Journal of Marine Science and Engineering

41 pages, 3722 KiB

Open AccessReview

Advances of Complex Marine Environmental Influences on Underwater Vehicles

by Sen Zhao, Haibao Hu, Abdellatif Ouahsine, Haochen Lu, Zhuoyue Li, Zhiming Yuan and Peng Du

J. Mar. Sci. Eng. 2025, 13(7), 1297; https://doi.org/10.3390/jmse13071297 - 1 Jul 2025

Abstract

Underwater vehicles serve as critical assets for global ocean exploration and naval capability enhancement. The marine environment exhibits intricate hydrodynamic phenomena that significantly threaten underwater vehicle navigation safety, particularly in four prevalent complex conditions: surface waves, oceanic currents, stratified fluids, and internal waves. [...] Read more.

Underwater vehicles serve as critical assets for global ocean exploration and naval capability enhancement. The marine environment exhibits intricate hydrodynamic phenomena that significantly threaten underwater vehicle navigation safety, particularly in four prevalent complex conditions: surface waves, oceanic currents, stratified fluids, and internal waves. This comprehensive review systematically examines the impacts of these four marine environments on underwater vehicles through critical analysis and synthesis of contemporary advances in theoretical frameworks, experimental methodologies, and numerical simulation approaches. The identified influences are categorized into five primary aspects: hydrodynamic characteristics, dynamic response patterns, load distribution mechanisms, navigation trajectory optimization, and stealth performance. Particular emphasis is placed on internal wave interactions, with rigorous analysis derived from experimental investigations and numerical modeling of internal wave dynamics and their coupling effects with underwater vehicles. In addition, this review points out and analyzes the shortcomings of the current research in various aspects and puts forward some thoughts and suggestions for future research directions that are worth further exploration, including enriching the research objects, upgrading the experimental techniques, and introducing artificial intelligence methods. Full article

(This article belongs to the Special Issue Application of CFD Simulations to Marine Hydrodynamic Problems (2nd Edition))

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17 pages, 3603 KiB

Open AccessArticle

Implementation of a Second-Order TVD Transport Algorithm in the General Ocean Model (GOM)

by Jungwoo Lee, Jun Lee, Sang-Leen Yun and Seog-Ku Kim

J. Mar. Sci. Eng. 2025, 13(7), 1296; https://doi.org/10.3390/jmse13071296 - 30 Jun 2025

Abstract

This study presents the implementation of a scalar transport algorithm in the recently developed General Ocean Model (GOM), a three-dimensional, unstructured grid, finite volume/finite difference model. Solving the advection–diffusion transport equation is an essential part of any ocean circulation model since the baroclinic [...] Read more.

This study presents the implementation of a scalar transport algorithm in the recently developed General Ocean Model (GOM), a three-dimensional, unstructured grid, finite volume/finite difference model. Solving the advection–diffusion transport equation is an essential part of any ocean circulation model since the baroclinic density gradient distinguishes saline water from freshwater. To achieve both high accuracy and computational efficiency, we adopted a second-order semi-implicit Total Variation Diminishing (TVD) scheme. The TVD approach, known for its ability to suppress non-physical oscillations near steep gradients, provides a higher-fidelity representation of salinity fronts without introducing significant numerical artifacts. The TVD algorithm is constructed with the first-order Upwind scheme, which is known for suffering from excessive numerical diffusion, and the higher-order anti-diffusive flux term. The implemented transport algorithm is evaluated using two standard test cases, an ideal lock exchange problem and a U-shaped channel problem, and it is further applied to simulate salinity dynamics in Mobile Bay, Alabama. The model results from both the first-order Upwind and second-order TVD schemes are compared. The results indicate that the TVD scheme marginally improves the resolution of salinity fronts while maintaining computational stability and efficiency. The implementation enables a flexible and straightforward transition between the first-order scheme, which is faster than the second-order scheme, and the second-order scheme, which is less diffusive than the first-order scheme, enhancing the GOM’s capability for realistic and efficient salinity simulations in a tidally driven estuarine system. Full article

(This article belongs to the Section Coastal Engineering)

19 pages, 26179 KiB

Open AccessArticle

Pectoral Fin-Assisted Braking and Agile Turning: A Biomimetic Approach to Improve Underwater Robot Maneuverability

by Qu He, Yunpeng Zhu, Weikun Li, Weicheng Cui and Dixia Fan

J. Mar. Sci. Eng. 2025, 13(7), 1295; https://doi.org/10.3390/jmse13071295 - 30 Jun 2025

Abstract

The integration of biomimetic pectoral fins into robotic fish presents a promising approach to enhancing maneuverability, stability, and braking efficiency in underwater robotics. This study investigates a 1-DOF (degree of freedom) pectoral fin mechanism integrated into the SpineWave robotic fish. Through force measurements [...] Read more.

