Journal of Marine Science and Engineering

12 pages, 472 KiB

Open AccessArticle

Miles Theory Revisited with Constant Vorticity in Water of Infinite Depth

by Christian Kharif and Malek Abid

J. Mar. Sci. Eng. 2020, 8(8), 623; https://doi.org/10.3390/jmse8080623 - 18 Aug 2020

Cited by 8 | Viewed by 2389

The generation of wind waves at the surface of a pre-existing underlying vertically sheared water flow of constant vorticity is considered. Emphasis is put on the role of the vorticity in water on wind-wave generation. The amplitude growth rate increases with the vorticity [...] Read more.

The generation of wind waves at the surface of a pre-existing underlying vertically sheared water flow of constant vorticity is considered. Emphasis is put on the role of the vorticity in water on wind-wave generation. The amplitude growth rate increases with the vorticity except for quite old waves. A limit to the wave energy growth is found in the case of negative vorticity, corresponding to the vanishing of the growth rate. Full article

(This article belongs to the Special Issue Wind Waves Excitation and Evolution)

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12 pages, 4040 KiB

Open AccessArticle

Wave Induced Effects on the Hydrodynamic Coefficients of an Oscillating Heave Plate in Offshore Wind Turbines

by Krish Thiagarajan and Javier Moreno

J. Mar. Sci. Eng. 2020, 8(8), 622; https://doi.org/10.3390/jmse8080622 - 18 Aug 2020

Cited by 16 | Viewed by 3731

Abstract

The research problem discussed in this paper is of relevance to floating offshore wind turbine design, where heave plates are attached to the columns of a semi-submersible in order to improve vertical plane stability and the power output. Because of the shallow draft [...] Read more.

The research problem discussed in this paper is of relevance to floating offshore wind turbine design, where heave plates are attached to the columns of a semi-submersible in order to improve vertical plane stability and the power output. Because of the shallow draft of these structures, the heave plates are proximal to the water surface. When subject to vertical plane motions the flow around a plate is altered by the presence of the free surface, resulting in changes in added mass and damping forces. In this paper, we present the experimental results for the added mass and damping coefficients for circular heave plates attached to a column, when oscillating in heave in the presence of oncoming waves. The results tend to indicate that applying the hydrodynamic coefficients obtained from still water experiments for a structure moving in waves may only be an approximation. For different relative phases of the wave and the motion, large variations could occur. We define a modified Keulegan—Carpenter (

K C

) number that depends on the relative amplitude of motion with respect to the wave. With this definition, the added mass and damping values are seen to be closer to the still water trends. However, at lower

K C

values, the added mass coefficients could differ by 30%, which can affect natural frequency estimates. Thus, caution needs to be exerted in the selection of hydrodynamic coefficients for heave plates oscillating in proximity to the free surface. Full article

(This article belongs to the Special Issue Waves and Ocean Structures)

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10 pages, 1896 KiB

Open AccessArticle

A State-Dependent Constitutive Model for Gas Hydrate-Bearing Sediments Considering Cementing Effect

by Qingmeng Yuan, Liang Kong, Rui Xu and Yapeng Zhao

J. Mar. Sci. Eng. 2020, 8(8), 621; https://doi.org/10.3390/jmse8080621 - 18 Aug 2020

Cited by 6 | Viewed by 2368

Abstract

This paper presents a state-dependent constitutive model for gas hydrate-bearing sediments (GHBS), considering the cementing effect for simulating the stress–strain behavior of GHBS. In this work, to consider the influence of hydrate on matrix samples in theory, some representative GHBS laboratory tests were [...] Read more.

This paper presents a state-dependent constitutive model for gas hydrate-bearing sediments (GHBS), considering the cementing effect for simulating the stress–strain behavior of GHBS. In this work, to consider the influence of hydrate on matrix samples in theory, some representative GHBS laboratory tests were analyzed, and it was found that GHBS has obvious state-related characteristics. At the same time, it was found that GHBS has high bonding strength. In order to describe these characteristics of GHBS, the cementation strength related to hydrate saturation is introduced in the framework of a sand state correlation model. In addition, in order to accurately reflect the influence of cementation on the hardening law of GHBS, the degradation rate of cementation strength is introduced, and the mixed hardening theory is adopted to establish the constitutive model. The model presented in this paper reproduces the experimental results of Masui et al. and Miyazaki et al., and the prediction performance of the model is satisfactory, which proves the rationality of this work. Full article

(This article belongs to the Special Issue Offshore Hydrocarbon Resources: Sustainable Development and Long-Term Forecasting)

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28 pages, 1155 KiB

Open AccessReview

Seaweeds, Intact and Processed, as a Valuable Component of Poultry Feeds

by Izabela Michalak and Khalid Mahrose

J. Mar. Sci. Eng. 2020, 8(8), 620; https://doi.org/10.3390/jmse8080620 - 18 Aug 2020

Cited by 36 | Viewed by 7998

Abstract

Poultry production is an important area of the agricultural economy. Nowadays, there is an interest in novel sources of feed additives that will improve production performance and poultry health. As an easily available and renewable biomass rich in biologically active compounds, seaweeds can [...] Read more.

Poultry production is an important area of the agricultural economy. Nowadays, there is an interest in novel sources of feed additives that will improve production performance and poultry health. As an easily available and renewable biomass rich in biologically active compounds, seaweeds can meet this demand. Different forms of seaweeds–seaweed powder from naturally occurring biomass, cultivated or waste biomass, extracted compounds, post-extraction residues or liquid extracts–may be used in poultry feeding. Inclusion of this unconventional material in the poultry nutrition can positively influence the poultry performance along with its health and enrich poultry products with active compounds, such as micro- and macroelements, polyunsaturated fatty acids and pigments. Seaweeds also reduce lipids and cholesterol in eggs. Moreover, due to their unique properties, they can serve as an alternative to antibiotic growth promoters. This review presents the latest developments in the use of seaweeds in poultry nutrition, as well as its limitations. Full article

(This article belongs to the Special Issue Marine Biologically Active Compounds as Feed Additives)

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21 pages, 3521 KiB

Open AccessArticle

Predicting Wind Wave Suppression on Irregular Long Waves

by Taylor Bailey, Lauren Ross, Mary Bryant and Duncan Bryant

J. Mar. Sci. Eng. 2020, 8(8), 619; https://doi.org/10.3390/jmse8080619 - 18 Aug 2020

Cited by 3 | Viewed by 3060

Abstract

The applicability of the wind wave suppression model developed by Chen and Belcher (2000) to irregular wave environments is investigated in this study. Monochromatic and irregular wave environments were simulated in the W² (Wind/Wave) laboratory at the University of Maine under varying [...] Read more.

