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J. Mar. Sci. Eng., Volume 7, Issue 7 (July 2019) – 42 articles

Cover Story (view full-size image): Following the fast and continuous degradation of coral reefs worldwide, new approaches for coral reef restoration and adaptation were raised, some are being tested. This manuscript describes 7 novel approaches that are further classified into three operation levels (improved methodologies/ecological engineering; “assisted” approaches; epigenetics/chimerism). While the literature discusses each approach separately, this concept paper unifies all under the single umbrella of the ‘coral gardening’ tenet, also revealing that each level is based on the accomplishment of the other levels. This is the first attempt to combine all reef restoration tactics under a single working rationale. Legend to the figure: Farmed Acropora coral colonies in the mid-water floating nursery at Eilat (Israel), the Red Sea. Each colony has started from a coral nubbin in the size of few mm length (Courtesy: S. Shafir). View this [...] Read more.
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19 pages, 22459 KiB  
Article
Experimental Investigations on Hydrodynamic Responses of a Semi-Submersible Offshore Fish Farm in Waves
by Yunpeng Zhao, Changtao Guan, Chunwei Bi, Hangfei Liu and Yong Cui
J. Mar. Sci. Eng. 2019, 7(7), 238; https://doi.org/10.3390/jmse7070238 - 23 Jul 2019
Cited by 89 | Viewed by 6978
Abstract
A series of physical model experiments was performed to investigate the hydrodynamic responses of a semi-submersible offshore fish farm in waves. The structural configuration of the fish farm primarily refers to that of the world’s first offshore fish farm, Ocean Farm 1, developed [...] Read more.
A series of physical model experiments was performed to investigate the hydrodynamic responses of a semi-submersible offshore fish farm in waves. The structural configuration of the fish farm primarily refers to that of the world’s first offshore fish farm, Ocean Farm 1, developed by SalMar in Norway. The mooring line tension and motion response of the fish farm were measured at three draughts. The study indicated that the tension on the windward mooring line is greater than that on the leeward mooring line. As the wave height increases, the mooring line tension and motion responses including the heave, surge, and pitch exhibit an upward trend. The windward mooring line tension decreased slightly with increasing draught. The existence of net resulted in approximately 42% reduction in mooring line tension and approximately 51% reduction in surge motion. However, the heave and pitch of the fish farm increased slightly with the existence of net. It was found that the wave parameters, draught, and net have noticeable effect on the hydrodynamic response. Thus, these factors are suggested to be considered in structural designs and optimization to guarantee the ability of the fish farm to resist destruction and ensure safety of workers during intense waves. Full article
(This article belongs to the Special Issue Ocean Renewable Energy Systems (ORES); Wave–Structure Interaction Analysis and Design Methods)
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18 pages, 11575 KiB  
Article
Experimental Study for Wave-Induced Pore-Water Pressures in a Porous Seabed around a Mono-Pile
by Shaohua Wang, Pandi Wang, Hualing Zhai, Qibo Zhang, Linya Chen, Lunliang Duan, Yifei Liu and Dong-Sheng Jeng
J. Mar. Sci. Eng. 2019, 7(7), 237; https://doi.org/10.3390/jmse7070237 - 21 Jul 2019
Cited by 23 | Viewed by 3971
Abstract
In this paper, the results of a series of experiments on wave-induced pore-water pressures around a mono-pile are presented. Unlike the previous study, in which the mono-pile was fully buried, the mono-pile in this study was installed at 0.6 m below the seabed [...] Read more.
In this paper, the results of a series of experiments on wave-induced pore-water pressures around a mono-pile are presented. Unlike the previous study, in which the mono-pile was fully buried, the mono-pile in this study was installed at 0.6 m below the seabed surface. In this study, we focus on the pore-water pressures around the mono-pile and beneath the pile. The experimental results lead to the following conclusions: (1) the seabed response is more pronounced near the surface (in the region above 30 cm deep), and the rate of pore pressure attenuation gradually slows down. For the region below 0.3 m, the response is much smaller; (2) in general, along the surface of the pile, pore pressures increase as the wave height and wave period increase; (3) the spatial distribution of pore pressure near the pile will vary with different wave periods, while the wave height only has a significant effect on the amplitude; and (4) At z = −0.15 m, the pore pressure in front of the pile is the largest, while at the point 0.1 m below the bottom of the pile, the largest pore pressure occurs behind the pile. Full article
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18 pages, 6812 KiB  
Article
A Method for Reducing Cogging Torque of Integrated Propulsion Motor
by Huanyu Ou, Yuli Hu, Zhaoyong Mao and Yukai Li
J. Mar. Sci. Eng. 2019, 7(7), 236; https://doi.org/10.3390/jmse7070236 - 21 Jul 2019
Cited by 7 | Viewed by 2848
Abstract
How to reduce the cogging torque of the integrated propeller motor is an important means to improve its noise performance because cogging torque is one of the key factors causing torque ripple. We proposed a method to reduce the cogging torque by optimizing [...] Read more.
How to reduce the cogging torque of the integrated propeller motor is an important means to improve its noise performance because cogging torque is one of the key factors causing torque ripple. We proposed a method to reduce the cogging torque by optimizing the size of the Halbach array’s auxiliary pole. First, an analytical model for the airgap magnetic field of Halbach array based on different dimensions (including the circumference ratio and the radial thickness) of the auxiliary pole is given. Then the finite element method is used to verify the analytical model. On the basis, we calculated the cogging torque of different size of auxiliary poles as sample data by combining different circumference ratio and radial thickness. Furthermore, using the two-variable single-objective neural network genetic optimization algorithm based on Backpropagation (BP), we obtain the optimal size of the auxiliary pole. Finally, comparing the motor cogging torque and torque ripple before and after optimization indicated that the cogging torque and torque ripple are effectively reduced after optimizing the size of the auxiliary pole. Full article
(This article belongs to the Section Ocean Engineering)
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16 pages, 6455 KiB  
Article
Study on the Softening Mechanism and Control of Red-Bed Soft Rock under Seawater Conditions
by Zhen Liu, Xinfu He, Jin Fan and Cuiying Zhou
J. Mar. Sci. Eng. 2019, 7(7), 235; https://doi.org/10.3390/jmse7070235 - 21 Jul 2019
Cited by 19 | Viewed by 4125
Abstract
Red-bed soft rock easily softens and disintegrates when it comes into contact with water, which is the main factor restricting the application of soft rock as an engineering filler. Therefore, research on the influence of seawater on soft rock softening has great significance [...] Read more.