The integration of biomimetic pectoral fins into robotic fish presents a promising approach to enhancing maneuverability, stability, and braking efficiency in underwater robotics. This study investigates a 1-DOF (degree of freedom) pectoral fin mechanism integrated into the SpineWave robotic fish. Through force measurements and particle image velocimetry (PIV), we optimized control parameters to improve braking and turning performances. The results show a 50% reduction in stopping distance, significantly enhancing agility and control. The fin-assisted braking and turning modes enable precise movements, making this approach valuable for autonomous underwater vehicles. This research lays the groundwork for adaptive fin designs and real-time control strategies, with applications in underwater exploration, environmental monitoring, and search-and-rescue operations. Full article

(This article belongs to the Special Issue Advancements in Deep-Sea Equipment and Technology, 3rd Edition)

42 pages, 4153 KiB

Open AccessArticle

Enhanced AUV Autonomy Through Fused Energy-Optimized Path Planning and Deep Reinforcement Learning for Integrated Navigation and Dynamic Obstacle Detection

by Kaijie Zhang, Yuchen Ye, Kaihao Chen, Zao Li and Kangshun Li

J. Mar. Sci. Eng. 2025, 13(7), 1294; https://doi.org/10.3390/jmse13071294 - 30 Jun 2025

Abstract

Autonomous Underwater Vehicles (AUVs) operating in dynamic, constrained underwater environments demand sophisticated navigation and detection fusion capabilities that traditional methods often fail to provide. This paper introduces a novel hybrid framework that synergistically fuses a Multithreaded Energy-Optimized Batch Informed Trees (MEO-BIT*) algorithm with [...] Read more.

Autonomous Underwater Vehicles (AUVs) operating in dynamic, constrained underwater environments demand sophisticated navigation and detection fusion capabilities that traditional methods often fail to provide. This paper introduces a novel hybrid framework that synergistically fuses a Multithreaded Energy-Optimized Batch Informed Trees (MEO-BIT*) algorithm with Deep Q-Networks (DQN) to achieve robust AUV autonomy. The MEO-BIT* component delivers efficient global path planning through (1) a multithreaded batch sampling mechanism for rapid state-space exploration, (2) heuristic-driven search accelerated by KD-tree spatial indexing for optimized path discovery, and (3) an energy-aware cost function balancing path length and steering effort for enhanced endurance. Critically, the DQN component facilitates dynamic obstacle detection and adaptive local navigation, enabling the AUV to adjust its trajectory intelligently in real time. This integrated approach leverages the strengths of both algorithms. The global path intelligence of MEO-BIT* is dynamically informed and refined by the DQN’s learned perception. This allows the DQN to make effective decisions to avoid moving obstacles. Experimental validation in a simulated Achao waterway (Chile) demonstrates the MEO-BIT* + DQN system’s superiority, achieving a 46% reduction in collision rates (directly reflecting improved detection and avoidance fusion), a 15.7% improvement in path smoothness, and a 78.9% faster execution time compared to conventional RRT* and BIT* methods. This work presents a robust solution that effectively fuses two key components: the computational efficiency of MEO-BIT* and the adaptive capabilities of DQN. This fusion significantly advances the integration of navigation with dynamic obstacle detection. Ultimately, it enhances AUV operational performance and autonomy in complex maritime scenarios. Full article

(This article belongs to the Special Issue Navigation and Detection Fusion for Autonomous Underwater Vehicles)

44 pages, 1683 KiB

Open AccessArticle

Modeling of Energy Management System for Fully Autonomous Vessels with Hybrid Renewable Energy Systems Using Nonlinear Model Predictive Control via Grey Wolf Optimization Algorithm

by Harriet Laryea and Andrea Schiffauerova

J. Mar. Sci. Eng. 2025, 13(7), 1293; https://doi.org/10.3390/jmse13071293 - 30 Jun 2025

Abstract

This study presents a multi-objective predictive energy management system (EMS) for optimizing hybrid renewable energy systems (HRES) in autonomous marine vessels. The objective is to minimize fuel consumption and emissions while maximizing renewable energy usage and pure-electric sailing durations. The EMS combines nonlinear [...] Read more.

This study presents a multi-objective predictive energy management system (EMS) for optimizing hybrid renewable energy systems (HRES) in autonomous marine vessels. The objective is to minimize fuel consumption and emissions while maximizing renewable energy usage and pure-electric sailing durations. The EMS combines nonlinear model predictive control (NMPC) with metaheuristic optimizers—Grey Wolf Optimization (GWO) and Genetic Algorithm (GA)—and is benchmarked against a conventional rule-based (RB) method. The HRES architecture comprises photovoltaic arrays, vertical-axis wind turbines (VAWTs), diesel engines, generators, and a battery storage system. A ship dynamics model was used to represent propulsion power under realistic sea conditions. Simulations were conducted using real-world operational and environmental datasets, with state prediction enhanced by an Extended Kalman Filter (EKF). Performance is evaluated using marine-relevant indicators—fuel consumption; emissions; battery state of charge (SOC); and emission cost—and validated using standard regression metrics. The NMPC-GWO algorithm consistently outperformed both NMPC-GA and RB approaches, achieving high prediction accuracy and greater energy efficiency. These results confirm the reliability and optimization capability of predictive EMS frameworks in reducing emissions and operational costs in autonomous maritime operations. Full article