The applicability of the wind wave suppression model developed by Chen and Belcher (2000) to irregular wave environments is investigated in this study. Monochromatic and irregular wave environments were simulated in the W² (Wind/Wave) laboratory at the University of Maine under varying wind speeds. The Chen and Belcher (2000) model accurately predicts the reduction of the energy density of the wind waves in the presence of the monochromatic waves as a function of wave steepness, but under predicts this energy dissipation for the irregular waves. This is due to the consideration of a single wave frequency in the estimation of the growth rate and wave-induced stress of the monochromatic waves. The same formulations for the growth rate and wave-induced stress cannot be applied to irregular waves because their spectra contain energy over a wide range of frequencies. A revised version of the model is proposed to account for the energy contained within multiple wave frequencies from the power spectra for the mechanically generated irregular waves. The revised model shows improved results when applied to irregular wave environments. Full article

(This article belongs to the Special Issue Wind Waves Excitation and Evolution)

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11 pages, 3496 KiB

Open AccessArticle

Acoustic Search and Detection of Oil Plumes Using an Autonomous Underwater Vehicle

by Jimin Hwang, Neil Bose, Hung Duc Nguyen and Guy Williams

J. Mar. Sci. Eng. 2020, 8(8), 618; https://doi.org/10.3390/jmse8080618 - 17 Aug 2020

Cited by 18 | Viewed by 3307

Abstract

We introduce an adaptive sampling method that has been developed to support the Backseat Driver control architecture of the Memorial University of Newfoundland (MUN) Explorer autonomous underwater vehicle (AUV). The design is based on an acoustic detection and in-situ analysis program that allows [...] Read more.

We introduce an adaptive sampling method that has been developed to support the Backseat Driver control architecture of the Memorial University of Newfoundland (MUN) Explorer autonomous underwater vehicle (AUV). The design is based on an acoustic detection and in-situ analysis program that allows an AUV to perform automatic detection and autonomous tracking of an oil plume. The method contains acoustic image acquisition, autonomous triggering, and thresholding in the search stage. A new biomimetic search pattern, the bumblebee flight path, was designed to maximize the spatial coverage in the oil plume detection phase. The effectiveness of the developed algorithm was validated through simulations using a two-dimensional planar plume model and a 90-degree scanning sensor model. The results demonstrate that the bumblebee search design combined with a genetic solution for the Traveling Salesperson Problem outperformed a conventional lawnmower survey, reducing the AUV travel distance by up to 75.3%. Our plume detection strategy, using acoustic sensing, provided data of plume location, distribution, and density, over a sector in contrast with traditional chemical oil sensors that only provide readings at a point. Full article

(This article belongs to the Special Issue Autonomous Underwater Vehicles in Extreme Environment)

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17 pages, 8275 KiB

Open AccessArticle

The Impact of Tides on the Bay of Biscay Dynamics

by John Karagiorgos, Vassilios Vervatis and Sarantis Sofianos

J. Mar. Sci. Eng. 2020, 8(8), 617; https://doi.org/10.3390/jmse8080617 - 17 Aug 2020

Cited by 9 | Viewed by 4184

Abstract

The impact of tides on the Bay of Biscay dynamics is investigated by means of an ocean model twin-experiment, consisted of two simulations with and without tidal forcing. The study is based on a high-resolution (

1 / 36^{\circ}

) regional configuration [...] Read more.

The impact of tides on the Bay of Biscay dynamics is investigated by means of an ocean model twin-experiment, consisted of two simulations with and without tidal forcing. The study is based on a high-resolution (

1 / 36^{\circ}

) regional configuration of NEMO (Nucleus for European Modelling of the Ocean) performing one-year simulations. The results highlight the imprint of tides on the thermohaline properties and circulation patterns in three distinct dynamical areas in the model domain: the abyssal plain, the Armorican shelf and the English Channel. When tides are activated, the bottom stress is increased in the shelf areas by about two orders of magnitude with respect to the open ocean, subsequently enhancing vertical mixing and weakening stratification in the bottom boundary layer. The most prominent feature reproduced only when tides are modelled, is the Ushant front near the entrance of the English Channel. Tides appear also to constrain the freshwater transport of rivers from the continental shelf to the open ocean. The spectral analysis revealed that the tidal forcing contributes to the SSH variance at high frequencies near the semidiurnal band and to the open ocean mesoscale and small-scale features in the presence of summer stratification pattern. Full article

(This article belongs to the Special Issue Monitoring and Modelling of Coastal Environment)

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16 pages, 2237 KiB

Open AccessFeature PaperArticle

Seasonal Predictions of Shoreline Change, Informed by Climate Indices

by Dan Hilton, Mark Davidson and Tim Scott

J. Mar. Sci. Eng. 2020, 8(8), 616; https://doi.org/10.3390/jmse8080616 - 17 Aug 2020

Cited by 3 | Viewed by 3140

Abstract

With sea level rise accelerating and coastal populations increasing, the requirement of coastal managers and scientists to produce accurate predictions of shoreline change is becoming ever more urgent. Waves are the primary driver of coastal evolution, and much of the interannual variability of [...] Read more.

With sea level rise accelerating and coastal populations increasing, the requirement of coastal managers and scientists to produce accurate predictions of shoreline change is becoming ever more urgent. Waves are the primary driver of coastal evolution, and much of the interannual variability of the wave conditions in the Northeast Atlantic can be explained by broadscale patterns in atmospheric circulation. Two of the dominant climate indices that capture the wave climate in western Europe’s coastal regions are the ‘Western Europe Pressure Anomaly’ (WEPA) and ‘North Atlantic Oscillation’ (NAO). This study utilises a shoreline prediction model (ShoreFor) which is forced by synthetic waves to investigate whether forecasts can be improved when the synthetic wave generation algorithm is informed by relevant climate indices. The climate index-informed predictions were tested against a baseline case where no climate indices were considered over eight winter periods at Perranporth, UK. A simple adaption to the synthetic wave-generating process has allowed for monthly climate index values to be considered before producing the 10³ random waves used to force the model. The results show that improved seasonal predictions of shoreline change are possible if climate indices are known a priori. For NAO, modest gains were made over the uninformed ShoreFor model, with a reduction in average root mean square error (RMSE) of 7% but an unchanged skill score. For WEPA, the gains were more significant, with the average RMSE 12% lower and skill score 5% higher. Highlighted is the importance of selecting an appropriate index for the site location. This work suggests that better forecasts of shoreline change could be gained from consideration of a priori knowledge of climatic indices in the generation of synthetic waves. Full article

(This article belongs to the Special Issue Numerical Models in Coastal Hazards and Coastal Environment)

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23 pages, 3397 KiB

Open AccessArticle

DSPIR Framework as Planning and Management Tools for the La Boquita Coastal System, Manzanillo, Mexico

by Julieta Hernández-López, Omar Cervantes, Aramis Olivos-Ortiz and Rubén Ricardo Guzmán-Reyna

J. Mar. Sci. Eng. 2020, 8(8), 615; https://doi.org/10.3390/jmse8080615 - 17 Aug 2020

Cited by 6 | Viewed by 3497

Abstract

Coastal ecosystems are attractive sites for tourism. In the central Pacific coast of Mexico in the La Boquita coastal system (LBCS), consisting of a beach and a coastal lagoon, the Driver-Pressure-State-Impact-Response (DPSIR) model was implemented for the spatial and temporal analysis of socio [...] Read more.

