Journal of Marine Science and Engineering

26 pages, 5622 KiB

Open AccessArticle

Life Cycle Assessment and Experimental Mechanical Investigation of Test Samples for High-Performance Racing Boats

by Marcello Raffaele, Pasqualino Corigliano, Filippo Cucinotta, Giulia Palomba and Fabio Salmeri

J. Mar. Sci. Eng. 2024, 12(11), 2028; https://doi.org/10.3390/jmse12112028 (registering DOI) - 9 Nov 2024

Abstract

This paper investigates the environmental impact and mechanical performance of two composite sandwich structures, named Series 1 and Series 2, used in high-performance racing boats. Mechanical tests, including four-point bending and drop impact tests, were performed. It was found on a general basis [...] Read more.

This paper investigates the environmental impact and mechanical performance of two composite sandwich structures, named Series 1 and Series 2, used in high-performance racing boats. Mechanical tests, including four-point bending and drop impact tests, were performed. It was found on a general basis that Series 2 has higher load-bearing capacity and limited deflection. Series 1, which has a higher density, was able to absorb more impact energy but was more susceptible to damage. A Life Cycle Assessment (LCA) was conducted to evaluate the environmental impact associated with the materials, considering also the testing phase, which plays an important role in the life cycle of materials and structures for advanced marine applications. In addition, two performance indexes were introduced to correlate the mechanical and environmental properties of the analyzed materials. This study emphasizes the importance of considering the testing phase in LCA, as the energy-intensive nature of mechanical testing contributes significantly to the overall environmental impact. The introduced indexes allow for a more comprehensive understanding of the balance between mechanical performance and environmental sustainability. The findings suggest a trade-off between mechanical performance and sustainability, calling for further research into recyclable composites and greener manufacturing processes to balance these competing priorities. Full article

(This article belongs to the Special Issue Design and Analysis of New and Retrofitted Eco-Friendly Ships and Offshore Structures)

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18 pages, 8141 KiB

Open AccessArticle

Cold Intermediate Water Formation in the Black Sea Triggered by March 2022 Cold Intrusions

by Tülay Çokacar

J. Mar. Sci. Eng. 2024, 12(11), 2027; https://doi.org/10.3390/jmse12112027 (registering DOI) - 9 Nov 2024

Abstract

In mid-March 2022, a Siberian High brought intense cold air masses, leading to severe weather conditions across southern Europe, including the Black Sea region. This study investigates the spatial and temporal evolution of cold intermediate water (CIW) masses in the Black Sea, with [...] Read more.

In mid-March 2022, a Siberian High brought intense cold air masses, leading to severe weather conditions across southern Europe, including the Black Sea region. This study investigates the spatial and temporal evolution of cold intermediate water (CIW) masses in the Black Sea, with a particular focus on the successive anomalously cold episodes that occurred in March 2022. The research underscores the significance of the northwestern continental slope and cyclonic gyres, especially as the only cold-water mass observations during the warm winters of 2020 and 2021 were concentrated in these areas. Following two warm winters, the cold episodes of March 2022 revealed notable convection and simultaneous cooling, particularly in the cyclonic interior and the Rim Current periphery, excluding the northeastern periphery. Subsequently, cold waters spreading isopycnally throughout the summer months were transported laterally and reached these regions. Argo float measurements provided clear evidence of widespread replenishment of the CIW, indicating that it is not confined to specific areas. The study also highlights regional variability in the characteristics of CIW formation, which is influenced by local dynamics and preconditioning temperatures. The temperatures of CIW increased from west to east, in line with the sea surface temperature gradient. Notably, thicker and colder CIW was found in the western cyclonic gyre compared to the eastern cyclonic area. Furthermore, the study confirms that the warming trend in CIW, identified in previous research, not only continues but has intensified during the recent period analyzed. These findings, observed under the extreme conditions analyzed in this research, offer valuable insights into the widespread occurrence of CIW formation in the Black Sea. Additionally, the study confirms that the warming trend in CIW, identified in previous studies, continued in the region throughout the warm winter period and after the cold spell in 2022. These insights contribute to a deeper understanding of CIW dynamics and their response to extreme weather events in the Black Sea. Full article

(This article belongs to the Section Physical Oceanography)

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29 pages, 1771 KiB

Open AccessArticle

Environmental and Cost Assessments of Marine Alternative Fuels for Fully Autonomous Short-Sea Shipping Vessels Based on the Global Warming Potential Approach

by Harriet Laryea and Andrea Schiffauerova

J. Mar. Sci. Eng. 2024, 12(11), 2026; https://doi.org/10.3390/jmse12112026 (registering DOI) - 9 Nov 2024

Abstract

This research paper presents an effective approach to reducing marine pollution and costs by determining the optimal marine alternative fuels framework for short-sea shipping vessels, with a focus on energy efficiency. Employing mathematical models in a Python environment, the analyses are tailored specifically [...] Read more.