(This article belongs to the Special Issue Advancements in Hybrid Power Systems for Marine Applications)

22 pages, 8507 KiB

Open AccessArticle

Lithofacies Types and Pore Structure Characteristics of Marine Shale in the Lower Cambrian Shuijingtuo Formation, Middle Yangtze Region, China

by Jialin Fan, Wei Liu, Yujing Qian, Jinku Li, Qin Zhou and Ping Gao

J. Mar. Sci. Eng. 2025, 13(7), 1292; https://doi.org/10.3390/jmse13071292 - 30 Jun 2025

Abstract

The lithofacies and pore structural characteristics of shale reservoirs directly affect the exploration and development of shale gas. To clarify the exploration and development potential of the Lower Cambrian Shuijingtuo Formation (SJT) shale in the Middle Yangtze region, China, this study employs integrated [...] Read more.

The lithofacies and pore structural characteristics of shale reservoirs directly affect the exploration and development of shale gas. To clarify the exploration and development potential of the Lower Cambrian Shuijingtuo Formation (SJT) shale in the Middle Yangtze region, China, this study employs integrated experimental approaches, including optical and scanning electron microscopy (SEM) observations, X-ray diffraction (XRD) mineralogical analysis, and low-pressure gas (N₂/CO₂) adsorption, to classify mudstone lithofacies within the SJT and elucidate pore structural characteristics and dominant geological control across different lithofacies. The research results show that (1) Six main types of shale lithofacies are found in the STJ, including low-TOC massive calcareous mudstone (LMCM), low-TOC laminated mixed mudstone (LLMM), medium-TOC massive mixed mudstone (MMMM), high-TOC massive mixed mudstone (HMMM), high-TOC laminated siliceous mudstone (HLSM), and laminated argillaceous mudstone (LAM). (2) The pore types of SJT mudstone primarily include organic pores, intragranular clay mineral pores, and microfractures. The pore structure of mudstone is mainly controlled by clay mineral content and TOC content. However, the controlling factors of pore structure vary among different mudstone lithofacies. LMCM and LLMM are dominated by intragranular clay mineral pores, with their pore structures mainly controlled by clay mineral content. The pore types of HLMM and HLSM are organic pores, with pore structures predominantly controlled by TOC content. (3) The SJT mudstone gas reservoir exhibits diverse types, including HLSM, LAM, and LLMM. HLSM is characterized by the highest brittleness index and elevated pore volume (PV) and it can be considered the optimum lithofacies in the study area. Additionally, LLMM has the highest PV and relatively high brittleness index, positioning it as another significant reservoir target in the study area. Therefore, the Lower Cambrian shale gas reservoirs in the Middle Yangtze region exhibit diverse reservoir types. These research findings provide a scientific basis for the next phase of shale gas exploration planning in the Lower Cambrian. Full article

(This article belongs to the Section Geological Oceanography)

24 pages, 6832 KiB

Open AccessArticle

Robust Forward-Looking Sonar-Image Mosaicking Without External Sensors for Autonomous Deep-Sea Mining

by Xinran Liu, Jianmin Yang, Changyu Lu, Enhua Zhang and Wenhao Xu

J. Mar. Sci. Eng. 2025, 13(7), 1291; https://doi.org/10.3390/jmse13071291 - 30 Jun 2025

Abstract

With the increasing significance of deep-sea resource development, Forward-Looking Sonar (FLS) has become an essential technology for real-time environmental mapping and navigation in deep-sea mining vehicles (DSMV). However, FLS images often suffer from a limited field of view, uneven imaging, and complex noise [...] Read more.

With the increasing significance of deep-sea resource development, Forward-Looking Sonar (FLS) has become an essential technology for real-time environmental mapping and navigation in deep-sea mining vehicles (DSMV). However, FLS images often suffer from a limited field of view, uneven imaging, and complex noise sources, making single-frame images insufficient for providing continuous and complete environmental awareness. Existing mosaicking methods typically rely on external sensors or controlled laboratory conditions, often failing to account for the high levels of uncertainty and error inherent in real deep-sea environments. Consequently, their performance during sea trials tends to be unsatisfactory. To address these challenges, this study introduces a robust FLS image mosaicking framework that functions without additional sensor input. The framework explicitly models the noise characteristics of sonar images captured in deep-sea environments and integrates bidirectional cyclic consistency filtering with a soft-weighted feature refinement strategy during the feature-matching stage. For image fusion, a radial adaptive fusion algorithm with a protective frame is proposed to improve edge transitions and preserve structural consistency in the resulting panoramic image. The experimental results demonstrate that the proposed framework achieves high robustness and accuracy under real deep-sea conditions, effectively supporting DSMV tasks such as path planning, obstacle avoidance, and simultaneous localization and mapping (SLAM), thus enabling reliable perceptual capabilities for intelligent underwater operations. Full article

