Acoustic Coupling Investigation in Three Dimensions Using Order-Reduced Isogeometric Finite Element/Boundary Element Method

by Yanming Xu, Xin Zhang, Jiachen Wang and Zhongming Hu

J. Mar. Sci. Eng. 2024, 12(8), 1330; https://doi.org/10.3390/jmse12081330 - 6 Aug 2024

Viewed by 181

Abstract

This study introduces an innovative model-order reduction (MOR) technique that integrates boundary element and finite element methodologies, streamlining the analysis of wideband vibro-acoustic interactions within aquatic and aerial environments. The external acoustic phenomena are efficiently simulated via the boundary element method (BEM), while [...] Read more.

This study introduces an innovative model-order reduction (MOR) technique that integrates boundary element and finite element methodologies, streamlining the analysis of wideband vibro-acoustic interactions within aquatic and aerial environments. The external acoustic phenomena are efficiently simulated via the boundary element method (BEM), while the finite element method (FEM) adeptly captures the dynamics of vibrating thin-walled structures. Furthermore, the integration of isogeometric analysis within the finite element/boundary element framework ensures geometric integrity and maintains high-order continuity for Kirchhoff–Love shell models, all without the intermediary step of meshing. Foundational to our reduced-order model is the application of the second-order Arnoldi method coupled with Taylor expansions, effectively eliminating the frequency dependence of system matrices. The proposed technique significantly enhances the computational efficiency of wideband vibro-acoustic coupling analyses, as demonstrated through numerical simulations. Full article

(This article belongs to the Special Issue The State of the Art of Marine Risers and Pipelines)

► Show Figures

Figure 1

14 pages, 4003 KiB

Open AccessArticle

Experimental and Numerical Investigation on the Motion Responses of a Spar-Type Floating Structure with Aquaculture Feeding Systems

by Qiao Li, Shenyi Bai, Shuchuang Dong, Jinxin Zhou and Daisuke Kitazawa

J. Mar. Sci. Eng. 2024, 12(8), 1329; https://doi.org/10.3390/jmse12081329 - 6 Aug 2024

Viewed by 194

Abstract

The combination of aquaculture industry with floating offshore wind turbines has the potential to generate significant economic advantages for both industries. To investigate this potential, the present study focuses on analyzing the heave, and pitch dynamic responses of a Spar-type floating offshore wind [...] Read more.

The combination of aquaculture industry with floating offshore wind turbines has the potential to generate significant economic advantages for both industries. To investigate this potential, the present study focuses on analyzing the heave, and pitch dynamic responses of a Spar-type floating offshore wind turbine that incorporates an aquaculture feeding system. A series of water tank model tests, together with numerical calculations, were conducted using a 1/56 scale model of a 2 MW, displacement 3500 tons, floating Spar-type wind turbine. The feeding system was placed inside the Spar and slightly above the waterline by adjusting the configuration of the total weight. The weight of the feeding system in the experiments is 100 tons, capable of sustaining 300 tons of fish for an entire week, and the realistic applications have been expanded using the numerical calculation. For this reason, the present study serves a good case study for general understanding, because the integration of the feeding system inevitably raises the center of gravity of the structure and potentially affects its overall stability. The experiments revealed no discernible increase in the heave motion. Moreover, the pitch motion theoretically increased, but occasionally decreased in the experiments with the overall inclination angles being less than 1.2 degrees during the experiments. As a result, the present study supports the practice of integrating a Spar-type wind turbine with feeding systems. Future research should continue to comprehensively examine, both experimentally and numerically, the motion responses of the wind turbine and aquaculture facilities with varying configurations. Full article

(This article belongs to the Special Issue Next-Generation Sustainable Marine Fisheries and Aquaculture Engineering)

► Show Figures

Figure 1

19 pages, 10406 KiB

Open AccessArticle

A Data-Driven DNN Model to Predict the Ultimate Strength of a Ship’s Bottom Structure

by Im-jun Ban, Chaeog Lim, Gi-yong Kim, Seo-young Choi and Sung-chul Shin

J. Mar. Sci. Eng. 2024, 12(8), 1328; https://doi.org/10.3390/jmse12081328 - 6 Aug 2024

Viewed by 193

Abstract

Plates and curved plates are essential components in ship construction. In the design stage, the methods used to evaluate the ultimate strength required to confirm the structural safety of plates include prediction through analytical methods, finite-element analysis (FEA), and empirical formulas. However, with [...] Read more.

