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Volume 9
Issue 11
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J. Mar. Sci. Eng., Volume 9, Issue 11 (November 2021) – 163 articles

Cover Story (view full-size image): The Humboldt Current hosts perpetually high levels of productivity along the western coast of South America. The paper by Collareta et al. aims at elucidating the deep-time history of this globally important ecosystem based on a detailed palaeoecological analysis of the exceptionally preserved, middle to upper Miocene fossil whales, dolphins, seals, seabirds, turtles, crocodiles, sharks, rays, and bony fishes of the Pisco Formation of Peru. Like today, this precursor of the Humboldt Current Ecosystem was based on sardines but notably differed from its modern equivalent in being dominated by extremely large-bodied apex predators such as Livyatan melvillei and Carcharocles megalodon. View this paper
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20 pages, 3716 KiB  
Article
Distributed Consensus of USVs under Heterogeneous UAV-USV Multi-Agent Systems Cooperative Control Scheme
by Kai Xue and Tingyi Wu
J. Mar. Sci. Eng. 2021, 9(11), 1314; https://doi.org/10.3390/jmse9111314 - 22 Nov 2021
Cited by 23 | Viewed by 3595
Abstract
This paper addresses the formation motion control of heterogeneous multi-agent unmanned systems via a distributed consensus approach. The considered heterogeneous system consisted of unmanned aerial vehicles (UAVs) and unmanned surface vehicles (USVs). A leader-following consensus scheme and APF method are used to construct [...] Read more.
This paper addresses the formation motion control of heterogeneous multi-agent unmanned systems via a distributed consensus approach. The considered heterogeneous system consisted of unmanned aerial vehicles (UAVs) and unmanned surface vehicles (USVs). A leader-following consensus scheme and APF method are used to construct UAV-USVs Formation task requirements. A fuzzy-based sliding mode control approach is proposed to ensure the formation assembles in a finite time, and the finite-time stability is proved by the Lyapunov stability theorem. To highlight the cooperation within the heterogeneous systems, such as UAV and USV, a novel vision-based path re-planning approach is proposed. Simulation results confirm the efficiency of the proposed approach. Full article
(This article belongs to the Special Issue Control, Guidance, Coordination, and Localization of Autonomous Marine Vehicles)
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18 pages, 6819 KiB  
Article
Gird Based Line Segment Detector and Application: Vision System for Autonomous Ship Small Assembly Line
by Jinhong Ding and Chongben Ni
J. Mar. Sci. Eng. 2021, 9(11), 1313; https://doi.org/10.3390/jmse9111313 - 22 Nov 2021
Cited by 2 | Viewed by 1959
Abstract
The shipbuilding industry demands intelligent robot, which is capable of various tasks without laborious pre-teaching or programming. Vision system guided robots could be a solution for autonomous working. This paper introduces the principle and technique details of a vision system that guides welding [...] Read more.
The shipbuilding industry demands intelligent robot, which is capable of various tasks without laborious pre-teaching or programming. Vision system guided robots could be a solution for autonomous working. This paper introduces the principle and technique details of a vision system that guides welding robots in ship small assembly production. TOF sensors are employed to collect spatial points of workpieces. Huge data amount and complex topology bring great difficulty in the reconstruction of small assemblies. A new unsupervised line segment detector is proposed to reconstruct ship small assemblies from spatial points. Verified using data from actual manufacturing, the method of this paper demonstrated good robustness which is a great advantage for industrial applications. This paper’s work has been implemented in shipyards and shows good commercial potential. Intelligent, flexible industrial robots could be implemented with the findings of this study, which will push forward intelligent manufacturing in the shipbuilding industry. Full article
(This article belongs to the Special Issue Smart Technologies for Shipbuilding)
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12 pages, 3000 KiB  
Article
High Levels of Tetrodotoxin in the Flesh, Usually an Edible Part of the Pufferfish Takifugu flavipterus, Caused by Migration from the Skin and the Regional Characteristics of Toxin Accumulation
by Naomasa Oshiro, Kyoko Kuniyoshi, Shigeyoshi Yamamoto, Ayano Hotta, Takuma Yamada, Takafumi Suzuki, Noriko Sugita, Keiichi Matsuura, Akie Nakashima, Yoichi Anzai and Hiroshi Asakura
J. Mar. Sci. Eng. 2021, 9(11), 1312; https://doi.org/10.3390/jmse9111312 - 22 Nov 2021
Cited by 3 | Viewed by 2276
Abstract
The consumption of a pufferfish, Takifugu flavipterus or komonfugu in Japanese, formerly known as Takifugu poecilonotus, is popular in Japan. However, T. flavipterus is frequently involved in cases of tetrodotoxin (TTX) poisoning in Japan. Although victims have usually consumed inedible parts, some [...] Read more.
The consumption of a pufferfish, Takifugu flavipterus or komonfugu in Japanese, formerly known as Takifugu poecilonotus, is popular in Japan. However, T. flavipterus is frequently involved in cases of tetrodotoxin (TTX) poisoning in Japan. Although victims have usually consumed inedible parts, some cases are related to consumption of flesh. To improve the risk management of pufferfish poisoning, we studied TTX level in the flesh and skin of T. flavipterus. Ninety-seven specimens obtained from the Seto Inland Sea and landed in Fukuoka Prefecture were analyzed by liquid chromatography-tandem mass spectrometry. The flesh from six specimens was toxic (>10 MU/g = 2.2 mg/kg): one was in poor condition (not freeze–thawed); three were freeze–thawed before sample preparation; and two freshly prepared and in good condition (not freeze–thawed). The fillets were divided into outer and inner portions; the TTX levels in the outer portions were notably higher. The skin of the six specimens was moderately to extremely toxic: 165 MU/g (36.3 mg/kg) in the fresh specimen not in good condition, 600–950 MU/g (132–200 mg/kg) in freeze–thawed specimens, and 4500 and 6000 MU/g (990 and 1320 mg/kg) in the two fresh specimens. We concluded that TTX in the flesh migrated from the highly toxic skin. In addition, TTX levels in the skin appeared to be regionally specific. We recommend that toxic portions of T. flavipterus are removed as soon as possible after individuals are caught, and that fish from known highly toxic areas are not consumed. Full article
(This article belongs to the Special Issue Chemistry, Toxicology and Etiology of Marine Biotoxins)
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13 pages, 48474 KiB  
Article
Simulations of the Concentration Fields of Rosette-Type Multiport Buoyant Discharges Using Combined CFD and Multigene Genetic Programming Techniques
by Xiaohui Yan, Yan Wang, Abdolmajid Mohammadian and Jianwei Liu
J. Mar. Sci. Eng. 2021, 9(11), 1311; https://doi.org/10.3390/jmse9111311 - 22 Nov 2021
Cited by 5 | Viewed by 1478
Abstract
Rosette-type diffusers are becoming popular nowadays for discharging wastewater effluents. Effluents are known as buoyant jets if they have a lower density than the receiving water, and they are often used for municipal and desalination purposes. These buoyant effluents discharged from rosette-type diffusers [...] Read more.