(This article belongs to the Section Geological Oceanography)

19 pages, 1274 KiB

Open AccessArticle

CFD-Based Parameter Calibration and Design of Subwater In Situ Cultivation Chambers Toward Well-Mixing Status but no Sediment Resuspension

by Liwen Zhang, Min Luo, Shanggui Gong, Zhiyang Han, Weihan Liu and Binbin Pan

J. Mar. Sci. Eng. 2025, 13(7), 1290; https://doi.org/10.3390/jmse13071290 - 30 Jun 2025

Abstract

The elemental exchange fluxes at the sediment–water interface play a crucial role in Earth's climate regulation, environmental change, and ecosystem dynamics. Accurate in situ measurements of these fluxes depend heavily on the performance of marine incubation devices, particularly their ability to achieve full [...] Read more.

The elemental exchange fluxes at the sediment–water interface play a crucial role in Earth's climate regulation, environmental change, and ecosystem dynamics. Accurate in situ measurements of these fluxes depend heavily on the performance of marine incubation devices, particularly their ability to achieve full mixing without causing sediment resuspension. This study presents a novel parameter calibration method for a marine in situ incubation device using a combination of computational fluid dynamics (CFD) simulations and laboratory experiments. The influence of the stirring paddle’s rotational speed on flow field distribution, complete mixing time, and sediment resus-pension was systematically analyzed. The CFD simulation results were validated against existing device data and actual experimental measurements. The deviation in complete mixing time between simulation and experiment was within −9.23% to 9.25% for 20 cm of sediment and −9.4% to 9.1% for 15 cm. The resuspension tests determined that optimal mixing without sediment disturbance occurs at rotational speeds of 25 r/min and 35 r/min for the two sediment depths, respectively. Further analysis showed that the stirring paddle effectively creates a uniform flow field within the chamber. This CFD-based calibration method provides a reliable approach to parameter tuning for various in situ devices by adjusting boundary conditions, offering a scientific foundation for device design and deployment, and introducing a new framework for future calibration efforts. Full article

(This article belongs to the Special Issue Application of CFD Simulations to Marine Hydrodynamic Problems (2nd Edition))

18 pages, 1457 KiB

Open AccessArticle

On Predicting Marine Engine Measurements with Synthetic Data in Scarce Dataset

by Sandi Baressi Šegota, Igor Poljak, Nikola Anđelić and Vedran Mrzljak

J. Mar. Sci. Eng. 2025, 13(7), 1289; https://doi.org/10.3390/jmse13071289 - 30 Jun 2025

Abstract

The scarcity of high-quality maritime datasets poses a significant challenge for machine learning (ML) applications in marine engineering, particularly in scenarios where real-world data collection is limited or impractical. This study investigates the effectiveness of synthetic data generation and cross-modeling in predicting operational [...] Read more.

The scarcity of high-quality maritime datasets poses a significant challenge for machine learning (ML) applications in marine engineering, particularly in scenarios where real-world data collection is limited or impractical. This study investigates the effectiveness of synthetic data generation and cross-modeling in predicting operational metrics of LNG carrier engines. A total of 38 real-world data points were collected from port and starboard engines, focusing on four target outputs: mechanical efficiency, fuel consumption, load, and effective power. CopulaGAN, a hybrid generative model combining statistical copulas and generative adversarial networks, was employed to produce synthetic datasets. These were used to train multilayer perceptron (MLP) regression models, which were optimized via grid search and validated through five-fold cross-validation. The results show that synthetic data can yield accurate models, with mean absolute percentage errors (MAPE) below 2% in most cases. The combined synthetic datasets consistently outperformed those generated from single-engine data. Cross-modeling was partially successful, as models trained on starboard data generalized well to port data but not vice versa. The engine load variable remained challenging to predict due to its narrow and low-range distribution. Overall, the study highlights synthetic data as a viable solution for enhancing the performance of ML models in data-scarce maritime applications. Full article

(This article belongs to the Section Ocean Engineering)

21 pages, 6036 KiB

Open AccessArticle

Investigation of the Asymmetric Features of X-Rudder Underwater Vehicle Vertical Maneuvring and Novel Motion Prediction Technology

by Yinghua Li, Ziying Pan, Yongcheng Li, Changyou Song, Minghui Zhang and Mengchen Ren

J. Mar. Sci. Eng. 2025, 13(7), 1288; https://doi.org/10.3390/jmse13071288 - 30 Jun 2025

Abstract

An X-rudder underwater vehicle’s hydrodynamic force acting on its rudder will display asymmetrical characteristics during vertical movement that are absent from a cross-rudder vehicle. This paper presents a novel hydrodynamic expression method based on rotational hydrodynamic transformation through a detailed analysis of the [...] Read more.