Plates and curved plates are essential components in ship construction. In the design stage, the methods used to evaluate the ultimate strength required to confirm the structural safety of plates include prediction through analytical methods, finite-element analysis (FEA), and empirical formulas. However, with nonlinear buckling, the results of the empirical formula and the FEA differ for small flank angles (1~9). As a result, the prediction of the nonlinear ultimate strength of flank angle (1~9) plates still requires significant computation time and cost. To compensate for this, this study performed an ultimate strength prediction method utilizing a deep neural network together with the 4050 curved plate analysis. In addition, this paper presents the analysis results of the nonlinear finite-element method and the geometric shape and ratio of curved plates as training data. Based on the results of this study, designers can more efficiently design appropriate curved plate members by considering the ultimate strength. Full article

(This article belongs to the Special Issue Data-Driven Methods for Marine Structures)

► Show Figures

Figure 1

16 pages, 6131 KiB

Open AccessArticle

Experimental Study on the Spring-like Effect on the Hydrodynamic Performance of an Oscillating Water Column Wave Energy Converter

by Ning Yuan, Chuanli Xu and Zhen Liu

J. Mar. Sci. Eng. 2024, 12(8), 1327; https://doi.org/10.3390/jmse12081327 - 6 Aug 2024

Viewed by 184

Abstract

The oscillating water column (OWC) wave energy converter has demonstrated significant potential for converting ocean wave energy. The spring-like effect of air compressibility can significantly affect the hydrodynamic behavior of the device, but it has rarely been investigated through experimental studies. In this [...] Read more.

The oscillating water column (OWC) wave energy converter has demonstrated significant potential for converting ocean wave energy. The spring-like effect of air compressibility can significantly affect the hydrodynamic behavior of the device, but it has rarely been investigated through experimental studies. In this study, an experimental test on a model-scaled OWC device was carried out in a wave flume using a series of regular and irregular waves. The spring-like effect was taken into account by the combination of the air chamber with an additional air reservoir of appropriate volume, where the total volume was scaled according to the square of the Froude scale. The hydrodynamic performance was compared with the results obtained without considering the spring-like effect. A phase difference between the air pressure and airflow rate was observed when employing the additional air reservoir. The amplitudes of free surface elevation and airflow rate increased, while the air pressure was reduced when the spring-like effect was considered. The results demonstrate that failure to consider the spring-like effect can lead to overestimation of the hydrodynamic efficiencies, and the errors were mainly affected by the incident wave frequency. Full article

(This article belongs to the Special Issue Study on the Performance of Wave Energy Converters)

► Show Figures

Figure 1

20 pages, 5149 KiB

Open AccessArticle

Evaluating Vegetation Effects on Wave Attenuation and Dune Erosion during Hurricane

by Mengdi Ma, Wenrui Huang, Sungmoon Jung, Christopher Oslon, Kai Yin and Sudong Xu

J. Mar. Sci. Eng. 2024, 12(8), 1326; https://doi.org/10.3390/jmse12081326 - 6 Aug 2024

Viewed by 287

Abstract

This study employs the XBeach surfbeat model (XBSB) to explore the effects of vegetation on wave attenuation and dune erosion in a case study of Mexico Beach during Hurricane Michael. The XBSB model was validated against laboratory experiments of wave-induced dune erosion and [...] Read more.