Rosette-type diffusers are becoming popular nowadays for discharging wastewater effluents. Effluents are known as buoyant jets if they have a lower density than the receiving water, and they are often used for municipal and desalination purposes. These buoyant effluents discharged from rosette-type diffusers are known as rosette-type multiport buoyant discharges. Investigating the mixing properties of these effluents is important for environmental impact assessment and optimal design of the diffusers. Due to the complex mixing and interacting processes, most of the traditional simple methods for studying free single jets become invalid for rosette-type multiport buoyant discharges. Three-dimensional computational fluid dynamics (3D CFD) techniques can satisfactorily model the concentration fields of rosette-type multiport buoyant discharges, but these techniques are typically computationally expensive. In this study, a new technique of simulating rosette-type multiport buoyant discharges using combined 3D CFD and multigene genetic programming (MGGP) techniques is developed. Modeling the concentration fields of rosette-type multiport buoyant discharges using the proposed approach has rarely been reported previously. A validated numerical model is used to carry out extensive simulations, and the generated dataset is used to train and test MGGP-based models. The study demonstrates that the proposed method can provide reasonable predictions and can significantly improve the prediction efficiency. Full article
(This article belongs to the Special Issue Advances in Coastal Hydrodynamics and Water Quality Modeling)
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16 pages, 1261 KiB  
Article
Understanding the Spatial and Temporal Distribution and Environmental Characteristics of Polychaete Assemblages in the Coastal Waters of Ulleungdo, East Sea of Korea
by Sang-Lyeol Kim and Ok-Hwan Yu
J. Mar. Sci. Eng. 2021, 9(11), 1310; https://doi.org/10.3390/jmse9111310 - 22 Nov 2021
Cited by 5 | Viewed by 1759
Abstract
The coastal area of Ulleungdo in the East Sea has experienced large climate and environmental changes. However, research on marine benthic animals in this area has been very limited. In the present study, we investigated the spatial and temporal distribution of benthic polychaetes [...] Read more.
The coastal area of Ulleungdo in the East Sea has experienced large climate and environmental changes. However, research on marine benthic animals in this area has been very limited. In the present study, we investigated the spatial and temporal distribution of benthic polychaetes to determine their seasonal adaptability to environmental changes in the coastal waters of Ulleungdo in 2019. In total, 116 species (34 families) of polychaetes were identified with an average of 25 species per site. The average density was 772.8 individuals m−2, with the highest density in August and the lowest in February. The dominant species were Pseudobranchiomma zebuensis (15.6%), Scolelepis sp. (8.6%), Haplosyllis spongiphila (7.3%), and Lumbrineris nipponica (6.3%). The main factors affecting polychaete community structure were water depth and sediment type (gravel, sand, silt, clay). Based on cluster analysis, the polychaetes tended to group mainly in winter and summer with P. zebuensis and Syllis sp. contributing to the grouping. The dominant species was the suspension feeder, which correlated highly with habitat sediment type and was substantially consistent with the coast of Dokdo. Some species overlapped in the East Sea coast, but the number and diversity of species were higher in Ulleungdo. Our study results confirm the ecological characteristics of benthic polychaetes of Ulleungdo and provide information for future monitoring of the environmental and biological changes in the East Sea. Full article
(This article belongs to the Special Issue Population Dynamics of Benthic-Pelagic Organisms in Relation to Oceanographic Features in East Sea, Korea)
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20 pages, 1957 KiB  
Article
Numerical Performance Model for Tensioned Mooring Tidal Turbine Operating in Combined Wave-Current Sea States
by Song Fu and Cameron Johnstone
J. Mar. Sci. Eng. 2021, 9(11), 1309; https://doi.org/10.3390/jmse9111309 - 22 Nov 2021
Cited by 2 | Viewed by 1920
Abstract
This study proposes the design of a tidal turbine station keeping system based on the adoption of a tensioned mooring system. Damping is introduced to investigate its effect on the reduction in the peak load experienced by tidal turbines during their operational lives [...] Read more.
This study proposes the design of a tidal turbine station keeping system based on the adoption of a tensioned mooring system. Damping is introduced to investigate its effect on the reduction in the peak load experienced by tidal turbines during their operational lives in high-energy wave–current environments. A neutrally buoyant turbine is supported using a tensioned cable-based mooring system, where tension is introduced using a buoy fully submersed in water. The loads on the turbine rotor blades and buoy are calculated using a wave and current-coupled model. A modelling algorithm is proposed based on inverted pendulums, which respond to various sea state conditions, to study the behaviour of the system as well as the loads on blades. The results indicate that the tensioned mooring system reduces the peak thrust on the turbine and validates the applicability of the model. Full article
(This article belongs to the Topic Marine Renewable Energy)
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18 pages, 7491 KiB  
Article
Pumping Rate and Size of Demosponges—Towards an Understanding Using Modeling
by Poul S. Larsen and Hans Ulrik Riisgård
J. Mar. Sci. Eng. 2021, 9(11), 1308; https://doi.org/10.3390/jmse9111308 - 22 Nov 2021
Cited by 3 | Viewed by 1917
Abstract
Filter-feeding sponges pump large amounts of water and contribute significantly to grazing impact, matter transport and nutrient cycling in many marine benthic communities. For ecological studies it is therefore of interest to be able to estimate the pumping rate of different species from [...] Read more.
Filter-feeding sponges pump large amounts of water and contribute significantly to grazing impact, matter transport and nutrient cycling in many marine benthic communities. For ecological studies it is therefore of interest to be able to estimate the pumping rate of different species from their volume size or osculum cross-sectional area by means of experimentally determined allometric correlations. To help understand allometric data correlations and observed large variations of volume-specific pumping rate among species we developed a model that determines the pumping rate as a function of the size (volume) of a tubular-type demosponge described by 4 geometric length scales. The model relies on a choanocyte-pump model and standard pressure loss relations for flow through the aquiferous system, and density and pumping rate per choanocyte is assumed to be constant. By selecting different possibilities for increase of the length scales, which may also simulate different growth forms, we demonstrate that the model can imitate the experimental allometric correlations. It is concluded that the observed dependence of pumping rate on size is primarily governed by the hydraulics of pump performance and pressure losses of the aquiferous system rather than, e.g., decreasing density of choanocytes with increasing sponge size. Full article
(This article belongs to the Special Issue Feature Papers in Marine Biology)
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27 pages, 1488 KiB  
Article
Sustainable Development of Oil and Gas Resources: A System of Environmental, Socio-Economic, and Innovation Indicators
by Alexey Cherepovitsyn, Evgeniya Rutenko and Victoria Solovyova
J. Mar. Sci. Eng. 2021, 9(11), 1307; https://doi.org/10.3390/jmse9111307 - 22 Nov 2021
Cited by 20 | Viewed by 5597
Abstract
Following the principles of sustainable development in the development of oil and gas fields in the Arctic will ensure that hydrocarbon production and transportation operations comply with stringent environmental regulations, the economies of the northern regions become integrated into the national economy of [...] Read more.
