Journal of Marine Science and Engineering

18 pages, 1959 KiB

Open AccessArticle

A Semi-Analytical Method to Design a Dynamic Vibration Absorber for Coupled Plate Structures of Offshore Platforms

by Yuan Du, Fuxin Jia, Yang Tang, Jiajun Zheng, Yucheng Zou and Yong Ma

J. Mar. Sci. Eng. 2025, 13(2), 283; https://doi.org/10.3390/jmse13020283 (registering DOI) - 3 Feb 2025

Coupled plate structures composed of stiffened plates and sub-plates have been widely used in marine engineering practice. Meanwhile, the low-frequency multi-linear spectrum vibration control of the coupled stiffened plate structures has become necessary and meaningful. However, the design efficiency of the dynamic vibration [...] Read more.

Coupled plate structures composed of stiffened plates and sub-plates have been widely used in marine engineering practice. Meanwhile, the low-frequency multi-linear spectrum vibration control of the coupled stiffened plate structures has become necessary and meaningful. However, the design efficiency of the dynamic vibration absorber of the corresponding structure is still low. In the present study, a mathematical model of coupled plate structures and a dynamic vibration absorber is introduced to improve design efficiency. Subsequently, an experiment is designed to verify the effectiveness and advantages of the current method. The reliability of the current mathematical model is verified by comparing it with modal experiment results. Moreover, the equivalent mass solution efficiency is greatly improved by comparing it with FEM. Finally, a comparison experiment of the dynamic vibration absorber has also been conducted to further verify the effectiveness of the current method. The semi-analytical method proposed in the current research may be useful when designing dynamic vibration absorbers for the coupled plate structures of offshore platforms. Full article

(This article belongs to the Special Issue Contemporary Research on Improving the Performance of Modern Marine Vehicles)

31 pages, 12008 KiB

Open AccessArticle

Probability Stability Evaluation of Coral Reef Limestone Reef Slopes Under Earthquake

by Ruize Ma, Baifeng Ji, Longya Zhang, Shuang Pan and Kaimeng Hu

J. Mar. Sci. Eng. 2025, 13(2), 284; https://doi.org/10.3390/jmse13020284 (registering DOI) - 1 Feb 2025

Abstract

With the rapid development of island construction and the frequent occurrence of natural disasters, the stability of coral reef slopes is attracting increasing attention. This study aims to assess the dynamic stability and instability risks of coral reef slopes under different earthquake intensities. [...] Read more.

With the rapid development of island construction and the frequent occurrence of natural disasters, the stability of coral reef slopes is attracting increasing attention. This study aims to assess the dynamic stability and instability risks of coral reef slopes under different earthquake intensities. Geological data were integrated, and the Newmark method and finite element analysis were employed for probabilistic stability assessment and permanent displacement evaluation, leading to the development of a validated model for slope stability assessment. The study explored the effects of varying earthquake intensities on slope stability. Results indicate that the stratified structure significantly influences stability. Reef limestone slopes exhibited higher stability, whereas multi-layered slopes, due to looseness, were less stable. Both slope types remained stable under static conditions. Earthquake intensity substantially impacted stability, with multi-layered slopes showing instability probabilities of 48% and 100% under peak ground accelerations (PGA) of 0.3 g and 0.4 g. Under extreme seismic conditions, the permanent displacement of multi-layered coral reef slopes significantly increased. This study aims to fill the gap in previous research by incorporating the random distribution of stratigraphic parameters, conducting probabilistic stability analysis based on the random distribution of geological parameters, and thereby providing references for island reef engineering construction. Full article

(This article belongs to the Section Ocean Engineering)

22 pages, 10973 KiB

Open AccessArticle

Optimization of Key Parameters of Fracturing Flooding Development in Offshore Reservoirs with Low Permeability Based on Numerical Modeling Approach

by Zitong Zhao, Shan Jiang, Ting Lei, Jinwei Wang and Yafei Zhang

J. Mar. Sci. Eng. 2025, 13(2), 282; https://doi.org/10.3390/jmse13020282 (registering DOI) - 1 Feb 2025

Abstract

Fracturing flooding is a new technology that combines traditional conventional water drive, chemical drive, and hydraulic fracturing technologies and injects water under proximity fracture pressure to increase the wave area. It is currently applied in onshore low-permeability oilfields with good results, but the [...] Read more.