Red-bed soft rock easily softens and disintegrates when it comes into contact with water, which is the main factor restricting the application of soft rock as an engineering filler. Therefore, research on the influence of seawater on soft rock softening has great significance for the application of soft rock in marine engineering. To examine the softening mechanism of soft rock under seawater conditions, two kinds of soft rock softening experiments, as well as ion inhibition tests of soft rock softening, were performed under seawater and pure water conditions, and the results were compared. The variation in the soft rock composition, the deformation and failure characteristics of soft rock under the influence of sea water, and the variation in main cations in the softening process of soft rock are examined successively; the influences of different ions on soft rock softening are further analysed. Based on the analyses, the softening mechanism and control method of soft rock under sea water conditions are expounded. The study showed that soft rock softening was inhibited by seawater, which decreased the softening degree of soft rock. The main cations in seawater had an inhibitory effect on soft rock softening, and the order of inhibition was Ca2+ > Mg2+ > Na+. According to the inhibitory effect of ions on soft rock softening, we propose that seawater or calcium salt should be added to reduce the softening of soft rock in soft rock engineering and improve the mechanical strength of soft rock; in addition, soft rock can be considered a raw material in marine engineering. The experimental results have great significance for studies of the disintegration mechanism and inhibitory rules of soft rock under the influence of seawater and provide a theoretical basis for the application of soft rock in marine engineering, such as in artificial reef engineering and coastal dike engineering. Full article
(This article belongs to the Section Coastal Engineering)
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13 pages, 5714 KiB  
Article
Test-Bed Performance of an Ice-Coring Drill Used with a Hot Water Drilling System
by An Liu, Rusheng Wang, Xiaopeng Fan, Yang Yang, Xingchen Li, Liang Wang and Pavel Talalay
J. Mar. Sci. Eng. 2019, 7(7), 234; https://doi.org/10.3390/jmse7070234 - 20 Jul 2019
Cited by 3 | Viewed by 4338
Abstract
Ice cores from ice shelves contain abundant paleoclimatic information and provide essential information concerned with the prediction of future climatic change and global sea level variations. Efficient retrieval of ice cores is always an engineering challenge in polar ice and marine research. Here, [...] Read more.
Ice cores from ice shelves contain abundant paleoclimatic information and provide essential information concerned with the prediction of future climatic change and global sea level variations. Efficient retrieval of ice cores is always an engineering challenge in polar ice and marine research. Here, we present design and other information of a new hot-water ice-coring drill used in combination with a hot-water drilling system that provides a rapid and environmentally friendly ice coring system. The coring system shares the surface equipment and hydraulic hose with the hot-water drilling system. Tests with the drill were carried out at an ice drill testing facility, and theoretical estimations were performed to predict the rate of penetration (ROP) and water flow rates. The results indicate the optimal water temperature for ice-coring to be 50 °C, and the most suitable water flow rate to be from 42 L/min to 55 L/min. With those drilling parameters, the maximum ROP is 27.8 m/h and the ice cores are 55–59 mm in diameter. Full article
(This article belongs to the Section Coastal Engineering)
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17 pages, 6433 KiB  
Article
Video Sensing of Nearshore Bathymetry Evolution with Error Estimate
by Duong Hai Thuan, Rafael Almar, Patrick Marchesiello and Nguyen Trung Viet
J. Mar. Sci. Eng. 2019, 7(7), 233; https://doi.org/10.3390/jmse7070233 - 19 Jul 2019
Cited by 27 | Viewed by 4700
Abstract
Although coastal morphology results essentially from underwater sediment transports, the evolution of underwater beach profiles along the diverse coastlines of the world is still poorly documented. Bathymetry inversion from shore-based video cameras set forth a more systematic evaluation and is becoming more commonly [...] Read more.
Although coastal morphology results essentially from underwater sediment transports, the evolution of underwater beach profiles along the diverse coastlines of the world is still poorly documented. Bathymetry inversion from shore-based video cameras set forth a more systematic evaluation and is becoming more commonly used. However, there are limitations to this profiling method that are insufficiently assessed, undermining confidence in operational applications. In this paper, we investigate the daily evolution of a low tide terrace (LTT) in Nha Trang beach, Vietnam, under strong seasonal forcing: from weak wind waves during summer monsoon to moderate waves during winter monsoon. A new error estimation for depth inversion is presented based on tidal evaluation. The method compares video-based estimate and direct measurement of tidal amplitudes to provide a quality criterion. It reveals three types of errors, the main one being a deep water error associated with physical limits—loss of celerity-bathymetry relationship in deep water. This error is dependent on wave period and thus has a strong seasonal pattern in Vietnam. It is generally detrimental to depth inversion where wind waves are dominant (in summer here). On the contrary, the second error type is larger for larger waves and is located at breakpoint, altering wave detection. The last error type is due to nonlinear effects and wave setup in shallow water. After removing the faulty data, we finally present the first reliable three-year time-series of a beach profile in Nha Trang, Vietnam. A main result is the overall stability demonstrated for the LTT beach, with rapid exchange of sediment between the terrace and the upper beach during typhoons, monsoon events or seasonal cycles. These tropical environments may provide faster beach recovery compared with mid-latitude configurations. Full article
(This article belongs to the Special Issue Application of Remote Sensing Methods to Monitor Coastal Zones)
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6 pages, 875 KiB  
Article
Evaluation of the Occurrence of Tetrodotoxin in Bivalve Mollusks from the Portuguese Coast
by Susana Margarida Rodrigues, Estefanía Pereira Pinto, Patrícia Oliveira, Sónia Pedro and Pedro Reis Costa
J. Mar. Sci. Eng. 2019, 7(7), 232; https://doi.org/10.3390/jmse7070232 - 19 Jul 2019
Cited by 14 | Viewed by 3415
Abstract
Occurrence of tetrodotoxin (TTX), a potent natural neurotoxin, in marine organisms and seafood from the European Union has been of increasing concern due to its relatively recent detection in bivalve mollusks and gastropods. Following a request of the European Food Safety Authority (EFSA) [...] Read more.
Occurrence of tetrodotoxin (TTX), a potent natural neurotoxin, in marine organisms and seafood from the European Union has been of increasing concern due to its relatively recent detection in bivalve mollusks and gastropods. Following a request of the European Food Safety Authority (EFSA) to EU Member States to obtain more data on TTX occurrence, this study collected 117 samples of bivalve mollusks, including mussels (Mytilus galloprovincialis), oysters (Crassostrea gigas) and clams (Ruditapes philippinarum and Donax spp.), from the South and Southwest Portuguese coast between May and October 2018, for TTX determination and microbiological analysis. The analyses carried out by hydrophilic interaction liquid chromatography tandem mass spectrometry (HILIC-MS/MS) did not detect TTX in any sample, and microbiological analysis did not reveal high concentrations of Vibrio spp., which has been linked to the presence of TTX. Although preliminary, results from this study, the first investigating the presence of TTX in bivalve mollusks from the Portuguese coast, suggest that TTX may not represent a risk for human consumption of bivalve mollusks. Full article
(This article belongs to the Special Issue Advances and Current Challenges in Marine Biotoxins Monitoring)
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22 pages, 10806 KiB  
Article
Effects of Different Design Parameters on the Vortex Induced Vibration of FRP Composite Risers Using Grey Relational Analysis
by Chunguang Wang, Shiquan Ge, Justin W. Jaworski, Liping Liu and Zhirong Jia
J. Mar. Sci. Eng. 2019, 7(7), 231; https://doi.org/10.3390/jmse7070231 - 19 Jul 2019
Cited by 5 | Viewed by 3207
Abstract
Risers are indispensable components of offshore platform systems that connect the wellhead at the sea bottom and to the platform at the sea surface and are normally made of high grade steel. Nowadays, fiber reinforced polymer (FRP) composite has been recognized as an [...] Read more.