This study employs the XBeach surfbeat model (XBSB) to explore the effects of vegetation on wave attenuation and dune erosion in a case study of Mexico Beach during Hurricane Michael. The XBSB model was validated against laboratory experiments of wave-induced dune erosion and wave attenuation by vegetation. In the case study of vegetation on dunes in Mexico Beach during Hurricane Michael, different vegetation drag coefficients were evaluated to investigate the effects of vegetation on wave attenuation and dune erosion. LiDAR data of dune profiles before and after Hurricane Michael were used for model validation. The findings reveal that vegetation on dunes significantly affects wave attenuation and dune erosion. Under vegetated conditions, as the vegetation drag coefficient value increases, wave attenuation also increases, leading to a reduction of dune erosion. An increase in vegetation density enhances wave attenuation in the vegetated area, including reductions in significant wave height and flow velocity. However, the rate of change in attenuation decreases as the vegetation density increases. Through simulations under regular wave condition on Mexico Beach, an optimal vegetation density was identified as 800 units/m². Beyond this density, additional vegetation does not substantially improve wave attenuation. Furthermore, the position of the dune crest elevation is related to the location where the alongshore flow velocity begins to decrease. The findings highlight the essential role of coastal vegetation in enhancing coastal resilience against hurricanes. Full article

(This article belongs to the Special Issue Coastal Disaster Assessment and Response)

► Show Figures

Figure 1

19 pages, 4428 KiB

Open AccessArticle

The Depth Distribution Law of the Polarization of the Vector Acoustic Field in the Ocean Waveguide

by Yizheng Wei and Chao Sun

J. Mar. Sci. Eng. 2024, 12(8), 1325; https://doi.org/10.3390/jmse12081325 - 5 Aug 2024

Viewed by 275

Abstract

The polarization of the acoustic field in the ocean waveguide environment is a unique property that can provide new ideas for locating and detecting the underwater target, so it is interesting to study the polarization. This paper extends the Stokes parameters to a [...] Read more.

The polarization of the acoustic field in the ocean waveguide environment is a unique property that can provide new ideas for locating and detecting the underwater target, so it is interesting to study the polarization. This paper extends the Stokes parameters to a broadband form, and uses the non-stationary phase approximation method to simplify the expressions, reducing the complexity of theoretical derivation. A physical phenomenon is observed where polarization exhibits significant variations concerning the sea surface, seafloor, source depth, and the source symmetrical depth. Simulation results demonstrate that the simplified equations using the non-stationary phase approximation are effective. Additionally, by normalizing the broadband Stokes parameters, the effects of horizontal range on the depth distribution law of polarization can be eliminated. Subsequently, using the normalized broadband Stokes parameters, the influence of environmental and source parameters on the depth distribution law of polarization is analyzed. The effectiveness of the non-stationary phase approximation and the range-independence property of the normalized broadband Stokes parameters are verified by processing RHUM-RUM experimental data. Based on the conclusions of this paper, it is expected that the polarization can be used for target depth estimation. Full article

(This article belongs to the Topic Advances in Underwater Acoustics and Aeroacoustics)

► Show Figures

Figure 1

18 pages, 31105 KiB

Open AccessArticle

Global Path Planning of Unmanned Surface Vehicle in Complex Sea Areas Based on Improved Streamline Method

by Haoran Liu, Qihe Shan, Yuchi Cao and Qi Xu

J. Mar. Sci. Eng. 2024, 12(8), 1324; https://doi.org/10.3390/jmse12081324 - 5 Aug 2024

Viewed by 270

Abstract

In this paper, an innovative method is proposed to improve the global path planning of Unmanned Surface Vehicles (USV) in complex sea areas, combining fluid mechanic calculations with an improved A* algorithm. This method not only generates smooth paths but also ensures feasible [...] Read more.