Fracturing flooding is a new technology that combines traditional conventional water drive, chemical drive, and hydraulic fracturing technologies and injects water under proximity fracture pressure to increase the wave area. It is currently applied in onshore low-permeability oilfields with good results, but the research on the design method of fracturing flooding in offshore low-permeability reservoirs is still lacking. Numerical simulation studies of well fracturing flooding are needed to optimize the key parameters of fracturing flooding development. This study simulates the real-time fracture dynamic expansion process of micro-level fracture expansion for hydraulic fracturing, combines it with a numerical simulation of well pressure-driving, and finally optimizes the parameters of hydraulic flooding. By studying the fracture expansion law, this study determined that the total amount of injection volume had a large influence on both fracture half-length and inflow capacity; the larger the injection rate, the larger the fracture half-length, but the inflow capacity was basically unchanged. It was also found that multiple rounds of fracturing flooding had no effect on fracture morphology or length. In studying the key fracturing flooding parameters in oil wells, it was concluded that the higher the total injection amount, the higher the oil increase in fracturing flooding and the wider the wave area of pressure-driving. Moreover, the higher the displacement, the higher the pressure near the bottom of the well, but there was little difference in the spreading area; in addition, the longer the well shut-in time, the higher the early oil production. Finally, these results were combined with the fracture expansion mechanism model and A21 well model, and the analysis of fracturing flooding parameters based on the simulation results allowed for the following recommendations to be made: the total amount of fracturing flooding injection should be 15,000 m³, the injection rate should be 6 m³/min, the simmering time should be 3–7 days, and only one round of fracturing flooding is required. The mechanism of fracture expansion revealed in this paper can guide the design of fracturing flooding programs in the process of reservoir fracturing flooding development, which is of some significance to the development of the fracturing flooding of offshore reservoirs with low permeability. Full article

(This article belongs to the Section Geological Oceanography)

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14 pages, 1614 KiB

Open AccessArticle

A Comparative Analysis of Growth, Survival, and Combining Ability Based on Diallel Crosses Among Three Selected Lines of the Fujian Oyster Crassostrea angulata with Normal, Golden, and Black Shell Colors

by Yuanxin Liang, Hong Hu, Zhenzong Pan, Chengxun Xu and Qi Li

J. Mar. Sci. Eng. 2025, 13(2), 281; https://doi.org/10.3390/jmse13020281 (registering DOI) - 31 Jan 2025

Abstract

Crossing between selected lines could combine the additive genetic variance accumulated within the lines and the non-additive genetic variance between the lines in the genetic improvement of aquatic animals, thus obtaining progeny with favorable traits. However, the value of this breeding strategy has [...] Read more.

Crossing between selected lines could combine the additive genetic variance accumulated within the lines and the non-additive genetic variance between the lines in the genetic improvement of aquatic animals, thus obtaining progeny with favorable traits. However, the value of this breeding strategy has not been investigated in the Fujian oyster Crassostrea angulata due to the lack of available sufficiently selected lines. In this study, a complete 3 × 3 diallel cross was established between the normal (N), golden (G), and black (B) shell lines of C. angulata. The growth (shell height and living weight) and survival of three purebred groups and six hybrid groups under three environments (Luoyu, Jiangkou, and Houhai) were comprehensively evaluated during the larval and grow-out stages. The general combining ability (GCA) of the parental lines and the specific combining ability (SCA) of the hybrid groups were also estimated. The shell heights of the hybrid groups were significantly lower than those of their parental groups on day 25, exhibiting negative heterosis (MPH: −13.01 to −1.45; HPH: −16.69 to −5.76). Meanwhile, the survival rates of the hybrids were significantly higher than those of the parental groups. A negative value of SCA was recorded for NG (N♀ × G♂) (−0.031), which was in line with its lower survival rate on day 25. Significant heterosis was observed in the growth and survival of each hybrid group during the grow-out stage. The shell height and living weight of the hybrid groups were significantly higher in Houhai than in Luoyu and Jiangkou, but the survival rate in Houhai was significantly lower than in the other two sites. BG (B♀ × G♂) and GB (G♀ × B♂) had higher SCA values than the other four groups, which was consistent with their superior traits. The heterosis of shell height, living weight, and survival rate of BG was significantly greater than in the other five hybrid groups, which could be used as potential parents for breeding high-quality diploid and triploid Fujian oysters. This study demonstrated that the traits of C. angulata could be significantly improved by crossing between different selected lines, providing a reference for evaluating the utilization value of non-additive genetic effects (heterosis) between selected lines in bivalves. Full article

(This article belongs to the Section Marine Aquaculture)

18 pages, 1735 KiB

Open AccessArticle

The Impact of Ekman Pumping and Transport on Dosidicus digas (Jumbo Flying Squid) Fishing Ground by Chinese Jiggers off the Coast of Peru

by Xingnan Fang, Xin Zhang, Xinjun Chen and Wei Yu

J. Mar. Sci. Eng. 2025, 13(2), 280; https://doi.org/10.3390/jmse13020280 (registering DOI) - 31 Jan 2025

Abstract

Upwelling is often associated with high productivity, biodiversity, and fishery resource abundance. This study employed a generalized additive model (GAM) to analyze the effects of Ekman pumping and transport on the abundance and distribution of jumbo flying squid (Dosidicus gigas) using [...] Read more.