Coastal ecosystems are attractive sites for tourism. In the central Pacific coast of Mexico in the La Boquita coastal system (LBCS), consisting of a beach and a coastal lagoon, the Driver-Pressure-State-Impact-Response (DPSIR) model was implemented for the spatial and temporal analysis of socio environmental indicators, aiming to gather information for decision-making and implementation of management strategies. The spatial occupation (umbrellas and tables) of the beach showed a 50–200% increase during the Easter season relative to the low season, while the area containing restaurants (called “ramadas”) increased by 396% in 15 years, representing pressure on land use for tourism purposes. The density of beach users ranged from moderate to high (<10 m²/user) during the holiday seasons in the tourism area. The Trophic index (TRIX), used as an indicator of trophic status, revealed mesotrophic-to-eutrophic conditions in lagoon water due to the limited water exchange with the adjacent ocean and to DIN and DIP inputs from adjacent tourist areas. The analysis of the environmental legislation showed that law enforcement in the LBCS is poor or nil, with most environmental regulations either ignored or having inadequate enforcement monitoring. This has led to the current state of socio environmental disruption. Full article

(This article belongs to the Special Issue Marine Observation and Monitoring towards an Ecosystem Approach)

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Graphical abstract

21 pages, 5639 KiB

Open AccessArticle

A Track Initiation Algorithm Using Residual Threshold for Shore-Based Radar in Heavy Clutter Environments

by Yaru Zhang, Aichao Liu, Chao Liu, Bo Ai and Xiao Zhang

J. Mar. Sci. Eng. 2020, 8(8), 614; https://doi.org/10.3390/jmse8080614 - 17 Aug 2020

Cited by 4 | Viewed by 2974

Abstract

There is a large error in the actual radar trajectory tracking process. Track initiation is the primary problem in trajectory tracking and the first step in target tracking. The current track initiation algorithms are greatly affected by heavy clutter environments, so it is [...] Read more.

There is a large error in the actual radar trajectory tracking process. Track initiation is the primary problem in trajectory tracking and the first step in target tracking. The current track initiation algorithms are greatly affected by heavy clutter environments, so it is necessary to propose an algorithm to solve the problem of low track initiation efficiency. This paper presents a track initiation algorithm using a residual threshold in heavy clutter environments. The falling probability of measured value and decision threshold are used to determine the correlation window. The angle limiting condition is added to establish the track association, and the residual threshold is used to further eliminate the false tracks. The initial track experiment with the trajectory data in the sea near Rizhao Port shows that the algorithm is superior to the traditional logic method and Kalman filter method in track quality. The experiment uses the AIS buffer zone to calculate track initiation probability and uses the multi-region AIS trajectory data for verification. The experimental result shows that track initiation probability with the proposed algorithm in this paper can reach 92.31%. Full article

(This article belongs to the Section Ocean Engineering)

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13 pages, 6250 KiB

Open AccessArticle

Torsional Vibration Stress and Fatigue Strength Analysis of Marine Propulsion Shafting System Based on Engine Operation Patterns

by Myeong-Ho Song, Xuan Duong Pham and Quang Dao Vuong

J. Mar. Sci. Eng. 2020, 8(8), 613; https://doi.org/10.3390/jmse8080613 - 16 Aug 2020

Cited by 14 | Viewed by 5286

Abstract

Modern merchant ships use marine propulsion systems equipped with an ultra-long-stroke diesel engine that directly drives a large slow-turning propeller. Such systems use fewer cylinders and generate greater power at slower shaft speeds, which affords improved propulsion performance as well as low repair [...] Read more.

Modern merchant ships use marine propulsion systems equipped with an ultra-long-stroke diesel engine that directly drives a large slow-turning propeller. Such systems use fewer cylinders and generate greater power at slower shaft speeds, which affords improved propulsion performance as well as low repair and maintenance costs. However, this also results in higher torsional vibrations, which can lead to the fatigue of the shafting system. Tests performed on various marine propulsion systems with 5- to 7-cylinder engines have shown that engines with fewer cylinders exhibit a correspondingly wider barred speed range (BSR) and higher torsional vibration stresses. Thus, it is necessary to investigate the optimal engine operation patterns required to quickly pass the BSR with smaller torsional vibration. In this study, we carried out a series of BSR passage experiments during actual sea trials to evaluate the intermediate shaft performance under different engine operation patterns. The fractional damage accumulations due to transient torsional vibration stresses were calculated to estimate the fatigue lifetime of the shafting system. Our analysis results show that the torsional fatigue damage during BSR decelerations are small and negligible; however, the fractional damage during accelerations is a matter of concern. Our study determines the optimal main engine operation pattern for quick passage through the BSR with the smallest torsional vibration amplitudes and the least fractional damage accumulation, which can therefore extend the fatigue lifetime of the entire propulsion shafting system. Based on this analysis, we also suggest the optimum engine pattern for safe BSR passage. Full article

(This article belongs to the Section Ocean Engineering)

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18 pages, 1426 KiB

Open AccessFeature PaperReview

The Evolution and Outcomes of a Collaborative Testbed for Predicting Coastal Threats

by Charles Reid Nichols and Lynn Donelson Wright

J. Mar. Sci. Eng. 2020, 8(8), 612; https://doi.org/10.3390/jmse8080612 - 16 Aug 2020

Cited by 6 | Viewed by 2591

Abstract

Beginning in 2003, the Southeastern Universities Research Association (SURA) enabled an open-access network of distributed sensors and linked computer models through the SURA Coastal Ocean Observing and Predicting (SCOOP) program. The goal was to support collaborations among universities, government, and industry to advance [...] Read more.