Risers are indispensable components of offshore platform systems that connect the wellhead at the sea bottom and to the platform at the sea surface and are normally made of high grade steel. Nowadays, fiber reinforced polymer (FRP) composite has been recognized as an attractive alternative riser material. Similarly to steel risers, FRP composite risers are also vulnerable to vortex induced vibration (VIV), and the effects of the composite makeup of these risers on VIV are the subject of the present investigation. Three risers (the tailored design composite riser, the composite riser with orthogonal reinforcements and the steel riser), three current velocities (0.36 m/s, 1.22 m/s and 2.13 m/s) and three water depths (12.5 m, 25 m and 37.5 m) are considered. In total, 9 study cases using orthogonal array (OA) sampling are investigated to study the risers’ VIV characteristics. The computational fluid dynamics (CFD) simulations with coupled fluid–structure interaction (FSI) are used to obtain the risers’ natural frequencies, global displacements, global stresses and the stress distributions in each composite lamina. The effect of 5 parameters (Etension, Ebending, L/Douter, tension force and current velocity) on the VIV amplitude in a cross flow direction of the risers is analyzed using Grey relational analysis (GRA) and the Grey relational grade of these parameters are: r 05 ( Velocity ) > r 03 ( L / D outer ) > r 04 ( Tension   Force ) > r 01 ( E t e n s i o n ) > r 02 ( E b e n d i n g ) . Full article
(This article belongs to the Section Ocean Engineering)
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24 pages, 6880 KiB  
Article
Fuel Consumption and CO2 Emission Reductions of Ships Powered by a Fuel-Cell-Based Hybrid Power Source
by Gilltae Roh, Hansung Kim, Hyeonmin Jeon and Kyoungkuk Yoon
J. Mar. Sci. Eng. 2019, 7(7), 230; https://doi.org/10.3390/jmse7070230 - 18 Jul 2019
Cited by 29 | Viewed by 7067
Abstract
The need for technological development to reduce the impact of air pollution caused by ships has been strongly emphasized by many authorities, including the International Maritime Organization (IMO). This has encouraged research to develop an electric propulsion system using hydrogen fuel with the [...] Read more.
The need for technological development to reduce the impact of air pollution caused by ships has been strongly emphasized by many authorities, including the International Maritime Organization (IMO). This has encouraged research to develop an electric propulsion system using hydrogen fuel with the aim of reducing emissions from ships. This paper describes the test bed we constructed to compare our electric propulsion system with existing power sources. Our system uses hybrid power and a diesel engine generator with a combined capacity of 180 kW. To utilize scale-down methodology, the linear interpolation method is applied. The proposed hybrid power source consists of a molten carbonate fuel cell (MCFC), a battery, and a diesel generator, the capacities of which are 100 kW, 30 Kw, and 50 kW, respectively. The experiments we conducted on the test bed were based on the outcome of an analysis of the electrical power consumed in each operating mode considering different types of merchant ships employed in practice. The output, fuel consumption, and CO2 emission reduction rates of the hybrid and conventional power sources were compared based on the load scenarios created for each type of ship. The CO2 emissions of the hybrid system was compared with the case of the diesel generator alone operation for each load scenario, with an average of 70%~74%. This analysis confirmed the effectiveness of using a ship with a fuel-cell-based hybrid power source. Full article
(This article belongs to the Special Issue Ship Lifecycle)
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17 pages, 3088 KiB  
Article
Modeling of Sediment Transport in Bothnian Bay in the Vicinity of the Nuclear Power Plant ‘Hanhikivi-1’ Construction Site
by Stanislav D. Martyanov, Anton Yu. Dvornikov, Vladimir A. Ryabchenko and Dmitry V. Sein
J. Mar. Sci. Eng. 2019, 7(7), 229; https://doi.org/10.3390/jmse7070229 - 18 Jul 2019
Cited by 3 | Viewed by 2709
Abstract
The intensity of sediment resuspension and sedimentation in the eastern part of the Bothnian Bay near the Hanhikivi cape, where the nuclear power plant ‘Hanhikivi-1’ will be constructed, has been assessed for the first time by means of numerical modeling under the realistic [...] Read more.
The intensity of sediment resuspension and sedimentation in the eastern part of the Bothnian Bay near the Hanhikivi cape, where the nuclear power plant ‘Hanhikivi-1’ will be constructed, has been assessed for the first time by means of numerical modeling under the realistic external forcing that occurred in 2014. A brief description of a coupled modeling system used in the study is given. The results of local resuspension intensity and sediment accumulation rates for one-year model run are presented. It has been determined that the main areas of sediment accumulation are located along the northern coast off the Hanhikivi peninsula and in the shallow region situated to the north-east off the cape. Sedimentation rates in the navigation channel have also been estimated. Model results obtained for 2014 suggest that sedimentation in the seaward part of the channel is absent, while sediment accumulation intensity is about 10 cm/year in the middle part of the channel and 70 cm/year in the coastal part. A temporal variability of the sedimentation rates during the year has been emphasized. Full article
(This article belongs to the Section Physical Oceanography)
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17 pages, 2012 KiB  
Article
The Role of Bacillus amyloliquefaciens on Litopenaeus vannamei During the Maturation of a Biofloc System
by Ferran Llario, Silvia Falco, María-Teresa Sebastiá-Frasquet, Julia Escrivá, Miguel Rodilla and Luís Henrique Poersch
J. Mar. Sci. Eng. 2019, 7(7), 228; https://doi.org/10.3390/jmse7070228 - 18 Jul 2019
Cited by 15 | Viewed by 5686
Abstract
Biofloc technology is a sustainable aquaculture production system which uses microorganisms to maintain water quality and to increase productivity. In this system, probiotics can enhance the positive effects of bioflocs on the cultured species. The objective of this research is to study the [...] Read more.