An X-rudder underwater vehicle’s hydrodynamic force acting on its rudder will display asymmetrical characteristics during vertical movement that are absent from a cross-rudder vehicle. This paper presents a novel hydrodynamic expression method based on rotational hydrodynamic transformation through a detailed analysis of the local flow characteristics around the tail attachment during the vertical plane maneuvering of the X-rudder vehicle, given that the conventional Taylor expansion-based hydrodynamic expression method is unable to characterize this asymmetric characteristic. With the help of this technique, a novel expression that can precisely describe the asymmetric hydrodynamic properties during the X-rudder vehicle’s underwater vertical plane maneuvering is created. This paper next concentrates on common vertical plane maneuvering motion situations and performs simulation predictions using both new and conventional expressions based on Taylor expansion. The asymmetric characteristics of the X-rudder underwater vehicle in vertical plane maneuvering have been experimentally confirmed, and the asymmetric characteristics become more pronounced as the speed increases, according to the results, which are compared with those of tests using self-driving models. Overall, the new model accurately describes the asymmetric features of the X-rudder vehicle’s vertical maneuvering motion and correlates well with the experimental findings. Full article

(This article belongs to the Section Ocean Engineering)

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22 pages, 2939 KiB

Open AccessArticle

Performance Evaluation of Combined Wind-Assisted Propulsion and Organic Rankine Cycle Systems in Ships

by Shibo Zhao, Kayvan Pazouki and Rosemary Norman

J. Mar. Sci. Eng. 2025, 13(7), 1287; https://doi.org/10.3390/jmse13071287 - 30 Jun 2025

Abstract

With the increasingly stringent regulation of ship carbon emissions by the International Maritime Organization (IMO), improving ship energy efficiency has become a key research direction in the current shipping industry. This paper proposes and evaluates a comprehensive energy-saving solution that integrates a wind-assisted [...] Read more.

With the increasingly stringent regulation of ship carbon emissions by the International Maritime Organization (IMO), improving ship energy efficiency has become a key research direction in the current shipping industry. This paper proposes and evaluates a comprehensive energy-saving solution that integrates a wind-assisted propulsion system (WAPS) and an organic Rankine cycle (ORC) waste heat power generation system. By establishing an energy efficiency simulation model of a typical ocean-going cargo ship, the appropriate optimal system configuration parameters and working fluids are determined based on minimizing the total fuel consumption, and the impact of these two energy-saving technologies on fuel consumption is systematically analyzed. The simulation results show that the simultaneous use of these two energy-saving technologies can achieve the highest energy efficiency, with the maximum fuel savings of approximately 21%. This study provides a theoretical basis and engineering reference for the design of ship energy-saving systems. Full article

(This article belongs to the Special Issue Ship Performance and Emission Prediction)

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20 pages, 1779 KiB

Open AccessArticle

An SWE-FEM Model with Application to Resonant Periods and Tide Components in the Western Mediterranean Sea Region

by Kostas Belibassakis and Vincent Rey

J. Mar. Sci. Eng. 2025, 13(7), 1286; https://doi.org/10.3390/jmse13071286 - 30 Jun 2025

Abstract

A FEM model of Shallow Wave Equations (SWE-FEM) is studied, taking into account the variable bathymetry of semi-enclosed sea basins. The model, with a spatially varying Coriolis term, is implemented for the description of combined refraction–diffraction effects, from which the eigenperiods and eigenmodes [...] Read more.

A FEM model of Shallow Wave Equations (SWE-FEM) is studied, taking into account the variable bathymetry of semi-enclosed sea basins. The model, with a spatially varying Coriolis term, is implemented for the description of combined refraction–diffraction effects, from which the eigenperiods and eigenmodes of extended geographical sea areas are calculated by means of a low-order FEM scheme. The model is applied to the western Mediterranean basin, illustrating its versatility to easily include the effects of geographical characteristics like islands and other coastal features. The calculated resonant frequencies and modes depend on the domain size and characteristics as well as the location of the open sea boundary, and it is shown to provide results compatible with tide measurements at several stations in the coastal region of France. The calculation of the natural oscillation modes in the western Mediterranean basin, bounded by open boundaries at the Strait of Gibraltar and the Strait of Sicily, reveals a natural period of around 6 hours corresponding to the quarter-diurnal tidal components, which are stationary and of roughly constant amplitude on the northern coast of the basin and on the west coast of Corsica (France). On the east coast of Corsica, on the other hand, these components are of very low amplitude and in phase opposition. The semi-diurnal tidal components observed on the same tide gauges north of the basin and west of Corsica are also quasi-stationary although they are not resonant. Resonant oscillations are also observed at lower periods, especially at a period of around 3 hours at the Sète station. This period corresponds to a higher-order natural mode of the western Mediterranean basin, but this resonance seems to be essentially linked to the presence of the Gulf of Lion, whose shallowness and the width of the shelf at this point induce a resonance. Other oscillations are also observed at lower periods (T = 1.5 h at station Fos-sur-Mer, T = 45 min in the Toulon harbour station), due to more local forcing. Full article