Beginning in 2003, the Southeastern Universities Research Association (SURA) enabled an open-access network of distributed sensors and linked computer models through the SURA Coastal Ocean Observing and Predicting (SCOOP) program. The goal was to support collaborations among universities, government, and industry to advance integrated observation and modeling systems. SCOOP improved the path to operational real-time data-guided predictions and forecasts of coastal ocean processes. This was critical to the maritime infrastructure of the U.S. and to the well-being of coastal communities. SCOOP integrated and expanded observations from the Gulf of Mexico, the South Atlantic Bight, the Middle Atlantic Bight, and the Chesapeake Bay. From these successes, a Coastal and Ocean Modeling Testbed (COMT) evolved with National Oceanic and Atmospheric Administration (NOAA) funding via the Integrated Ocean Observing System (IOOS) to facilitate the transition of key models from research to operations. Since 2010, COMT has been a conduit between the research community and the federal government for sharing and improving models and software tools. SCOOP and COMT have been based on strong partnerships among universities and U.S. agencies that have missions in ocean and coastal environmental prediction. During SURA’s COMT project, which ended September 2018, significant progress was made in evaluating the performance of models that are progressively becoming operational. COMT successes are ongoing. Full article

(This article belongs to the Special Issue Feature Reviews in Marine Science and Engineering)

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12 pages, 1825 KiB

Open AccessArticle

Effects of Ethinylestradiol (EE2) and an Organophosphorus Flame Retardant (TCPP) on Gonadal Maturation in the Sea Urchin, Paracentrotus lividus

by Pedro Campoy-López, Estefanía Pereira-Pinto, Leonardo Mantilla-Aldana and Ricardo Beiras

J. Mar. Sci. Eng. 2020, 8(8), 611; https://doi.org/10.3390/jmse8080611 - 16 Aug 2020

Cited by 3 | Viewed by 3736

Abstract

The sea urchin (Paracentrotus lividus) was used to test the effects of one of the most abundant flame retardant additives for plastics, tris (1-chloro-2-propyl) phosphate (TCPP), and the synthetic hormone ethinylestradiol (EE2) on gametogenesis and gonad development of adults. With this [...] Read more.

The sea urchin (Paracentrotus lividus) was used to test the effects of one of the most abundant flame retardant additives for plastics, tris (1-chloro-2-propyl) phosphate (TCPP), and the synthetic hormone ethinylestradiol (EE2) on gametogenesis and gonad development of adults. With this aim, 403 individuals of both sexes were exposed to TCPP concentrations ranging from 0.2 to 10 µg/L, EE2 (0.01 µg/L), seawater and solvent controls for 7 and 28 days. EE2 and TCPP exposure did not cause histological damage in the gonads. Some evidence of estrogenic effects of TCPP within the µg/L range and EE2 within the ng/L range is reported. Females exposed to 1 µg/L TCPP for 7 days showed a significant increase in gonad development assessed as gametogenic stage, females exposed to 10 µg/L TCPP showed increased gonad development both in terms of weight (Gonad Index, GI, at both 7 and 28 days) and maturation (Pixelar Index, PI), and females exposed to 10 ng/L EE2 showed increased PI after 28 days exposure. Male sea urchins exposed to both TCPP and EE2 for 7 days showed increased frequencies of low development gonad stage. However, the patterns of response are affected by the high inter-individual variability, the differing initial stage of the gonad, as well as the dosage administered. Full article

(This article belongs to the Special Issue Effects of Emerging Contaminants to Marine Organisms: In Vitro and In Vivo Studies)

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20 pages, 11985 KiB

Open AccessArticle

Power Prediction of Wind Farms via a Simplified Actuator Disk Model

by Yen-Cheng Chiang, Yu-Cheng Hsu and Shiu-Wu Chau

J. Mar. Sci. Eng. 2020, 8(8), 610; https://doi.org/10.3390/jmse8080610 - 16 Aug 2020

Cited by 3 | Viewed by 2635

Abstract

This paper aims to demonstrate a simplified nonlinear wake model that fills the technical gap between the low-cost and less-accurate linear formulation and the high-cost and high-accuracy large eddy simulation, to offer a suitable balance between the prediction accuracy and the computational cost, [...] Read more.

This paper aims to demonstrate a simplified nonlinear wake model that fills the technical gap between the low-cost and less-accurate linear formulation and the high-cost and high-accuracy large eddy simulation, to offer a suitable balance between the prediction accuracy and the computational cost, and also to establish a robust approach for long-term wind farm power prediction. A simplified actuator disk model based on the momentum theory is proposed to predict the wake interaction among wind turbines along with their power output. The three-dimensional flow field of a wind farm is described by the steady continuity and momentum equation coupled with a k-

ε

turbulence model, where the body force representing the aerodynamic impact of the rotor blade on the airflow is uniformly distributed in the Cartesian cells within the actuator disk. The characteristic wind conditions identified from the data of the supervisory control and data acquisition (SCADA) system were employed to build the power matrix of these typical wind conditions for reducing the computation demands to estimate the yearly power production. The proposed model was favorably validated with the offshore measurement of Horns Rev wind farm, and three Taiwanese onshore wind farms were forecasted for their yearly capacity factors with an average error less than 5%, where the required computational cost is estimated about two orders of magnitude smaller than that of the large eddy simulation. However, the proposed model fails to pronouncedly reproduce the individual power difference among wind turbines in the investigated wind farm due to its time-averaging nature. Full article

(This article belongs to the Special Issue Waves and Ocean Structures)

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18 pages, 4401 KiB

Open AccessArticle

An Improved Danger Sector Model for Identifying the Collision Risk of Encountering Ships

by Zihao Liu, Zhaolin Wu and Zhongyi Zheng

J. Mar. Sci. Eng. 2020, 8(8), 609; https://doi.org/10.3390/jmse8080609 - 15 Aug 2020

Cited by 9 | Viewed by 2347

Abstract

In order to avoid collision, ships usually take collision avoidance manoeuvres, such as course alteration. However, the effect of such a manoeuvre is influenced by ship manoeuvrability. This paper proposed an improved danger sector model to identify the collision risk between two encountering [...] Read more.

In order to avoid collision, ships usually take collision avoidance manoeuvres, such as course alteration. However, the effect of such a manoeuvre is influenced by ship manoeuvrability. This paper proposed an improved danger sector model to identify the collision risk between two encountering ships. The proposed model is improved from the danger sector model, which is based on a course alteration manoeuvre by taking ship manoeuvrability into consideration. To involve ship manoeuvrability in the proposed model, the turning circle of a ship is determined when it calculates the size of the danger sector. For validating the proposed model, the Automatic Identification System (AIS) data in the northern Yellow Sea of China were used to carry out some experiments of different encountering scenarios. The results show that the proposed improved danger sector model can identify the collision risk between two encountering ships effectively and has advantages compared with the original danger sector model. The proposed model can help mariners and maritime surveillance operators have a more accurate and effective assessment of ship collision risk in the water area, which can contribute to the improvement of navigational safety. Full article

(This article belongs to the Section Ocean Engineering)

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22 pages, 6185 KiB

Open AccessArticle

Phytoplankton Dynamics in the Middle Adriatic Estuary, with a Focus on the Potentially Toxic Genus Pseudo-nitzschia

by Jasna Arapov, Mia Bužančić, Sanda Skejić, Jelena Mandić, Ana Bakrač, Maja Straka and Živana Ninčević Gladan

J. Mar. Sci. Eng. 2020, 8(8), 608; https://doi.org/10.3390/jmse8080608 - 15 Aug 2020

Cited by 12 | Viewed by 2842

Abstract

The Krka River estuary is a karstic, permanently stratified estuary due to the strong freshwater inflow. It is a special environment in which to study the phytoplankton community, especially because this area is an important aquaculture site. Among other potentially toxic phytoplankton species, [...] Read more.