Following the principles of sustainable development in the development of oil and gas fields in the Arctic will ensure that hydrocarbon production and transportation operations comply with stringent environmental regulations, the economies of the northern regions become integrated into the national economy of Russia, production systems in the oil and gas sector are upgraded in an innovative manner, and further development of this region is balanced from the environmental perspective. The purpose of the study is to develop and provide a rationale for a balanced system of environmental, socio-economic, and innovative indicators for assessing whether the development of the Arctic’s unique hydrocarbon reserves is sustainable. The theoretical framework of the study draws upon the foundations and key principles of the sustainable development concept and upon modern approaches and methods for assessing the sustainability of production systems. The study presents an analysis of conceptual approaches to defining sustainable development in reference to oil and gas resources, including those found in the Arctic, defines target priorities for the sustainable development of the Arctic’s resource potential, and identifies the relationship between the environmental, socio-economic, and innovative domains of sustainability in the context of Arctic resource development. The results of the study demonstrate how large-scale gas projects can influence regional development and provide for making informed conclusions about whether the development of the Arctic’s oil and gas reserves can be considered sustainable (in accordance with the basic principles of the sustainable development concept). Full article
(This article belongs to the Special Issue The Future of Offshore Hydrocarbon Resources: Adaptation to a New Economic Reality)
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24 pages, 4511 KiB  
Article
Motion Control of Autonomous Underwater Vehicle Based on Fractional Calculus Active Disturbance Rejection
by Junhe Wan, Hailin Liu, Jian Yuan, Yue Shen, Hao Zhang, Haoxiang Wang and Yi Zheng
J. Mar. Sci. Eng. 2021, 9(11), 1306; https://doi.org/10.3390/jmse9111306 - 22 Nov 2021
Cited by 6 | Viewed by 2142
Abstract
An active disturbance rejection control based on fractional calculus is proposed to improve the motion performance and robustness of autonomous underwater vehicle (AUV). The active disturbance rejection control (ADRC) method can estimate and compensate the total disturbance of AUV automatically. The fractional-order PID [...] Read more.
An active disturbance rejection control based on fractional calculus is proposed to improve the motion performance and robustness of autonomous underwater vehicle (AUV). The active disturbance rejection control (ADRC) method can estimate and compensate the total disturbance of AUV automatically. The fractional-order PID (proportional integral derivative) has fast dynamic response, which can eliminate the estimation error of extended state observer. The fractional calculus active disturbance rejection strategy combines the advantages of the above two algorithms, and it is designed for AUV heading and pitch subsystems. In addition, the stability of fractional calculus ADRC heading subsystem is proven by Lyapunov stability theorem. The numerical simulations and experimental results document that the superior performance has been achieved. The fractional calculus ADRC strategy has more excellent abilities for disturbance rejection, performs better than ADRC and PID, and has important theoretical and practical value. Full article
(This article belongs to the Section Ocean Engineering)
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23 pages, 17324 KiB  
Article
Station-Keeping Control of Autonomous and Remotely-Operated Vehicles for Free Floating Manipulation
by Ningning Ding, Yuangui Tang, Zhibin Jiang, Yunfei Bai and Shixun Liang
J. Mar. Sci. Eng. 2021, 9(11), 1305; https://doi.org/10.3390/jmse9111305 - 21 Nov 2021
Cited by 4 | Viewed by 1835
Abstract
This paper investigates the station-keeping control of autonomous and remotely-operated vehicles (ARVs) for free-floating manipulation under model uncertainties and external disturbances. A modified adaptive generalized super-twisting algorithm (AGSTA) enhanced by adaptive tracking differentiator (ATD) and reduced-order extended state observer (RESO) is proposed. The [...] Read more.
This paper investigates the station-keeping control of autonomous and remotely-operated vehicles (ARVs) for free-floating manipulation under model uncertainties and external disturbances. A modified adaptive generalized super-twisting algorithm (AGSTA) enhanced by adaptive tracking differentiator (ATD) and reduced-order extended state observer (RESO) is proposed. The ATD is used to obtain the smooth reference signal and its derivative. The RESO is used to estimate and compensate for the model uncertainties and external disturbances in real-time, which enhances the robustness of the controller. The modified AGSTA ensures the fast convergence of the system states and maintains them in a predefined neighborhood of origin without overestimating control gains. Besides, the proposed new variable gain strategy completely avoids the control gains vibrating near the set minimum value. Thanks to the RESO, the proposed controller is model-free and can be easily implemented in practice. The stability of the closed-loop system is analyzed based on Lyapunov’s direct method in the time domain. Finally, the proposed control scheme is applied to the station-keeping control of Haidou-1 ARV, and the simulation results confirm the superiority of the proposed control scheme over the original AGSTA. Full article
(This article belongs to the Special Issue Control Theory and Applications in Marine Autonomous Vehicles)
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15 pages, 3144 KiB  
Article
Seasonal Dynamics of Bathyarchaeota-Dominated Benthic Archaeal Communities Associated with Seagrass (Zostera japonica) Meadows
by Pengyuan Liu, Haikun Zhang, Zenglei Song, Yanyan Huang and Xiaoke Hu
J. Mar. Sci. Eng. 2021, 9(11), 1304; https://doi.org/10.3390/jmse9111304 - 21 Nov 2021
Cited by 5 | Viewed by 2107
Abstract
Little is known about the seasonal dynamic of archaeal communities and their potential ecological functions in temperate seagrass ecosystems. In this study, seasonal changes in diversity, community structure, and potential metabolic functions of benthic archaea in surface sediments of two seagrass meadows along [...] Read more.