(This article belongs to the Special Issue New Developments of Ocean Wind, Wave and Tidal Energy)

21 pages, 6238 KiB

Open AccessArticle

Overtopping over Vertical Walls with Storm Walls on Steep Foreshores

by Damjan Bujak, Nino Krvavica, Goran Lončar and Dalibor Carević

J. Mar. Sci. Eng. 2025, 13(7), 1285; https://doi.org/10.3390/jmse13071285 - 30 Jun 2025

Abstract

As sea levels rise and extreme weather events become more frequent due to climate change, coastal urban areas are increasingly vulnerable to wave overtopping and flooding. Retrofitting existing vertical seawalls with retreated storm walls represents a key adaptive strategy, especially in the Mediterranean, [...] Read more.

As sea levels rise and extreme weather events become more frequent due to climate change, coastal urban areas are increasingly vulnerable to wave overtopping and flooding. Retrofitting existing vertical seawalls with retreated storm walls represents a key adaptive strategy, especially in the Mediterranean, where steep foreshores and limited public space constrain conventional coastal defenses. This study investigates the effectiveness of storm walls in reducing wave overtopping on vertical walls with steep foreshores (1:7 to 1:10) through high-fidelity numerical simulations using the SWASH model. A comprehensive parametric study, involving 450 test cases, was conducted using Latin Hypercube Sampling to explore the influence of geometric and hydrodynamic variables on overtopping rate. Model validation against Eurotop/CLASH physical data demonstrated strong agreement (r = 0.96), confirming the reliability of SWASH for such applications. Key findings indicate that longer promenades (Gc) and reduced impulsiveness of the wave conditions reduce overtopping. A new empirical reduction factor, calibrated for integration into the Eurotop overtopping equation for plain vertical walls, is proposed based on dimensionless promenade width and water depth. The modified empirical model shows strong predictive performance (r = 0.94) against SWASH-calculated overtopping rates. This work highlights the practical value of integrating storm walls into urban seawall design and offers engineers a validated tool for enhancing coastal resilience. Future research should extend the framework to other superstructure adaptations, such as parapets or stilling basins, to further improve flood protection in the face of climate change. Full article

(This article belongs to the Special Issue Climate Change Adaptation Strategies in Coastal and Ocean Engineering)

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36 pages, 8655 KiB

Open AccessArticle

A Novel Transfer Learning-Based OFDM Receiver Design for Enhanced Underwater Acoustic Communication

by Muhammad Adil, Songzuo Liu, Suleman Mazhar, Ayman Alharbi, Honglu Yan and Muhammad Muzzammil

J. Mar. Sci. Eng. 2025, 13(7), 1284; https://doi.org/10.3390/jmse13071284 - 30 Jun 2025

Abstract

The underwater acoustic (UWA) communication system faces challenges due to environmental factors, extensive multipath spread, and rapidly changing propagation conditions. Deep learning based solutions, especially for orthogonal frequency division multiplexing (OFDM) receivers, have been shown to improve performance. However, the UWA channel characteristics [...] Read more.

The underwater acoustic (UWA) communication system faces challenges due to environmental factors, extensive multipath spread, and rapidly changing propagation conditions. Deep learning based solutions, especially for orthogonal frequency division multiplexing (OFDM) receivers, have been shown to improve performance. However, the UWA channel characteristics are highly dynamic and depend on the specific underwater conditions. Therefore, these models suffer from model mismatch when deployed in environments different from those used for training, leading to performance degradation and requiring costly, time-consuming retraining. To address these issues, we propose a transfer learning (TL)-based pre-trained model for OFDM based UWA communication. Rather than training separate models for each underwater channel, we aggregate received signals from five distinct WATERMARK channels, across varying signal to noise ratios (SNRs), into a unified dataset. This diverse training set enables the model to generalize across various underwater conditions, ensuring robust performance without extensive retraining. We evaluate the pre-trained model using real-world data from Qingdao Lake in Hangzhou, China, which serves as the target environment. Our experiments show that the model adapts well to these challenging environment, overcoming model mismatch and minimizing computational costs. The proposed TL-based OFDM receiver outperforms traditional methods in terms of bit error rate (BER) and other evaluation metrics. It demonstrates strong adaptability to varying channel conditions. This includes scenarios where training and testing occur on the same channel, under channel mismatch, and with or without fine-tuning on target data. At 10 dB SNR, it achieves an approximately 80% improvement in BER compared to other methods. Full article

(This article belongs to the Special Issue Advances in Underwater Acoustic Communication and Ocean Sensor Networks)

22 pages, 1265 KiB

Open AccessArticle

Novel Hybrid Aquatic–Aerial Vehicle to Survey in High Sea States: Initial Flow Dynamics on Dive and Breach

by Matthew J. Ericksen, Keith F. Joiner, Nicholas J. Lawson, Andrew Truslove, Georgia Warren, Jisheng Zhao and Ahmed Swidan

J. Mar. Sci. Eng. 2025, 13(7), 1283; https://doi.org/10.3390/jmse13071283 - 30 Jun 2025

Abstract

Few studies have examined Hybrid Aquatic–Aerial Vehicles (HAAVs), autonomous vehicles designed to operate in both air and water, especially those that are aircraft-launched and recovered, with a variable-sweep design to free dive into a body of water and breach under buoyant and propulsive [...] Read more.