This research paper presents an effective approach to reducing marine pollution and costs by determining the optimal marine alternative fuels framework for short-sea shipping vessels, with a focus on energy efficiency. Employing mathematical models in a Python environment, the analyses are tailored specifically for conventional and fully autonomous high-speed passenger ferries (HSPFs) and tugboats, utilizing bottom-up methodologies, ship operating phases, and the global warming potential approach. The study aims to identify the optimal marine fuel that offers the highest Net Present Value (NPV) and minimal emissions, aligning with International Maritime Organization (IMO) regulations and environmental objectives. Data from the ship’s Automatic Identification System (AIS), along with specifications and port information, were integrated to assess power, energy, and fuel consumption, incorporating parameters of proposed marine alternative fuels. This study examines key performance indicators (KPIs) for marine alternative fuels used in both conventional and autonomous vessels, specifically analyzing total mass emission rate (TMER), total global warming potential (TGWP), total environmental impact (TEI), total environmental damage cost (TEDC), and NPV. The results show that hydrogen (H2-Ren, H2-F) fuels and electric options produce zero emissions, while traditional fuels like HFO and MDO exhibit the highest TMER. Sensitivity and stochastic analyses identify critical input variables affecting NPV, such as fuel costs, emission costs, and vessel speed. Findings indicate that LNG consistently yields the highest NPV, particularly for autonomous vessels, suggesting economic advantages and reduced emissions. These insights are crucial for optimizing fuel selection and operational strategies in marine transportation and offer valuable guidance for decision-making and investment in the marine sector, ensuring regulatory compliance and environmental sustainability. Full article

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

19 pages, 5079 KiB

Open AccessArticle

Predefined-Time Hybrid Tracking Control for Dynamic Positioning Vessels Based on Fully Actuated Approach

by Yujie Xu, Yingjie Wang, Mingyu Fu and Hao Chen

J. Mar. Sci. Eng. 2024, 12(11), 2025; https://doi.org/10.3390/jmse12112025 (registering DOI) - 9 Nov 2024

Abstract

This study investigates the problem of tracking the trajectory of a dynamic positioning (DP) ship under sudden surges of elevated sea states. First, the tracking problem is reformulated as an error calibration problem through the introduction of fully actuated system (FAS) approaches, thereby [...] Read more.

This study investigates the problem of tracking the trajectory of a dynamic positioning (DP) ship under sudden surges of elevated sea states. First, the tracking problem is reformulated as an error calibration problem through the introduction of fully actuated system (FAS) approaches, thereby simplifying controller design. Second, a predefined-time control term is designed to maintain the convergence time of the trajectory tracking error within a specified range; however, the upper bound of the perturbation must be estimated in advance. The high sea state during operation can result in an abrupt change in the upper bound of disturbance, thereby affecting the control accuracy and stability of the system. Therefore, a linear control matrix is developed to eliminate the system’s dependence on the estimation of the upper bound of disturbance following smooth switching, thereby achieving control decoupling and providing a conservative switching time. Additionally, a nonlinear reduced-order expansion observer (RESO) is constructed for feedforward compensation. The stability of the system is demonstrated using the Lyapunov function, indicating that the selection of appropriate poles can theoretically enhance the system’s convergence with greater control accuracy and robustness after switching. Finally, the effectiveness of the proposed method is validated through simulations and comparative experiments. Full article

(This article belongs to the Section Ocean Engineering)

18 pages, 9761 KiB

Open AccessArticle

Study on the Hydrodynamics of a Cownose Ray’s Flapping Pectoral Fin Model near the Ground

by Yang Luo, Zhexing Hou, Dongyang Chen, Tongshi Xu, Qiaogao Huang, Pengcheng Ye and Guang Pan

J. Mar. Sci. Eng. 2024, 12(11), 2024; https://doi.org/10.3390/jmse12112024 (registering DOI) - 9 Nov 2024

Abstract

Cownose rays typically swim close to the ocean floor, and the nearby substrate inevitably influences their swimming performance. In this research, we numerically investigate the propulsive capability of cownose rays swimming near the ground by resolving three-dimensional viscous unsteady Navier–Stokes equations. The ground [...] Read more.