Little is known about the seasonal dynamic of archaeal communities and their potential ecological functions in temperate seagrass ecosystems. In this study, seasonal changes in diversity, community structure, and potential metabolic functions of benthic archaea in surface sediments of two seagrass meadows along the northern Bohai Sea in China were investigated using Miseq sequencing of the 16S rRNA gene and Tax4Fun2 functional prediction. Overall, Crenarchaeota (mainly Bathy-15, Bathy-8, and Bathy-6) dominated, followed by Thermoplasmatota, Asgardarchaeota, and Halobacterota, in terms of alpha diversities and relative abundance. Significant seasonal changes in the entire archaeal community structure were observed. The major phyla Methanobacteria, Nitrosopumilales, and genus Methanolobus had higher proportions in spring, while MBG-D and Bathyarchaeota were more abundant in summer and autumn, respectively. Alpha diversities (Shannon and Simpson) were the highest in summer and the lowest in autumn (ANOVA test, p < 0.05). Salinity, total organic carbon, and total organic nitrogen were the most significant factors influencing the entire archaeal community. Higher cellulose and hemicellulose degradation potentials occurred in summer, while methane metabolism potentials were higher in winter. This study indicated that season had strong effects in modulating benthic archaeal diversity and functional potentials in the temperate seagrass ecosystems. Full article
(This article belongs to the Section Marine Ecology)
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18 pages, 3075 KiB  
Article
Effect of Database Generation on Damage Consequences’ Assessment Based on Random Forests
by Luca Braidotti, Jasna Prpić-Oršić and Marko Valčić
J. Mar. Sci. Eng. 2021, 9(11), 1303; https://doi.org/10.3390/jmse9111303 - 21 Nov 2021
Cited by 4 | Viewed by 1392
Abstract
Recently, the application of machine learning has been explored to assess the main damage consequences without employing flooding sensors. This method can be the base of a new generation of onboard decision support systems to help the master during the progressive flooding of [...] Read more.
Recently, the application of machine learning has been explored to assess the main damage consequences without employing flooding sensors. This method can be the base of a new generation of onboard decision support systems to help the master during the progressive flooding of the ship. In particular, the application of random forests has been found suitable to assess the final fate of the ship and the damaged compartments’ set and estimate the time-to-flood. Random forests have to be trained using a database of precalculated progressive flooding simulations. In the present work, multiple options for database generation were tested and compared: three based on Monte Carlo (MC) sampling based on different probability distributions of the damage parameters and a parametric one. The methods were tested on a barge geometry to highlight the main effects on the damage consequences’ assessment in order to ease the further development of flooding-sensor-agnostic decision support systems for flooding emergencies. Full article
(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)
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19 pages, 9916 KiB  
Article
Robust Parameter Estimation of an Empirical Manoeuvring Model Using Free-Running Model Tests
by Ana Catarina Costa, Haitong Xu and Carlos Guedes Soares
J. Mar. Sci. Eng. 2021, 9(11), 1302; https://doi.org/10.3390/jmse9111302 - 20 Nov 2021
Cited by 12 | Viewed by 2027
Abstract
The work presents the identification and validation of the hydrodynamic coefficients for the surge, sway, and yaw motion. This is performed in two ways: using simulated data and free-running test data. The identification and validation with the simulation data are carried out using [...] Read more.
The work presents the identification and validation of the hydrodynamic coefficients for the surge, sway, and yaw motion. This is performed in two ways: using simulated data and free-running test data. The identification and validation with the simulation data are carried out using a 25° turning test and a 20°−20° zigzag manoeuvring test. For the free-running test data, two zigzag manoeuvres are used: 30°−30° zigzag for identification and 20°−20° zigzag for validation. A nonlinear manoeuvring model is proposed based on the standard Euler equations, and the hydrodynamic coefficients are computed using empirical equations. To obtain robust results, the truncated singular value decomposition is employed to diminish the multicollinearity and the parameter uncertainties due to noise. The validation is carried out by comparing the result of the measured values with the predictions obtained using the manoeuvring models. Finally, a sensitivity analysis for the simulation data is performed to understand the influence of the parameters in the manoeuvres. Full article
(This article belongs to the Special Issue Maritime Autonomous Vessels)
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16 pages, 5374 KiB  
Article
Surface Chlorophyll-A Fronts in the Yellow and Bohai Seas Based on Satellite Data
by Lu Xia, Hao Liu, Lei Lin and Yueqi Wang
J. Mar. Sci. Eng. 2021, 9(11), 1301; https://doi.org/10.3390/jmse9111301 - 20 Nov 2021
Cited by 5 | Viewed by 2212
Abstract
Chlorophyll fronts are important to monitor and map the oceanic front, especially in the season when sea surface temperature (SST) fronts weaken. In this study, surface chlorophyll-a (chl-a) fronts in the Yellow and Bohai seas were characterized for the first time using satellite [...] Read more.
Chlorophyll fronts are important to monitor and map the oceanic front, especially in the season when sea surface temperature (SST) fronts weaken. In this study, surface chlorophyll-a (chl-a) fronts in the Yellow and Bohai seas were characterized for the first time using satellite data. Five distinct chl-a fronts (i.e., the Bohai Strait, Shandong Peninsula, Jiangsu, Liaodong Peninsula, and Korean Peninsula fronts) were observed in summer along the 40 m isobaths and faded in other seasons. Notably, these fronts coincided with SST fronts. Strong chl-a fronts emerged during summer due to chl-a blooms in eutrophic coastal waters paired with surface chl-a fading in strongly stratified offshore waters and coastal physical fronts. Although SST fronts were strong during winter, light limitation and strong vertical mixing in offshore waters led to low chl-a in both coastal and offshore waters, suppressing chl-a front formation. Both chl-a and SST fronts coincided with steep seabed slopes (slope ratio > 1), suggesting that seabed slope may be an indicator of oceanic front location. Full article
(This article belongs to the Special Issue Satellite Monitoring of Ocean)
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27 pages, 5335 KiB  
Review
Surf Zone Turbulence and Suspended Sediment Dynamics—A Review
by Troels Aagaard, Joost Brinkkemper, Drude F. Christensen, Michael G. Hughes and Gerben Ruessink
J. Mar. Sci. Eng. 2021, 9(11), 1300; https://doi.org/10.3390/jmse9111300 - 20 Nov 2021
Cited by 7 | Viewed by 2695
Abstract
The existence of sandy beaches relies on the onshore transport of sand by waves during post-storm conditions. Most operational sediment transport models employ wave-averaged terms, and/or the instantaneous cross-shore velocity signal, but the models often fail in predictions of the onshore-directed transport rates. [...] Read more.