In this paper, an innovative method is proposed to improve the global path planning of Unmanned Surface Vehicles (USV) in complex sea areas, combining fluid mechanic calculations with an improved A* algorithm. This method not only generates smooth paths but also ensures feasible global solutions, significantly enhancing the efficiency and safety of path planning. Firstly, in response to the water depths limitation, this study set up safe water depths, providing strong guarantees for the safe navigation of USVs in complex waters. Secondly, based on the hydrological and geographical characteristics of the study sea area, an accurate ocean environment model was constructed using Ansys Fluent software and computational fluid dynamics (CFD) technology, thus providing USVs with a feasible path solution on a global scale. Then, the local sea area with complex obstacles was converted into a grid map to facilitate detailed planning. Meanwhile, the improved A* algorithm was utilized for meticulous route optimization. Furthermore, by combining the results of local and global planning, the approach generated a comprehensive route that accounts for the complexities of the maritime environment while avoiding local optima. Finally, simulation results demonstrated that the algorithm proposed in this study shows faster pathfinding speed, shorter route distances, and higher route safety compared to other algorithms. Moreover, it remains stable and effective in real-world scenarios. Full article

(This article belongs to the Special Issue Unmanned Marine Vehicles: Perception, Planning, Control and Swarm)

► Show Figures

Figure 1

18 pages, 8602 KiB

Open AccessArticle

Experimental Validation of a Modular All-Electric Power Take-Off Topology for Wave Energy Converter Enabling Marine Renewable Energy Interconnection

by Hamed Nademi, Brent Joel Galindez, Michael Ross and Miguel Lopez

J. Mar. Sci. Eng. 2024, 12(8), 1323; https://doi.org/10.3390/jmse12081323 - 5 Aug 2024

Viewed by 314

Abstract

Power electronic converters are an enabling technology for the emerging marine energy applications, such as using ocean waves to produce electricity. This paper outlines the power take-off system and its key components used in a wave energy converter offering modularity and scalability to [...] Read more.

Power electronic converters are an enabling technology for the emerging marine energy applications, such as using ocean waves to produce electricity. This paper outlines the power take-off system and its key components used in a wave energy converter offering modularity and scalability to generate power efficiently. The proposed power take-off system was implemented based on a modular multilevel converter and could be deployed to convert any alternating current electrical energy to a different alternating current for interconnection to grid or non-grid applications. Examples of widespread deployment are supplying electricity to coastal communities or producing clean drinking water. The analysis using both the simulation tests and laboratory experiments verified the design objectives and basic functionality of the developed power take-off system. An acceptable response using a field programmable gate array-based controlled laboratory testbench was achieved, complying with guidelines specified in the prevalent industry standards. Seamless operation during steady-state and transients for the studied wave energy converter was achieved as supported by the obtained results. The key findings of this work were experimentally examined under different load conditions, direct current bus voltage fluctuations, and generator speed–torque regulation. The ability of the power take-off system to generate high-power quality of the waveforms, e.g., against adhering to the IEEE 519-2022 standard for total harmonic distortion limits, is also confirmed. Full article

(This article belongs to the Special Issue The Control, Modeling, and the Development of Wave Energy Convertors)

► Show Figures

Figure 1

17 pages, 2930 KiB

Open AccessArticle

Design and Simulation-Based Validation of an AI Model for Predicting Grab-Type Ship Unloader Operation Data

by Ga-Eun Jung, Woo-Hee Jeong, Seok-Ju Lee, Jae-In Lee, Tae-Won Kim and Hae-Jin Sung

J. Mar. Sci. Eng. 2024, 12(8), 1322; https://doi.org/10.3390/jmse12081322 - 5 Aug 2024

Viewed by 289

Abstract

Along with seaports automation, there is growing interest in the automation of Grab-Type Ship Unloader (GTSU) that unloads coal and iron ore from bulk carriers. Autonomous unloading operations of GTSU offer the potential for significant productivity improvement and cost savings. In this paper, [...] Read more.