Cownose rays typically swim close to the ocean floor, and the nearby substrate inevitably influences their swimming performance. In this research, we numerically investigate the propulsive capability of cownose rays swimming near the ground by resolving three-dimensional viscous unsteady Navier–Stokes equations. The ground effect generally has a favorable impact on swimming. The thrust and lift increase as the near-substrate distance decreases. Nevertheless, a body length is the recommended distance from the ground, at which the flapping efficiency and swimming stability obtain a good trade-off. The increase in lift is due to the pressure difference between the dorsal and ventral surfaces of the ray, and the thrust boost is due to the enhanced shear vortex at the fin’s leading edge when swimming near the substrate. Our results indicate that the ground effect is more noticeable when the fin flaps are symmetrical compared to asymmetrical. In asymmetric flapping, the hydrodynamic performance improves at a smaller value than the half-amplitude ratio (HAR). The frequency of flapping also significantly affects swimming performance. We find that a superior flapping frequency, at which maximum efficiency is reached, occurs when flapping close to the substrate, and this superior frequency is consistent with the behavior of our model’s biological counterpart. Full article

(This article belongs to the Section Ocean Engineering)

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18 pages, 6115 KiB

Open AccessArticle

TDOF PID Controller for Enhanced Disturbance Rejection with MS-Constraints for Speed Control of Marine Diesel Engine

by Gun-Baek So, Gang-Gyoo Jin, Chan-Ha Lee, Hye-Rim So, Dae-Jeong Kim and Jong-Kap Ahn

J. Mar. Sci. Eng. 2024, 12(11), 2023; https://doi.org/10.3390/jmse12112023 (registering DOI) - 9 Nov 2024

Abstract

This study proposes a two-degree-of-freedom PID controller design and tuning method based on a simple pole placement approach to enhance servo and regulatory performance while ensuring the stability of diesel engines. In the modeling of the control target, the actuator is analytically modeled. [...] Read more.

This study proposes a two-degree-of-freedom PID controller design and tuning method based on a simple pole placement approach to enhance servo and regulatory performance while ensuring the stability of diesel engines. In the modeling of the control target, the actuator is analytically modeled. In contrast, the type of model for the diesel engine is derived analytically, and its parameter estimation uses operational data from naval ships. The proposed controller consists of a PID controller to improve regulatory performance and a set-point filter to enhance servo response. PID controller parameters consist of the parameters of the controlled plant model and a single tuning variable. At the same time, the set-point filter comprises the controller parameters and a single weighting factor. To ensure the robust stability of the controller, the controller parameters are tuned based on the maximum sensitivity. To verify the effectiveness of this study, simulations for the speed control of a diesel engine with inherent nonlinearity were conducted under three scenarios. Performance was quantitatively analyzed using the integral of time-weighted absolute error, 2% settling time, 2% recovery time, specified maximum sensitivity, and maximum peak response value, and was compared with Skogestad’s IMC and Lee’s IMC. Based on evaluation indices, the proposed controller demonstrated superior performance in both servo and regulatory responses compared to the two existing control techniques while ensuring stability. Full article

(This article belongs to the Section Ocean Engineering)

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21 pages, 589 KiB

Open AccessArticle

The Study of Risk Assessment Method for Ship Berthing Based on the “Human-Ship-Environment” Synergy

by Chunxu Li, Jun Zhao, Gege Ding, Ke Zhang, Wantong Li, Yabin Li, Yanjuan Wang and Jie Wen

J. Mar. Sci. Eng. 2024, 12(11), 2022; https://doi.org/10.3390/jmse12112022 (registering DOI) - 9 Nov 2024

Abstract

Berthing is one of the most dangerous phases in the process of ship navigation, and its risk assessment is crucial for both ship safety and port scheduling. To effectively enhance the safety and reliability of the berthing process, a berthing risk assessment method [...] Read more.

Berthing is one of the most dangerous phases in the process of ship navigation, and its risk assessment is crucial for both ship safety and port scheduling. To effectively enhance the safety and reliability of the berthing process, a berthing risk assessment method based on the synergy of “human-ship-environment” has been established. First, the impact of the human, ship, and environmental factors on berthing risk was analyzed, and a risk assessment index system for ship berthing was constructed. Then, the analytic hierarchy process (AHP) and fuzzy comprehensive evaluation (FCE) methods were employed for a comprehensive risk assessment. AHP was used to determine the weight of each factor reasonably, while FCE was applied for the evaluation of the berthing risk. Finally, the proposed method was applied to evaluate the berthing operations of two ships, namely the KCS ship type and the S-175 large passenger ship type, at the Qingdao Intelligent Ship Testing Field, China. The experiment’s results indicate that the evaluation results of the method proposed here have good consistency with the expert survey method. Full article

(This article belongs to the Section Coastal Engineering)

19 pages, 4106 KiB

Open AccessArticle

Design and Computational Modelling of AUV Tunnel Thruster Covers for Efficient Operation

by Christopher McNeill, Zachary Cooper-Baldock and Karl Sammut

J. Mar. Sci. Eng. 2024, 12(11), 2021; https://doi.org/10.3390/jmse12112021 (registering DOI) - 9 Nov 2024

Abstract

Autonomous underwater vehicles have seen widespread adoption across industrial, scientific, and defence applications. They are typically utilized to perform oceanic mapping, surveillance, and inspection-type missions. Hovering AUVs, used for inspection applications, are over-actuated vehicles incorporating multiple thrusters to enable multiple degrees of freedom [...] Read more.