Few studies have examined Hybrid Aquatic–Aerial Vehicles (HAAVs), autonomous vehicles designed to operate in both air and water, especially those that are aircraft-launched and recovered, with a variable-sweep design to free dive into a body of water and breach under buoyant and propulsive force to re-achieve flight. The novel design research examines the viability of a recoverable sonar-search child aircraft for maritime patrol, one which can overcome the prohibitive sea state limitations of all current HAAV designs in the research literature. This paper reports on the analysis from computational fluid dynamic (CFD) simulations of such an HAAV diving into static seawater at low speeds due to the reverse thrust of two retractable electric-ducted fans (EDFs) and its subsequent breach back into flight initially using a fast buoyancy engine developed for deep-sea research vessels. The HAAV model entered the water column at speeds around 10 ms⁻¹ and exited at 5 ms⁻¹ under various buoyancy cases, normal to the surface. Results revealed that impact force magnitudes varied with entry speed and were more acute according to vehicle mass, while a sufficient portion of the fuselage was able to clear typical wave heights during its breach for its EDF propulsors and wings to protract unhindered. Examining the medium transition dynamics of such a novel HAAV has provided insight into the structural, propulsive, buoyancy, and control requirements for future conceptual design iterations. Research is now focused on validating these unperturbed CFD dive and breach cases with pool experiments before then parametrically and numerically examining the effects of realistic ocean sea states. Full article

(This article belongs to the Section Ocean Engineering)

23 pages, 20593 KiB

Open AccessArticle

Comparative Research on Vessel Navigability on the Northern Sea Route Based on the NSR Admission Criteria and POLARIS Methodology

by Long Ma, Sihan Qian, Xiaoguang Mou, Jiemin Fan, Jin Xu, Liang Cao, Bo Xu, Boxi Yao, Xiaowen Li and Yabin Li

J. Mar. Sci. Eng. 2025, 13(7), 1282; https://doi.org/10.3390/jmse13071282 - 30 Jun 2025

Abstract

At present, sea ice remains a critical factor affecting the safety of vessel operations along the Northern Sea Route (NSR). However, inconsistencies between the navigability outcomes derived from the criteria for the admission of ships in the area of the Northern Sea Route [...] Read more.

At present, sea ice remains a critical factor affecting the safety of vessel operations along the Northern Sea Route (NSR). However, inconsistencies between the navigability outcomes derived from the criteria for the admission of ships in the area of the Northern Sea Route (NSR criteria) and the polar operational limit assessment risk indexing system (POLARIS) methodology present challenges for navigational decision-making. This study aims to conduct a systematic comparison of the POLARIS methodology and the NSR criteria in evaluating the navigability of independently operating vessels classified as Arc4 to Arc9. Through comparative calculations of navigability and the navigability rates for six ice-class vessels across 27 districts using the two methods, this study reveals the consistencies and discrepancies in their navigability outcomes. Firstly, using the POLARIS methodology, the risk index outcome (RIO) is calculated for six ice-class vessels across 27 districts. For these districts, the navigability threshold is defined when 95% or more of the area exhibits an RIO greater than or equal to zero. Secondly, using the NSR criteria, navigability ratios for six ice-class vessels under varying ice conditions are evaluated. A navigability threshold is defined when 95% or more of the ice conditions in a district are classified as navigable. Finally, a quantitative comparison of the weekly navigability ratios obtained by the two methods is conducted to reveal the consistencies and discrepancies in the navigability outcomes of each ice-class vessel across different NSR districts. The results indicate that the consistency between the navigability outcomes of the two methods decreases with lower vessel ice classes, particularly in September and March. In general, the consistency of performance between the two methods in terms of navigability outcomes deteriorates as the vessel ice class decreases and ice conditions become more complex. This study provides a scientific foundation and data-based support for route planning and real-time decision-making in polar waters. Full article

(This article belongs to the Special Issue Navigation Performance and Experimental Research of Ships in Ice-Covered Areas)

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26 pages, 1509 KiB

Open AccessArticle

Vortex-Induced Vibration Analysis of FRP Composite Risers Using Multivariate Nonlinear Regression

by Lin Zhang, Chunguang Wang, Wentao He, Keshun Ma, Run Zheng, Chiemela Victor Amaechi and Zhenyang Zhang

J. Mar. Sci. Eng. 2025, 13(7), 1281; https://doi.org/10.3390/jmse13071281 - 30 Jun 2025

Abstract

Marine risers are essential for offshore resource extraction, yet traditional metal risers encounter limitations in deep-sea applications due to their substantial weight. Fiber-reinforced polymer (FRP) composites offer a promising alternative with advantages including low density and enhanced corrosion/fatigue resistance. However, FRP risers remain [...] Read more.