The Krka River estuary is a karstic, permanently stratified estuary due to the strong freshwater inflow. It is a special environment in which to study the phytoplankton community, especially because this area is an important aquaculture site. Among other potentially toxic phytoplankton species, the diatom genus Pseudo-nitzschia occurs frequently and is a potential source of domoic acid (DA), causing shellfish toxicity and human intoxication. The main objective was to examine the dynamics of the phytoplankton community and, in particular, the genus Pseudo-nitzschia in the upper part of the Krka estuary, through monthly sampling over two years. The phytoplankton community was analysed using light microscopy and scanning electron microscopy to determine the diversity of Pseudo-nitzschia species and characterise the environmental parameters associated with a high abundance of Pseudo-nitzschia species. Seven Pseudo-nitzschia species were identified in the investigation, with higher frequencies and abundances in the less variable layer, at a 7 m depth. Blooms of Pseudo-nitzschia were noted in the late summer/early autumn, dominated by P. delicatissima/arenysensis. Winter assemblages were characterised by P. pseudodelicatissima/cuspidata, P. calliantha, and P. subfraudulenta, and were associated with domoic acid occurrence in shellfish. Full article

(This article belongs to the Special Issue Marine Shellfish Toxicity)

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13 pages, 3280 KiB

Open AccessArticle

Environmental Influence on the Spatiotemporal Variability of Spawning Grounds in the Western Guangdong Waters, South China Sea

by Yao Lu, Jing Yu, Zhaojin Lin and Pimao Chen

J. Mar. Sci. Eng. 2020, 8(8), 607; https://doi.org/10.3390/jmse8080607 - 15 Aug 2020

Cited by 12 | Viewed by 2972

Abstract

Spawning grounds occupy an important position in the supplementary population of fishery resources, especially in Western Guangdong waters (WGWs) in the northern South China Sea (SCS), where fishery resources are being depleted. This study investigated the environmental effects on the spatiotemporal variability of [...] Read more.

Spawning grounds occupy an important position in the supplementary population of fishery resources, especially in Western Guangdong waters (WGWs) in the northern South China Sea (SCS), where fishery resources are being depleted. This study investigated the environmental effects on the spatiotemporal variability of spawning grounds in WGWs, on the basis of generalized additive models (GAMs) and central spawning-ground gravity (CoSGG) by using satellite and in situ observations. Results showed that 57.2% of the total variation in fish-egg density in WGWs was explained. On the basis of stepwise GAMs, the most important factor was sea surface salinity (SSS), with a contribution of 32.1%, followed by sea surface temperature (SST), water depth, month, and chlorophyll a concentration (Chl-a), with contributions of 10.7%, 8.8%, 2.6%, and 2.6%, respectively. Offshore distance had slight influence on the model, explaining approximately 0.4% of the variation in fish-egg density. In summary, fish eggs in WGWs were mainly distributed in the area with SSS of 32.0–34.0 Practical Salinity Unit (PSU), SST of 24–27 °C, and depth of 0–18 m. CoSGG shifted eastwards by 0.38° N and northwards by 0.26° E from April to June. The distribution of spawning grounds in the WGW was affected by the Western Guangdong coastal current (WGCC), cyclonic circulation, the SCS warm current (SCSWC), and changes in the habitat environment (such as SST). Fish in WGWs tend to spawn in areas with a high seabed slope and steep terrain (near the Qiongzhou Strait). Full article

(This article belongs to the Special Issue Coastal Fish Research)

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15 pages, 5177 KiB

Open AccessArticle

Data-Driven Analysis of Stratified Flow Effect on Suspended Sediment Concentration in an Estuary

by Heui-Jung Seo, Minsang Cho and Hyun-Doug Yoon

J. Mar. Sci. Eng. 2020, 8(8), 606; https://doi.org/10.3390/jmse8080606 - 14 Aug 2020

Cited by 2 | Viewed by 2241

Abstract

An estuary is an area where a complex circulation pattern appears due to various hydrodynamic parameters such as tides, river discharge, salinity and water density. Especially during a flood, a large amount of freshwater discharge from a river can cause stratified flows due [...] Read more.

An estuary is an area where a complex circulation pattern appears due to various hydrodynamic parameters such as tides, river discharge, salinity and water density. Especially during a flood, a large amount of freshwater discharge from a river can cause stratified flows due to the difference in density between freshwater and seawater. This makes it difficult to understand the mechanism of behavior of the suspended sediment concentration in an estuary. To elucidate this problem, we investigated field observation data in the Gyeongin Port area in South Korea during the rainy period. It was found that there were stratified flow features of flow velocity, salinity and temperature between the upper and lower layers due to the abruptly increased amount of freshwater from a river in the rainy period. An artificial neural network (ANN), one of the data-driven modeling techniques, was applied to inductively analyze the hydrodynamic factors affecting the suspended sediment concentration in the estuary. The ANN model showed the best performance when including river discharge, and flow velocity and salinity measured at the surface and bottom layer. This shows that stratified flow is important to understand the behavior of suspended sediment concentration in the estuary. Full article

(This article belongs to the Special Issue Observational and Numerical Approaches in Coastal Sediment Dynamics and Hydrodynamics)

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23 pages, 10284 KiB

Open AccessArticle

Ultimate Compressive Strength of Stiffened Panel: An Empirical Formulation for Flat-Bar Type

by Do Kyun Kim, Su Young Yu, Hui Ling Lim and Nak-Kyun Cho

J. Mar. Sci. Eng. 2020, 8(8), 605; https://doi.org/10.3390/jmse8080605 - 13 Aug 2020

Cited by 25 | Viewed by 4417

Abstract

This research aims to study the ultimate limit state (ULS) behaviour of stiffened panel under longitudinal compression by a non-linear finite element method (NLFEM). There are different types of stiffeners mainly being used in shipbuilding, i.e., T-bar, flat-bar, and angle-bar. However, this research [...] Read more.