Upwelling is often associated with high productivity, biodiversity, and fishery resource abundance. This study employed a generalized additive model (GAM) to analyze the effects of Ekman pumping and transport on the abundance and distribution of jumbo flying squid (Dosidicus gigas) using wind field data and Chinese commercial fishing catch data off Peru from 2012 to 2020. The results indicate that the spatial distribution of Ekman pumping and transport exhibited significant monthly variation and exerted a considerable impact on the abundance and distribution of D. gigas. Ekman pumping fluctuated between 4.98 × 10^⁻⁹ to 6.84 × 10^⁻7 m/s, with the strongest upwelling effects observed from February to March and October to December. Ekman transport varied from 0.89 to 2.56 m³/s and peaked in August. The GAM results indicate that the catch per unit effort (CPUE) of D. gigas was significantly affected by Ekman pumping, while the latitudinal gravity centers (LATG) of D. gigas were significantly influenced by Ekman transport and chlorophyll-a concentration (Chl-a). Both hydrodynamic processes had a significant influence on Chl-a. Ekman pumping contributed greatly to upwelling formation, significantly increasing Chl-a concentration in the northern region, while strong Ekman transport pushed high-Chl-a coastal waters offshore in the central and southern regions when Ekman pumping was weaker, resulting in increasing offshore Chl-a concentrations. Furthermore, Chl-a concentration was significantly positively correlated with Ekman pumping after a two-month lag. An El Niño weakened the intensity of Ekman pumping, leading to notable declines in Chl-a concentration and D. gigas CPUE. These findings demonstrate that Ekman pumping and transport significantly influence the distribution of Chl-a, to which D. gigas is sensitive, influencing the abundance and distribution of this species off the coast of Peru. Full article

(This article belongs to the Section Marine Biology)

54 pages, 18402 KiB

Open AccessReview

Innovations in Wave Energy: A Case Study of TALOS-WEC’s Multi-Axis Technology

by Fatemeh Nasr Esfahani, Wanan Sheng, Xiandong Ma, Carrie M. Hall and George Aggidis

J. Mar. Sci. Eng. 2025, 13(2), 279; https://doi.org/10.3390/jmse13020279 (registering DOI) - 31 Jan 2025

Abstract

The technologically advanced learning ocean system—wave energy converter (TALOS-WEC) project addresses the urgent need for sustainable and efficient energy solutions by leveraging the vast potential of wave energy. This project presents a pioneering approach to wave energy capture through its unique multi-axis and [...] Read more.

The technologically advanced learning ocean system—wave energy converter (TALOS-WEC) project addresses the urgent need for sustainable and efficient energy solutions by leveraging the vast potential of wave energy. This project presents a pioneering approach to wave energy capture through its unique multi-axis and omnidirectional point absorber design. Featuring a fully enclosed power take-off (PTO) system, the TALOS-WEC harnesses energy across six degrees of freedom (DoFs) using an innovative internal reaction mass (IRM) mechanism. This configuration enables efficient energy extraction from the relative motion between the IRM and the hull, aiming for energy conversion efficiencies ranging between 75–80% under optimal conditions, while ensuring enhanced durability in harsh marine environments. The system’s adaptability is reflected in its versatile geometric configurations, including triangular, octagonal, and circular designs, customised for diverse marine conditions. Developed at Lancaster University, UK, and supported by international collaborations, the TALOS-WEC project emphasises cutting-edge advancements in hydrodynamic modelling, geometric optimisation, and control systems. Computational methodologies leverage hybrid frequency-time domain models and advanced panel codes (WAMIT, HAMS, and NEMOH) to address non-linearities in the PTO system, ensuring precise simulations and optimal performance. Structured work packages (WPs) guide the project, addressing critical aspects such as energy capture optimisation, reliability enhancement, and cost-effectiveness through innovative monitoring and control strategies. This paper provides a comprehensive overview of the TALOS-WEC, detailing its conceptual design, development, and validation. Findings demonstrate TALOS’s potential to achieve scalable, efficient, and robust wave energy conversion, contributing to the broader advancement of renewable energy technologies. The results underscore the TALOS-WEC’s role as a cutting-edge solution for harnessing oceanic energy resources, offering perspectives into its commercial viability and future scalability. Full article

(This article belongs to the Special Issue Exploitation and Optimization of Ocean Energy Conversion Infrastructure)

32 pages, 4011 KiB

Open AccessArticle

Enhancing Underwater Acoustic Target Recognition Through Advanced Feature Fusion and Deep Learning

by Yanghong Zhao, Guohao Xie, Haoyu Chen, Mingsong Chen and Li Huang

J. Mar. Sci. Eng. 2025, 13(2), 278; https://doi.org/10.3390/jmse13020278 (registering DOI) - 31 Jan 2025

Abstract

Underwater Acoustic Target Recognition (UATR) is critical to maritime traffic management and ocean monitoring. However, underwater acoustic analysis is fraught with difficulties. The underwater environment is highly complex, with ambient noise, variable water conditions (such as temperature and salinity), and multi-path propagation of [...] Read more.