Marine risers are essential for offshore resource extraction, yet traditional metal risers encounter limitations in deep-sea applications due to their substantial weight. Fiber-reinforced polymer (FRP) composites offer a promising alternative with advantages including low density and enhanced corrosion/fatigue resistance. However, FRP risers remain susceptible to fatigue damage from vortex-induced vibration (VIV). Therefore, this study investigated VIV behavior of FRP composite risers considering the coupled effect of tensile-flexural moduli, top tensions, slenderness ratios, and flow velocities. Through an orthogonal experimental design, eighteen cases were analyzed using multivariate nonlinear fitting. Results indicated that FRP composite risers exhibited larger vibration amplitudes than metal counterparts, with amplitudes increasing to both riser length and flow velocity. It was also found that the optimized FRP configuration demonstrated enhanced fiber strength utilization. Parameter coupling analysis revealed that the multivariate nonlinear fitting model achieved sufficient accuracy when incorporating two coupled parameters, with the most significant interaction occurring between flexural modulus and top tension. Full article

(This article belongs to the Section Ocean Engineering)

25 pages, 4027 KiB

Open AccessArticle

Sea Surface Temperature Fronts and North Atlantic Right Whale Sightings in the Western Gulf of St. Lawrence

by Jing Tao, Hui Shen, Richard E. Danielson and William Perrie

J. Mar. Sci. Eng. 2025, 13(7), 1280; https://doi.org/10.3390/jmse13071280 - 30 Jun 2025

Abstract

Sea surface temperature (SST) fronts during 2000–2021 are examined in the Western Gulf of St. Lawrence (wGSL), where North Atlantic right whales (NARW, Eubalaena glacialis) have begun to aggregate and feed. During 2017–2020, from May to October, NARW spatial distributions reveal regional, [...] Read more.

Sea surface temperature (SST) fronts during 2000–2021 are examined in the Western Gulf of St. Lawrence (wGSL), where North Atlantic right whales (NARW, Eubalaena glacialis) have begun to aggregate and feed. During 2017–2020, from May to October, NARW spatial distributions reveal regional, seasonal, and interannual variations in the Shediac Valley and off the Northern Gaspé Peninsula, and preferentially in waters with relatively strong temperature gradients. Correspondence between SST fronts and NARW sightings is explored using a monthly probability of occurrence, based on an SST gradient threshold and water depths in the range 50–200 m. Spring and summer associations suggest that satellite-derived SST gradients may aid in short-timescale NARW monitoring by way of providing spatial distribution maps of the regional probability of occurrence. Full article

(This article belongs to the Special Issue Marine Modelling and Environmental Statistics in Honor of Professor Keith Thompson)

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27 pages, 7468 KiB

Open AccessArticle

Delamination-Driven Nonlinear Buckling of Metal–Composite Cylindrical Shells with Different Interfacial Strengths

by Chenyang Di, Yunsen Hu, Huifeng Jiao, Sakdirat Kaewunruen and Jian Zhang

J. Mar. Sci. Eng. 2025, 13(7), 1279; https://doi.org/10.3390/jmse13071279 - 30 Jun 2025

Abstract

This study delves into the delamination-driven nonlinear buckling characteristics of metal–composite cylindrical shells with different interfacial strengths. Although surface treatments are known to affect bonding performance, their specific influences on the delamination buckling behavior of metal–composite cylindrical shells remain underexplored. Accordingly, sandblasting and [...] Read more.

This study delves into the delamination-driven nonlinear buckling characteristics of metal–composite cylindrical shells with different interfacial strengths. Although surface treatments are known to affect bonding performance, their specific influences on the delamination buckling behavior of metal–composite cylindrical shells remain underexplored. Accordingly, sandblasting and polishing processes were employed to the fabrication of single-lap shear specimens. The topography of the treated surface was then characterized through scanning electron microscopy, optical profilometry, and contact angle measurements. For topography characterization and performance tests, sandblasted and polished metal–composite cylindrical shells were fabricated for hydrostatic tests. A cohesive zone model was used to analyze the influences of interfacial strength on the nonlinear buckling characteristics of metal–composite cylindrical shells, and the modeling results were validated by benchmarking them with experimental results. Subsequently, a detailed parametric study was conducted to investigate the effects of cohesive zone parameters and geometric imperfection on the load-bearing capacity of the shells. The new findings reveal that among the fabricated steel specimens, the specimens subjected to 80-mesh sandblasting exhibited the highest bond strength in single-lap shear tests, with the bond strength being 2.56 times higher than that of polished specimens. Moreover, sandblasted metal–composite cylindrical shells exhibited a 55.0% higher average collapse load than that of polished metal–composite cylindrical shells. Full article

(This article belongs to the Section Ocean Engineering)

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