This research aims to study the ultimate limit state (ULS) behaviour of stiffened panel under longitudinal compression by a non-linear finite element method (NLFEM). There are different types of stiffeners mainly being used in shipbuilding, i.e., T-bar, flat-bar, and angle-bar. However, this research focuses on the ultimate compressive strength behaviour of flat-bar stiffened panel. A total of 420 reliable scenarios of flat-bar stiffened panel were selected for numerical simulation by the ANSYS NLFEM. The ultimate strength behaviours obtained were used as data for the development of closed form shape empirical formulation. Recently, our group proposed an advanced empirical formulation for T-bar stiffened panel, and the applicability of the proposed formulation to flat-bar stiffened panel is confirmed by this study. The accuracy of the empirical formulation obtained for flat-bar stiffened panel was validated by finite element (FE) simulation results of statistical analysis (R² = 0.9435). The outcome obtained will be useful for ship structural designers in predicting the ultimate strength performance of flat-bar type stiffened panel under longitudinal compression. Full article

(This article belongs to the Special Issue Ocean and Shore Technology (OST))

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26 pages, 7971 KiB

Open AccessFeature PaperArticle

Effects of Antibiotics on the Bacterial Community, Metabolic Functions and Antibiotic Resistance Genes in Mariculture Sediments during Enrichment Culturing

by Meng-Qi Ye, Guan-Jun Chen and Zong-Jun Du

J. Mar. Sci. Eng. 2020, 8(8), 604; https://doi.org/10.3390/jmse8080604 - 13 Aug 2020

Cited by 5 | Viewed by 2886

Abstract

The effect of antibiotics on the diversity and functioning of indigenous microorganisms in the environment has attracted much attention. In this study, effects of exposure to six different antibiotics on the bacterial community, metabolic functions and antibiotic resistance genes (ARGs) in marine sediments [...] Read more.

The effect of antibiotics on the diversity and functioning of indigenous microorganisms in the environment has attracted much attention. In this study, effects of exposure to six different antibiotics on the bacterial community, metabolic functions and antibiotic resistance genes (ARGs) in marine sediments during enrichment culturing were investigated. Classical culture-dependent method and high-throughput 16S rRNA gene sequencing method were both applied. In the culture-dependent analysis, the obtained 1549 isolates belonged to four phyla (Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria) and 155 genera. Proteobacteria and Firmicutes were the dominant phyla. The diversity and abundance of obtained bacteria after antibiotic processing exhibited different degrees of decrease. Enrichment culturing for different time could also affect the bacterial community composition. Some genera of bacteria were not isolated in the control group, but they could be isolated in the antibiotic-treated groups. In high-throughput 16S rRNA gene amplicon sequencing analyses, all the effective reads were clustered into 2822 OTUs at 97% similarity cutoff; they were annotated to 49 phyla, 103 class, 220 orders, 347 families, 624 genera and 1122 species. An alpha diversity analysis indicated that the community diversity and richness decreased under antibiotic exposure. The changes at the genus level were much more obvious. Only 48 genera of 129 genera were shared by all the samples. A total of 29 genera which were not detected in the initial control sample could be detected in at least one antibiotic-treated group. SIMPER analysis showed that OTU2543 and OTU1450 were the most common taxa to the dissimilarity of bacterial community between antibiotic-treated groups and the control group. OTU2034 and OUT2543 were the most contributive taxa to dissimilarity of groups incubating for different time. Metabolism was the predominant bacterial function. A total of 30 ARGs were detected in the samples. This study mainly focused on the changes of microbiota under the selective pressure of antibiotics for different time and the results demonstrated that the antibiotic could affect the bacterial diversity and richness in the marine ecosystem. Full article

(This article belongs to the Special Issue Diversity and Biotechnological Potential of Marine Microorganisms)

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20 pages, 13923 KiB

Open AccessArticle

Analysis of Wind-Induced Vibration of a Spoke-Wise Cable–Membrane Structure

by Hua Huang, Yaoqiang Xian, Wei Zhang, Mengxue Guo, Kun Yang and Kailin Xi

J. Mar. Sci. Eng. 2020, 8(8), 603; https://doi.org/10.3390/jmse8080603 - 13 Aug 2020

Cited by 4 | Viewed by 2901

Abstract

Lightweight cable–membrane structures can span large distances and undertake aesthetically pleasing shapes. They are widely used for roofs and modern structural canopies and in the aerospace industry for large on-board antenna reflectors that are to be deployed in space. This paper studies a [...] Read more.

Lightweight cable–membrane structures can span large distances and undertake aesthetically pleasing shapes. They are widely used for roofs and modern structural canopies and in the aerospace industry for large on-board antenna reflectors that are to be deployed in space. This paper studies a wind-induced vibration under different cable stress relaxation conditions based on the wind load time-history to obtain the dynamic behavior of such a structure. Particularly, the focus is put upon its wind resistance in the event of stress relaxation. This research can provide an important reference for the design of wind resistance, damage assessment, and emergency maintenance for the spoke-wise cable–membrane structure (SCMS). Full article

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21 pages, 9776 KiB

Open AccessArticle

Research on Risk Evaluation and Dynamic Escape Path Planning Algorithm Based on Real-Time Spread of Ship Comprehensive Fire

by Jian Ji, Zhihao Ma, Jiajun He, Yingjun Xu and Zhiqiang Liu

J. Mar. Sci. Eng. 2020, 8(8), 602; https://doi.org/10.3390/jmse8080602 - 12 Aug 2020

Cited by 16 | Viewed by 2753

Abstract

As an independent building entity on the sea, the ship has a large number of internal electrical equipment and a compact space structure, which is prone to fire. This paper proposes a key technology of virtual dynamic escape of ships based on the [...] Read more.

As an independent building entity on the sea, the ship has a large number of internal electrical equipment and a compact space structure, which is prone to fire. This paper proposes a key technology of virtual dynamic escape of ships based on the fire spread prediction model for research. Taking the 63,500 DWT(Dead Weight Tonnage) tanker cabin as a research entity, the mathematical and physical models of ship fire simulation are established. Through the graphical analysis of the experimental data of the fire spread simulation, the temperature, CO concentration, and smoke concentration change rules under different working conditions at the fixed detection point position are obtained. Then, based on temperature, CO concentration and smoke concentration three impact factors, set up a comprehensive fire real-time situational risk evaluation index system. Using the MATLAB software, based on the principle of the fuzzy neural network fire ship’s integrated real-time situational risk evaluation model structure design and simulation test, obtained the corresponding training to comprehensive risk evaluation model of the network. Generate navigation grid according to the law of fire sprawl, and plan escape path. The traditional A* algorithm is improved, and an example is used to prove that the path-finding result after the improved algorithm is shorter than the path found by the traditional algorithm, which meets the path-finding requirements in a three-dimensional environment. Full article

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17 pages, 5668 KiB

Open AccessArticle

Investigation of Optimal Coupling Velocities of the Sample and Sheath Flows for Hydrodynamic Focusing

by Dingpeng Huang, Hangzhou Wang, Xiaoping Wang, Kan Guo, Zhuoli Yuan, Jiawang Chen and Ying Chen

J. Mar. Sci. Eng. 2020, 8(8), 601; https://doi.org/10.3390/jmse8080601 - 12 Aug 2020

Cited by 2 | Viewed by 2048

Abstract

Focusing performance is a major concern for systems based on hydrodynamic focusing. In this study, the hydrodynamic focusing subsystem of a microscopic imaging system was analysed and modelled. The theoretical model was used to analyse the velocity and distribution range of sample particles [...] Read more.

