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J. Mar. Sci. Eng., Volume 7, Issue 4 (April 2019)

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Cover Story (view full-size image) This paper presents the Structural Health Monitoring system developed for a port wharf of a freight [...] Read more.
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Open AccessArticle
Evaluation of the Viscous Drag for a Domed Cylindrical Moored Wave Energy Converter
J. Mar. Sci. Eng. 2019, 7(4), 120; https://doi.org/10.3390/jmse7040120
Received: 14 March 2019 / Revised: 11 April 2019 / Accepted: 16 April 2019 / Published: 25 April 2019
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Abstract
Viscous drag, nonlinear in nature, is an important aspect of the fluid–structure interaction modelling and is usually not taken into account when the fluid is assumed to be inviscid. Potential flow solvers can competently compute radiation damping, which is related to the radiated [...] Read more.
Viscous drag, nonlinear in nature, is an important aspect of the fluid–structure interaction modelling and is usually not taken into account when the fluid is assumed to be inviscid. Potential flow solvers can competently compute radiation damping, which is related to the radiated wave field. However, the drag damping primarily related to the viscous effects is usually neglected in the radiation/diffraction problems solved by the boundary element method (BEM), also known as the boundary integral element method (BIEM). This drag force can have a significant impact in the case of structures extending much deeper below the free surface, or for those that are completely submerged. In this paper, the drag coefficient C d was quantified for the heave and surge response of a structure which consists of a moored horizontally oriented domed cylinder with two surface piercing square columns located at the top surface. The domed cylinder is the primary part and is submerged. The drag coefficient is estimated using the experimental measurements related to harmonic monochromatic wave–structure interaction. Finally, this estimated drag coefficient was used in the modified time domain model, which includes the nonlinear viscous correction term, and the resulting device response in heave and surge directions is presented for an irregular incoming wave field. The comparison of the numerical model and the experiments validates the estimated C d values obtained earlier. Prior to the time domain model, frequency-dependent parameters such as added mass, radiation damping, and excitation force were computed using three mainstream potential flow packages (that is, ANSYS AQWA, WAMIT, and NEMOH), and a comparison is presented. The effect of free surface on the drag coefficient is investigated through differences in C d values between heave and surge modes. Full article
(This article belongs to the Special Issue Nonlinear Numerical Modelling of Wave Energy Converters)
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Open AccessCase Report
Environmental Management Systems and Balanced Scorecard: An Integrated Analysis of the Marine Transport
J. Mar. Sci. Eng. 2019, 7(4), 119; https://doi.org/10.3390/jmse7040119
Received: 19 February 2019 / Revised: 26 March 2019 / Accepted: 23 April 2019 / Published: 25 April 2019
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Abstract
Critical aspects of the environment can reduce the efficiency of Environmental Management Systems (EMS) when applied to Marine Transport. Accordingly, this paper focuses on the improvement of the traditional EMS approach through the usage of Balanced Scorecard (BSC). The BSC represents a managing [...] Read more.
Critical aspects of the environment can reduce the efficiency of Environmental Management Systems (EMS) when applied to Marine Transport. Accordingly, this paper focuses on the improvement of the traditional EMS approach through the usage of Balanced Scorecard (BSC). The BSC represents a managing tool able to measure and increase organizational performance, taking into consideration environmental aspects. The proposed method, based on the ISO 14001 standard, allows management of environmental metrics through conventional BSC systems and it is applied to the biggest organization for marine transport in Montenegro as a case study methodology. In this qualitative investigation, particular attention was paid to creating EMS criteria able to orient the complete business operation of the organization but also to test their potential linkage to the conventional BSC approach. Four models of the BSC were created, each one including to a different extent the issue of environmental protection. Finally, an expert’s evaluation of model efficiency, based on the ISO 9126, was carried out. As a result, the best ranked model is recommended for the selection of an approach toward environmental protection based on the use of the EMS metric in a conventional BSC system. This method—in short ECO-BSC—was developed for the specific benefit of those organizations operating on the marine transport market. Full article
(This article belongs to the Special Issue Engineering Mathematics in Ship Design)
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Open AccessArticle
Understanding Ocean Acoustics by Eigenray Analysis
J. Mar. Sci. Eng. 2019, 7(4), 118; https://doi.org/10.3390/jmse7040118
Received: 23 March 2019 / Revised: 13 April 2019 / Accepted: 18 April 2019 / Published: 25 April 2019
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Abstract
Acoustics is important for all underwater systems for object detection, classification, surveillance systems, and communication. However, underwater acoustics is often difficult to understand, and even the most carefully conducted measurements may often give unexpected results. The use of theory and acoustic modelling in [...] Read more.