Autonomous underwater vehicles have seen widespread adoption across industrial, scientific, and defence applications. They are typically utilized to perform oceanic mapping, surveillance, and inspection-type missions. Hovering AUVs, used for inspection applications, are over-actuated vehicles incorporating multiple thrusters to enable multiple degrees of freedom control at a low velocity. These vehicles, however, are extremely energy-limited, owing to their restrictive structural design that prohibits large batteries. This necessitates careful hydrodynamic design to best utilize this limited energy storage. Of particular importance are the hydrodynamic propulsion efficiencies of these vehicles. Whilst the external structure of AUV platforms is relatively well-defined and hydrodynamically optimized, one area has seen limited focus and optimization. This is the immediate surroundings of the propulsion geometry and housing. In this body of work, we propose an adaptation to the traditional through-body tunnel thruster geometry of an over-actuated AUV platform. The modification is the inclusion of a retractable internal thruster cover. Subsequently, a comparison is provided between a clean-hull AUV configuration, one with open through-body thrusters, and one fitted with the designed cover geometry. A comprehensive computational fluid dynamics analysis is then converged and assessed using the Reynolds-Averaged Navier–Stokes equations. The drag and local flow fields are determined, where the covers are found to reduce the drag coefficient and total drag of the AUV by 9.51%, primarily due to a reduction of 9.91% in the pressure drag. These findings highlight the increased operational efficiency of the cover geometry and support the adoption of such covers for energy-constrained AUVs. Full article

(This article belongs to the Special Issue Maritime Efficiency and Energy Transition)

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22 pages, 15112 KiB

Open AccessArticle

Evidence of 2024 Summer as the Warmest During the Last Four Decades in the Aegean, Ionian, and Cretan Seas

by Yannis Androulidakis, Vassilis Kolovoyiannis, Christos Makris and Yannis Krestenitis

J. Mar. Sci. Eng. 2024, 12(11), 2020; https://doi.org/10.3390/jmse12112020 (registering DOI) - 9 Nov 2024

Abstract

The summer of 2024 witnessed record-high sea surface temperatures (SST) across the Aegean, Ionian, and Cretan Seas (AICS), following unprecedented air heatwaves over the sea under a long-term warming trend of 0.46 °C/decade for the mean atmospheric temperature (1982–2024). The respective mean SST [...] Read more.

The summer of 2024 witnessed record-high sea surface temperatures (SST) across the Aegean, Ionian, and Cretan Seas (AICS), following unprecedented air heatwaves over the sea under a long-term warming trend of 0.46 °C/decade for the mean atmospheric temperature (1982–2024). The respective mean SST trend for the same period is even steeper, increasing by 0.59 °C/decade. With mean summer surface waters surpassing 28 °C, particularly in the Ionian Sea, the southern Cretan, and northern Aegean basins, this summer marked the warmest ocean conditions over the past four decades. Despite a relatively lower number of marine heatwaves (MHWs) compared to previous warm years, the duration and cumulative intensity of these events in 2024 were the highest on record, reaching nearly twice the levels seen in 2018, which was the warmest until now. Intense MHWs were recorded, especially in the northern Aegean, with extensive biological consequences to ecosystems like the Thermaikos Gulf, a recognized MHW hotspot. The strong downward atmospheric heat fluxes in the summer of 2024, following an interannual increasing four-decade trend, contributed to the extreme warming of the water masses together with other met-ocean conditions such as lateral exchanges and vertical processes. The high temperatures were not limited to the surface but extended to depths of 50 m in some regions, indicating a deep and widespread warming of the upper ocean. Mechanisms typically mitigating SST rises, such as the Black Sea water (BSW) inflow and coastal upwelling over the eastern Aegean Sea, were weaker in 2024. Cooler water influx from the BSW decreased, as indicated by satellite-derived chlorophyll-a concentrations, while upwelled waters from depths of 40 to 80 m at certain areas showed elevated temperatures, likely limiting their cooling effects on the surface. Prolonged warming of ocean waters in a semi-enclosed basin such as the Mediterranean and its marginal sea sub-basins can have substantial physical, biological, and socioeconomic impacts on the AICS. This research highlights the urgent need for targeted monitoring and mitigation strategies to address the growing impact of MHWs in the region. Full article

(This article belongs to the Section Physical Oceanography)

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33 pages, 7303 KiB

Open AccessArticle

A Comparison of the Capture Width and Interaction Factors of WEC Arrays That Are Co-Located with Semi-Submersible-, Spar- and Barge-Supported Floating Offshore Wind Turbines

by Zhi Yung Tay, Nyan Lin Htoo and Dimitrios Konovessis

J. Mar. Sci. Eng. 2024, 12(11), 2019; https://doi.org/10.3390/jmse12112019 (registering DOI) - 8 Nov 2024

Abstract

This research paper explores an approach to enhancing the economic viability of the heaving wave energy converters (WECs) of both cylinder-shaped and torus-shaped devices, by integrating them with four established, floating offshore wind turbines (FOWTs). Specifically, the approach focused on the wave power [...] Read more.