The existence of sandy beaches relies on the onshore transport of sand by waves during post-storm conditions. Most operational sediment transport models employ wave-averaged terms, and/or the instantaneous cross-shore velocity signal, but the models often fail in predictions of the onshore-directed transport rates. An important reason is that they rarely consider the phase relationships between wave orbital velocity and the suspended sediment concentration. This relationship depends on the intra-wave structure of the bed shear stress and hence on the timing and magnitude of turbulence production in the water column. This paper provides an up-to-date review of recent experimental advances on intra-wave turbulence characteristics, sediment mobilization, and suspended sediment transport in laboratory and natural surf zones. Experimental results generally show that peaks in the suspended sediment concentration are shifted forward on the wave phase with increasing turbulence levels and instantaneous near-bed sediment concentration scales with instantaneous turbulent kinetic energy. The magnitude and intra-wave phase of turbulence production and sediment concentration are shown to depend on wave (breaker) type, seabed configuration, and relative wave height, which opens up the possibility of more robust predictions of transport rates for different wave and beach conditions. Full article
(This article belongs to the Special Issue Recent Advances in Coastal Sediment Dynamics and Transport)
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11 pages, 5081 KiB  
Article
Dynamic Pressure Test and Analysis of Marine Ballasted Centrifugal Pump under Rapid Changing Conditions
by Zhipeng Zhu and Houlin Liu
J. Mar. Sci. Eng. 2021, 9(11), 1299; https://doi.org/10.3390/jmse9111299 - 19 Nov 2021
Cited by 2 | Viewed by 1709
Abstract
Ship ballast pumps have stringent requirements for their transient characteristics. Here, the pneumatic control valve and programmable logic controller (PLC) are applied to realize the rapid reduction in flow rate for ballast pumps, and the dynamic pressure of steady and transient conditions and [...] Read more.
Ship ballast pumps have stringent requirements for their transient characteristics. Here, the pneumatic control valve and programmable logic controller (PLC) are applied to realize the rapid reduction in flow rate for ballast pumps, and the dynamic pressure of steady and transient conditions and inner flow for the ballast pump are tested and analyzed. The results show that the dynamic pressure of each study scheme has cyclical increasing trends, however, the larger the amplitude of the flow rate reduction is, the greater the pressure increasing rate of the two measuring points. While the flow rate decreases to 0.4× Qd and 0.2× Qd, the rate of pressure increase is first fast and then slow. The dynamic pressure pulsation intensity is higher than the corresponding steady-state conditions after the transient conditions. With the increase in flow rate reduction, the characteristic frequencies of the dynamic pressure are 1APF (axial passing frequency) and 1BPF (blade passing frequency) and their harmonic frequency. The rapid decrease in flow rate causes the separation vortex in the impeller channel to be generated in advance, and the scale increases, which reduces the pulsation intensity of the pump outlet to prevent an increase in the level of broadband pulsation between 2APF and 1BPF. Full article
(This article belongs to the Special Issue Maritime Engineering, Industry Development Prospects)
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20 pages, 57458 KiB  
Article
Sedimentary Sequence, Evolution Model and Petroleum Geological Significance of Forced Regression: A Case Study of the Miocene Zhujiang Formation of the Pearl River Mouth Basin in the Northern South China Sea
by Ye Yu, Linghui Cai, Changmin Zhang, Li Wang, Rui Zhu, Yanran Huang and Taotao Cao
J. Mar. Sci. Eng. 2021, 9(11), 1298; https://doi.org/10.3390/jmse9111298 - 19 Nov 2021
Cited by 3 | Viewed by 2055
Abstract
Using 2D/3D seismic data and a large number of drilling and logging data and applying sequence stratigraphy, seismic sedimentology, and petroleum geology concepts, the characteristics of the sedimentary sequence of the forced regression have been analysed, the migration trajectory of the coastline have [...] Read more.
Using 2D/3D seismic data and a large number of drilling and logging data and applying sequence stratigraphy, seismic sedimentology, and petroleum geology concepts, the characteristics of the sedimentary sequence of the forced regression have been analysed, the migration trajectory of the coastline have been reconstructed, the evolution model of the forced regression have been presented, and the significance for petroleum geology of the forced regressive sandbodies have been discussed. The falling stage systems tract (FSST) of the Zhujiang Formation present offlap high-angle oblique foreset reflection structure in the seismic profiles of the depositional trends and turbidite fan deposits with strong amplitude mound reflection structure are developed in the downdip direction of its front. The trajectory of migration of the shoreline shows a terraced downtrend in the direction of basin. The FSST is characterized by the shelf-edge delta without topset beds. The FSST was formed in the fall of relative sea-level. Five sets of foreset beds controlled by high-frequency relative eustatic were developed, therefore ordinal regressive overlap can be observed for the five sets of shelf-edge deltas in the depositional trends. The favourable reservoirs which were located close to the upper boundary of the falling stage systems tract and the basal surface of forced regression are sandbodies of the shelf-edge delta front and wave-dominated shoreface sands and the sandbodies of the turbidite fan. Those sandbodies favour the formation of lithologic oil–gas reservoirs by means of good trap sealing conditions, excellent oil–gas reserving performance, and effective oil source communication of fracture system. Full article
(This article belongs to the Special Issue Marine Measurements: Theory, Methods and Applications)
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16 pages, 5904 KiB  
Article
Theoretical and Numerical Analysis of Blasting Pressure of Cylindrical Shells under Internal Explosive Loading
by Zhan-Feng Chen, Hui-Jie Wang, Zhiqian Sang, Wen Wang, He Yang, Wei-Ming Meng and Yu-Xing Li
J. Mar. Sci. Eng. 2021, 9(11), 1297; https://doi.org/10.3390/jmse9111297 - 19 Nov 2021
Cited by 3 | Viewed by 1844
Abstract
Cylindrical shells are principal structural elements that are used for many purposes, such as offshore, sub-marine, and airborne structures. The nonlinear mechanics model of internal blast loading was established to predict the dynamic blast pressure of cylindrical shells. However, due to the complexity [...] Read more.
Cylindrical shells are principal structural elements that are used for many purposes, such as offshore, sub-marine, and airborne structures. The nonlinear mechanics model of internal blast loading was established to predict the dynamic blast pressure of cylindrical shells. However, due to the complexity of the nonlinear mechanical model, the solution process is time-consuming. In this study, the nonlinear mechanics model of internal blast loading is linearized, and the dynamic blast pressure of cylindrical shells is solved. First, a mechanical model of cylindrical shells subjected to internal blast loading is proposed. To simplify the calculation, the internal blast loading is reduced to linearly uniform variations. Second, according to the stress function method, the dynamic blast pressure equation of cylindrical shells subjected to blast loading is derived. Third, the calculated results are compared with those of the finite element method (FEM) under different durations of dynamic pressure pulse. Finally, to reduce the errors, the dynamic blast pressure equation is further optimized. The results demonstrate that the optimized equation is in good agreement with the FEM, and is feasible to linearize the internal blast loading of cylindrical shells. Full article
(This article belongs to the Section Ocean Engineering)
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8 pages, 35386 KiB  
Communication
Morphological Significance and Relation of Ecosystems of Submarine Canyons off SW Taiwan
by Cheng-Shing Chiang and Ho-Shing Yu
J. Mar. Sci. Eng. 2021, 9(11), 1296; https://doi.org/10.3390/jmse9111296 - 19 Nov 2021
Cited by 1 | Viewed by 1822
Abstract
There are four shelf-incising submarine canyons off SW Taiwan. They are distributed along the active continental margin, which is periodically flushed by gravity flows. Shelf-incising canyons, such as Kaoping Canyon, may not only be affected by oceanographic conditions but also by extreme climate [...] Read more.