Biofloc technology is a sustainable aquaculture production system which uses microorganisms to maintain water quality and to increase productivity. In this system, probiotics can enhance the positive effects of bioflocs on the cultured species. The objective of this research is to study the role of the probiotic bacterium Bacillus amyloliquefaciens during the formation of a biofloc system for the culture of Litopenaeus vannamei. Two doses of probiotic were assayed and applied directly to the water. The experiment was developed in nine tanks distributed as follows: Three control tanks with no probiotic, three tanks with a probiotic dose of 103 cfu/mL, and three tanks with a dose of 104 cfu/mL. Water quality, microbial activity, growth parameters and the immune system state of shrimps were monitored throughout the maturation process. The results indicate a positive effect upon the shrimp immune system throughout the study period, where specifically there was an increase in granular hemocytes in the shrimp hemolymph. During the immature biofloc phase, granular hemocytes were 5% higher in tanks supplemented with the probiotic. During the mature biofloc phase, granular hemocytes were 7% higher in those same tanks. During the maturation of the biofloc, environmental conditions are more unfavorable for shrimp growth, due to the accumulation of nitrites. So, the effect of the probiotic is especially important during this stage when the shrimp are stressed and are more vulnerable to diseases. However, the effects on microbial activity, water quality and Litopenaeus vannamei growth did not increase the benefits of the biofloc system. Full article
(This article belongs to the Special Issue Marine Aquaculture)
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25 pages, 24762 KiB  
Article
Large Eddy Simulation of Flow over Wavy Cylinders with Different Twisted Angles at a Subcritical Reynolds Number
by Chunyu Guo, Hang Guo, Jian Hu, Kewei Song, Weipeng Zhang and Wei Wang
J. Mar. Sci. Eng. 2019, 7(7), 227; https://doi.org/10.3390/jmse7070227 - 18 Jul 2019
Cited by 11 | Viewed by 4313
Abstract
The deformation of the cylinder has been proved to greatly reduce the fluctuation of lift and the vortex-induced vibration. In this article, a new form of deformation mode for the smooth cylinder is proposed in order to reduce the vortex-induced vibrations, which can [...] Read more.
The deformation of the cylinder has been proved to greatly reduce the fluctuation of lift and the vortex-induced vibration. In this article, a new form of deformation mode for the smooth cylinder is proposed in order to reduce the vortex-induced vibrations, which can be applied to marine risers and submarine pipelines to ensure the working performance and safety of offshore platforms. Large eddy simulation (LES) is adopted to simulate the turbulent flow over wavy cylinders with three different twisted angles at a subcritical Reynolds number Re = 28,712. Comparing with the results of smooth cylinder, the maximum drag and lift reduction of wavy cylinder A3 with α = 40° can reach 17% and 84%, respectively, and the corresponding vortex formation length increases significantly, while the turbulence intensity decreases relatively. Meanwhile, the circumferential minimum pressure coefficient is greater than that of the smooth cylinder, which also provides a greater drag reduction for the cylinder. The surface separation line, turbulent kinetic energy distribution, and wake vortex structure indicate that the elongation of separated shear layer and wake shedding position is larger than that of the smooth cylinder, and the vorticity value in the near wake region decreases. A periodic vortex structure is generated along the spanwise direction, and a weaker and more stable Karman vortex street is reformed at a further downstream position, which ultimately leads to the reduction of drag and fluctuating lift of the wavy cylinder. Full article
(This article belongs to the Special Issue Advances in Marine Dynamic Simulation)
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13 pages, 5707 KiB  
Article
Application of the Design of Experiments and Computational Fluid Dynamics to Bow Design Improvement
by Woochan Seok, Gwan Hoon Kim, Jeonghwa Seo and Shin Hyung Rhee
J. Mar. Sci. Eng. 2019, 7(7), 226; https://doi.org/10.3390/jmse7070226 - 17 Jul 2019
Cited by 18 | Viewed by 4643
Abstract
Techniques of the design of experiments (DOE) and computational fluid dynamics (CFD) were applied for improving the bow shape of a tanker hull. Through this, a hull that could reduce the added resistance in waves was derived. The key design elements of the [...] Read more.
Techniques of the design of experiments (DOE) and computational fluid dynamics (CFD) were applied for improving the bow shape of a tanker hull. Through this, a hull that could reduce the added resistance in waves was derived. The key design elements of the bow shape were selected as parameters for design optimization and added resistance in the short-wavelength region was interpreted through CFD considering the operational condition of the full scale ship. For design parameter changes, the number of analyses was minimized by applying DOE. The regression equation for calculating added resistance was derived using bow-shape design parameters by applying the response surface method and regression analysis to obtain the optimal hull with minimal added resistance was derived. The methodology was applied to an Aframax tanker hull form, and the derived added resistance regression equation and the added resistance value obtained through CFD analysis showed a difference of approximately 1%. The model test results of the improved hull form showed that the added resistance was reduced by 52% in comparison to that obtained for the original hull form. Full article
(This article belongs to the Section Ocean Engineering)
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23 pages, 10626 KiB  
Article
Steps towards Modeling Community Resilience under Climate Change: Hazard Model Development
by Kendra M. Dresback, Christine M. Szpilka, Xianwu Xue, Humberto Vergara, Naiyu Wang, Randall L. Kolar, Jia Xu and Kevin M. Geoghegan
J. Mar. Sci. Eng. 2019, 7(7), 225; https://doi.org/10.3390/jmse7070225 - 16 Jul 2019
Cited by 6 | Viewed by 3539
Abstract
With a growing population (over 40%) living in coastal counties within the U.S., there is an increasing risk that coastal communities will be significantly impacted by riverine/coastal flooding and high winds associated with tropical cyclones. Climate change could exacerbate these risks; thus, it [...] Read more.
With a growing population (over 40%) living in coastal counties within the U.S., there is an increasing risk that coastal communities will be significantly impacted by riverine/coastal flooding and high winds associated with tropical cyclones. Climate change could exacerbate these risks; thus, it would be prudent for coastal communities to plan for resilience in the face of these uncertainties. In order to address all of these risks, a coupled physics-based modeling system has been developed that simulates total water levels. This system uses parametric models for both rainfall and wind, which only require essential information (e.g., track and central pressure) generated by a hurricane model. The system is validated with Hurricane Isabel hindcasts: One using the parametric system and another using data assimilated fields. The results show a good agreement to the available data, indicating that the system is able to adequately capture the hazards using parametric models, as compared to optimized fields. The validated system was then utilized to simulate randomly generated scenarios that account for future uncertainty, i.e., amount of sea level rise and storm strength/track, as influenced by projected climate change scenarios. Results are then used in next step in the development of a system-wide, community resilience model. Full article
(This article belongs to the Special Issue Extreme Events in Nearshore and River Integrated Region)
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24 pages, 8290 KiB  
Article
Motion Control of Pentapod Offshore Wind Turbines under Earthquakes by Tuned Mass Damper
by Wenhua Wang, Xin Li, Zuxing Pan and Zhixin Zhao
J. Mar. Sci. Eng. 2019, 7(7), 224; https://doi.org/10.3390/jmse7070224 - 16 Jul 2019
Cited by 20 | Viewed by 3468
Abstract
The dynamic characteristics of a bottom-fixed offshore wind turbine (OWT) under earthquakes are analyzed by developing an integrated analysis model of the OWT. Further, the influence of the interactions between the rotor and support system on the structural responses of the OWT subjected [...] Read more.