Underwater Acoustic Target Recognition (UATR) is critical to maritime traffic management and ocean monitoring. However, underwater acoustic analysis is fraught with difficulties. The underwater environment is highly complex, with ambient noise, variable water conditions (such as temperature and salinity), and multi-path propagation of acoustic signals. These factors make it challenging to accurately acquire and analyze target features. Traditional UATR methods struggle with feature fusion representations and model generalization. This study introduces a novel high-dimensional feature fusion method, CM3F, grounded in signal analysis and brain-like features, and integrates it with the Boundary-Aware Hybrid Transformer Network (BAHTNet), a deep-learning architecture tailored for UATR. BAHTNet comprises CBCARM and XCAT modules, leveraging a Kan network for classification and a large-margin aware focal (LMF) loss function for predictive losses. Experimental results on real-world datasets demonstrate the model’s robust generalization capabilities, achieving 99.8% accuracy on the ShipsEar dataset and 94.57% accuracy on the Deepship dataset. These findings underscore the potential of BAHTNet to significantly improve UATR performance. Full article

(This article belongs to the Special Issue Underwater Target Detection and Recognition)

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11 pages, 1759 KiB

Open AccessArticle

Quantitative Real-Time Polymerase Chain Reaction (PCR) Assay for Rapid Monitoring of the Harmful Algal Bloom Species Cochlodinium polykrikoides

by Min-Jeong Kim, Hyun-Jung Kim, Joon Sang Park, Donhyug Kang, Sungho Cho, Hansoo Kim, Seung Ho Baek, Jordan Jun Chul Park, Jeonghoon Han, Kang Eun Kim and Seung Won Jung

J. Mar. Sci. Eng. 2025, 13(2), 277; https://doi.org/10.3390/jmse13020277 - 31 Jan 2025

Abstract

Harmful blooms of the dinoflagellate Cochlodinium polykrikoides (Margalefidinium polykrikoides) had detrimental aquacultural and economic effects globally, and to reduce the damage caused by these blooms, early biomonitoring and quantitative analysis of C. polykrikoides are of the utmost importance. Here, for the detection [...] Read more.

Harmful blooms of the dinoflagellate Cochlodinium polykrikoides (Margalefidinium polykrikoides) had detrimental aquacultural and economic effects globally, and to reduce the damage caused by these blooms, early biomonitoring and quantitative analysis of C. polykrikoides are of the utmost importance. Here, for the detection of C. polykrikoides using quantitative real-time polymerase chain reactions, we developed specific primers targeting the large subunit ribosomal DNA (LSU rDNA) and evaluated their applicability in the field during the occurrence of a C. polykrikoides bloom. The specific primers not only accurately detected C. polykirkoides but also had a detection performance comparable with that obtained using microscopic observations. Accordingly, we developed a system that can be used in the field and applied when red tides occur, with accurate results being obtained more than five times more rapidly than those obtained based on microscopic analysis. Collectively, our findings indicate that the C. polykrikoides bloom detection system developed in this study can be applied to rapidly detect and accurately quantify C. polykrikoides in environmental samples. Data obtained using this system could be used as a basis for developing prompt monitoring and warning systems for the early detection of C. polykrikoides blooms in the field. Full article

(This article belongs to the Special Issue From Source to Sea: Navigating the Ecotoxicological Challenges of Emerging Contaminants in Marine Ecosystems)

25 pages, 7853 KiB

Open AccessArticle

System Identification and Navigation of an Underactuated Underwater Vehicle Based on LSTM

by Changhao Li, Zetao Hu, Desheng Zhang and Xin Wang

J. Mar. Sci. Eng. 2025, 13(2), 276; https://doi.org/10.3390/jmse13020276 - 31 Jan 2025

Abstract

Modeling and system identification are critical for the design, simulation, and navigation of underwater vehicles. This study presents a six degree-of-freedom (DoF) nonlinear model for a finless underactuated underwater vehicle, incorporating port-starboard symmetry and cross-flow terms. Then, hydrodynamic damping parameters are identified using [...] Read more.