This research paper explores an approach to enhancing the economic viability of the heaving wave energy converters (WECs) of both cylinder-shaped and torus-shaped devices, by integrating them with four established, floating offshore wind turbines (FOWTs). Specifically, the approach focused on the wave power performance matrix. This integration of WECs and FOWTs not only offers the potential for shared construction and maintenance costs but also presents synergistic advantages in terms of power generation and platform stability. The study began by conducting a comprehensive review of the current State-of-the-Art in co-locating different types of WECs with various foundation platforms for FOWTs, taking into consideration the semi-submersible, spar and barge platforms commonly employed in the offshore wind industry. The research took a unified approach to investigate more and new WEC arrays, totaling 20 configurations across four distinct FOWTs. The scope of this study’s assumption primarily focused on the hydrodynamic wave power performance matrix, without the inclusion of aerodynamic loads. It then compared their outcomes to determine which array demonstrated superior wave energy under the key metrics of total absorbed power, capture width, and interaction factor. Additionally, the investigation could serve to reinforce the ongoing research and development efforts in the allocation of renewable energy resources. Full article

(This article belongs to the Special Issue Advances in the Performance of Ships and Offshore Structures)

35 pages, 3283 KiB

Open AccessArticle

An ADCP Attitude Dynamic Errors Correction Method Based on Angular Velocity Tensor and Radius Vector Estimation

by Zhaowen Sun, Shuai Yao, Ning Gao and Ke Zhang

J. Mar. Sci. Eng. 2024, 12(11), 2018; https://doi.org/10.3390/jmse12112018 (registering DOI) - 8 Nov 2024

Abstract

An acoustic Doppler current profiler (ADCP) installed on a platform produces rotational tangential velocity as a result of variations in the platform’s attitude, with both the tangential velocity and radial orientation varying between each pulse’s transmission and reception by the transducer. These factors [...] Read more.

An acoustic Doppler current profiler (ADCP) installed on a platform produces rotational tangential velocity as a result of variations in the platform’s attitude, with both the tangential velocity and radial orientation varying between each pulse’s transmission and reception by the transducer. These factors introduce errors into the measurements of vessel velocity and flow velocity. In this study, we address the errors induced by dynamic factors related to variations in attitude and propose an ADCP attitude dynamic error correction method based on angular velocity tensor and radius vector estimation. This method utilizes a low-sampling-rate inclinometer and compass data and estimates the angular velocity tensor based on a physical model of vessel motion combined with nonlinear least-squares estimation. The angular velocity tensor is then used to estimate the transducers’ radius vectors. Finally, the radius vectors are employed to correct the instantaneous tangential velocity within the measured velocities of the vessel and flow. To verify the effectiveness of the proposed method, field tests were conducted in a water pool. The results demonstrate that the proposed method surpasses the attitude static correction approach. In comparison with the ASC method, the average relative error in vessel velocity during free-swaying movement decreased by 20.94%, while the relative standard deviation of the error was reduced by 17.38%. Full article

(This article belongs to the Section Ocean Engineering)

10 pages, 279 KiB

Open AccessEditorial

Natural and Human Impacts on Coastal Areas

by Francisco Asensio-Montesinos, Rosa Molina, Giorgio Anfuso, Giorgio Manno and Carlo Lo Re

J. Mar. Sci. Eng. 2024, 12(11), 2017; https://doi.org/10.3390/jmse12112017 (registering DOI) - 8 Nov 2024

Abstract

Coasts are the most densely populated regions in the world and are vulnerable to different natural and human factors, e.g., sea-level rise, coastal accretion and erosion processes, the intensification of sea storms and hurricanes, the presence of marine litter, chronic pollution and beach [...] Read more.

Coasts are the most densely populated regions in the world and are vulnerable to different natural and human factors, e.g., sea-level rise, coastal accretion and erosion processes, the intensification of sea storms and hurricanes, the presence of marine litter, chronic pollution and beach oil spill accidents, etc. Although coastal zones have been affected by local anthropic activities for decades, their impacts on coastal ecosystems is often unclear. Several papers are presented in this Special Issue detailing the interactions between natural processes and human impacts in coastal ecosystems all around the world. A better understanding of such natural and human impacts is therefore of great relevance to confidently predict their negative effects on coastal areas and thus promote different conservation strategies. The implementation of adequate management measures will help coastal communities adapt to future scenarios in the short and long term and prevent damage due to different pollution types, e.g., beach oil spill accidents, through the establishment of Environmental Sensitivity Maps. Full article

(This article belongs to the Special Issue Natural and Human Impacts in Coastal Areas)

16 pages, 1926 KiB

Open AccessArticle

TLR2/TLR5 Signaling and Gut Microbiota Mediate Soybean-Meal-Induced Enteritis and Declined Growth and Antioxidant Capabilities in Large Yellow Croaker (Larimichthys crocea)

by Lei Zheng, Chao Zeng, Wanqin Zhu, Jiaonan Zhang, Lei Wang, Jianchun Shao and Wei Zhao

J. Mar. Sci. Eng. 2024, 12(11), 2016; https://doi.org/10.3390/jmse12112016 (registering DOI) - 8 Nov 2024

Abstract

Soybean meal, renowned for its high yield, cost efficiency, and protein richness, serves as a pivotal plant-based alternative to fish meal. However, high soybean meal inclusion in Larimichthys crocea diets is linked to enteritis and oxidative damage, with unknown mechanisms. Our study aims [...] Read more.

Soybean meal, renowned for its high yield, cost efficiency, and protein richness, serves as a pivotal plant-based alternative to fish meal. However, high soybean meal inclusion in Larimichthys crocea diets is linked to enteritis and oxidative damage, with unknown mechanisms. Our study aims to elucidate the molecular basis of soybean-meal-induced enteritis and its impact on intestinal microbiota in L. crocea. To this end, four isonitrogenous and isolipidic diets with varying soybean meal levels (0% FM, 15% SBM15, 30% SBM30, and 45% SBM45) were administered to L. crocea for 8 weeks. The results indicated that the SBM30 and SBM45 treatments significantly hindered fish growth, digestive efficiency, and protein utilization. Furthermore, high soybean meal levels (SBM30 and SBM45) activated intestinal Toll-like receptors (TLR2A, TLR2B, TLR5, and TLR22), stimulating C-Rel and mTOR protein expression and elevating ERK phosphorylation. This led to increased pro-inflammatory cytokine production (IL-1β, IL-6, and TNF-α) and decreased anti-inflammatory cytokine expression (IL-4/13A, IL-4/13B, and TGF-β), suggesting a potential signaling pathway for soybean-meal-induced enteritis. Furthermore, enteritis induced by high soybean meal levels led to oxidative damage, evident from increased MDA levels and decreased antioxidant enzyme activities (SOD and CAT). The SBM30 and SBM45 treatments increased Firmicutes and Bacteroidetes abundance in fish gut microbiota, while Proteobacteria abundance decreased. This microbiota shift may enhance soybean meal nutrient utilization, yet high soybean meal concentrations still impair growth. A soybean-meal-rich diet promotes harmful bacteria like Rhodococcus and depletes probiotics like Ralstonia, increasing disease risks. L. crocea has limited tolerance for soybean meal, necessitating advanced processing to mitigate anti-nutritional factors. Ultimately, exploring alternative protein sources beyond soybean meal for fish meal replacement is optimal for L. crocea. Full article

(This article belongs to the Special Issue Nutrition and Physiology of Marine Fish)

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18 pages, 3704 KiB

Open AccessArticle

Study on the Vertical Distribution Characteristics of Suspended Sediment Driven by Waves and Currents

by Feng Wu, Jijian Lian, Fang Liu and Ye Yao

J. Mar. Sci. Eng. 2024, 12(11), 2015; https://doi.org/10.3390/jmse12112015 - 8 Nov 2024

Abstract

Port coasts are affected by waves and tidal currents, and sediment continues to silt up, leading to a reduction in the depth of water in the channel, blocking the channel and seriously affecting the safe operation of ports. The main cause of sediment [...] Read more.

Port coasts are affected by waves and tidal currents, and sediment continues to silt up, leading to a reduction in the depth of water in the channel, blocking the channel and seriously affecting the safe operation of ports. The main cause of sediment deposition in ports is suspended sediment transport, and the characteristics of the vertical distribution of suspended sediment concentrations are the embodiment of the suspended sediment transport law. This paper is divided into three parts to study the vertical distribution characteristics of suspended sediment concentrations. Firstly, the shortcomings of the traditional diffusion model were analysed by using the finite mixing theory (FMT); secondly, the sediment mixing length coefficient κ_s model was introduced and combined with the sediment group settling velocity model to establish the vertical distribution model of suspended sediment concentrations under wave–current; finally, the effects of various factors on the vertical distribution of the suspended sediment concentration were investigated. The results show that the model in this paper has the characteristics of “low variance and low bias”, which solves the problem that κ_s is difficult to determine. When the model κ_s < κ_s_′ (κ_s_′ = 0.4), the concentration of suspended sediment predicted by κ_s_′ is overestimated, and vice versa. As the sediment concentration increases, the interaction between particles increases and the vertical distribution of the suspended sediment concentration shows the pattern of “small top and large bottom”. The larger the particle size, the greater the sedimentation rate of the suspended sediment, and a large amount of sediment will be suspended near the bottom without mixing. The higher the wave height, the stronger the boundary layer turbulence and the movement of the water particles’ trajectory, and the smaller the difference in sediment concentration between the bottom and the sea surface. Full article