The dynamic characteristics of a bottom-fixed offshore wind turbine (OWT) under earthquakes are analyzed by developing an integrated analysis model of the OWT. Further, the influence of the interactions between the rotor and support system on the structural responses of the OWT subjected to an earthquake is discussed. Moreover, a passive control method using a tuned mass damper (TMD) is applied to the OWT to control the responses under earthquakes. The effects of the mass ratio, location and tuned frequency of the TMD on controlling structural responses of the OWT under different recorded seismic waves are studied. Full article
(This article belongs to the Special Issue Ocean Renewable Energy Systems (ORES); Wave–Structure Interaction Analysis and Design Methods)
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25 pages, 11259 KiB  
Article
Using Flexible Blades to Improve the Performance of Novel Small-Scale Counter-Rotating Self-Adaptable Wave Energy Converter for Unmanned Marine Equipment
by Chongfei Sun, Jianzhong Shang, Zirong Luo, Zhongyue Lu, Guoheng Wu and Yiming Zhu
J. Mar. Sci. Eng. 2019, 7(7), 223; https://doi.org/10.3390/jmse7070223 - 15 Jul 2019
Cited by 7 | Viewed by 4194
Abstract
Unmanned marine equipment has been increasingly developed for open seas. The lack of efficient and reliable power supply is currently one of the bottlenecks restricting the practical application of these devices. In order to provide a viable power supply method for unmanned marine [...] Read more.
Unmanned marine equipment has been increasingly developed for open seas. The lack of efficient and reliable power supply is currently one of the bottlenecks restricting the practical application of these devices. In order to provide a viable power supply method for unmanned marine equipment, such as sonic buoys and sea robots, we originally propose a novel small-scale flexible blade wave energy converter (WEC) based on self-adaptable counter-rotating operation mechanism. The flexible blade WEC is designed on the basis of the rigid blade WEC with the caging device. This paper identifies the key factors affecting WEC performance through theoretical analysis. According to the numerical simulation analysis, the output mechanical power of the double-layer absorber is 12.8 W, and the hydraulic efficiency is 36.3%. The results of the verification experiment show that the peak power of WEC is 5.8 W and the average power is 3.2 W. The WEC with 65Mn flexible blade under most experimental conditions has the best performance when the blade thickness is 0.10 mm. The study shows that the new generation WEC can effectively overcome the excessive fluctuation of the output power of the previous generation WEC. The output power curve of the novel WEC is relatively smooth, which is conducive to its smooth operation and subsequent utilization and storage of electrical energy. Full article
(This article belongs to the Section Ocean Engineering)
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25 pages, 22946 KiB  
Article
Design and Construction of a Modular Pump-Jet Thruster for Autonomous Surface Vehicle Operations in Extremely Shallow Water
by Angelo Odetti, Marco Altosole, Gabriele Bruzzone, Massimo Caccia and Michele Viviani
J. Mar. Sci. Eng. 2019, 7(7), 222; https://doi.org/10.3390/jmse7070222 - 15 Jul 2019
Cited by 31 | Viewed by 9908
Abstract
This paper describes a customized thruster for Autonomous Surface Vehicles (ASV). The thruster is a Pump-Jet Module (PJM), which has been expressly designed, modeled, constructed, and tested for small-/medium-sized ASVs that perform environmental monitoring in extremely shallow waters such as wetlands (rivers, lakes, [...] Read more.
This paper describes a customized thruster for Autonomous Surface Vehicles (ASV). The thruster is a Pump-Jet Module (PJM), which has been expressly designed, modeled, constructed, and tested for small-/medium-sized ASVs that perform environmental monitoring in extremely shallow waters such as wetlands (rivers, lakes, swamps, marshes), where water depth is only a few centimeters. The PJM is a fully-electric propulsion unit with a 360-degree continuous steering capability. Its main advantage is that the unit is flush with the flat bottom of the vehicle. This makes the PJM suitable for operation in extremely shallow waters because the risk of damaging the thrusting unit in case of grounding is very limited. The PJM was produced using innovative materials, and the hydraulic components were all constructed using a 3D printer. Full article
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19 pages, 5265 KiB  
Article
Case Study of Dam Overtopping from Waves Generated by Landslides Impinging Perpendicular to a Reservoir’s Longitudinal Axis
by Netsanet Nigatu Tessema, Fjóla G. Sigtryggsdóttir, Leif Lia and Asie Kemal Jabir
J. Mar. Sci. Eng. 2019, 7(7), 221; https://doi.org/10.3390/jmse7070221 - 15 Jul 2019
Cited by 11 | Viewed by 5811
Abstract
Landslide-generated impulse waves in dammed reservoirs run up the reservoir banks as well as the upstream dam slope. If large enough, the waves may overtop and even breach the dam and cause flooding of the downstream area with hazardous consequences. Hence, for reservoirs [...] Read more.
Landslide-generated impulse waves in dammed reservoirs run up the reservoir banks as well as the upstream dam slope. If large enough, the waves may overtop and even breach the dam and cause flooding of the downstream area with hazardous consequences. Hence, for reservoirs in landslide-prone areas, it is important to provide a means to estimate the potential size of an event triggered by landslides along the reservoir banks. This research deals with landslide-generated waves and the overtopping process over the dam crest in a three-dimensional (3D) physical model test, presenting a case study. The model set-up describes the landslide impacting the reservoir in a perpendicular manner, which is often the case in natural settings. Based on the experimental results, dimensionless empirical relations are derived between the overtopping volume and the governing parameters, namely the slide volume, slide release height, slide impact velocity, still-water depth, and upstream dam face slope. Predictive relations for the overtopping volume are presented as applicable for cases relating to the specific model set-up. Measured overtopping volumes are further compared to a two-dimensional (2D) case reported in the literature. An important feature regarding the overtopping process for the 3D case is the variation in time and space, resulting in an uneven distribution of the volume of water overtopping the dam crest. This observation is made possible by the 3D model set-up, and is of value for dam safety considerations as well as for foundation-related issues, including erosion and scouring. Full article
(This article belongs to the Special Issue Tsunami Science and Engineering II)
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14 pages, 1759 KiB  
Article
Extraction and Analysis of Compounds with Antibacterial Potential from the Red Alga Grateloupia turuturu
by Isabel Cardoso, João Cotas, Ana Rodrigues, Daniel Ferreira, Nádia Osório and Leonel Pereira
J. Mar. Sci. Eng. 2019, 7(7), 220; https://doi.org/10.3390/jmse7070220 - 15 Jul 2019
Cited by 24 | Viewed by 6344
Abstract
Nowadays, the development of new drugs only relies on a small number of molecules and 50% of all existent drugs are extracted or synthetically obtained. This work intends to evaluate the antibacterial potential of the ethanolic and polysaccharide extracts obtained from Grateloupia turuturu [...] Read more.