There are four shelf-incising submarine canyons off SW Taiwan. They are distributed along the active continental margin, which is periodically flushed by gravity flows. Shelf-incising canyons, such as Kaoping Canyon, may not only be affected by oceanographic conditions but also by extreme climate change due to the direct input of river sediment. In the canyons along the SW margin of Taiwan, strong sedimentary flows are reflected in highly abundant nutrient input and physical disturbances. The Kaoping Canyon possesses habitats that promote biodiversity but that are sensitive to environmental change. The aims of this study are to review the canyons along the SW margin of Taiwan and to present their geomorphological features and associated ecosystems. Full article
(This article belongs to the Special Issue Interannual Variation of Planktonic Species and Fish Populations)
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23 pages, 9952 KiB  
Article
Performance of the Car Carrier Shipping Sector in the Iberian Peninsula under the COVID-19 Scenario
by Jerónimo Esteve-Pérez, José Enrique Gutiérrez-Romero and Carlos Mascaraque-Ramírez
J. Mar. Sci. Eng. 2021, 9(11), 1295; https://doi.org/10.3390/jmse9111295 - 19 Nov 2021
Cited by 4 | Viewed by 1930
Abstract
The Iberian Peninsula represents the second European producer and the eighth world producer of vehicles in 2020. The pandemic of SARS-CoV2 introduced severe challenges for the worldwide population and for the industrial production and supply chains. The car carrier shipping sector has not [...] Read more.
The Iberian Peninsula represents the second European producer and the eighth world producer of vehicles in 2020. The pandemic of SARS-CoV2 introduced severe challenges for the worldwide population and for the industrial production and supply chains. The car carrier shipping sector has not been studied in depth in the Maritime Transportation and Port Logistics literature. This research pays special attention to the performance of this traffic in the Iberian Peninsula in the pre-pandemic era and under COVID-19 pandemic conditions, in which seven ports with car-carrier ship traffic in the Iberian Peninsula are analyzed. First, a dynamic portfolio analysis about how the COVID-19 pandemic affected the evolution of competitive positions of Iberian Peninsula ports is performed. Second, studies of the seasonality patterns of vehicle movements in ports of the Iberian Peninsula were carried out using time series of the periods from 2012 to 2019 and from 2012 to 2020. The Seasonal Variation Index (SVI) was employed to determine the seasonality of vehicle traffic in the periods considered and analyses were performed independently for both embarking and disembarking traffic. Important conclusions are revealed, e.g., during a year of COVID-19, the seven ports had decreased vehicle movements for disembarking traffic and only one port increased the traffic for embarking traffic. Furthermore, COVID-19 introduced important changes in the seasonality patterns of vehicle movements during the first months of the pandemic. Full article
(This article belongs to the Section Ocean Engineering)
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20 pages, 5908 KiB  
Article
Deep-Sea Fish Fauna on the Seamounts of Southern Japan with Taxonomic Notes on the Observed Species
by Keita Koeda, Soutarou Takashima, Takehisa Yamakita, Shinji Tsuchida and Yoshihiro Fujiwara
J. Mar. Sci. Eng. 2021, 9(11), 1294; https://doi.org/10.3390/jmse9111294 - 19 Nov 2021
Cited by 8 | Viewed by 3878
Abstract
Several volcanic islands and submarine volcanoes exist in the sea connecting the Izu-Bonin Islands with the Mariana Islands, with trenches and islands formed by the submergence of the Pacific Plate under the Philippine Sea Plate. Although designated as a Marine Protected Area (MPA) [...] Read more.
Several volcanic islands and submarine volcanoes exist in the sea connecting the Izu-Bonin Islands with the Mariana Islands, with trenches and islands formed by the submergence of the Pacific Plate under the Philippine Sea Plate. Although designated as a Marine Protected Area (MPA) in December 2020, the seamounts’ biodiversity has not been sufficiently researched. Therefore, direct observations and specimen sampling were conducted on four seamounts in this area using a remotely operated vehicle (ROV), autonomous underwater vehicle (AUV), and baited cameras (BCs). The ROV survey was conducted for 2–4 days on each seamount and divided into shallow and deep areas. During the expedition, 20 orders and 51 families of 81 deep-sea fish species were observed, including several potentially undescribed species, new genus or species records from Japanese waters, new depth records, new ecological information, and several rare fishes. The fish fauna and biodiversity abundance clearly differed among the seamounts; the seamount with a hydrothermal vent had the lowest diversity among the four seamounts. In shallow water, 23, 7, and 12 species were recorded only by ROV, AUV, and BC, respectively, indicating that combining these methods is beneficial for understanding the fish fauna of seamounts. Full article
(This article belongs to the Special Issue Deepwater Fishes)
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17 pages, 689 KiB  
Article
The Coevolutionary Process of Maritime Management of Shipping Industry in the Context of the COVID-19 Pandemic
by Yan Zhang and Zhikuan Sun
J. Mar. Sci. Eng. 2021, 9(11), 1293; https://doi.org/10.3390/jmse9111293 - 19 Nov 2021
Cited by 10 | Viewed by 2999
Abstract
This study investigates how international organizations, International Maritime Organization (IMO) member states, and associate members have embarked on maritime management (MM) measures to address dire situations in the context of the COVID-19 pandemic. It explores the evolution of MM practices from international organizations, [...] Read more.
This study investigates how international organizations, International Maritime Organization (IMO) member states, and associate members have embarked on maritime management (MM) measures to address dire situations in the context of the COVID-19 pandemic. It explores the evolution of MM practices from international organizations, IMO member states, and associate members to ensure the resilience and sustainability of the shipping industry. Corpus linguistics was employed as a computer-assisted method to assess a large number of naturally occurring texts. Circular letters from international organizations and member states listed on the IMO website from January 2020 to July 2021 were curated and built into three corpora. Through corpus linguistic analysis of circulars from three different crisis phases (Pre-/early-crisis, Crisis in progress, Post-COVID-19 crisis phase), we discovered an MM progression mechanism developed between stakeholders in conjunction with the post-crisis period. The study presented the “MM-as-process” vision to emphasize the time-varying dynamic nature of MM development during the disruption. Full article
(This article belongs to the Special Issue Marine Policy)
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18 pages, 2120 KiB  
Article
Assessment of Seasonal and Spatial Variations of Coastal Water Quality Using Multivariate Statistical Techniques
by Mohamad Alkhalidi, Abdalrahman Alsulaili, Badreyah Almarshed, Majed Bouresly and Sarah Alshawish
J. Mar. Sci. Eng. 2021, 9(11), 1292; https://doi.org/10.3390/jmse9111292 - 19 Nov 2021
Cited by 5 | Viewed by 2377
Abstract
This study investigates the seasonal and spatial trends in Kuwait’s coastal water’s physical, chemical, and biological parameters by applying multivariate statistical techniques, including cluster analysis (CA), principal component/factor analysis (PCA/FA), and the Pearson correlation (PC) method to the average daily reading of water [...] Read more.