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12 pages, 3824 KiB

Open AccessArticle

Numerical Simulation and Experimental Validation of the Acoustical Target Strength of Bluefin Tuna Swimbladders Derived from 3D Computed Tomographic Images

by Anderson Ladino, Isabel Pérez-Arjona, Victor Espinosa, Vicent Puig-Pons, Fernando de la Gándara, Aurelio Ortega, Edurne Blanco and Luis Godinho

J. Mar. Sci. Eng. 2024, 12(11), 2014; https://doi.org/10.3390/jmse12112014 (registering DOI) - 8 Nov 2024

Abstract

The swimbladder, when present, is the main contributor to the acoustical target strength (TS) of fish. Numerical modeling of target strength must include swimbladder dimensions, orientation, and shape for the proper estimation of target strength and its directivity. Several Atlantic Bluefin tuna ( [...] Read more.

The swimbladder, when present, is the main contributor to the acoustical target strength (TS) of fish. Numerical modeling of target strength must include swimbladder dimensions, orientation, and shape for the proper estimation of target strength and its directivity. Several Atlantic Bluefin tuna (Thunnus thynnus, ABFT) specimens between 90 and 100 cm of fork length were studied by performing computed tomographic (CT) post-mortems in both fresh and frozen states. ABFT swimbladder 3D models were derived for the first time to be compared with experimental TS measurements through numerical simulation methods, using the Method of Fundamental Solutions (MFS). The numerical estimation (−23.3 dB) agreed with the experimental measurement of TS (−22.1 dB) performed in a tank with tuna with a mean fork length of 100 cm, showing the importance of considering realistic swimbladder shapes and swimming behavior in the numerical simulation of TS. Full article

(This article belongs to the Special Issue New Challenges in Marine Aquaculture Research—2nd Edition)

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25 pages, 11128 KiB

Open AccessArticle

Spatiotemporal Changes and Utilization Intensity of the Zhoushan Archipelago Coastline over Four Decades

by Zhuocheng Liu, Lianqiang Shi, Junli Guo, Tinglu Cai, Xinkai Wang and Xiaoming Xia

J. Mar. Sci. Eng. 2024, 12(11), 2013; https://doi.org/10.3390/jmse12112013 - 8 Nov 2024

Abstract

Coastal changes in China, notably in the Zhoushan Islands, have primarily been driven by coastal reclamation since the establishment of New China. This study conducted a comprehensive analysis of the Zhoushan Archipelago shoreline spanning four decades, employing remote sensing, aerial photographs, and shoreline [...] Read more.

Coastal changes in China, notably in the Zhoushan Islands, have primarily been driven by coastal reclamation since the establishment of New China. This study conducted a comprehensive analysis of the Zhoushan Archipelago shoreline spanning four decades, employing remote sensing, aerial photographs, and shoreline data since 1984, along with GIS (Geographic Information System) technology. We assessed shoreline changes using the shoreline change index and shoreline artificialization index, as well as examined the influence of the Yangtze River’s suspended sediment and impoldering activities on Zhoushan’s shoreline. Furthermore, the correlation between local economic development and shoreline development was explored. The results revealed the following key findings: (1) From 1984 to 2018, the Zhoushan Archipelago shoreline decreased by 7.05 km. Temporally, the shoreline change index was −0.08%, with the most significant reduction occurring between 2008 and 2018. Spatially, differences among island groups were not pronounced. (2) The shoreline diversity index consistently increased, indicating greater diversity and complexity in shoreline use over the four decades. (3) The shoreline artificiality index steadily rose, particularly after 2000. It was highest in the south, followed by the center, and lowest in the north. (4) The intensity index of coastal land use continuously increased, with the southern island group having a higher index compared to the Zhoushan Islands. (5) The Yangtze River contributed significantly to sand inflow, influencing shoreline changes and beach shaping in Zhejiang. However, reclamation projects were identified as the primary and direct factor. (6) A positive correlation existed between Zhoushan City’s economic development and the intensity of coastal land use. This study emphasized the need for improving the control over reclamation projects and the better management of coastal protection and use. These measures could optimize resource allocation and establish a more scientific and rational coastal zone pattern. Full article

(This article belongs to the Section Coastal Engineering)

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21 pages, 9157 KiB

Open AccessArticle

Numerical Study of Air Cushion Effect in Notched Disk Water Entry Process Using Structured Arbitrary Lagrangian–Eulerian Method

by Zhe Zhang, Nana Yang, Jinlong Ju, Xingzhi Bai, Houcun Zhou and Wenhua Wu

J. Mar. Sci. Eng. 2024, 12(11), 2012; https://doi.org/10.3390/jmse12112012 - 8 Nov 2024

Abstract

This paper presents a novel numerical investigation into the air cushion effect and impact loads during the water entry of notched discs, utilizing the Structured Arbitrary Lagrangian–Eulerian (S-ALE) algorithm in LS-DYNA. Unlike prior studies that focused on smooth or unnotched geometries, the present [...] Read more.