Nowadays, the development of new drugs only relies on a small number of molecules and 50% of all existent drugs are extracted or synthetically obtained. This work intends to evaluate the antibacterial potential of the ethanolic and polysaccharide extracts obtained from Grateloupia turuturu and to characterize the composition of the alga’s polysaccharides by FTIR-ATR. We used sequential extraction to obtain the extracts that were tested against S. aureus and E. coli. The ethanolic extracts in E. coli, at the highest concentration used (15 mg mL−1) showed 45.7% (Tetrasporophyte extract) and 55.1% (Carposporophyte extract) of growth reduction and in S. aureus 56.2% (T extract) and 51.8% (C extract). Polysaccharide extracts started showing significant reduction effect on E. coli and S. aureus growth at 7.5 mg mL−1 with a reduction of 54.9% and 39.5%, respectively. At 15 mg mL−1 the reduction observed was 88.5% and 85.4%. The FTIR-ATR allowed to characterize G. turuturu’s polysaccharides concluding that it is composed by a hybrid kappa/iota carrageenan with traces of agar, in both phases of the life cycle. This work allows us to conclude about the antibacterial properties of this alga and the compounds that might be behind this activity, showing that there’s a lot more than a small number of molecules that can be used as natural drugs. Full article
(This article belongs to the Special Issue Biotechnological Valorization of Marine Resources and By-Products)
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21 pages, 2869 KiB  
Article
Wave Energy in Tropical Regions: Deployment Challenges, Environmental and Social Perspectives
by Angélica Felix, Jassiel V. Hernández-Fontes, Débora Lithgow, Edgar Mendoza, Gregorio Posada, Michael Ring and Rodolfo Silva
J. Mar. Sci. Eng. 2019, 7(7), 219; https://doi.org/10.3390/jmse7070219 - 14 Jul 2019
Cited by 38 | Viewed by 11346
Abstract
The harnessing of renewable sources of marine energy has become a promising solution for a number of problems, namely satisfying the increasing demand for electricity, the reduction of greenhouse gas emissions, and the provision of energy to regions unconnected to a national grid. [...] Read more.
The harnessing of renewable sources of marine energy has become a promising solution for a number of problems, namely satisfying the increasing demand for electricity, the reduction of greenhouse gas emissions, and the provision of energy to regions unconnected to a national grid. Tropical countries have an interesting dichotomy: Despite their varied potential sources of marine energy, their environmental and social conditions impose severe constraints on the development of a renewable energy industry. Moreover, the exploitation of these opportunities is limited by national economies’ reliance on fossil fuels, political and social restraints, and technological immaturity. The present work addresses challenges and opportunities common to wave energy implementation in tropical nations, as a first approach to a regional diagnosis. The motivation for this work is to encourage research on wave energy policies in the Tropics. Technical, environmental, and social challenges to be overcome in wave energy projects are discussed. The technical challenges are grouped into development, deployment, and operation stages of wave energy converters; environmental challenges are divided into biodiversity, cumulative effects, and monitoring aspects, whilst social issues include population growth and energy access matters. The Mexican strategy for developing sustainable technology throughout the wave energy production chain is also presented. Full article
(This article belongs to the Special Issue The Development of Marine Energy Extraction)
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27 pages, 5850 KiB  
Article
Numerical and Experimental Modelling of a Wave Energy Converter Pitching in Close Proximity to a Fixed Structure
by Pilar Heras, Sarah Thomas, Morten Kramer and Jens Peter Kofoed
J. Mar. Sci. Eng. 2019, 7(7), 218; https://doi.org/10.3390/jmse7070218 - 13 Jul 2019
Cited by 9 | Viewed by 3734
Abstract
Free-floating bodies are commonly modelled using Cummins’ equation based on linear potential flow theory and including non-linear forces when necessary. In this paper, this methodology is applied to a body pitching around a fixed hinge (not free-floating) located close to a second bottom-fixed [...] Read more.
Free-floating bodies are commonly modelled using Cummins’ equation based on linear potential flow theory and including non-linear forces when necessary. In this paper, this methodology is applied to a body pitching around a fixed hinge (not free-floating) located close to a second bottom-fixed body. Due to the configuration of the setup, strong hydrodynamic interactions occur between the two bodies. An investigation is made into which non-linear forces need to be included in the model in order to accurately represent reality without losing computational efficiency. The non-linear forces investigated include hydrostatic restoring stiffness and different formulations of excitation forces and quadratic drag forces. Based on a numerical comparison, it is concluded that the different non-linear forces, except for the quadratic drag force, have a minor influence on the calculated motion of the pitching body. Two formulations of the quadratic drag force are shown to result in similar motions, hence the most efficient one is preferred. Comparisons to wave basin experiments show that this model is, to a large extent, representative of reality. At the wave periods where the hydrodynamic interactions between the bodies are largest, however, the amplitudes of motion measured in the wave basin are lower than those calculated numerically. Full article
(This article belongs to the Special Issue Nonlinear Numerical Modelling of Wave Energy Converters)
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18 pages, 9128 KiB  
Article
Experimental Analysis of Wave Overtopping: A New Small Scale Laboratory Dataset for the Assessment of Uncertainty for Smooth Sloped and Vertical Coastal Structures
by Hannah E Williams, Riccardo Briganti, Alessandro Romano and Nicholas Dodd
J. Mar. Sci. Eng. 2019, 7(7), 217; https://doi.org/10.3390/jmse7070217 - 13 Jul 2019
Cited by 29 | Viewed by 4314
Abstract
Most physical model tests carried out to quantify wave overtopping are conducted using a wave energy spectrum, which is then used to generate a free surface wave time series at the wave paddle. This method means that an infinite number of time series [...] Read more.
Most physical model tests carried out to quantify wave overtopping are conducted using a wave energy spectrum, which is then used to generate a free surface wave time series at the wave paddle. This method means that an infinite number of time series can be generated, but, due to the expense of running physical models, often only a single time series is considered. The aim of this work is to investigate the variation in the main overtopping measures when multiple wave times series generated from the same spectrum are used. Physical model tests in a flume measuring 15 m (length) by 0.23 m (width) with an operating depth up to 0.22 m were carried out using a stochastic approach on two types of structures (a smooth slope and a vertical wall), and a variety of wave conditions. Results show variation of overtopping discharge, computed by normalising the range of the discharges at a certain wave condition with the maximum value of the discharge in the range up to 10 % , when the same wave time series is used, but this range increases to 75 % when different time series are used. This variation is found to be of a similar magnitude to both the one found with similar experiments looking at the phenomena in numerical models, and that specified by the confidence bounds in empirical methods. Full article
(This article belongs to the Special Issue Dynamics of the Coastal Zone)
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20 pages, 2480 KiB  
Article
Mapping of Ecological Vulnerability of Sea-Coastal Zones to Oil Spills: A Preliminary Method Applied to Kola Bay, the Barents Sea
by Anatoly Shavykin and Andrey Karnatov
J. Mar. Sci. Eng. 2019, 7(7), 216; https://doi.org/10.3390/jmse7070216 - 12 Jul 2019
Cited by 4 | Viewed by 3655
Abstract
Preparedness for oil spill response is a challenge for many coastal countries. Responders are unable to take effective action unless maps that indicate areas with different vulnerability to oil pollution are available. Such maps, developed in many countries, are usually based on calculations [...] Read more.