Along with seaports automation, there is growing interest in the automation of Grab-Type Ship Unloader (GTSU) that unloads coal and iron ore from bulk carriers. Autonomous unloading operations of GTSU offer the potential for significant productivity improvement and cost savings. In this paper, an AI model trained with manual operation data was designed for GTSU automation operation, and the AI model was verified through the equation-of-motion-based GTSU operation simulator. The operation data of hoist, grab, and trolley were predicted by training the designed AI model with the manual operation data of GTSU. Before applying the predicted data to the actual equipment, the predicted driving data was verified using the equation-of-motion-based GTSU operation simulator. The AI prediction model was designed using the Multi-Layer Perception network, a type of artificial neural network. The AI prediction model was evaluated with the Mean-Squared Error indicator, and the validation loss was found to be less than 0.02. In addition, verification of the prediction data was performed using the GTSU dynamics-based simulator. The Mean Relative Error was up to 0.50, and the R² score value exceeded 0.92, indicating that the model is effective in predicting operation data. The proposed AI prediction model will be effectively utilized to implement a fully automated unloading system. Full article

(This article belongs to the Section Ocean Engineering)

► Show Figures

Figure 1

19 pages, 7542 KiB

Open AccessArticle

The Mamba Model: A Novel Approach for Predicting Ship Trajectories

by Yongfeng Suo, Zhengnian Ding and Tao Zhang

J. Mar. Sci. Eng. 2024, 12(8), 1321; https://doi.org/10.3390/jmse12081321 - 5 Aug 2024

Viewed by 270

Abstract

To address the complexity of ship trajectory prediction, this study explored the efficacy of the Mamba model, a relatively new deep-learning framework. In order to evaluate the performance of the Mamba model relative to traditional models, which often struggle to cope with the [...] Read more.

To address the complexity of ship trajectory prediction, this study explored the efficacy of the Mamba model, a relatively new deep-learning framework. In order to evaluate the performance of the Mamba model relative to traditional models, which often struggle to cope with the dynamic and nonlinear nature of maritime navigation data, we analyzed a dataset consisting of intricate ship trajectory data. The prediction accuracy and inference speed of the model were evaluated using metrics such as the mean absolute error (MAE) and root mean square error (RMSE). The Mamba model not only excelled in terms of the computational efficiency, with inference times of 0.1759 s per batch—approximately 7.84 times faster than the widely used Transformer model—it also processed 3.9052 samples per second, which is higher than the Transformer model’s 0.7246 samples per second. Additionally, it demonstrated high prediction accuracy and the lowest loss among the evaluated models. The Mamba model provides a new tool for ship trajectory prediction, which represents an advancement in addressing the challenges of maritime trajectory analysis when compared to existing deep-learning methods. Full article

(This article belongs to the Section Ocean Engineering)

► Show Figures

Figure 1

18 pages, 10772 KiB

Open AccessArticle

Properties and Model of Pore-Scale Methane Displacing Water in Hydrate-Bearing Sediments

by Dongfeng Ge, Jicheng Zhang, Youxun Cao, Cheng Liu, Bin Wu, Haotian Chu, Jialin Lu and Wentao Li

J. Mar. Sci. Eng. 2024, 12(8), 1320; https://doi.org/10.3390/jmse12081320 - 5 Aug 2024

Viewed by 260

Abstract

The flow characteristics of methane and water in sedimentary layers are important factors that affect the beneficial exploitation of marine hydrates. To study the influencing factors of methane drive-off water processes in porous media, we constructed nonhomogeneous geometric models using MATLAB 2020a random [...] Read more.