Modeling and system identification are critical for the design, simulation, and navigation of underwater vehicles. This study presents a six degree-of-freedom (DoF) nonlinear model for a finless underactuated underwater vehicle, incorporating port-starboard symmetry and cross-flow terms. Then, hydrodynamic damping parameters are identified using an optimized Extended Kalman Filter (EKF), establishing a steady validation framework for computational fluid dynamics (CFD) simulation coefficients. Additionally, system identification is further enhanced with a Long Short-Term Memory (LSTM) neural network and a comprehensive dataset construction method, enabling time-series predictions of linear and angular velocities. To mitigate position divergence in dead reckoning (DR) caused by LSTM, a Nonlinear Explicit Complementary Filter (NECF) is integrated for attitude estimation, providing accurate yaw computation and reliable localization without dependence on acoustic sensors or machine vision. Finally, validation and evaluation are conducted to demonstrate model accuracy, EKF convergence, and the reliability of LSTM-based navigation. Full article

(This article belongs to the Special Issue Design and Application of Underwater Robots for Navigation and Manipulation)

19 pages, 6136 KiB

Open AccessArticle

Numerical Simulation Study of the Motion Characteristics of Autonomous Underwater Vehicles During Mooring Lurking Procedure

by Yuyang Hu, Zhaoyong Mao, Bo Cheng, Bo Li and Wenlong Tian

J. Mar. Sci. Eng. 2025, 13(2), 275; https://doi.org/10.3390/jmse13020275 - 31 Jan 2025

Abstract

A two-dimensional coupled dynamics model for a moored autonomous underwater vehicle (AUV) was developed using the lumped mass method for mooring cable dynamics and the Newton-Euler method for rigid body dynamics. This model enables the integrated simulation of AUV motion, flow field interactions, [...] Read more.

A two-dimensional coupled dynamics model for a moored autonomous underwater vehicle (AUV) was developed using the lumped mass method for mooring cable dynamics and the Newton-Euler method for rigid body dynamics. This model enables the integrated simulation of AUV motion, flow field interactions, and mooring cable behavior. The study investigates the effects of varying ocean current velocities and mooring cable lengths on AUV motion responses. The results indicate that under the influence of mooring forces, the AUV stabilizes near its equilibrium position after release and undergoes periodic oscillatory motion. Specifically, when the X-direction oscillation completes two cycles and the Y-direction oscillation completes four cycles, the AUV demonstrates an 8-shaped trajectory, with maximum motion amplitudes observed. These findings provide insights into the dynamic behavior of moored AUVs in ocean environments, contributing to the design and operation of long-term underwater monitoring systems. Full article

(This article belongs to the Section Ocean Engineering)

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24 pages, 7005 KiB

Open AccessArticle

Inlet Passage Hydraulic Performance Optimization of Coastal Drainage Pump System Based on Machine Learning Algorithms

by Tao Jiang, Weigang Lu, Linguang Lu, Lei Xu, Wang Xi, Jianfeng Liu and Ye Zhu

J. Mar. Sci. Eng. 2025, 13(2), 274; https://doi.org/10.3390/jmse13020274 - 31 Jan 2025

Abstract

The axial-flow pump system has been widely applied to coastal drainage pump stations, but the hydraulic performance optimization based on the contraction angles of the inlet passage has not been studied. This paper combined the computational fluid dynamics (CFD) method, machine learning (ML) [...] Read more.

The axial-flow pump system has been widely applied to coastal drainage pump stations, but the hydraulic performance optimization based on the contraction angles of the inlet passage has not been studied. This paper combined the computational fluid dynamics (CFD) method, machine learning (ML) algorithms and genetic algorithm (GA) to find the optimal contraction angles of the inlet passage. The 125 sets of comprehensive objective function were obtained by the CFD method. Three contraction angles and comprehensive objective function values were regressed by three ML algorithms. After hyperparameter optimization, the Gaussian process regression (GPR) model had the highest R²= 0.958 in the test set and had the strongest generalization ability among the three models. The impact degree of the three contraction angles on the objective function of the GPR model was investigated by the Sobol sensitivity analysis method; the results indicated that the order of impact degree from high to low was θ₃ > θ₂> θ₁. The optimal objective function values of the GPR model and corresponding contraction angles were searched through GA; the maximum objective function value was 0.963 and corresponding contraction angles were θ₁= 13.34°, θ₂= 28.36° and θ₃= 3.64°, respectively. The results of this study can provide reference for the optimization of inlet passages in coastal drainage pump systems. Full article

32 pages, 15864 KiB

Open AccessArticle

Coupled Aerodynamic–Hydrodynamic Analysis of Spar-Type Floating Foundations with Normal and Lightweight Concrete for Offshore Wind Energy in Colombia

by Jose Calderón, Andrés Guzmán and William Gómez

J. Mar. Sci. Eng. 2025, 13(2), 273; https://doi.org/10.3390/jmse13020273 - 31 Jan 2025

Abstract

Foundations for offshore wind turbines come in various types, with spar-type floating foundations being the most promising for different depths. This research analyzed the hydrodynamic–mechanical response of a 5 MW spar-type floating foundation under conditions typical of the Colombian Caribbean following the DNV [...] Read more.