Preparedness for oil spill response is a challenge for many coastal countries. Responders are unable to take effective action unless maps that indicate areas with different vulnerability to oil pollution are available. Such maps, developed in many countries, are usually based on calculations with rank (ordinal) values. However, arithmetic operations with them cannot be allowed. The article describes a method of constructing maps using metric values. The calculations take into account the biomass and the quantity of important biota components, especially significant socio-economic objects and protected areas. The biota distribution densities are represented in the identical units. The vulnerability factors are assessed based on the potential impact of spilled oil on biota, as well as its sensitivity and recoverability after disturbance. The proposed method takes into account the different sensitivity of biota inhabiting in the water column and on the sea surface. Oil vulnerability maps for Kola Bay using the proposed algorithm are presented. Full article
(This article belongs to the Special Issue Coastal Zone Management)
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30 pages, 16562 KiB  
Article
Coastal Processes and Influence on Damage to Urban Structures during Hurricane Irma (St-Martin & St-Barthélemy, French West Indies)
by Tony Rey, Frédéric Leone, Thomas Candela, Ali Belmadani, Philippe Palany, Yann Krien, Raphael Cécé, Monique Gherardi, Matthieu Péroche and Narcisse Zahibo
J. Mar. Sci. Eng. 2019, 7(7), 215; https://doi.org/10.3390/jmse7070215 - 12 Jul 2019
Cited by 23 | Viewed by 6555
Abstract
This study aims to better understand coastal processes associated with extreme cyclonic events through the study of the coastal changes, flooding and damage that resulted from the passage of a category 5 hurricane (Irma) on 6 September 2017 over the islands of Saint-Martin [...] Read more.
This study aims to better understand coastal processes associated with extreme cyclonic events through the study of the coastal changes, flooding and damage that resulted from the passage of a category 5 hurricane (Irma) on 6 September 2017 over the islands of Saint-Martin and Saint-Barthélemy in the Lesser Antilles. Hurricane Irma was contextualized from tropical cyclone track data and local weather observations collected by Météo-France, as well as high-resolution numerical modelling. Field work involved the study of accretion coasts through qualitative observations, topo-morphological and sedimentary surveys, as well as image acquisition with Unmanned Aerial Vehicle (UAV) surveys during two trips that were made 2 and 8 months after the catastrophe. Wave propagation and flood numerical models are presented and compared to field data. Our field analysis also reports on the devastating impacts of storm surges and waves, which reached 4 and 10 meters height, respectively, especially along east-facing shores. The approaches reveal a variety of morpho-sedimentary responses over both natural and highly urbanized coasts. The analysis shows the effects of coastal structures and streets on flow channeling, on the amplification of some erosion types, and on water level increase. Positive spatial correlation is found between damage intensity and marine flood depth. The signatures of ocean-induced damage are clear and tend to validate the relevance of the intensity scale used in this study. Full article
(This article belongs to the Special Issue Storm Erosion)
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14 pages, 1637 KiB  
Article
Optimization on Emergency Materials Dispatching Considering the Characteristics of Integrated Emergency Response for Large-Scale Marine Oil Spills
by Song Li, Manel Grifoll, Miquel Estrada, Pengjun Zheng and Hongxiang Feng
J. Mar. Sci. Eng. 2019, 7(7), 214; https://doi.org/10.3390/jmse7070214 - 12 Jul 2019
Cited by 19 | Viewed by 3741
Abstract
Many governments have been strengthening the construction of hardware facilities and equipment to prevent and control marine oil spills. However, in order to deal with large-scale marine oil spills more efficiently, emergency materials dispatching algorithm still needs further optimization. The present study presents [...] Read more.
Many governments have been strengthening the construction of hardware facilities and equipment to prevent and control marine oil spills. However, in order to deal with large-scale marine oil spills more efficiently, emergency materials dispatching algorithm still needs further optimization. The present study presents a methodology for emergency materials dispatching optimization based on four steps, combined with the construction of Chinese oil spill response capacity. First, the present emergency response procedure for large-scale marine oil spills should be analyzed. Second, in accordance with different grade accidents, the demands of all kinds of emergency materials are replaced by an equivalent volume that can unify the units. Third, constraint conditions of the emergency materials dispatching optimization model should be presented, and the objective function of the model should be postulated with the purpose of minimizing the largest sailing time of all oil spill emergency disposal vessels, and the difference in sailing time among vessels that belong to the same emergency materials collection and distribution point. Finally, the present study applies a toolbox and optimization solver to optimize the emergency materials dispatching problem. A calculation example is presented, highlighting the sensibility of the results at different grades of oil spills. The present research would be helpful for emergency managers in tackling an efficient materials dispatching scheme, while considering the integrated emergency response procedure. Full article
(This article belongs to the Special Issue Regulatory Framework and Integrated Marine Management)
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12 pages, 2792 KiB  
Article
Assessing the Unreliability of Systems during the Early Operation Period of a Ship—A Case Study
by Leszek Chybowski, Katarzyna Gawdzińska and Rafał Laskowski
J. Mar. Sci. Eng. 2019, 7(7), 213; https://doi.org/10.3390/jmse7070213 - 11 Jul 2019
Cited by 16 | Viewed by 3617
Abstract
Sea-going ships are unique systems, and each ship—even those which are mass-produced—are different. Once in service, they are subjected to unique environmental exposure due to a variety of factors, including, but not limited to, their mode of operation, sailing area, cargo, hydrometeorological conditions, [...] Read more.