This study investigates the seasonal and spatial trends in Kuwait’s coastal water’s physical, chemical, and biological parameters by applying multivariate statistical techniques, including cluster analysis (CA), principal component/factor analysis (PCA/FA), and the Pearson correlation (PC) method to the average daily reading of water quality parameters from fifteen stations over one year. The investigated parameters are pH, turbidity, chlorophyll-a, conductivity, dissolved oxygen (DO), phycoerythrin, salinity, and temperature. The results show that the coastal water of Kuwait is subjected to high environmental pressure due to natural and human interferences. During 2017, the DO levels were below the threshold limit, and at the same time, the water temperature and salinity were very high, causing a series of fish death events. CA resulted in three different regions based on the turbidity, including high, moderate, and low regions, and three seasons (winter, summer, and autumn). Spring is very short and overlaps with winter and summer. PCA/FA applied on the datasets assisted in extracting and identifying parameters responsible for the variations in the seasons and regions obtained from CA. Additionally, Pearson’s correlation resulted in a strong positive relation between chlorophyll and phycoerythrin in 7 out of the 15 stations. However, at high turbidity regions (stations 1 and 2), chlorophyll concentration was low. Additionally, the negative correlation between DO and temperature was observed at stations with rare human activities. Full article
(This article belongs to the Section Marine Pollution)
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15 pages, 6898 KiB  
Article
Quantitative Relationships between the Tidal Current Limit, Tidal Level Limit and River Discharge in the Changjiang River Estuary
by Chengcheng Hou, Jianrong Zhu, Ju Huang and Xinyue Cheng
J. Mar. Sci. Eng. 2021, 9(11), 1291; https://doi.org/10.3390/jmse9111291 - 19 Nov 2021
Cited by 1 | Viewed by 1611
Abstract
Estuaries are areas where runoff and tide interact. Tidal waves propagate upstream from river mouths and produce tidal currents and tidal level variations along rivers. Based on the hydrological frequency analysis of river discharge in the dry season and flood season at the [...] Read more.
Estuaries are areas where runoff and tide interact. Tidal waves propagate upstream from river mouths and produce tidal currents and tidal level variations along rivers. Based on the hydrological frequency analysis of river discharge in the dry season and flood season at the Datong hydrological station over the past 70 years, a three-dimensional estuary numerical model was used to produce the quantitative relationships between the tidal current limit, tidal level limit and river discharge in the Changjiang River estuary. The positions of tidal current limit and tidal level limit depend not only on river discharge but also on river topography. When river discharge varies from a hydrological frequency of 95% to 5%, the relationship between the tidal current limit and river discharge is y=2×10−13x3+3 × 10−8x2− 0.0074x+359.35 in the flood season, with a variation range of 90 km, and y=−4×10−10x3−1 × 10−5x2−0.1937x − 1232.9 in the dry season, with a variation range of 200 km. The relationship between the tidal level limit and river discharge is y=6×10−8x2−0.0096x+775.94 in the flood season, with a variation range of 127 km, and y=0.3428x2−17.9x+777.55 in the dry season, with a variation range of 83 km, which is located far upstream of the Datong hydrological station. Full article
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12 pages, 3465 KiB  
Article
Investigation of the Dynamic Characteristics of an Eccentric Annular Seal on the Basis of a Transient CFD Method with Three Whirl Models
by Fengqin Li, Lulu Zhai, Baoling Cui, Jia Guo and Guoyou Chen
J. Mar. Sci. Eng. 2021, 9(11), 1290; https://doi.org/10.3390/jmse9111290 - 19 Nov 2021
Cited by 3 | Viewed by 1784
Abstract
Many annular seals suffer eccentricity because of rotor–stator misalignment or the deflection of a flexible rotor, which has a strong influence on the vibration characteristics and stability of rotating machines. In this article, a transient CFD method based on three whirl models is [...] Read more.
Many annular seals suffer eccentricity because of rotor–stator misalignment or the deflection of a flexible rotor, which has a strong influence on the vibration characteristics and stability of rotating machines. In this article, a transient CFD method based on three whirl models is employed to research the dynamic characteristics of annular seals at various static eccentricities. The influence of the whirl amplitude on the dynamic characteristics of eccentric annular seals are also explored. The results of the transient CFD method are compared with the bulk flow model results and the experimental results. It is shown that the transient CFD method possesses high prediction precision for direct damping, with a maximum error of 25%. Negative kyx increases by 166% when the static eccentricity ratio is increased from 0 to 0.5. The dynamic characteristics of the annular seal operating at high static eccentric ratio are sensitive to whirl amplitude, and the model with an amplitude of 1% Cr has great advantages for the prediction of direct virtual-mass, while the model with an amplitude of 10% Cr has great advantages for the prediction of cross-coupled damping. Full article
(This article belongs to the Section Ocean Engineering)
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6 pages, 852 KiB  
Communication
Garbage Patches and Their Environmental Implications in a Plastisphere
by Walter Leal Filho, Julian Hunt and Marina Kovaleva
J. Mar. Sci. Eng. 2021, 9(11), 1289; https://doi.org/10.3390/jmse9111289 - 19 Nov 2021
Cited by 14 | Viewed by 16452
Abstract
This Communication reports on the increases in the sizes of garbage patches, and their environmental implications, outlining the dimensions of what is a growing problem connected with the “plastisphere”. The paper presents some data on the distribution of garbage patches in the world’s [...] Read more.
This Communication reports on the increases in the sizes of garbage patches, and their environmental implications, outlining the dimensions of what is a growing problem connected with the “plastisphere”. The paper presents some data on the distribution of garbage patches in the world’s oceans and makes some predictions on future growth, which is partly associated with the future increases in worldwide plastics production. The findings demonstrate that the size of the main garbage patches is increasing, posing a threat to the environment and marine life. The paper urges for better plastic waste management to prevent it from reaching the oceans, along with concerted actions in respect of plastic collection and cleaning up the oceans, which may include new technological solutions. Full article
(This article belongs to the Section Marine Pollution)
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19 pages, 8017 KiB  
Article
3D Numerical Study of the Impact of Macro-Roughnesses on a Tidal Turbine, on Its Performance and Hydrodynamic Wake
by Ilan Robin, Anne-Claire Bennis and Jean-Claude Dauvin
J. Mar. Sci. Eng. 2021, 9(11), 1288; https://doi.org/10.3390/jmse9111288 - 18 Nov 2021
Cited by 2 | Viewed by 1699
Abstract
Biofouling is an important factor to consider when calculating the energetic efficiency of tidal farms. Despite the fact that biofouling effects have been widely investigated in the past for naval applications, very few studies concern tidal turbines. This paper proposes a numerical approach [...] Read more.