The flow characteristics of methane and water in sedimentary layers are important factors that affect the beneficial exploitation of marine hydrates. To study the influencing factors of methane drive-off water processes in porous media, we constructed nonhomogeneous geometric models using MATLAB 2020a random distribution functions. We developed a mathematical model of gas–water two-phase flow based on the Navier–Stokes equation. The gas-driven water processes in porous media were described using the level-set method and solved through the finite element method. We investigated the effects of the nonhomogeneous structure of pore media, wettability, and repulsion rate on gas-driven water channeling. The nonhomogeneity of the pore medium is the most critical factor influencing the flow. The size of the throat within the hydrophilic environment determines the level of difficulty of gas-driven water flow. In regions with a high concentration of narrow passages, the formation of extensive air-locked areas is more likely, leading to a decrease in the efficiency of the flow channel. In the gas–water drive process, water saturation changes over time according to a negative exponential function relationship. The more hydrophilic the pore medium, the more difficult the gas-phase drive becomes, and this correlation is particularly noticeable at higher drive rates. The significant pressure differentials caused by the high drive-off velocities lead to quicker methane breakthroughs. Instantaneous flow rates at narrow throats can be up to two orders of magnitude higher than average. Additionally, there is a susceptibility to vortex flow in the area where the throat connects to the orifice. The results of this study can enhance our understanding of gas–water two-phase flow in porous media and help commercialize the exploitation of clean energy in the deep ocean. Full article

(This article belongs to the Special Issue Exploration and Drilling Technology of Deep-Sea Natural Gas Hydrate)

► Show Figures

Figure 1

16 pages, 5958 KiB

Open AccessArticle

Numerical Simulation of Vertical Cyclic Responses of a Bucket in Over-Consolidated Clay

by Jun Jiang, Chengxi Luo and Dong Wang

J. Mar. Sci. Eng. 2024, 12(8), 1319; https://doi.org/10.3390/jmse12081319 - 4 Aug 2024

Viewed by 276

Abstract

Multi-bucket foundations have become an alternative for large offshore wind turbines, with the expansion of offshore wind energy into deeper waters. The vertical cyclic loading–displacement responses of the individual bucket of the tripod foundation are relevant to the deflection of multi-bucket foundations and [...] Read more.

Multi-bucket foundations have become an alternative for large offshore wind turbines, with the expansion of offshore wind energy into deeper waters. The vertical cyclic loading–displacement responses of the individual bucket of the tripod foundation are relevant to the deflection of multi-bucket foundations and crucial for serviceability design. Finite element analyses are used to investigate the responses of a bucket subjected to symmetric vertical cyclic loading in over-consolidated clay. The Undrained Cyclic Accumulation Model (UDCAM) is adopted to characterize the stress–strain properties of clay, the parameters of which are calibrated through monotonic and cyclic direct simple shear tests. The performance of the finite element (FE) model combined with UDCAM in simulating vertical displacement amplitudes is evaluated by comparison with existing centrifuge tests. Moreover, the impact of the bucket’s aspect ratio on vertical displacement amplitude is investigated through a parametric study. A predictive equation is proposed to estimate the vertical displacement amplitudes of bucket foundations with various aspect ratios, based on the cyclic displacement amplitude of a bucket with an aspect ratio of unity. Full article

(This article belongs to the Special Issue Advances in Marine Geological and Geotechnical Hazards)

► Show Figures

Figure 1

12 pages, 4364 KiB

Open AccessArticle

Modeling Fluid Flow in Ship Systems for Controller Tuning Using an Artificial Neural Network

by Nur Assani, Petar Matić, Danko Kezić and Nikolina Pleić

J. Mar. Sci. Eng. 2024, 12(8), 1318; https://doi.org/10.3390/jmse12081318 - 4 Aug 2024

Viewed by 293

Abstract

Flow processes onboard ships are common in order to transport fluids like oil, gas, and water. These processes are controlled by PID controllers, acting on the regulation valves as actuators. In case of a malfunction or refitting, a PID controller needs to be [...] Read more.