Sea-going ships are unique systems, and each ship—even those which are mass-produced—are different. Once in service, they are subjected to unique environmental exposure due to a variety of factors, including, but not limited to, their mode of operation, sailing area, cargo, hydrometeorological conditions, crew training, etc. This makes it very difficult, if not impossible, to compare individual units. The aim of this study is to present the damage data and analysis of a selected vessel—a complex technical system—during its first year of operation. To that end, the paper analyses the unreliability of a bulk cargo ship’s technical and energetic system components during its first year of operation. The paper also introduces the failure susceptibility of its technical systems, defines concepts of wear and failure and describes the object of analysis. Observed failures in subsystem components of the marine power plant, in the general systems and in the technological system of the ship, were presented in tabular form. Each failure was described by considering the time of operation until the first failure, type of failure, type of wear, nature of an event and methods used to regain efficiency. Selected failures were described in great detail, and the statistics of the ship’s components’ susceptibility to failure were presented by considering the wear type that caused a failure, the component type and the time to the first failure. Additionally the severity of each failure is discussed. Finally, conclusions regarding the susceptibility to failure of particular ship components were presented. Full article
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9 pages, 1095 KiB  
Article
Prediction of Grouting Penetration Height Along the Shaft of Base Grouted Pile
by Kai Fang, Tongbin Zhao, Yunliang Tan and Yue Qiu
J. Mar. Sci. Eng. 2019, 7(7), 212; https://doi.org/10.3390/jmse7070212 - 10 Jul 2019
Cited by 11 | Viewed by 3206
Abstract
Post-pressure grouting is an effective method to improve bearing capacity of ordinary bored cast-in-situ piles. The migration of the grout along the pile side is regarded as an important mechanism responsible for the improvement of the pile capacity. Research into the penetration height [...] Read more.
Post-pressure grouting is an effective method to improve bearing capacity of ordinary bored cast-in-situ piles. The migration of the grout along the pile side is regarded as an important mechanism responsible for the improvement of the pile capacity. Research into the penetration height of the grout is of great important in evaluating the behavior of base grouted piles. In this paper, a prediction method of grouting penetration height along the shaft of the base grouted pile was proposed. Considering the balance and losses of the grout pressure during grouting, an iterative procedure was given to determine the penetration height of the grout in layered soils. Field test results were also provided to indicate the validity of the proposed method. Full article
(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)
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15 pages, 4384 KiB  
Article
A Numerical Investigation on the Flooding Process of Multiple Compartments Based on the Volume of Fluid Method
by XinLong Zhang, Zhuang Lin, Simone Mancini, Ping Li, Ze Li and Fei Liu
J. Mar. Sci. Eng. 2019, 7(7), 211; https://doi.org/10.3390/jmse7070211 - 10 Jul 2019
Cited by 22 | Viewed by 3605
Abstract
A detailed description of the flooding process is crucial to analyze the complex hydrodynamic behaviors and enhance the survivability of the damaged ship. In this paper, through establishing three typical damage scenarios with various locations, the commercial software CD Adapco STAR-CCM+ based on [...] Read more.
A detailed description of the flooding process is crucial to analyze the complex hydrodynamic behaviors and enhance the survivability of the damaged ship. In this paper, through establishing three typical damage scenarios with various locations, the commercial software CD Adapco STAR-CCM+ based on the Reynolds-Averaged Navier-Stokes (RANS) solver is applied to simulate the flooding process involving multiple compartments. The basic computational fluid dynamics (CFD) models and specific simulation settings are elaborated. The volume of fluid (VOF) method combined with the user defined field function is developed to distribute the initial free surface. The captured flooding process indicates that the air compression due to the restricted ventilation decreases the flooding amount. The obtained flooding time can provide necessary data to support for appropriate rescue management and evacuation options. Full article
(This article belongs to the Section Ocean Engineering)
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27 pages, 3914 KiB  
Article
Sediment Transport Processes during Barrier Island Inundation under Variations in Cross-Shore Geometry and Hydrodynamic Forcing
by Anita Engelstad, Gerben Ruessink, Piet Hoekstra and Maarten van der Vegt
J. Mar. Sci. Eng. 2019, 7(7), 210; https://doi.org/10.3390/jmse7070210 - 8 Jul 2019
Cited by 2 | Viewed by 3243
Abstract
Inundation of barrier islands can cause severe morphological changes, from the break-up of islands to sediment accretion. The response will depend on island geometry and hydrodynamic forcing. To explore this dependence, the non-hydrostatic wave model SWASH was used to investigate the relative importance [...] Read more.
Inundation of barrier islands can cause severe morphological changes, from the break-up of islands to sediment accretion. The response will depend on island geometry and hydrodynamic forcing. To explore this dependence, the non-hydrostatic wave model SWASH was used to investigate the relative importance of bedload transport processes, such as transport by mean flow, short- (0.05–1 Hz) and infragravity (0.005–0.05 Hz) waves during barrier island inundation for different island configurations and hydrodynamic conditions. The boundary conditions for the model are based on field observations on a Dutch barrier island. Model results indicate that waves dominate the sediment transport processes from outer surfzone until landwards of the island crest, either by transporting sediment directly or by providing sediment stirring for the mean flow transport. Transport by short waves was continuously landwards directed, while infragravity wave and mean flow transport was seaward or landward directed. Landward of the crest, sediment transport was mostly dominated by the mean flow. It was forced by the water level gradient, which determined the mean flow transport direction and magnitude in the inner surfzone and on the island top. Simulations suggest that short wave and mean flow transport are generally larger on steeper slopes, since wave energy dissipation is less and mean flow velocities are higher. The slope of the island top and the width of the island foremost affect the mean flow transport, while variations in inundation depth will additionally affect transport by short-wave acceleration skewness. Full article
(This article belongs to the Special Issue Storm Erosion)
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16 pages, 5396 KiB  
Article
The Interpretation of Biogeochemical Growths on Gold Coins from the SS Central America Shipwreck: Applications for Biogeochemistry and Geoarchaeology
by Erik B. Melchiorre, Bryan H. Seymour and Robert D. Evans
J. Mar. Sci. Eng. 2019, 7(7), 209; https://doi.org/10.3390/jmse7070209 - 5 Jul 2019
Cited by 1 | Viewed by 4084
Abstract
Black crusts that formed on gold coins recovered from the 1857 shipwreck of the SS Central America played a key role in their preservation in a near original state. Within a few years of the sinking, the significant quantities of iron and steel [...] Read more.
Black crusts that formed on gold coins recovered from the 1857 shipwreck of the SS Central America played a key role in their preservation in a near original state. Within a few years of the sinking, the significant quantities of iron and steel on the shipwreck produced laminar geochemical precipitates of fine-grained iron minerals on the coins. This coating served to armor the coins from future chemical or biological attacks. Once coated, the coins were colonized by at least two distinct populations of gold-tolerant bacteria that precipitated abundant nanoparticulate gold in the black crust material and produced biomineralized bacteria in a web-like mat. Above this middle layer of black crust, the outer layer consisted of a geochemical reaction front of euhedral crystals of iron sulfate and iron oxy-hydroxide species, formed by the interaction of seawater with the chemical wastes of the bacterial mat. Understanding this process has application for assessing the diverse and extreme conditions under which nano-particulate gold may form through biological processes, as well as understanding the conditions that contribute to the preservation or degradation of marine archaeological materials. Full article
(This article belongs to the Section Chemical Oceanography)
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