This paper presents a novel numerical investigation into the air cushion effect and impact loads during the water entry of notched discs, utilizing the Structured Arbitrary Lagrangian–Eulerian (S-ALE) algorithm in LS-DYNA. Unlike prior studies that focused on smooth or unnotched geometries, the present study explores how varying notch parameters influence the fluid–solid coupling process during high-speed water entry. The reliability and accuracy of the computational method are validated through grid independence verification and comparisons with experimental data and empirical formulas. Systematic analysis of the effects of notch size, water entry velocity, and entry angle on the evolution of the free surface, impact loads, and structural responses uncovers several novel findings. Notably, increasing the notch diameter significantly enhances the formation and stability of the air cushion, leading to a considerable reduction in peak impact loads—a phenomenon not previously quantified. Additionally, higher water entry Froude numbers are shown to accelerate air cushion compression and formation, markedly affecting free surface morphology and force distribution. The results also reveal that varying the water entry angle alters the air cushion’s morphological characteristics, where larger angles induce a more pronounced but less stable air cushion, influencing the internal structural response differently across regions. Full article

(This article belongs to the Section Ocean Engineering)

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14 pages, 897 KiB

Open AccessArticle

Global Sensitivity Analysis of the Fundamental Frequency of Jacket-Supported Offshore Wind Turbines Using Artificial Neural Networks

by Román Quevedo-Reina, Guillermo M. Álamo and Juan J. Aznárez

J. Mar. Sci. Eng. 2024, 12(11), 2011; https://doi.org/10.3390/jmse12112011 - 8 Nov 2024

Abstract

Determining the fundamental frequency of Offshore Wind Turbines (OWTs) is crucial to ensure the reliability and longevity of the structure. This study presents a global sensitivity analysis of the fundamental frequency of OWTs on jacket foundations. Monte Carlo sampling was employed to generate [...] Read more.

Determining the fundamental frequency of Offshore Wind Turbines (OWTs) is crucial to ensure the reliability and longevity of the structure. This study presents a global sensitivity analysis of the fundamental frequency of OWTs on jacket foundations. Monte Carlo sampling was employed to generate a diverse set of wind turbines, emplacements, and jacket designs, ensuring that the generated samples are realistic and yield relevant conclusions. The fundamental frequency and its partial derivatives were obtained via a previously developed ANN model. The relative sensitivities were computed to facilitate the comparison of their influence. The results demonstrate that wind turbine properties are the most relevant variables affecting the fundamental frequency, with a decrement in frequency caused by tower height and rotor-nacelle assembly mass, as well as an increment due to the section dimensions of the tower, particularly at its base. Soil properties have a significant effect on foundation stiffness for soft and light soils but can be neglected for hard and heavy soils. The diameter and thickness of the braces also show different relevance depending on their dimensions, producing rigid links between legs for greater sections. This study provides a measure of the variables influencing the fundamental frequency, facilitating a deeper comprehension of this phenomenon. Full article

(This article belongs to the Special Issue Advances in Ships and Marine Structures)

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22 pages, 5932 KiB

Open AccessArticle

Data-Driven Analysis of Ocean Fronts’ Impact on Acoustic Propagation: Process Understanding and Machine Learning Applications, Focusing on the Kuroshio Extension Front

by Weishuai Xu, Lei Zhang, Ming Li, Xiaodong Ma and Maolin Li

J. Mar. Sci. Eng. 2024, 12(11), 2010; https://doi.org/10.3390/jmse12112010 - 7 Nov 2024

Abstract

Ocean fronts, widespread across the global ocean, cause abrupt shifts in physical properties such as temperature, salinity, and sound speed, significantly affecting underwater acoustic communication and detection. While past research has concentrated on qualitative analysis and small-scale research on ocean front sections, a [...] Read more.

Ocean fronts, widespread across the global ocean, cause abrupt shifts in physical properties such as temperature, salinity, and sound speed, significantly affecting underwater acoustic communication and detection. While past research has concentrated on qualitative analysis and small-scale research on ocean front sections, a comprehensive analysis of ocean fronts’ characteristics and their impact on underwater acoustics is lacking. This study employs high-resolution reanalysis data and in situ observations to accurately identify ocean fronts, sound speed structures, and acoustic propagation features from over six hundred thousand Kuroshio Extension Front (KEF) sections. Utilizing marine big data statistics and machine learning evaluation metrics such as out-of-bag (OOB) error and Shapley values, this study quantitatively assesses the variations in sound speed structures across the KEF and their effects on acoustic propagation shifts. This study’s key findings reveal that differences in sound speed structure are significantly correlated with KEF strength, with the channel axis depth and conjugate depth increasing with front strength, while the thermocline intensity and depth excess decrease. Acoustic propagation features in the KEF environment exhibit notable seasonal variations. Full article

(This article belongs to the Special Issue Applications of Underwater Acoustics in Ocean Engineering)

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