Flow processes onboard ships are common in order to transport fluids like oil, gas, and water. These processes are controlled by PID controllers, acting on the regulation valves as actuators. In case of a malfunction or refitting, a PID controller needs to be re-adjusted for the optimal control of the process. To avoid experimenting on operational real systems, models are convenient alternatives. When real-time information is needed, digital twin (DT) concepts become highly valuable. The aim of this paper is to analyze and determine the optimal NARX model architecture in order to achieve a higher-accuracy model of a ship’s flow process. An artificial neural network (ANN) was used to model the process in MATLAB. The experiments were performed using a multi-start approach to prevent overtraining. To prove the thesis, statistical analysis of the experimental results was performed. Models were evaluated for generalization using mean squared error (MSE), best fit, and goodness of fit (GoF) measures on two independent datasets. The results indicate the correlation between the number of input delays and the performance of the model. A permuted k-fold cross-validation analysis was used to determine the optimal number of voltage and flow delays, thus defining the number of model inputs. Permutations of training, test, and validation datasets were applied to examine bias due to the data arrangement during training. Full article

(This article belongs to the Special Issue Data-Driven Methods for Marine Structures)

► Show Figures

Figure 1

19 pages, 6697 KiB

Open AccessArticle

SSL-LRN: A Lightweight Semi-Supervised-Learning-Based Approach for UWA Modulation Recognition

by Chaojin Ding, Wei Su, Zehong Xu, Daqing Gao and En Cheng

J. Mar. Sci. Eng. 2024, 12(8), 1317; https://doi.org/10.3390/jmse12081317 - 4 Aug 2024

Viewed by 284

Abstract

Due to the lack of sufficient valid labeled data and severe channel fading, the recognition of various underwater acoustic (UWA) communication modulation types still faces significant challenges. In this paper, we propose a lightweight UWA communication type recognition network based on semi-supervised learning, [...] Read more.

Due to the lack of sufficient valid labeled data and severe channel fading, the recognition of various underwater acoustic (UWA) communication modulation types still faces significant challenges. In this paper, we propose a lightweight UWA communication type recognition network based on semi-supervised learning, named the SSL-LRN. In the SSL-LRN, a mean teacher–student mechanism is developed to improve learning performance by averaging the weights of multiple models, thereby improving recognition accuracy for insufficiently labeled data. The SSL-LRN employs techniques such as quantization and small convolutional kernels to reduce floating-point operations (FLOPs), enabling its deployment on underwater mobile nodes. To mitigate the performance loss caused by quantization, the SSL-LRN adopts a channel expansion module to optimize the neuron distribution. It also employs an attention mechanism to enhance the recognition robustness for frequency-selective-fading channels. Pool and lake experiments demonstrate that the framework effectively recognizes most modulation types, achieving a more than 5% increase in recognition accuracy at a 0 dB signal-to-noise ratio (SNRs) while reducing FLOPs by 84.9% compared with baseline algorithms. Even with only 10% labeled data, the performance of the SSL-LRN approaches that of the fully supervised LRN algorithm. Full article

(This article belongs to the Section Ocean Engineering)

► Show Figures

Figure 1

29 pages, 13503 KiB

Open AccessArticle

YOSMR: A Ship Detection Method for Marine Radar Based on Customized Lightweight Convolutional Networks

by Zhe Kang, Feng Ma, Chen Chen and Jie Sun

J. Mar. Sci. Eng. 2024, 12(8), 1316; https://doi.org/10.3390/jmse12081316 - 3 Aug 2024

Viewed by 464

Abstract

In scenarios such as nearshore and inland waterways, the ship spots in a marine radar are easily confused with reefs and shorelines, leading to difficulties in ship identification. In such settings, the conventional ARPA method based on fractal detection and filter tracking performs [...] Read more.