Focusing performance is a major concern for systems based on hydrodynamic focusing. In this study, the hydrodynamic focusing subsystem of a microscopic imaging system was analysed and modelled. The theoretical model was used to analyse the velocity and distribution range of sample particles in the focused sample flow in the micro-channel of the hydrodynamic focusing subsystem, when the velocities of the sample and sheath flows were varied. The results were used to optimise the coupling velocities of the sample and sheath flows for the microscopic imaging system, to keep working efficiency and image quality of the system simultaneously. An independent experiment was then conducted for verification, and the results agreed well with the theoretical investigation. The results of this study provide a general framework for adjusting the sample and sheath flow velocities to optimise the hydrodynamic focusing performance. Full article

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18 pages, 4216 KiB

Open AccessArticle

Phytoplankton Distribution in Mar Menor Coastal Lagoon (SE Spain) during 2017

by Juan Soria, Gema Caniego, Nuria Hernández-Sáez, Jose Antonio Dominguez-Gomez and Manuel Erena

J. Mar. Sci. Eng. 2020, 8(8), 600; https://doi.org/10.3390/jmse8080600 - 12 Aug 2020

Cited by 9 | Viewed by 3116

Abstract

The Mar Menor is a Spanish coastal lagoon of great ecological and economic interest. The agricultural and tourist activities developed in the surroundings of the lagoon, together with the modifications in its channels of connection with the Mediterranean Sea, have notably affected the [...] Read more.

The Mar Menor is a Spanish coastal lagoon of great ecological and economic interest. The agricultural and tourist activities developed in the surroundings of the lagoon, together with the modifications in its channels of connection with the Mediterranean Sea, have notably affected the quality of its waters, which is altering the natural balance of the ecosystem. In this work, an analysis of the density of phytoplankton present in the lagoon between the months of May to December 2017 was carried out. The results indicate a significant increase in phytoplankton density between 2500 and 67,300 cells/mL compared to previous data of 1981 (between 10 and 500 cells/mL). Concentration of Chlorophyll-a arrives to 13 µg/L and transparency of water reduces to 1.3 m according to Secchi disk depth. The presence of Chlorophyceae, Chrysophyceae, and nanoplanktonic Cryptophyceae stands out, while species diversity drops significantly. Observing the evolution of the lagoon, we can deduce that eutrophication process could increase. To avoid this, it would be necessary to implement control measures for the use of fertilizers in nearby growing areas and to study water treatment techniques to reduce nitrogen inputs so that phytoplankton densities can decrease. Full article

(This article belongs to the Special Issue Long-term Phytoplankton Dynamics in Ecosystem)

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23 pages, 5538 KiB

Open AccessArticle

Expected Distribution of Surfing Days in the Iberian Peninsula

by Anna Boqué Ciurana and Enric Aguilar

J. Mar. Sci. Eng. 2020, 8(8), 599; https://doi.org/10.3390/jmse8080599 - 11 Aug 2020

Cited by 7 | Viewed by 4633

Abstract

This study presents, for the first time, a comprehensive characterization of the surf spots around the Iberian Peninsula and provides surfers and stakeholders an evaluation of the expected surfing days per year on each region and spot. The provision of this climate information [...] Read more.

This study presents, for the first time, a comprehensive characterization of the surf spots around the Iberian Peninsula and provides surfers and stakeholders an evaluation of the expected surfing days per year on each region and spot. The provision of this climate information can help to decision-making and limit the economic and social damages caused by climate-related disasters. This product aligns with the concept of climate services, increasingly requested to help economic activities to achieve optimal performances. We employ use in our study of two sources of data: meteorological buoys (Redcos, Redex and Costeira) and citizen science data, specifically information mined from surfers reanalyzed, namely the information contained in the Glassy app for smartphones (GAC & GAS). The surf spots are characterized using bottom type, surf break type and optimal wind (O_wd) and optimal swell direction (O_sd). Then, we define a surfing day as the ones in which optimal swell direction and waves bigger than 0.9 m occur; using three parameters mean swell direction (D_md), significant wave height (H_m₀) and optimal swell direction for each surf spot (O_sd) and compute the expected frequency of surfing days per year. Once this is done, we attempt to validate the approach taken to characterize a surfing day using buoys parameters (H_m0, H_max, T_p and D_md) and information about actual surf sessions for a small subset of our spots (i.e., Costa Tarragona). Our findings confirm that the area of western shore is the best suited for surfing, with over 300 days/year, followed by northern shore (300, 200 days/year) and southern and southeastern shores (<100 days/year). We expect that these values may modestly contribute to a climate-informed planning and management of the surfing activities. Full article

(This article belongs to the Special Issue Spatially Distributed Sea Wave Measurements)

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26 pages, 8721 KiB

Open AccessArticle

Reduction of Wave Overtopping and Force Impact at Harbor Quays Due to Very Oblique Waves

by Sebastian Dan, Corrado Altomare, Tomohiro Suzuki, Tim Spiesschaert and Toon Verwaest

J. Mar. Sci. Eng. 2020, 8(8), 598; https://doi.org/10.3390/jmse8080598 - 11 Aug 2020

Cited by 5 | Viewed by 3776

Abstract

Physical model experiments were conducted in a wave tank at Flanders Hydraulics Research, Antwerp, Belgium, to characterize the wave overtopping and impact force on vertical quay walls and sloping sea dike (1:2.5) under very oblique wave attack (angle between 45° and 80°). This [...] Read more.

Physical model experiments were conducted in a wave tank at Flanders Hydraulics Research, Antwerp, Belgium, to characterize the wave overtopping and impact force on vertical quay walls and sloping sea dike (1:2.5) under very oblique wave attack (angle between 45° and 80°). This study was triggered by the scarce scientific literature on the overtopping and force reduction due to very oblique waves since large reduction is expected for both when compared with the perpendicular wave attack. The study aimed to compare the results from the experimental tests with formulas derived from previous experiments and applicable to a Belgian harbor generic case. The influence of storm return walls and crest berm width on top of the dikes has been analyzed in combination with the wave obliqueness. The results indicate significant reduction of the overtopping due to very oblique waves and new reduction coefficients were proposed. When compared with formulas from previous studies the proposed coefficients indicate the best fit for the overtopping reduction. Position of the storm return wall respect to the quay edge rather than its height was found to be more important for preventing wave induced overtopping. The force reduction is up to approximately 50% for the oblique waves with respect to the perpendicular wave impact and reduction coefficients were proposed for two different configurations a sea dike and vertical quay wall, respectively. Full article

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

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26 pages, 5445 KiB

Open AccessArticle

A Wave Input-Reduction Method Incorporating Initiation of Sediment Motion

by Andreas Papadimitriou, Loukianos Panagopoulos, Michalis Chondros and Vasiliki Tsoukala

J. Mar. Sci. Eng. 2020, 8(8), 597; https://doi.org/10.3390/jmse8080597 - 10 Aug 2020

Cited by 9 | Viewed by 3008

Abstract

The long-term prediction of morphological bed evolution has been of interest to engineers and scientists for many decades. Usually, process-based models are employed to simulate bed-level changes in the scale of years to decades. To compensate for the major computational effort required by [...] Read more.

The long-term prediction of morphological bed evolution has been of interest to engineers and scientists for many decades. Usually, process-based models are employed to simulate bed-level changes in the scale of years to decades. To compensate for the major computational effort required by these models, various acceleration techniques have been developed, namely input-reduction, model-reduction and behaviour-oriented modelling. The present paper presents a new input-reduction method to obtain representative wave conditions based on the Shields criterion of incipient motion and subsequent calculation of the sediment pick-up rate. Elimination of waves unable to initiate sediment movement leads to additional reduction of model run-times. The proposed method was implemented in the sandy coastline adjusted to the port of Rethymno, Greece, and validated against two datasets consisting of 7 and 20 and 365 days, respectively, using the model MIKE21 Coupled Model FM. The method was compared with a well-established method of wave schematization and evaluation of the model’s skill deemed the simulations based on the pick-up rate schematization method as “excellent”. Additionally, a model run-time reduction of about 50% was observed, rendering this input-reduction method a valuable tool for the medium to long-term modelling of bed evolution. Full article

(This article belongs to the Special Issue Modelling of Harbour and Coastal Structures)

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16 pages, 5888 KiB

Open AccessArticle

Research and Analysis of Pressure-Maintaining Trapping Instrument for Macro-Organisms in Hadal Trenches

by Hao Wang, Jiawang Chen, Yuhong Wang, Jiasong Fang and Yuping Fang

J. Mar. Sci. Eng. 2020, 8(8), 596; https://doi.org/10.3390/jmse8080596 - 10 Aug 2020

Cited by 11 | Viewed by 2381

Abstract

The ecosystem of the abyss is one of the fields that humans hardly know. The ultra-high hydrostatic pressure makes it very difficult to obtain abyssal organisms. Samples are often severely broken during recovery due to changes in environmental pressure, temperature, and other factors. [...] Read more.

The ecosystem of the abyss is one of the fields that humans hardly know. The ultra-high hydrostatic pressure makes it very difficult to obtain abyssal organisms. Samples are often severely broken during recovery due to changes in environmental pressure, temperature, and other factors. Currently, there are no macro-organism samplers suitable for the abyss. The development of a pressure-maintaining sampler for the abyss is a prerequisite for abyssal ecosystem research. This paper mainly proposed a pressure-maintaining trapping instrument (PMTI) designed to work at a depth above 10,000 m. Unlike typical deep-sea equipment, this instrument is lightweight (about 65 kg in water). The instrument adopts a new structure, using a hollow piston as the sampling space and sealing the mechanism with O-rings at both ends of the piston, thus avoiding sealing methods such as ball valves and greatly reducing the weight of the equipment. The structure and working process of the instrument are described in detail in this paper. Meanwhile, in this paper, the movement resistance of the piston (mainly the resistance of the O-ring) is analyzed using a dynamic explicit method in Abaqus. The factors affecting the friction of the O-rings are analyzed via the method of orthogonal tests and ANOVA. In addition, high-pressure tests were conducted on key parts of the instrument, and the results showed that the instrument works well at 100 MPa. Full article

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20 pages, 12388 KiB

Open AccessArticle

An Integrated Strategy toward the Extraction of Contour and Region of Sonar Images

by Huipu Xu, Wenjie Lu and Meng Joo Er

J. Mar. Sci. Eng. 2020, 8(8), 595; https://doi.org/10.3390/jmse8080595 - 10 Aug 2020

Cited by 4 | Viewed by 2135

Abstract

In this paper, an integrated underwater sonar image extraction strategy, which combines two improved methods, namely the level set method (LSM) and the Lattice Boltzmann Method (LBM), is proposed. First, sonar images are processed by a clustering method and a connected domain analysis [...] Read more.

In this paper, an integrated underwater sonar image extraction strategy, which combines two improved methods, namely the level set method (LSM) and the Lattice Boltzmann Method (LBM), is proposed. First, sonar images are processed by a clustering method and a connected domain analysis to generate the target minimum rectangle frame. Next, the segmentation task is decomposed into two subtasks, namely a coarse segmentation task to obtain the initial contour and a fine segmentation task after embedding the initial contour. Finally, the improved LSM is used to obtain the target contour, and the coarse contour of the segment is embedded into the LBM to obtain the region segmentation of the target in the sonar images. The main contributions of the paper are as follows: (1) The contours and regions of the sonar images are extracted simultaneously. (2) The original LBM method is enhanced to solve the level set iteration problem. (3) The region segmentation with the original image background is extracted, and a more intuitive region segmentation result than that of directly extracting the contour of the level set is achieved. Experimental results based on four evaluation indices of image segmentation show that our method is effective, accurate, and superior to other existing methods. Full article

(This article belongs to the Section Ocean Engineering)

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14 pages, 4440 KiB

Open AccessArticle

Antimicrobial Activities of Sponge-Derived Microorganisms from Coastal Waters of Central Vietnam

by Pham Thi Mien, Dao Viet Ha, Hoang Xuan Ben, Bin Chen, Lan Liu and Phan Minh-Thu

J. Mar. Sci. Eng. 2020, 8(8), 594; https://doi.org/10.3390/jmse8080594 - 8 Aug 2020

Cited by 3 | Viewed by 3894

Abstract

Bacteria associated with invertebrates are considered as good sources for biologically active compounds. Sponge-derived bacteria were screened for antimicrobial activities, the presence of the cluster genes of polyketide synthases (PKSs) and non-ribosomal peptide synthetases (NRPSs), and through a colony picking method. Crude extracts [...] Read more.

Bacteria associated with invertebrates are considered as good sources for biologically active compounds. Sponge-derived bacteria were screened for antimicrobial activities, the presence of the cluster genes of polyketide synthases (PKSs) and non-ribosomal peptide synthetases (NRPSs), and through a colony picking method. Crude extracts of broth cultures were tested for microbial inhibition. Eleven out of 25 isolated strains showed inhibition of at least one of eight tested indicator microorganisms. Antimicrobial activities were observed in the strains coded HM5, HM6, and HM9 with the presence of NRPS and PKSII genes, whereas the isolate HM21 held both NRPS and PKSII and inhibited only the growth of Bacillus subtilis by the well diffusion method and only inhibited Serratia marcescens by the colony picking method. Two isolates, HM5 and HM6, belonged to the species of Bacillus. Interestingly, the isolate HM9 was nearest to Streptomyces mexicanus^T NBRC100915 (GenBank accession number AB249966) with 94% sequence similarity. This potent strain HM9 could possibly be considered as a new species and a good source for bioactive compound discovery. Some isolates showed NRPS/PKS genes but did not exhibit antimicrobial activity. Thus, we suggested that both molecular and traditional methods should be conducted for the screening of antimicrobial producers. Full article

(This article belongs to the Section Marine Biology)

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