Biofouling is an important factor to consider when calculating the energetic efficiency of tidal farms. Despite the fact that biofouling effects have been widely investigated in the past for naval applications, very few studies concern tidal turbines. This paper proposes a numerical approach to assess the impact of biofouling on tidal turbines, which is efficient for testing many configurations. Two turbulence models are tested (RANS k-ω SST and LES Smagorinsky) for the motionless blade case to validate them. Then we chose to use the Smagorinsky model for the case of a complete tidal turbine rotor with realistically fouled blades. The pressure coefficient is strongly affected by the barnacle in the motionless blade case and the power coefficient is slightly degraded in the complete rotor case. Motionless blade cases do not represent the real biofouling behaviour for two reasons. First, sessile species settle in the down flow part of the chord where their impact is less important. Then, the surrounding turbulence provoked by the blades rotation in the rotor case reduces the impact of biofouling. In the wake, biofouling generates small vortexes that propagate into the larger ones, causing them to spread their energy. Full article
(This article belongs to the Topic Marine Renewable Energy)
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12 pages, 17251 KiB  
Article
Minimum Propulsion Power Assessment of a VLCC to Maintain the Maneuverability in Adverse Conditions
by Peiyuan Feng, Shukui Liu, Baoguo Shang and Apostolos Papanikolaou
J. Mar. Sci. Eng. 2021, 9(11), 1287; https://doi.org/10.3390/jmse9111287 - 18 Nov 2021
Cited by 2 | Viewed by 2117
Abstract
The International Maritime Organization (IMO) Guidelines for Determining Minimum Propulsion Power to Maintain the Maneuverability in Adverse Conditions is the sole regulation imposed on the routine design and approval of all new-built ships as a part of EEDI requirements. This study reviews the [...] Read more.
The International Maritime Organization (IMO) Guidelines for Determining Minimum Propulsion Power to Maintain the Maneuverability in Adverse Conditions is the sole regulation imposed on the routine design and approval of all new-built ships as a part of EEDI requirements. This study reviews the development of the guidelines and summarizes the recent amendments of MEPC76(2021). The present assessment is conducted for a new VLCC design following the new guidelines aiming at investigating the influence of alternative wave added resistance evaluation methods and the propeller design features on the assessment results. It is found that the most simple empirical formula method proposed by MEPC76 is not conservative enough, as could have been expected. On the other hand, spectral analysis methods based on empirically obtained and properly validated wave added resistance responses can produce consistent results. Moreover, discussions are made from the perspective of propeller design to meet the regulatory requirements. It is pointed out that the light running margin is a key design parameter, and propellers with larger light running margins are more advantageous for satisfying the minimum propulsion power regulation, thus ensuring the navigation safety in adverse conditions. These obtained insights and know-how can support the engineers in obtaining optimal design solutions. Full article
(This article belongs to the Section Ocean Engineering)
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31 pages, 14972 KiB  
Review
Development and Research Status of Tidal Current Power Generation Systems in China
by Hao Chen, Qi Li, Mohamed Benbouzid, Jingang Han and Nadia Aït-Ahmed
J. Mar. Sci. Eng. 2021, 9(11), 1286; https://doi.org/10.3390/jmse9111286 - 18 Nov 2021
Cited by 6 | Viewed by 3848
Abstract
Considering the depletion of oil, coal, gas and other fossil energy, and the increasingly serious environmental pollution, all countries in the world are developing clean and renewable energy, such as wind energy, water energy, solar energy, etc., to alleviate the current energy crisis. [...] Read more.
Considering the depletion of oil, coal, gas and other fossil energy, and the increasingly serious environmental pollution, all countries in the world are developing clean and renewable energy, such as wind energy, water energy, solar energy, etc., to alleviate the current energy crisis. Tidal current energy belongs to the marine renewable energy. It is clean, pollution-free, and abundant, with a good prospect of development due to its similarity with wind energy. This paper firstly analyses the reserves and distribution of tidal current energy in China. Then the early exploration of Tidal Current Power Generation System (TCPGS) in China is briefly introduced. Subsequently, it gives the details of the devices and experimental platforms of TCPGS that were researched and developed by various universities, research institutes and enterprises in China. The information mainly includes: the size and the capacity of the system, the support structure, turbine type, the selection of generator, and some river and offshore test information, etc. Finally, it discusses the similarities and differences between China and other countries in tidal current power generation technology, and summaries the current development status and gives the prospect of the TCPGS technology in China. Full article
(This article belongs to the Special Issue Review Papers in Ocean Engineering)
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18 pages, 2822 KiB  
Article
Evolution of the Seismic Response of Monopile-Supported Offshore Wind Turbines of Increasing Size from 5 to 15 MW including Dynamic Soil-Structure Interaction
by Cristina Medina, Guillermo M. Álamo and Román Quevedo-Reina
J. Mar. Sci. Eng. 2021, 9(11), 1285; https://doi.org/10.3390/jmse9111285 - 18 Nov 2021
Cited by 6 | Viewed by 1873
Abstract
As a result of wind power’s expansion over the globe, offshore wind turbines (OWTs) are being projected in seismic prone areas. In parallel, the industry develops increasingly larger and more powerful generators. Many of the seismic response analyses of wind turbines conducted so [...] Read more.
As a result of wind power’s expansion over the globe, offshore wind turbines (OWTs) are being projected in seismic prone areas. In parallel, the industry develops increasingly larger and more powerful generators. Many of the seismic response analyses of wind turbines conducted so far only consider smaller units. In this paper, a finite element substructuring model in frequency domain is used to compute the seismic response of four reference OWTs from 5 to 15 MW founded on monopiles embedded in several homogeneous soil profiles with shear wave velocities from 100 to 300 m/s and subjected to different accelerograms. The foundation behaviour is obtained through a continuum model including kinematic and inertial interaction. The relevance of soil-structure interaction and main trends of the seismic response of OWTs are inferred from the presented results. Although the seismic maximum bending moments increase with the size of the OWT system, their relevance with respect to the ones produced by design loads decreases as the turbine gets bigger. The same effect is observed for the shear forces if the soil is soft enough. The inclusion of SSI effects almost duplicates the seismic response when compared to the rigid base scenario. Full article
(This article belongs to the Section Ocean Engineering)
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