Foundations for offshore wind turbines come in various types, with spar-type floating foundations being the most promising for different depths. This research analyzed the hydrodynamic–mechanical response of a 5 MW spar-type floating foundation under conditions typical of the Colombian Caribbean following the DNV standard. Two types of concrete were evaluated through numerical modeling: one with normal density (2400 kg/m³) and another with lightweight density (1900 kg/m³). Based on the hydrodynamic and structural dynamic response, it was concluded that the variation in concrete density only affected pitch rotation, with better performance observed in the lightweight concrete, achieving maximum rotations of 10°. The coupled model between QBlade and Aqwa was validated by code-to-code comparisons with QBlade’s fully coupled system with its ocean module. This study contributes to offshore engineering in Colombia by providing a detailed methodology for developing a coupled simulation, serving as a reference for both academia and industry amid the ongoing and projected wind energy development initiatives in the country. Full article

(This article belongs to the Special Issue Modelling Techniques for Floating Offshore Wind Turbines)

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23 pages, 1997 KiB

Open AccessArticle

Enhanced MILP Approach for Long-Term Multi-Vessel Maritime Inventory Routing with Application to Antarctic Logistics

by Dagoberto Cifuentes-Lobos, Lorena Pradenas and Victor Parada

J. Mar. Sci. Eng. 2025, 13(2), 272; https://doi.org/10.3390/jmse13020272 - 31 Jan 2025

Abstract

The maritime inventory routing problem (MIRP) integrates vessel routing and inventory management over a planning horizon to optimize logistical operations in marine environments. While existing models predominantly address short-term planning with single vessels, this research advances the field by presenting a tightened mixed-integer [...] Read more.

The maritime inventory routing problem (MIRP) integrates vessel routing and inventory management over a planning horizon to optimize logistical operations in marine environments. While existing models predominantly address short-term planning with single vessels, this research advances the field by presenting a tightened mixed-integer linear programming (MILP) model designed for long-term planning with multiple vessels. The proposed model leverages an improved mathematical formulation and state-of-the-art optimization solvers to enhance computational performance. To demonstrate its applicability, the model was evaluated using benchmark instances from the literature and new instances derived from the logistics of Chilean scientific bases in Antarctica, a challenging and underexplored maritime environment. The results show computational time reductions of up to 98% for small to medium-sized instances, achieved through the incorporation of valid inequalities into the model and the use of advanced hardware and solvers. For larger instances, optimal or near-optimal solutions were achieved within one hour for a planning horizon of 60 time units, with optimality gaps below 24.7% for a 120-time-unit horizon. These findings highlight the potential of the model to support decision-making in complex maritime logistics scenarios, extending its application to long-term, multi-vessel operations in remote and environmentally sensitive regions. The proposed framework provides a valuable tool for enhancing the sustainability and efficiency of maritime logistics systems. Full article

(This article belongs to the Special Issue Maritime Logistics and Green Shipping)

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17 pages, 5413 KiB

Open AccessArticle

Effects of Oxygen Enrichment and Air Humidification on the Combustion and Emissions of the Biodiesel Marine Diesel Engine

by Peng Geng, Xiong Hu and Xiaohu Lin

J. Mar. Sci. Eng. 2025, 13(2), 271; https://doi.org/10.3390/jmse13020271 - 31 Jan 2025

Abstract

With increasingly strict emission regulations, research on diesel engine combustion and emissions is urgently needed. This study conducted computational fluid dynamics modeling on diesel engines. The effects of intake humidity and oxygen concentration of a diesel engine on the combustion emission of biodiesel [...] Read more.

With increasingly strict emission regulations, research on diesel engine combustion and emissions is urgently needed. This study conducted computational fluid dynamics modeling on diesel engines. The effects of intake humidity and oxygen concentration of a diesel engine on the combustion emission of biodiesel were studied. The results indicate that when the humidity ratio is below 0.4 (WR = 0.4), intake humidification has a certain promoting effect on the combustion reaction process. Water molecule pyrolysis can promote the pyrolysis of biodiesel, and the peak pressure in the cylinder slightly increases. As the intake humidification ratio increases, the cylinder temperature decreases, and the oxygen concentration also decreases due to the increase in water molecular weight. The combustion reaction process is suppressed, and the cylinder pressure decreases. When the humidity ratio is 1 (WR = 1), the peak pressure decreases by 2.61% compared to when it is not humidified (WR = 0). The concentration of O radicals decreases with an increase in humidity ratio. When WR = 1.0, the emissions of NO_x decreased by 55.02%, but with the decrease in oxygen concentration in the high-temperature area, the emissions of soot increased. The results indicate that as the oxygen concentration increases, the cylinder pressure and average temperature increase, the ignition-delay time decreases, the heat-release rate increases, and it ultimately leads to an increase in NO_x emissions. Full article

(This article belongs to the Section Ocean Engineering)

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24 pages, 5819 KiB

Open AccessArticle

Dynamic Characteristics of Bidirectional Misaligned Marine Water-Lubricated Bearings Considering Turbulence, Surface Roughness and Bush Deformation

by Ziqi Chen, Ji Wang, Rui Li and Yujun Liu

J. Mar. Sci. Eng. 2025, 13(2), 270; https://doi.org/10.3390/jmse13020270 - 31 Jan 2025

Abstract

The marine water-lubricated bearing’s (WLBs) dynamic properties are essential for ensuring the shaft system’s operational dependability. The coupled model of mixed lubrication and turbulence under the impact of bidirectional misalignment is proposed in this research, and the perturbation equations of marine WLBs with [...] Read more.