In scenarios such as nearshore and inland waterways, the ship spots in a marine radar are easily confused with reefs and shorelines, leading to difficulties in ship identification. In such settings, the conventional ARPA method based on fractal detection and filter tracking performs relatively poorly. To accurately identify radar targets in such scenarios, a novel algorithm, namely YOSMR, based on the deep convolutional network, is proposed. The YOSMR uses the MobileNetV3(Large) network to extract ship imaging data of diverse depths and acquire feature data of various ships. Meanwhile, taking into account the issue of feature suppression for small-scale targets in algorithms composed of deep convolutional networks, the feature fusion module known as PANet has been subject to a lightweight reconstruction leveraging depthwise separable convolutions to enhance the extraction of salient features for small-scale ships while reducing model parameters and computational complexity to mitigate overfitting problems. To enhance the scale invariance of convolutional features, the feature extraction backbone is followed by an SPP module, which employs a design of four max-pooling constructs to preserve the prominent ship features within the feature representations. In the prediction head, the Cluster-NMS method and α-DIoU function are used to optimize non-maximum suppression (NMS) and positioning loss of prediction boxes, improving the accuracy and convergence speed of the algorithm. The experiments showed that the recall, accuracy, and precision of YOSMR reached 0.9308, 0.9204, and 0.9215, respectively. The identification efficacy of this algorithm exceeds that of various YOLO algorithms and other lightweight algorithms. In addition, the parameter size and calculational consumption were controlled to only 12.4 M and 8.63 G, respectively, exhibiting an 80.18% and 86.9% decrease compared to the standard YOLO model. As a result, the YOSMR displays a substantial advantage in terms of convolutional computation. Hence, the algorithm achieves an accurate identification of ships with different trail features and various scenes in marine radar images, especially in different interference and extreme scenarios, showing good robustness and applicability. Full article

(This article belongs to the Special Issue Intelligent Ships and Waterways: Design, Operation and Advanced Technology)

► Show Figures

Figure 1

32 pages, 17131 KiB

Open AccessFeature PaperArticle

Power Generation Optimization for Next-Generation Cruise Ships with MVDC Architecture: A Dynamic Modeling and Simulation Approach

by Chalermkiat Nuchturee, Tie Li and Xinyi Zhou

J. Mar. Sci. Eng. 2024, 12(8), 1315; https://doi.org/10.3390/jmse12081315 - 3 Aug 2024

Viewed by 269

Abstract

The cruise industry is obliged by economic and environmental initiatives to pursue fuel-efficient solutions and lower ship exhaust emissions. The medium voltage DC (MVDC) distribution with intelligent power management has become a concept for next-generation onboard power systems as its energy-saving feature is [...] Read more.

The cruise industry is obliged by economic and environmental initiatives to pursue fuel-efficient solutions and lower ship exhaust emissions. The medium voltage DC (MVDC) distribution with intelligent power management has become a concept for next-generation onboard power systems as its energy-saving feature is to eliminate the frequency constraint and simultaneously optimize engine loads and speed in response to load variations. The incentive for this transition lies on one hand in the fuel efficiency consideration and the reduction of power losses from serial conversion stages. On the other hand, the DC-based technology has been conceived as high-power density design, thus significantly increasing the payload. This study investigates such potential benefits focusing exclusively on large cruise vessels. A highly representative model of the integrated power platform that incorporates all dynamic interactions from the ship hull and essential machinery typically installed on board cruise ships is proposed. The power management strategy also takes account of actual sea conditions and real-time operation requirements. The simulation results demonstrate that the optimization-based MVDC system is able to maximize the opportunity of search agents in finding optimum fuel efficiency areas throughout the scenario time. An analysis of the system structure weight and space reduction of the MVDC architecture is also performed through the utilization of more compact electrical distribution devices and very high power-dense combustion turbines. Full article

(This article belongs to the Special Issue Co-optimization of Fuel, Engine and After-Treatment towards the IMO 2050 Target)

► Show Figures

Figure 1

Journal Menu

Journal Browser

J. Mar. Sci. Eng., Volume 12, Issue 8 (August 2024) – 106 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI