Journal of Marine Science and Engineering

26 pages, 18346 KiB

Open AccessArticle

Wave Motion and Seabed Response around a Vertical Structure Sheltered by Submerged Breakwaters with Fabry–Pérot Resonance

by Lai Jiang, Jisheng Zhang, Linlong Tong, Yakun Guo, Rui He and Ke Sun

J. Mar. Sci. Eng. 2022, 10(11), 1797; https://doi.org/10.3390/jmse10111797 - 21 Nov 2022

Cited by 3 | Viewed by 1607

Abstract

This paper presents the results from a numerical simulation study to investigate wave trapping by a series of trapezoidal porous submerged breakwaters near a vertical breakwater, as well as the seabed response around the vertical breakwater. An integrated model, based on the volume-averaged [...] Read more.

This paper presents the results from a numerical simulation study to investigate wave trapping by a series of trapezoidal porous submerged breakwaters near a vertical breakwater, as well as the seabed response around the vertical breakwater. An integrated model, based on the volume-averaged Reynolds-averaged Navier–Stokes (VARANS) equations is developed to simulate the flow field, while the dynamic Biot’s equations are used for simulating the wave-induced seabed response. The reflection of the wave energy over the submerged breakwaters, caused by the vertical breakwater, can be reserved, indicating that the existence of the submerged breakwaters in the front of the vertical breakwater can either provide shelter or worsen the hazards to the vertical breakwater. Numerical examples show two different modes under the Fabry–Pérot (F–P) resonance condition of the wave transformation, namely the wave reflection (Mode 1) and the wave trapping (Mode 2). The distance between the submerged breakwaters and the vertical breakwater, is a key parameter dominating the local hydrodynamic process and the resultant dynamic stresses around the vertical breakwater. The numerical results indicated that more submerged breakwaters and a higher porosity of submerged breakwaters will obviously dissipate more wave energy, and hence induce a smaller wave force on the rear vertical breakwater and liquefaction area around the vertical breakwater. Full article

(This article belongs to the Special Issue Wave Interactions with Coastal Structures II)

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20 pages, 4053 KiB

Open AccessArticle

Dietary Curcumin Supplementation Enhanced Ammonia Nitrogen Stress Tolerance in Greater Amberjack (Seriola dumerili): Growth, Serum Biochemistry and Expression of Stress-Related Genes

by Jiawei Hong, Zhengyi Fu, Jing Hu, Shengjie Zhou, Gang Yu and Zhenhua Ma

J. Mar. Sci. Eng. 2022, 10(11), 1796; https://doi.org/10.3390/jmse10111796 - 21 Nov 2022

Cited by 4 | Viewed by 1416

Abstract

This study was conducted to determine whether curcumin has a positive effect in greater amberjack (Seriola dumerili), especially the ammonia nitrogen stress tolerance ability. The results showed that the stress recovery process of digestive enzymes amylase and trypsin, as well as [...] Read more.

This study was conducted to determine whether curcumin has a positive effect in greater amberjack (Seriola dumerili), especially the ammonia nitrogen stress tolerance ability. The results showed that the stress recovery process of digestive enzymes amylase and trypsin, as well as absorptive enzymes Na⁺/K⁺-ATPase, γ-GT and CK, was accelerated. Lysozyme activity increased in the fish fortified with both curcumin diets. Aspartate aminotransferase activity restriction was activated at a low curcumin level. However, alanine aminotransferase activity restriction happened only at 0.02% dietary curcumin. Facilitation of lipid metabolism by curcumin was very clear, as triglyceride and total cholesterol content was basically maintained at the original level or even showed a slight decrease after recovery. HSP70 and HSP90 genes were not evidently stimulated to express in liver, kidney and spleen tissues. In addition, curcumin showed its inhibition capacity on IL1β and IFN-γ and a promoting effect on TGF-β1. The expression of NF-κB1 decreased in a higher degree in fish fed with 0.02% dietary curcumin, while 0.01% dietary curcumin accelerated the recovery pace of C3 and lgT after stress. This study showed that dietary curcumin supplementation can enhance ammonia nitrogen stress tolerance in greater amberjack, and its application prospect can be confirmed. Full article

(This article belongs to the Special Issue New Techniques in Marine Aquaculture)

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16 pages, 7259 KiB

Open AccessArticle

Study on Distribution Law of Gas Phase and Cavitation in the Pressurization Unit of Helical Axial Flow Multiphase Pump

by Yexiang Xiao, Zhonghua Gui, Xuesong Li, Sijia Tao, Guangtai Shi and Chunwei Gu

J. Mar. Sci. Eng. 2022, 10(11), 1795; https://doi.org/10.3390/jmse10111795 - 21 Nov 2022

Cited by 4 | Viewed by 999

Abstract

Due to the irregular change of gas void fraction (GVF) in multiphase pumps, the pressure distribution in the pump is often uneven, which leads to the formation of low-pressure area and thus the occurrence of cavitation. In order to study the gas phase [...] Read more.

Due to the irregular change of gas void fraction (GVF) in multiphase pumps, the pressure distribution in the pump is often uneven, which leads to the formation of low-pressure area and thus the occurrence of cavitation. In order to study the gas phase and cavitation distribution in the impeller region of a multiphase pump under different cavitation stages and GVF conditions, this study used numerical calculations as the main method and experimental verification as a secondary method to investigate the cavitation phenomenon in the pump under different stages and GVF conditions. The results showed that at different stages, both the volume fraction and the covering area of the gas phase were reduced to a certain extent with the increase in blade height, and the distribution law of the gas phase on the blade changed with the development of the cavitation stage, especially on the blade surface. At different GVFs, cavitation first occurred at the inlet of the blade SS and then extended along the blade streamline from the inlet to outlet, with the volume fraction and distribution of cavitation gradually increasing and then extending to the blade PS. The results showed that the presence of the gas phase inhibited the development of cavitation in the multiphase pump to some extent, and the cavitation performance of the multiphase pump was better in the presence of the gas phase than in pure water conditions. The results of this study provide a theoretical basis for improving the cavitation performance of multiphase pumps. Full article

(This article belongs to the Special Issue CFD Simulation of Floating Offshore Structures)

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28 pages, 17396 KiB

Open AccessArticle

Sedimentology and Diagenesis of the Early–Middle Eocene Carbonate Deposits of the Ceno-Tethys Ocean

by Ahmer Bilal, Renchao Yang, Muhammad Saleem Mughal, Hammad Tariq Janjuhah, Muhammad Zaheer and George Kontakiotis

J. Mar. Sci. Eng. 2022, 10(11), 1794; https://doi.org/10.3390/jmse10111794 - 21 Nov 2022

Cited by 13 | Viewed by 2046

Abstract

An integrated study based on field observation, petrography, and scanning electron microscopy (SEM) on the Early–Middle Eocene carbonate rocks has been carried out, which were deposited in the Ceno-Tethys Ocean. The study area of the Yadgaar Section lies on the eastern margin of [...] Read more.

An integrated study based on field observation, petrography, and scanning electron microscopy (SEM) on the Early–Middle Eocene carbonate rocks has been carried out, which were deposited in the Ceno-Tethys Ocean. The study area of the Yadgaar Section lies on the eastern margin of the Upper Indus Basin, Pakistan. The Early–Middle Eocene Margalla Hill Limestone and Chorgali Formation act as reservoir rocks in other parts of the basin and are also present in the Yadgaar Section. The lack of comprehensive study in this area makes these reservoir rocks highly attractive for sedimentological evaluations and future exploration of hydrocarbons. The Early–Middle Eocene carbonate rocks are divided into nine microfacies: dolomicritic foraminiferal mudstone–wackestone microfacies (EMI); green algae dominated, mixed foraminiferal wackestone–packstone microfacies (EMII); ostracod, green algae and gypsum dominating mudstone–wackestone microfacies (EMIII); algae and mixed foraminiferal wackestone–packstone microfacies (EMIV); Nummulites dominating mudstone–wackestone microfacies (EMV); algal limestone mudstone microfacies (EMVI); Assilina bed wackestone–packstone microfacies (EMVII); micritized larger benthic foraminiferal wackestone–packstone microfacies (EMVIII); and algal limestone, mudstone microfacies (EMIX). The transgressive-regressive environment in the Ceno-Tethys Ocean leads to the deposition of these microfacies in the platform interior, open marine platform, platform edge, platform margin reef, toe of the slope apron, arid–humid platform interior, platform edge, open marine platform interior, and restricted marine platform interior, respectively. Initial post-depositional diagenetic stages are identified from the base to the top of the strata by their respective cement types, i.e., the base–lower middle part of the strata demonstrates an eogenetic sub-stage with the appearance of drusy cement, the middle section indicates a mesogenetic sub-stage by the appearance of blocky cement, while the top portion again reveals an eogenetic sub-stage of diagenesis by the presence of drusy and blocky types of cement. The ascending–descending hierarchy of cement generations is directly proportional to the grade of diagenesis from the base to the top of the carbonate strata. Variable diagenetic effects on the various microfacies also increase the secondary porosity range and enhance the reservoir characteristics of the Formations. The presence of foraminifera microfossils determined that these carbonate formations date from the Early–Middle Eocene. Full article

(This article belongs to the Special Issue Recent Advances in Sedimentology)

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17 pages, 5622 KiB

Open AccessArticle

Framework for Process Analysis of Maritime Accidents Caused by the Unsafe Acts of Seafarers: A Case Study of Ship Collision

by Ying Wang and Shanshan Fu

J. Mar. Sci. Eng. 2022, 10(11), 1793; https://doi.org/10.3390/jmse10111793 - 21 Nov 2022

Cited by 7 | Viewed by 2367

Abstract

Accurately describing and evaluating the effects of unsafe acts on maritime accidents is critical to establishing practical accident prevention and control options. This paper proposes a framework for the probabilistic analysis of maritime accidents caused by seafarers’ unsafe acts by incorporating a navigation [...] Read more.

Accurately describing and evaluating the effects of unsafe acts on maritime accidents is critical to establishing practical accident prevention and control options. This paper proposes a framework for the probabilistic analysis of maritime accidents caused by seafarers’ unsafe acts by incorporating a navigation simulation and dynamic Bayesian network (DBN) modeling. First, the unsafe acts of seafarers are identified according to an in-depth analysis of global maritime investigation reports. Then, a navigation simulation experiment is designed to collect the ship-handling data of seafarers during hazardous accident scenarios. Consequently, a dynamic probabilistic model is proposed using a DBN to describe the phases of maritime accidents based on the navigation simulation experiment data. Furthermore, an evolution analysis of maritime accidents is conducted to explore the causal chain of such accidents through sensitivity analysis. The typical navigational accident-collision is chosen as the case to interpret the proposed framework, considering the formation process of ship collision risks, from the occurrence of ship collision risk (phase 1) to the close-quarters situation (phase 2) and to immediate danger (phase 3). This framework is applied to explore the causal chain of collision accidents caused by the unsafe acts of seafarers. Full article

(This article belongs to the Topic Ship Dynamics, Stability and Safety)

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13 pages, 1997 KiB

Open AccessArticle

Frequency Characteristics of Sloshing Resonance in a Three-Dimensional Shallow-Water Rectangular Tank

by Xinyi Yuan, Yan Su and Peng Xie

J. Mar. Sci. Eng. 2022, 10(11), 1792; https://doi.org/10.3390/jmse10111792 - 21 Nov 2022

Cited by 3 | Viewed by 1268

Abstract

The frequency characteristics of free surface elevation time histories of shallow-water sloshing in a three-dimensional rectangular tank is presented. The numerical model for sloshing motion uses an accurate velocity potential Boussinesq-type equation. A particular solution is adopted to express the external excitations and [...] Read more.

The frequency characteristics of free surface elevation time histories of shallow-water sloshing in a three-dimensional rectangular tank is presented. The numerical model for sloshing motion uses an accurate velocity potential Boussinesq-type equation. A particular solution is adopted to express the external excitations and a linear damping term is introduced to replace a friction effect produced by tank walls. The excitation amplitude of the forced movement of the tank is tiny, while the excitation frequency varies around the first resonance frequency. The numerical results show that the wave energy in the rectangular tank under resonance is concentrated in the integer multiple of excitation frequencies, the sum excitation frequencies, and the difference excitation frequencies. Full article

(This article belongs to the Section Ocean Engineering)

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21 pages, 11388 KiB

Open AccessArticle

Formation of MASS Collision Avoidance and Path following Based on Artificial Potential Field in Constrained Environment

by Xiangyu Chen, Miao Gao, Zhen Kang, Jian Zhou, Shuai Chen, Zihao Liao, Haixin Sun and Anmin Zhang

J. Mar. Sci. Eng. 2022, 10(11), 1791; https://doi.org/10.3390/jmse10111791 - 21 Nov 2022

Cited by 5 | Viewed by 1639

Abstract

It is essential to promote the intelligence and autonomy of Maritime Autonomous Surface Ships (MASSs). This study proposed an automatic collision-avoidance method based on an improved Artificial Potential Field (APF) with the formation of MASSs (F-MASSs). Firstly, the navigation environment model was constructed [...] Read more.

It is essential to promote the intelligence and autonomy of Maritime Autonomous Surface Ships (MASSs). This study proposed an automatic collision-avoidance method based on an improved Artificial Potential Field (APF) with the formation of MASSs (F-MASSs). Firstly, the navigation environment model was constructed by the S-57 Electronic Navigation Chart (ENC) data in Tianjin Port. The Formation Ship State Parameter (FSSP) definition was proposed for the port environment under multiple constraints that considered the navigation conditions of the MASSs. The formation pattern transformation was settled by changing the formation ship state parameter. Considering the constraints of an ‘unmanned–manned’ encounter situation, the static obstacles, and the design of the channel area improved artificial potential method for the formation. Finally, the simulation experiment was carried out in the sea near Tianjin Port to verify the effectiveness of the algorithm under multiple constraints. The results indicate that the method can satisfy the integrated operation of collision avoidance and path following in a constrained environment, and it can support the application of merchant F-MASS autonomous navigation in the future. Full article

(This article belongs to the Special Issue Application of Advanced Technologies in Maritime Safety)

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14 pages, 4686 KiB

Open AccessArticle

Design, Simulation, and Experimental Study on the Hydraulic Drive System of an AUV Docking Device with Multi-Degree Freedom

by Xiaofei Du, Chaoyong Zong, Bo Zhang and Maolin Shi

J. Mar. Sci. Eng. 2022, 10(11), 1790; https://doi.org/10.3390/jmse10111790 - 21 Nov 2022

Cited by 4 | Viewed by 1843

Abstract

AUV docking devices have the ability to achieve homing of the AUV, supply the AUV with energy, and exchange data with it, thus improving the endurance and ensuring the continuous long-term and large-scale operation of the AUV. To improve the successful docking rate [...] Read more.

AUV docking devices have the ability to achieve homing of the AUV, supply the AUV with energy, and exchange data with it, thus improving the endurance and ensuring the continuous long-term and large-scale operation of the AUV. To improve the successful docking rate of the AUV, a funnel-shaped underwater docking device with multi-degree freedom based on a deep-sea platform was designed in this paper. The heading angle, pitch angle, and roller angle of the docking device could be adjusted in a timely manner according to the current flow direction and the position of the AUV. In order to realize the timely adjustment of the heading angle, pitch angle, and roll angle of the docking device, a set of underwater hydraulic systems was developed as the power source to drive the corresponding hydraulic cylinders, hydraulic motors, and other executive components. The model of the heading angle adjustment circuit of the hydraulic system was established and the open-loop transfer function of the heading angle adjustment circuit was derived. The dynamic response performance of the hydraulic circuit was simulated and the optimized PID algorithm was used to improve the dynamic response performance. Finally, the accuracy of the heading angle adjustment circuit model and the effectiveness of the control algorithm were validated by experiment of the docking device in a water pool. Full article

(This article belongs to the Special Issue Frontiers in Deep-Sea Equipment and Technology II)

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15 pages, 12984 KiB

Open AccessArticle

Marine-Hydraulic-Oil-Particle Contaminant Identification Study Based on OpenCV

by Chenyong Wang, Chao Yang, Hongpeng Zhang, Shengzhao Wang, Zhaoxu Yang, Jingguo Fu and Yuqing Sun

J. Mar. Sci. Eng. 2022, 10(11), 1789; https://doi.org/10.3390/jmse10111789 - 21 Nov 2022

Cited by 5 | Viewed by 1647

Abstract

Particulate pollutants mixed in hydraulic oil will lead to the failure of the marine hydraulic system. Nowadays, the current identification methods of particulate pollutants in oil make it challenging to obtain the specific parameters of pollutants. For this reason, this paper proposes a [...] Read more.

Particulate pollutants mixed in hydraulic oil will lead to the failure of the marine hydraulic system. Nowadays, the current identification methods of particulate pollutants in oil make it challenging to obtain the specific parameters of pollutants. For this reason, this paper proposes a recognition method of marine-hydraulic-oil-particle pollutants based on OpenCV. The image of particles in the marine hydraulic oil was preprocessed by OpenCV software and using the Canny operator edge detection algorithm to extract the contour of particle pollutants to obtain their area and perimeter. The recognition accuracy reached 95%. Using the Douglas–Peucker algorithm for fit polygons, then image moments to obtain the angle-distance waveform of particulate pollutants, the shape of marine-hydraulic-oil particulate pollutants was successfully identified. The designed method has the advantages of fast calculation efficiency, high accuracy, and real-time detection of various parameters of particulate pollutants in marine hydraulic oil. It has great significance for the fault diagnosis of hydraulic systems and prolonging the working life of hydraulic equipment. This research provides a new idea for the condition monitoring and fault diagnosis of ships and offshore engineering equipment. Full article

(This article belongs to the Special Issue Advances in Sensor Technology in Smart Ships and Offshore Facilities)

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16 pages, 3545 KiB

Open AccessArticle

Marine Archaeal Extracellular Polymeric Substances from Halococcus AMS12, Their Characterization, and Biological Properties

by Kamala Kannan, Sivaperumal Pitchiah, Jeevankumar Guduri Joseph, Dhanraj Ganapathy, Subramanian Sundarrajan and Seeram Ramakrishna

J. Mar. Sci. Eng. 2022, 10(11), 1788; https://doi.org/10.3390/jmse10111788 - 21 Nov 2022

Cited by 2 | Viewed by 1739

Abstract

In the present study, halophilic archaea were isolated from a marine sediment sample. Totally, 15 isolates (AMS 1–15) were identified by molecular identification as belonging to the ten genera. Further, their extracellular polymeric substances (EPS) were extracted (3.172 g/L), and their bioactivity was [...] Read more.

In the present study, halophilic archaea were isolated from a marine sediment sample. Totally, 15 isolates (AMS 1–15) were identified by molecular identification as belonging to the ten genera. Further, their extracellular polymeric substances (EPS) were extracted (3.172 g/L), and their bioactivity was determined in terms of biosurfactant, emulsification, enzymatic and non-enzymatic antioxidants, and anticancer activity. The highest amount of EPS has been produced by Halococcus sp., AMS12. It is made up of 54.28% carbohydrates, 32.91% proteins, 2.41% lipids, and other compounds. Further, EPS has 43.69 ± 1.89 U/mg of gelatinase enzyme by degrading the substrate. The potential total antioxidant activity of 103.80 ± 0.02 (ascorbic acid equivalence (AAE)), total reducing power of 86.1 ± 0.25 AAE, 1,1-diphenyl-2-picrylhydrazyl (DPPH) activity of 97.23 ± 0.21%, the hydrogen peroxide scavenging of 60.8 ± 0.21%, and nitric oxide scavenging activity of 89.37 ± 0.24% were observed at 100 μg/mL of EPS. Hence, we conclude that the archeal EPS is multifunctional and useful for developing natural polymers for industrial, food, and pharmaceutical applications. Full article

(This article belongs to the Special Issue Feature Papers in Marine Biology)

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18 pages, 4890 KiB

Open AccessArticle

Water Circulation, Temperature, Salinity, and pCO₂ Distribution in the Surface Layer of the East Kamchatka Current

by Andrey Andreev and Irina Pipko

J. Mar. Sci. Eng. 2022, 10(11), 1787; https://doi.org/10.3390/jmse10111787 - 20 Nov 2022

Cited by 2 | Viewed by 1854

Abstract

The ship-borne observations of the temperature, salinity, pCO₂ (1995–2020) and satellite geostrophic velocity fields, SST, and chlorophyll concentration are used to identify the factors that determine the spatio-temporal variability of seawater parameters on the western boundary of the subarctic North Pacific. In [...] Read more.

The ship-borne observations of the temperature, salinity, pCO₂ (1995–2020) and satellite geostrophic velocity fields, SST, and chlorophyll concentration are used to identify the factors that determine the spatio-temporal variability of seawater parameters on the western boundary of the subarctic North Pacific. In winter, the surface layer of the East Kamchatka Current (EKC) was characterized by two types of water: the waters with a negative temperature (−1.0–−0.5 °C) and salinity of 32.4–32.9 and waters with a positive temperature (0.4–1.7 °C) and salinity of 33.0–33.1. The source of water with negative (positive) temperature and decreased (increased) salinity for the EKC zone is the Bering Sea shelf (Aleutian Basin). The surface waters in the eastern Kamchatka area in winter were close to gas equilibrium with the atmosphere or supersaturated with carbon dioxide (pCO₂ = 380–460 µatm). In summer, extremely low pCO₂ values (140–220 µatm) in the surface layer of the eastern Kamchatka and the northern Kuril Islands regions have been associated with the decreased salinity (32.1–32.6) of the waters. The distributions of the temperature, salinity, and pCO₂ in the surface layer of the central Kuril Islands are determined by the location and intensity of the Kuril eddies and the EKC stream jets. The water mixing in the central Kuril Straits and the Kruzenshterna Bank area leads to increased salinity (33.2–33.4) and high values of pCO₂ (480–670 µatm) in the surface layer of the EKC. The comparison of the pCO₂ data collected in winter demonstrates an increase in pCO₂ between 1998/2001 and 2018/2020 at about 50 µatm in the surface waters with a salinity of 33.0–33.1, which is in agreement with an increase in pCO₂ in the atmosphere at 46 µatm (from 368 to 414 µatm) during this period. Full article

(This article belongs to the Section Chemical Oceanography)

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29 pages, 43301 KiB

Open AccessArticle

Simulating the Interconnected Eastern Mediterranean–Black Sea System on Climatic Timescales: A 30-Year Realistic Hindcast

by Stamatios Petalas, Elina Tragou, Ioannis G. Mamoutos and Vassilis Zervakis

J. Mar. Sci. Eng. 2022, 10(11), 1786; https://doi.org/10.3390/jmse10111786 - 20 Nov 2022

Cited by 2 | Viewed by 1642

Abstract

Inter-basin water exchanges can be quite important in climatic-scale numerical studies simulating the circulation and hydrographic characteristics of neighboring oceanic basins connected through narrow straits. The crucial role of the interaction between the Mediterranean and the Black Seas is often overseen in simulations, [...] Read more.

Inter-basin water exchanges can be quite important in climatic-scale numerical studies simulating the circulation and hydrographic characteristics of neighboring oceanic basins connected through narrow straits. The crucial role of the interaction between the Mediterranean and the Black Seas is often overseen in simulations, which rely mostly on parameterizations to describe the exchange, essentially decoupling the two basins. In this study, the fully interconnected Eastern Mediterranean–Black Sea system is simulated for the historical period (1985–2015) using realistic boundary conditions (lateral, atmospheric and hydrological), with a hydrodynamic fully three-dimensional ocean modeling system. The setup of such a configuration is thoroughly described and the performance of the 30-year hindcast product is validated exhaustively against observations and model results, by evaluating the representation of surface fields, circulation, three-dimensional hydrographic characteristics, volumetric water exchanges, and the spatio-temporal variability of the above. The comparison shows exceptional performance, minimal drift, and substantial improvement compared to modeling studies that do not include the interaction. Moreover, due to the free-run configuration of the simulation (i.e., absence of assimilation schemes) no additional input is required other than the respective boundary conditions, making it possible to reliably extend the same setup for scenarios where observational data are not available, such as in future projections. Full article

(This article belongs to the Special Issue Hydrodynamic Circulation Modelling in the Marine Environment)

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18 pages, 6474 KiB

Open AccessArticle

A Study on the Vortex Induced Vibration of a Cylindrical Structure with Surface Bulges

by Haoyuan Xu, Jie Wang, Zhiqing Li, Kaihua Liu, Jiawei Yu and Bo Zhou

J. Mar. Sci. Eng. 2022, 10(11), 1785; https://doi.org/10.3390/jmse10111785 - 19 Nov 2022

Cited by 3 | Viewed by 1800

Abstract

Inspired by the cactus in nature, a cactus-like cross-sectional structure was proposed to achieve the VIV suppression. The VIV of the elastically mounted cylinder was realized based on the ANSYS Fluent and User Defined Function (UDF). The dynamic motion of the cylinder was [...] Read more.

Inspired by the cactus in nature, a cactus-like cross-sectional structure was proposed to achieve the VIV suppression. The VIV of the elastically mounted cylinder was realized based on the ANSYS Fluent and User Defined Function (UDF). The dynamic motion of the cylinder was solved by the single-step time integration algorithms Newmark-

β

method. The in-house code was first validated by studying the 2DOF VIV of a circular cylinder with small mass ratio over the range

U^{*} = 2 ~ 13

, and the results agree well with the published literature. Then, the performance of surface bulge on VIV suppression was studied and four different coverage ratios (CR) were considered, i.e., 0%, 20%, 33%, and 40%. The VIV of a bulged cylinder can be effectively suppressed. CR20 performs the best in VIV suppression and the suppression efficiency in streamwise and transverse direction are 44.6% and 63.1%, respectively. The mechanism of surface bulge on the VIV suppression is the shift of separation point of the shear layer and vortices form between the surface bulges. Full article

(This article belongs to the Special Issue Design and Analysis of Offshore Structures)

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11 pages, 1433 KiB

Open AccessArticle

Toxicity of Antifouling Biocides and Wastes from Ships’ Surfaces during High-Pressure Water-Blasting Cleaning Activities in the Nauplii and Eggs of the Estuarine Copepod Paracalanus parvus sl

by Bonggil Hyun, Pung-Guk Jang, Kyoungsoon Shin, Moonkoo Kim, Ju-Hak Jung, Hyung-Gon Cha and Min-Chul Jang

J. Mar. Sci. Eng. 2022, 10(11), 1784; https://doi.org/10.3390/jmse10111784 - 19 Nov 2022

Cited by 3 | Viewed by 1635

Abstract

Copepods, the dominant member of zooplankton and major grazers of phytoplankton in the pelagic ecosystem, are at risk from exposure to antifouling biocides. To evaluate the developmental toxicity of antifouling biocides (Diuron, Irgarol 1051, Sea-nine 211) and wastewater (from high-pressure water blasting (WHPB) [...] Read more.

Copepods, the dominant member of zooplankton and major grazers of phytoplankton in the pelagic ecosystem, are at risk from exposure to antifouling biocides. To evaluate the developmental toxicity of antifouling biocides (Diuron, Irgarol 1051, Sea-nine 211) and wastewater (from high-pressure water blasting (WHPB) and its MeOH extract (WHPB-MeOH)) in the copepod Paracalanus parvus sl, we investigated the chemical concentration, egg-hatching rate, and nauplius mortality. WHPB samples were obtained through hull-cleaning activities involving WHPB in a dry dock. Among the biocides, Sea-nine 211 had the strongest effects on hatching rates and nauplius mortality, which was followed by Diuron and Irgarol 1051. In the WHPB and WHPB-MeOH samples, there was no significant difference between the experimental groups in terms of the egg-hatching rate; however, WHPB was found to be more toxic in terms of nauplius mortality, suggesting that metals in WHPB may also adversely affect nauplius survival in P. parvus sl. A comparison of the LC₅₀ results of Sea-nine 211 and WHPB revealed that WHPB had a negative effect on nauplius mortality even at a 100-fold lower concentration. Therefore, if chemical contaminants generated during in-water cleaning activity are discharged continuously into the ports without being properly collected through a post-treatment system, they are expected to negatively impact the population of copepods near the port. Although verification is needed through additional experiments, our results could be used for a baseline study concerning the toxicity of antifouling biocides on marine copepod species. Full article

(This article belongs to the Section Marine Biology)

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20 pages, 85581 KiB

Open AccessArticle

Multi-Scale Object Detection Model for Autonomous Ship Navigation in Maritime Environment

by Zeyuan Shao, Hongguang Lyu, Yong Yin, Tao Cheng, Xiaowei Gao, Wenjun Zhang, Qianfeng Jing, Yanjie Zhao and Lunping Zhang

J. Mar. Sci. Eng. 2022, 10(11), 1783; https://doi.org/10.3390/jmse10111783 - 19 Nov 2022

Cited by 9 | Viewed by 2724

Abstract

Accurate detection of sea-surface objects is vital for the safe navigation of autonomous ships. With the continuous development of artificial intelligence, electro-optical (EO) sensors such as video cameras are used to supplement marine radar to improve the detection of objects that produce weak [...] Read more.

Accurate detection of sea-surface objects is vital for the safe navigation of autonomous ships. With the continuous development of artificial intelligence, electro-optical (EO) sensors such as video cameras are used to supplement marine radar to improve the detection of objects that produce weak radar signals and small sizes. In this study, we propose an enhanced convolutional neural network (CNN) named VarifocalNet * that improves object detection in harsh maritime environments. Specifically, the feature representation and learning ability of the VarifocalNet model are improved by using a deformable convolution module, redesigning the loss function, introducing a soft non-maximum suppression algorithm, and incorporating multi-scale prediction methods. These strategies improve the accuracy and reliability of our CNN-based detection results under complex sea conditions, such as in turbulent waves, sea fog, and water reflection. Experimental results under different maritime conditions show that our method significantly outperforms similar methods (such as SSD, YOLOv3, RetinaNet, Faster R-CNN, Cascade R-CNN) in terms of the detection accuracy and robustness for small objects. The maritime obstacle detection results were obtained under harsh imaging conditions to demonstrate the performance of our network model. Full article

(This article belongs to the Special Issue Application of Advanced Technologies in Maritime Safety)

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20 pages, 2209 KiB

Open AccessArticle

Adaptive Second-Order Fast Terminal Sliding-Mode Formation Control for Unmanned Surface Vehicles

by Duansong Wang, Min Kong, Gang Zhang and Xiaoling Liang

J. Mar. Sci. Eng. 2022, 10(11), 1782; https://doi.org/10.3390/jmse10111782 - 19 Nov 2022

Cited by 5 | Viewed by 1366

Abstract

The formation control of unmanned surface vehicles (USVs) while considering communication topology, dynamic model uncertainties, environmental disturbances, and a fast convergence rate is addressed in this paper. First, graph theory is introduced to describe the connective relationships and establish generalized formation errors among [...] Read more.

The formation control of unmanned surface vehicles (USVs) while considering communication topology, dynamic model uncertainties, environmental disturbances, and a fast convergence rate is addressed in this paper. First, graph theory is introduced to describe the connective relationships and establish generalized formation errors among USVs. Then, a second-order fast nonsingular terminal sliding-mode control (SOFNTSMC) is designed to guarantee that the system converges quickly and without chatter. An adaptive update law is designed in order to estimate the model uncertainties and external disturbances without the requirement of the boundary information of the system uncertainties. With the application of the adaptive SOFNTSMC (ASOFNTSMC) and graph theory, a distributed control is developed for every USV to perform the desired formation pattern. Finally, the results of simulations and comparisons demonstrate the effectiveness of the proposed method. Full article

(This article belongs to the Section Ocean Engineering)

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15 pages, 4408 KiB

Open AccessArticle

Long-Term Spatiotemporal Changes in Ecosystem Services Caused by Coastal Wetland Type Transformation in China’s Hangzhou Bay

by Haiji Liang, Chong Chen, Kexin Wang and Guanqiong Ye

J. Mar. Sci. Eng. 2022, 10(11), 1781; https://doi.org/10.3390/jmse10111781 - 19 Nov 2022

Cited by 1 | Viewed by 1602

Abstract

Coastal wetlands provide essential ecosystem services, while usually experiencing land transformation or degradation mainly due to intense anthropogenic activities and climate changes. Understanding the changes in wetlands ecosystem services is essential to decision makers for generating sound coastal planning. Hangzhou Bay is rich [...] Read more.

Coastal wetlands provide essential ecosystem services, while usually experiencing land transformation or degradation mainly due to intense anthropogenic activities and climate changes. Understanding the changes in wetlands ecosystem services is essential to decision makers for generating sound coastal planning. Hangzhou Bay is rich in wetland resources, and the urbanization of Hangzhou Bay in the past three decades has caused fundamental changes in the wetlands in the region. Based on the remote sensing images of the Hangzhou Bay area from 1990 to 2020, this paper analyzes the land use situation of the Hangzhou Bay area in seven periods. This paper calculates the area transfer matrix of various types of wetlands. It uses the InVEST model to evaluate the changes in the function of wetland ecosystem services in the Hangzhou Bay area. Hangzhou Bay wetlands show a trend of transferring natural wetlands to artificial and non-wetlands from 1990 to 2020. Carbon stocks fell by 14.24%. The annual water production decreased by 33.93% and then returned to the original level. The area of habitat degradation increased by 79.94%. The main influencing factors are paddy field degradation, increase in non-wetland area, and decrease in sea area. This paper proposes that the development and construction of farmland in the “red line” area and established wetland reserves are prohibited, and to strengthen the training of wetland management personnel, establish a sound decision-making consultation mechanism, and increase the scientific research expenditure on wetlands in the region. Full article

(This article belongs to the Section Coastal Engineering)

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12 pages, 1810 KiB

Open AccessArticle

Guidance-Based Path Following of an Underactuated Ship Based on Event-Triggered Sliding Mode Control

by Yuxi Zhang and Yong Liu

J. Mar. Sci. Eng. 2022, 10(11), 1780; https://doi.org/10.3390/jmse10111780 - 18 Nov 2022

Cited by 4 | Viewed by 1279

Abstract

In this paper, the path following of an underactuated ship as a fundamental application for autonomous sailing in seaways is studied. First, the guidance system based on the line of sight (LOS) method is established to handle underactuated dynamics of ship motion. Then, [...] Read more.

In this paper, the path following of an underactuated ship as a fundamental application for autonomous sailing in seaways is studied. First, the guidance system based on the line of sight (LOS) method is established to handle underactuated dynamics of ship motion. Then, path following control is converted to heading control with fewer dimensions. Second, the extended state observer (ESO) is used to observe unknown dynamics of ship motion. Third, the sliding mode control method is highly robust to external disturbance and is employed to design the controller. Fourth, the event-triggered mechanism (ETM) is included to reduce the trigger time. All the closed-loop signals are shown to be bounded by the Lyapunov theory. Simulations are carried out to verify the effectiveness of the proposed method. Full article

(This article belongs to the Special Issue Advances in Marine Vehicles, Automation and Robotics)

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15 pages, 2440 KiB

Open AccessArticle

Sea-Breeze Front Research Based on Remote Sensing Methods in Coastal Baltic Sea Climate: Case of Lithuania

by Remigijus Dailidė, Greta Dailidė, Indrė Razbadauskaitė-Venskė, Ramūnas Povilanskas and Inga Dailidienė

J. Mar. Sci. Eng. 2022, 10(11), 1779; https://doi.org/10.3390/jmse10111779 - 18 Nov 2022

Cited by 3 | Viewed by 1794

Abstract

Sea breezes, as one of the most important local varieties of daily wind dynamics, are responsible for the formation of the climate by coasts of large bodies of water. In recent decades, due to climate change, the air temperature is rising, causing larger [...] Read more.

Sea breezes, as one of the most important local varieties of daily wind dynamics, are responsible for the formation of the climate by coasts of large bodies of water. In recent decades, due to climate change, the air temperature is rising, causing larger temperature gradients to form and the dynamics of the atmosphere to change globally and locally. This research investigated the spread of sea breezes in the years 2018–2019 during the warm period of the year (June, July, and August) to the mainland territory of the southeastern Baltic and coastal Lithuania by applying in situ and remote methods. The results of the study showed that sea-breeze fronts are better identified by the formation line of convective clouds in the continental part seen in remote images. During the first half of the day (until noon), the effect of sea breezes extends on average about 20–30 km from the coast of the sea. However, maximum extension of the breeze fronts can penetrate the continent much further than previously thought. During the summer, when the westward movement of air masses prevails, the band of cumulus (Cu) clouds formed by the sea breeze marks the front of the sea breeze, and at the time of the most extended spread (around 5 pm) in the continental part of Lithuania, the sea-breeze front is an average of around 60 km away from the seacoast. Until noon, the area covered by sea breezes in the western part of Lithuania extends over 1886.2 km². During the second half of the day, the spatial spread of the breeze impacts an average area of about 6445.2 km² by around 5 pm. Hence, the sea breeze affects not only the coastal climate region of Lithuania, as previously recognized, but it also affects the climate of part of the region of the Samogitian (Žemaitijos) Uplands of Lithuania. Remote-sensing methods helped to identify sea-breeze fronts and evaluate the limits of marine climate expansion along the seashore. The methods used in this work can play a role in answering the question of how climate change can affect the coastal climate. Full article

(This article belongs to the Special Issue Changes of the Coastal Zones Due to Climate Change)

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32 pages, 34025 KiB

Open AccessArticle

A Fully Coupled CFD-DMB Approach on the Ship Hydroelasticity of a Containership in Extreme Wave Conditions

by Yujia Wei, Atilla Incecik and Tahsin Tezdogan

J. Mar. Sci. Eng. 2022, 10(11), 1778; https://doi.org/10.3390/jmse10111778 - 18 Nov 2022

Cited by 9 | Viewed by 2441

Abstract

In this paper, we present a fully coupled computational fluid dynamic (CFD) and discrete module beam (DMB) method for the numerical prediction of nonlinear hydroelastic responses of a ship advancing in regular and focused wave conditions. A two-way data communication scheme is applied [...] Read more.

In this paper, we present a fully coupled computational fluid dynamic (CFD) and discrete module beam (DMB) method for the numerical prediction of nonlinear hydroelastic responses of a ship advancing in regular and focused wave conditions. A two-way data communication scheme is applied between two solvers, whereby the external fluid pressure exported from the CFD simulation is used to derive the structural responses in the DMB solver, and the structural deformations are fed back into the CFD solver to deform the mesh. We first conduct a series of verification and validation studies by using the present CFD–DMB method to investigate the global ship motion, vertical bending moments (VBMs), and green water phenomenon of the ship in different regular wave conditions. The numerical results agreed favourably with the CFD–FEA model and experimental measurements. Then, the extreme ship motions are studied in focused wave conditions to represent extreme sea conditions that a ship may experience in a real sea state. According to the conclusion drawn from the numerical simulations, it is founded that the focused wave case will lead to the increase of the longitudinal responses of the hull compared to regular wave condition, i.e., the heave, pitch, and total VBMs rise about

25 %

,

20 %

and

9 %

, respectively. In focused wave conditions, intensive ship responses and severe waves cause stronger slamming phenomena. It is found that the instantaneous impact pressure from the focused wave is higher and sharper compared to the regular waves and comes along with the obvious green-water-on-deck phenomena. Full article

(This article belongs to the Special Issue Ship Motions and Wave Loads)

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23 pages, 10298 KiB

Open AccessArticle

Numerical Investigation of Depressurization through Horizontal Wells in Methane-Hydrate-Bearing Sediments Considering Sand Production

by Xuyang Guo, Yan Jin, Jingyu Zi, Jiaying Lin, Bolong Zhu, Qian Wen and Qi Jing

J. Mar. Sci. Eng. 2022, 10(11), 1777; https://doi.org/10.3390/jmse10111777 - 18 Nov 2022

Cited by 2 | Viewed by 1232

Abstract

Sand production has been identified as a key reason limiting sustained and commercial gas production in methane-hydrate-bearing sediments. Production tests in Canada and Japan were terminated partially because of excessive sand production in pilot wells. It is meaningful to carry out numerical investigations [...] Read more.

Sand production has been identified as a key reason limiting sustained and commercial gas production in methane-hydrate-bearing sediments. Production tests in Canada and Japan were terminated partially because of excessive sand production in pilot wells. It is meaningful to carry out numerical investigations and sensitivity analyses to improve the understanding of sand production mechanisms during the exploitation of methane hydrates. This study introduces a numerical model to describe the coupled thermal–hydraulic–mechanical–chemical responses and sand production patterns during horizontal well depressurization in methane-hydrate-bearing sediments. The model is benchmarked with a variety of methane hydrate reservoir simulators. Results show that the spatial and temporal evolution patterns of multi-physical fields are different and the hydromechanical evolutions are the fastest. Gas production and sand production rates are oscillatory in the early stages and long-term rates become stable. Gas production is sensitive to rock physical and operational parameters and insensitive to rock mechanical properties such as cohesion. In contrast, sand production is sensitive to cohesion and insensitive to rock physical and operational parameters. Although cohesion does not directly affect gas productivity, gas productivity can be impaired if excessive sand production impedes production operations. This study provides insights into the sand production mechanism and quantifies how relevant parameters affect sand production during the depressurization in methane-hydrate-bearing sediments. Full article

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28 pages, 12579 KiB

Open AccessArticle

Hydrology and Dynamics in the Gulf of Naples during Spring of 2016: In Situ and Model Data

by Luigi Gifuni, Paola de Ruggiero, Daniela Cianelli, Enrico Zambianchi and Stefano Pierini

J. Mar. Sci. Eng. 2022, 10(11), 1776; https://doi.org/10.3390/jmse10111776 - 18 Nov 2022

Cited by 1 | Viewed by 1657

Abstract

The hydrology and circulation in the northwestern part of the Gulf of Naples are analyzed during the transition period from spring to summer (April–June) 2016 through numerical simulations and in situ observations. The simulations were performed with the high-resolution sigma-coordinate Campania Regional Ocean [...] Read more.

The hydrology and circulation in the northwestern part of the Gulf of Naples are analyzed during the transition period from spring to summer (April–June) 2016 through numerical simulations and in situ observations. The simulations were performed with the high-resolution sigma-coordinate Campania Regional Ocean Model (CROM) encompassing the wider Campania coastal system. Temperature, salinity and density were measured at the Long Term Ecological Research Program Mare-Chiara sampling site located two miles from the coast, while current intensity and direction were measured in situ by an acoustic Doppler current profiler connected to an elastic beacon anchored at a short distance from the city of Naples. The modeled circulation scenarios and the marine hydrology provided by the model on a regular grid allow interpreting the observational data during the selected period. In turn, the model-data comparison clarifies the model performance in reproducing the nearshore marine dynamics, which goes beyond the actual model resolution. Full article

(This article belongs to the Special Issue Dynamics in Coastal Areas)

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18 pages, 7451 KiB

Open AccessArticle

Distributed Robust Fast Finite-Time Formation Control of Underactuated ASVs in Presence of Information Interruption

by Guoqing Zhang, Jun Han, Jiqiang Li and Xianku Zhang

J. Mar. Sci. Eng. 2022, 10(11), 1775; https://doi.org/10.3390/jmse10111775 - 18 Nov 2022

Cited by 1 | Viewed by 1095

Abstract

To adapt to complex navigation conditions, this paper addresses the coordination formation of autonomous surface vehicles (ASVs) with the constraint of information interruption. For this purpose, a distributed robust fast finite-time formation control algorithm is proposed by fusion of the directed graph and [...] Read more.

To adapt to complex navigation conditions, this paper addresses the coordination formation of autonomous surface vehicles (ASVs) with the constraint of information interruption. For this purpose, a distributed robust fast finite-time formation control algorithm is proposed by fusion of the directed graph and neural network method. In the strategy, the graph theory is utilized for the channel of information transmission to maintain the stability of the formation system. In addition, the radial basic function (RBF) neural network is employed to approximate the structure uncertainty. Due to the merits of the robust neural damping technique, only two adaptive parameters are designed to compensate the perturbation from the model uncertainty and external environmental. Furthermore, an improved dynamic surface control (DSC) technology is developed for constituting the exponential term of the Lyapunov function. It is proven that the proposed scheme is able to achieve consensus tracking in finite time quickly, and the errors rapidly approach a small region around the origin. Finally, the feasibility and effectiveness of the algorithm are verified by two numerical simulations. Full article

(This article belongs to the Special Issue Motion Control and Path Planning of Marine Vehicles)

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19 pages, 7663 KiB

Open AccessArticle

Experimental Investigation of Mooring Performance and Energy-Harvesting Performance of Eccentric Rotor Wave Energy Converter

by Gang Xue, Jian Qin, Zhenquan Zhang, Shuting Huang and Yanjun Liu

J. Mar. Sci. Eng. 2022, 10(11), 1774; https://doi.org/10.3390/jmse10111774 - 18 Nov 2022

Cited by 2 | Viewed by 1263

Abstract

To obtain the optimal mooring mode and the best-matching wave condition of an eccentric rotor wave energy converter (ERWEC), a physical model of the ERWEC was developed. Ten mooring modes and eight wave conditions were set up. Several experiments were carried out to [...] Read more.

To obtain the optimal mooring mode and the best-matching wave condition of an eccentric rotor wave energy converter (ERWEC), a physical model of the ERWEC was developed. Ten mooring modes and eight wave conditions were set up. Several experiments were carried out to analyze the influence of mooring modes and wave conditions on the mooring and energy-harvesting performances of the ERWEC. The results showed that the mooring and energy-harvesting performances changed significantly for the same mooring mode under various regular wave conditions, but the opposite situation was found under irregular wave conditions. The wave-facing direction of the buoy was a critical factor affecting the mooring and energy-harvesting performances, while the number of anchor lines had little effect on them. In addition, a method to evaluate the motion response of the buoy based on the number of effective excitations and a method to evaluate the comprehensive performance based on the cloud chart are proposed. The mooring mode and wave condition combination that obtained the optimal mooring and energy-harvesting performances for the ERWEC was determined. This paper provides a novel perspective on how to balance the efficiency and reliability of wave energy converters. Full article

(This article belongs to the Special Issue Tidal and Wave Energy)

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14 pages, 1598 KiB

Open AccessArticle

Towards Mannosylerythritol Lipids (MELs) for Bioremediation: Effects of NaCl on M. antarcticus Physiology and Biosurfactant and Lipid Production; Ecotoxicity of MELs

by Petar Keković, Margarida Borges, Nuno Torres Faria and Frederico Castelo Ferreira

J. Mar. Sci. Eng. 2022, 10(11), 1773; https://doi.org/10.3390/jmse10111773 - 18 Nov 2022

Cited by 1 | Viewed by 1696

Abstract

Mannosylerythritol lipids (MELs) are a group of biosurfactants with a wide range of potential applications, due to their excellent tensioactive properties, biocompatibility, and biodegradability. One of the envisioned uses for MELs is in bioremediation in marine and terrestrial environments. However, knowledge regarding their [...] Read more.

Mannosylerythritol lipids (MELs) are a group of biosurfactants with a wide range of potential applications, due to their excellent tensioactive properties, biocompatibility, and biodegradability. One of the envisioned uses for MELs is in bioremediation in marine and terrestrial environments. However, knowledge regarding their ecotoxicity is limited. The current costs of production for this biosurfactant are too high to make it competitive in the surfactant market. In an effort to facilitate the use of MELs for marine bioremediation purposes, their production using sea water in medium formulation was explored. Cells were exposed to different levels of NaCl during fermentation, and the effects of increased salinity on the cells and their performance was monitored. In addition, cells were briefly exposed to an osmotic shock, by introducing pure NaCl into the broth, to measure their physiological response. Although the overall effect of NaCl in the medium was negative, cells produced more lipases in these stress conditions. Furthermore, the changes triggered by the osmotic shock caused changes in the cell surface and affected their hydrophobicity, reducing the levels of MELs adsorbed to the cells, which in turn led to an increase in formation of MEL-rich beads. Marine-level salinity (3.5%) was found to be sufficient to enable production of MELs in unsterile conditions and inhibited an introduced bacterial contaminant. Finally, the toxicity levels of MELs to a model marine organism and plant model were lower than other biosurfactants and that of a commercial chemical dispersant used for bioremediation. Full article

(This article belongs to the Special Issue Feature Papers in Marine Biology)

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19 pages, 4014 KiB

Open AccessArticle

Vibration Cascade Control for Motor-Driven Deep-Sea Robot Cable System with Actuator Fault

by Hangyu Rao, Naige Wang and Rui Du

J. Mar. Sci. Eng. 2022, 10(11), 1772; https://doi.org/10.3390/jmse10111772 - 17 Nov 2022

Cited by 1 | Viewed by 1104

Abstract

In this paper, we investigated the cascade controller of a motor-driven deep-sea robot cable system (MDRCS), which consists of the outer loop system and the inner loop system connected by a motor thrust with unknown factors, typically forming a crucial problem along with [...] Read more.

In this paper, we investigated the cascade controller of a motor-driven deep-sea robot cable system (MDRCS), which consists of the outer loop system and the inner loop system connected by a motor thrust with unknown factors, typically forming a crucial problem along with actuator failures, and is accommodated by a fault control created for the deep-sea model. Furthermore, the non-linear disturbance observer compensates for the external disturbance by using the high-gain state observer to estimate parameters and reduce the effects of measurement inaccuracy from the sensors. We suggested an output feedback boundary controller for the outer loop system to get the thrust and eliminate the transverse cable vibration as well as a multiplicative inverse controller for the motor system to form a cascade controller. The Lyapunov approach is then used to demonstrate the stability of the deep-sea robot cable system and motor system. The results demonstrated the effectiveness of the suggested controller and fault control in the presence of the actuator fault, presented with the appropriate parameters on MDRCS. Full article

(This article belongs to the Section Ocean Engineering)

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14 pages, 12229 KiB

Open AccessArticle

Assessment of Wave Energy Resources in China

by Hongyuan Shi, Xuri Zhang, Wenyan Du, Qingjie Li, Hengliang Qu and Zaijin You

J. Mar. Sci. Eng. 2022, 10(11), 1771; https://doi.org/10.3390/jmse10111771 - 17 Nov 2022

Cited by 4 | Viewed by 1543

Abstract

The evolution of renewable energy technologies may surmount fossil fuel disadvantages. Wave energy is considered one of the best alternatives to fossil energy due to its advantages. The 40-year (1979–2018) spatio-temporal distribution of wave energy is presented using European Centre for Medium-Range Weather [...] Read more.

The evolution of renewable energy technologies may surmount fossil fuel disadvantages. Wave energy is considered one of the best alternatives to fossil energy due to its advantages. The 40-year (1979–2018) spatio-temporal distribution of wave energy is presented using European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5) datasets. In addition, the common formula used for wave energy evaluation is derived from the linear wave theory in deep water, which is not applicable in shallow water. Therefore, a new equation that is suitable for both shallow and deep water is derived, which improves the accuracy of the wave energy evaluation for various water depths. The main aim is to investigate the spatio-temporal wave energy for offshore China from 1979 to 2018 and combine the new standard of classification to recommend the optimal area. The nearshore zone from Zhejiang province to Guandong province is considered the ideal zone, and the average annual wave energy density in this area is above 10 kW/m. Full article

(This article belongs to the Section Marine Energy)

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13 pages, 4820 KiB

Open AccessArticle

Sea Turtles Employ Drag-Reducing Techniques to Conserve Energy

by Nick van der Geest, Lorenzo Garcia, Roy Nates and Alberto Gonzalez-Vazquez

J. Mar. Sci. Eng. 2022, 10(11), 1770; https://doi.org/10.3390/jmse10111770 - 17 Nov 2022

Cited by 3 | Viewed by 2332

Abstract

Sea turtles are recognised as one of the ocean’s most remarkable migratory species, accomplishing journeys that cover thousands of kilometres. This fact is even more extraordinary when considering sea turtles consume mostly low-energy foods. The biology of sea turtles dominates the literature; however, [...] Read more.

Sea turtles are recognised as one of the ocean’s most remarkable migratory species, accomplishing journeys that cover thousands of kilometres. This fact is even more extraordinary when considering sea turtles consume mostly low-energy foods. The biology of sea turtles dominates the literature; however, the swimming strategies they employ to achieve their migratory success from a biomechanical and hydrodynamic viewpoint is relatively unexplored. In past research, the sea turtle’s upstroke has been debated among researchers as to whether it is passive or for thrust production. In this work, we recreate a model based on the green sea turtle (Chelonia mydas) and develop an ad hoc testing rig to uncover the secrets behind the sea turtle’s upstroke. Our findings suggest sea turtles utilise a passive upstroke that can substantially lower the animal’s drag coefficient to levels that cause insignificant losses in swim speed despite not developing any thrust force. This can conceivably save the animal a notable amount of energy as the upstroke is responsible for a large percentage of the overall limb beat cycle. These findings could potentially pave a path towards developing high-efficiency bioinspired underwater drone technologies. Full article

(This article belongs to the Section Marine Biology)

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18 pages, 5327 KiB

Open AccessArticle

Hybrid Optimized Fuzzy Pitch Controller of a Floating Wind Turbine with Fatigue Analysis

by Carlos Serrano, Jesus-Enrique Sierra-Garcia and Matilde Santos

J. Mar. Sci. Eng. 2022, 10(11), 1769; https://doi.org/10.3390/jmse10111769 - 17 Nov 2022

Cited by 5 | Viewed by 1546

Abstract

Floating offshore wind turbines (FOWTs) are systems with complex and highly nonlinear dynamics; they are subjected to heavy loads, making control with classical strategies a challenge. In addition, they experience vibrations due to wind and waves. Furthermore, the control of the blade angle [...] Read more.

Floating offshore wind turbines (FOWTs) are systems with complex and highly nonlinear dynamics; they are subjected to heavy loads, making control with classical strategies a challenge. In addition, they experience vibrations due to wind and waves. Furthermore, the control of the blade angle itself may generate vibrations. To address this issue, in this work we propose the design of an intelligent control system based on fuzzy logic to maintain the rated power of an FOWT while reducing the vibrations. A gain scheduling incremental proportional–derivative fuzzy controller is tuned by genetic algorithms (GAs) and combined with a fuzzy-lookup table to generate the pitch reference. The control gains optimized by the GA are stored in a database to ensure a proper operation for different wind and wave conditions. The software Matlab/Simulink and the simulation tool FAST are used. The latter simulates the nonlinear dynamics of a real 5 MW barge-type FOWT with irregular waves. The hybrid control strategy has been evaluated against the reference baseline controller embedded in FAST in different environmental scenarios. The comparison is assessed in terms of output power and structure stability, with up to 23% and 33% vibration suppression rate for tower top displacement and platform pitch, respectively, with the new control scheme. Fatigue damage equivalent load (DEL) of the blades has been also estimated with satisfactory results. Full article

(This article belongs to the Section Ocean Engineering)

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16 pages, 3323 KiB

Open AccessArticle

Influences of Seasonal Variability and Potential Diets on Stable Isotopes and Fatty Acid Compositions in Dominant Zooplankton in the East Sea, Korea

by Jieun Kim, Hee-Young Yun, Eun-Ji Won, Hyuntae Choi, Seok-Hyeon Youn and Kyung-Hoon Shin

J. Mar. Sci. Eng. 2022, 10(11), 1768; https://doi.org/10.3390/jmse10111768 - 17 Nov 2022

Cited by 2 | Viewed by 1439

Abstract

Despite their crucial roles in transporting primary productions in marine food webs, the trophic dynamics of zooplankton throughout the seasons have rarely been studied. In this study, four dominant zooplankton taxa with phytoplankton size composition and productivity were collected over four seasons in [...] Read more.

Despite their crucial roles in transporting primary productions in marine food webs, the trophic dynamics of zooplankton throughout the seasons have rarely been studied. In this study, four dominant zooplankton taxa with phytoplankton size composition and productivity were collected over four seasons in the East Sea, which is known to change more rapidly than global trends. We then analyzed the δ¹³C and δ¹⁵N values and fatty acid composition of zooplankton. The heavy δ¹³C values in February and August 2021 were observed with high concentrations of total chlorophyll-a, and the δ¹³C differences among the four zooplankton taxa in the coastal region (site 105-05) were most pronounced in February 2021. The relative amounts of eicosapentaenoic acid (C20:5(n-3)) and docosahexaenoic acid (C22:6(n-3)), indicators of phytoplankton nutritional quality, were also highest in February 2021. Non-metric multivariate analyses showed dissimilarity among zooplankton taxa during the high productivity period based on chlorophyll-a concentrations (51.6%), which may be due to an increase in available foods during the highly productive season. In conclusion, the dietary intake of zooplankton can be reduced by the transition of phytoplankton, which has important implications for the impact of climate change on planktonic ecosystems in the East Sea. Full article

(This article belongs to the Special Issue Integrated Ecosystem Assessments for Fisheries Management in the Yellow Sea, the East China Sea, and the East/Japan Sea)

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J. Mar. Sci. Eng., Volume 10, Issue 11 (November 2022) – 231 articles

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