The marine water-lubricated bearing’s (WLBs) dynamic properties are essential for ensuring the shaft system’s operational dependability. The coupled model of mixed lubrication and turbulence under the impact of bidirectional misalignment is proposed in this research, and the perturbation equations of marine WLBs with 32 coefficients are derived. The finite difference method (FDM) is used to solve the steady-state and perturbation equations, and the impacts of turbulence, bearing bush deformation, surface roughness, and bidirectional shaft misalignment on the dynamic characteristics of the WLBs are systematically investigated. The results reveal that under mixed lubrication, surface roughness and the turbulence effect can both greatly improve the stiffness and damping of the bearings, but that there is a threshold phenomenon for the turbulence effect’s influence on these properties. Neglecting the elastic deformation of the bush may lead to an overestimation of the bearings’ stiffness and damping, causing substantial inaccuracies in conditions of heavy load or declined Young’s modulus. The 32 coefficients of the WLB exhibit considerable variation with the misalignment angle; hence, a more comprehensive dynamic model should be developed for misaligned marine WLBs. The study’s findings provide valuable insights for rotor dynamics research and optimal design of lubrication performance in marine WLBs. Full article

(This article belongs to the Section Ocean Engineering)

22 pages, 8765 KiB

Open AccessArticle

Nonlinear Model Predictive Control Energy Management Strategy for Hybrid Power Ships Based on Working Condition Identification

by Yucheng Yan, Zhichao Chen and Diju Gao

J. Mar. Sci. Eng. 2025, 13(2), 269; https://doi.org/10.3390/jmse13020269 - 31 Jan 2025

Abstract

Hybrid power technology for ships is an effective way to promote the green and low-carbon development of the maritime industry. The development of pattern recognition technology provides new research ideas for the rational allocation and utilization of energy in hybrid power ships. To [...] Read more.

Hybrid power technology for ships is an effective way to promote the green and low-carbon development of the maritime industry. The development of pattern recognition technology provides new research ideas for the rational allocation and utilization of energy in hybrid power ships. To reduce fuel consumption, a nonlinear model predictive control energy management strategy based on working condition identification is proposed for optimal energy management to solve the problem of real-time optimal adjustment of generators and batteries. The core of the strategy is to identify the ship’s working conditions and the nonlinear model predictive control algorithm. Firstly, to achieve the working condition identification task, a ship working condition dataset based on a hybrid supply power ship data is constructed. The labeled dataset is trained using deep learning techniques. Secondly, based on the identification results, a nonlinear model predictive control algorithm is designed to adjust the generator speed and the battery current to achieve energy optimization control under constraints. Finally, the effectiveness of the proposed strategy in optimizing energy control and reducing fuel consumption is verified through simulation. The proposed strategy can reduce the generator fuel consumption by 5.5% under no noise disturbance when compared with conventional predictive control. Under 10% noise disturbance, it is still able to reduce the fuel consumption by 2.6%. Full article

(This article belongs to the Special Issue Advancements in Power Management Systems for Hybrid Electric Vessels)

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17 pages, 7551 KiB

Open AccessArticle

Effect of a Compression Ratio Increase and High-Flow-Rate Injection on the Combustion Characteristics of an Ammonia Direct Injection Spark-Ignited Engine

by Cheolwoong Park, Ilpum Jang, Jeongwoo Lee, Minki Kim, Chansoo Park, Yongrae Kim and Young Choi

J. Mar. Sci. Eng. 2025, 13(2), 268; https://doi.org/10.3390/jmse13020268 - 31 Jan 2025

Abstract

Despite efforts to use ammonia as a fuel, there remain problems with low combustion speeds and high unburned ammonia (NH₃) emissions. Therefore, methods to compensate for slow combustion speeds and stabilize combustion have been studied. This study aims to analyze how [...] Read more.

Despite efforts to use ammonia as a fuel, there remain problems with low combustion speeds and high unburned ammonia (NH₃) emissions. Therefore, methods to compensate for slow combustion speeds and stabilize combustion have been studied. This study aims to analyze how increasing the compression ratio affects engine performance to enhance thermal efficiency and reduce unburned emissions in a high-pressure ammonia direct injection spark-ignited engine. In addition, by applying a high-flow-rate (HFR) injector, an improvement in the combustion of ammonia fuel and exhaust gas emissions is observed through changes in the air–fuel mixture formation of high-pressure directly injected ammonia fuel. Compared with the existing compression ratio, the incomplete combustion loss due to unburned NH₃ increases significantly, and the thermal efficiency does not increase under an increased compression ratio. When HFR injectors are applied with an increase in the compression ratio, the net work increases by 4.7%, as incomplete combustion and energy losses of fuel are reduced by reducing the amount of unburned NH₃. Full article

(This article belongs to the Special Issue Performance and Emission Characteristics of Marine Engines)

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25 pages, 3877 KiB

Open AccessArticle

Numerical Simulation on Hybrid Lifting Operation of Polymetallic Nodules and Rare-Earth Elements-Rich Mud by Air-Lift Pump in Deep Sea around Minamitorishima Island

by Yoshiyuki Shimizu, Masatoshi Sugihara, Koichiro Fujinaga, Kentaro Nakamura and Yasuhiro Kato

J. Mar. Sci. Eng. 2025, 13(2), 267; https://doi.org/10.3390/jmse13020267 - 31 Jan 2025

Abstract

Polymetallic nodules and REE-rich mud under the seabed of 5500–5700 m water depth around Minamitorishima island are promising and attractive for exploration and development. Following our previous research, numerical analysis was used to investigate the unsteady flow characteristics and the lifting performance of [...] Read more.

Polymetallic nodules and REE-rich mud under the seabed of 5500–5700 m water depth around Minamitorishima island are promising and attractive for exploration and development. Following our previous research, numerical analysis was used to investigate the unsteady flow characteristics and the lifting performance of a commercial production system using an air-lift pump for hybrid lifting, lifting both polymetallic nodules and REE-rich mud. Gas–liquid–solid three-phase flow and gas–liquid two-phase flow in the system were analyzed using the one-dimensional drift–flux model. First, the reliability of the schemes and program was verified by comparing the numerical results with the experimental ones. Next, numerical simulations were conducted, in which the model’s dimensions were related to a commercial production system operated in the deep sea around Minamitorishima island, and the conditions fit the expected production rate. The results revealed the unsteady flow characteristics under the operations, such as start-up, shut-down, feed of polymetallic nodules and REE-rich mud, and those associated with disturbances, such as feed rate fluctuations. We demonstrate that the program and the schemes can simulate the unsteady flow characteristics and the lifting performance of a commercial production system with an air-lift pump well, and they can derive useful information and know-how in advance for the safe and continuous operation of the system. Full article

(This article belongs to the Special Issue Deep-Sea Mining Technologies: Recent Developments and Challenges)

26 pages, 2648 KiB

Open AccessArticle

Scour near Offshore Monopiles, Jacket-Type and Caisson-Type Structures

by L. C. van Rijn, N. Geleynse, L. Perk and D. Schoonhoven

J. Mar. Sci. Eng. 2025, 13(2), 266; https://doi.org/10.3390/jmse13020266 - 30 Jan 2025

Abstract

Scour near various offshore structures (monopile, caisson foundation and jacket structure) was studied by performing laboratory flume tests and numerical solutions with a semi-empirical model (SEDSCOUR) and a sophisticated 2DV model (SUSTIM2DV). The laboratory test results show that the maximum free scour depth [...] Read more.

Scour near various offshore structures (monopile, caisson foundation and jacket structure) was studied by performing laboratory flume tests and numerical solutions with a semi-empirical model (SEDSCOUR) and a sophisticated 2DV model (SUSTIM2DV). The laboratory test results show that the maximum free scour depth around a monopile without bed protection is slightly higher than the pile diameter. The maximum scour consisting of pile scour and global scour around an open jacket structure standing on four piles is much lower than the scour near the other structures (monopile and caisson). The maximum scour depth along a circular caisson foundation is found to be related to the base diameter of the structure. The main cause of the scour near these types of structures is the increase in the velocity along the flanks of the structure. Six cases have been used for validation: two laboratory cases (A and B) and four field cases (C, D, E and F). The measured scour values of the new physical model tests with the monopile and the open jacket structure presented in this paper are in reasonably good agreement with other laboratory and field scour data from the literature. The semi-empirical SEDSCOUR model proposed in this paper can be used for the reliable prediction of free scour and global scour near monopiles and jacket structures in a sandy bed (even with a small percentage of mud, up to 30%). The maximum scour depth along a large-scale caisson structure is more difficult to predict because the scour depth depends on the precise geometry and dimensions of the structure and the prevailing flow and sediment conditions. A detailed 2DV model with a fine horizontal grid (2 m) along a stream tube following the contour of the caisson is explored for scour predictions. The 2DV model simulates the flow and sediment transport at 50 to 100 points over the depth along the stream tube and can be run on a time-scale of 1 year. Full article

(This article belongs to the Section Coastal Engineering)

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