Acoustics is important for all underwater systems for object detection, classification, surveillance systems, and communication. However, underwater acoustics is often difficult to understand, and even the most carefully conducted measurements may often give unexpected results. The use of theory and acoustic modelling in support of measurements is very important since theory tends to be better behaved and more consistent than experiments, and useful to acquire better knowledge about the physics principle. This paper, having a tutorial flair, concerns the use of ray modelling and in particular eigenray analysis to obtain increased knowledge and understanding of underwater acoustic propagation. Full article
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Open AccessArticle
Modeling the Impact of the Implementation of a Submerged Structure on Surf Zone Sandbar Dynamics
J. Mar. Sci. Eng. 2019, 7(4), 117; https://doi.org/10.3390/jmse7040117
Received: 4 April 2019 / Revised: 18 April 2019 / Accepted: 19 April 2019 / Published: 25 April 2019
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Abstract
Coastal defense strategies based on structures are increasingly unpopular as they are costly, leave lasting scars on the landscape, and sometimes have limited effectiveness or even adverse impacts. While a clear improvement concerning aesthetic considerations using soft submerged breakwater is undeniable, their design [...] Read more.
Coastal defense strategies based on structures are increasingly unpopular as they are costly, leave lasting scars on the landscape, and sometimes have limited effectiveness or even adverse impacts. While a clear improvement concerning aesthetic considerations using soft submerged breakwater is undeniable, their design has often focused on wave transmission processes across the crest of the structure, overlooking short- to medium-term morphodynamic responses. In this study, we used a time- and depth-averaged morphodynamic model to investigate the impact of the implementation of a submerged breakwater on surf zone sandbar dynamics at the beach of Sète, SE France. The hydrodynamic module was calibrated with data collected during a field experiment using three current profilers deployed to capture rip-cell circulation at the edge of the structure. The model showed good agreement with measurements, particularly for the longshore component of the flow (RMSE = 0.07 m/s). Results showed that alongshore differential wave breaking at the edge of the submerged breakwater drove an intense (0.4 m/s) two-dimensional circulation for low- to moderate-energy waves. Simulations indicated that inner-bar rip channel development, which was observed prior to the submerged reef implementation, was inhibited in the lee of the structure as rip-cell circulation across the inner bar disappeared owing to persistently low-energy breaking waves. The cross-shore sandbar dynamics in the lee of the structure were also impacted due to the drastic decrease of the offshore-directed flow over the inner-bar during energetic events. This paper highlights that implementation of a submerged breakwater results in larges changes in nearshore hydrodynamics that, in turn, can affect overall surf zone sandbar behavior. Full article
(This article belongs to the Special Issue Reefs)
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Open AccessArticle
Regionally-Coherent Embayment Rotation: Behavioural Response to Bi-Directional Waves and Atmospheric Forcing
J. Mar. Sci. Eng. 2019, 7(4), 116; https://doi.org/10.3390/jmse7040116
Received: 30 March 2019 / Revised: 11 April 2019 / Accepted: 16 April 2019 / Published: 23 April 2019
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Abstract
Bi-directional wave climates often drive beach rotation, increasing erosional risk at semi-sheltered locations. Identification of rotation and forcing mechanisms is vital to future coastal defence. In this study, regional investigation of modelled wave data revealed strong bi-directionality between dominant south-westerly and sub-dominant easterly [...] Read more.
Bi-directional wave climates often drive beach rotation, increasing erosional risk at semi-sheltered locations. Identification of rotation and forcing mechanisms is vital to future coastal defence. In this study, regional investigation of modelled wave data revealed strong bi-directionality between dominant south-westerly and sub-dominant easterly waves for 14 offshore locations along the length of the south coast of England, U.K. South-westerly wave power was well correlated to positive phases of the West Europe Pressure Anomaly (WEPA), whilst easterly wave power was well correlated with negative phases of the North Atlantic Oscillation (NAO). Additionally, decadal records of beach morphological change and associated wave forcing, were investigated for 22 coastal sites across the same region. Significant rotational behaviour was identified at 11 sites, leading to the creation of a rotation index. Beach rotation was attributed to shoreline angle, with the strongest rotation occurring at south-east-facing beaches, with high obliquity to dominant south-westerly waves. The beach rotation index was well correlated with the normalized balance of wave power from opposing south-westerly and easterly directions. Direct correlations between beach rotation and WEPA at two sites showed that future forecasts of atmospheric indices may allow prediction of rotational beach state, at seasonal scales. Full article
(This article belongs to the Special Issue Storm Erosion)
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Open AccessArticle
Dynamic Response for a Submerged Floating Offshore Wind Turbine with Different Mooring Configurations
J. Mar. Sci. Eng. 2019, 7(4), 115; https://doi.org/10.3390/jmse7040115
Received: 30 January 2019 / Revised: 5 April 2019 / Accepted: 15 April 2019 / Published: 22 April 2019
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Abstract
The paper discusses the effects of mooring configurations on the dynamic response of a submerged floating offshore wind turbine (SFOWT) for intermediate water depths. A coupled dynamic model of a wind turbine-tower-floating platform-mooring system is established, and the dynamic response of the platform, [...] Read more.
The paper discusses the effects of mooring configurations on the dynamic response of a submerged floating offshore wind turbine (SFOWT) for intermediate water depths. A coupled dynamic model of a wind turbine-tower-floating platform-mooring system is established, and the dynamic response of the platform, tensions in mooring lines, and bending moment at the tower base and blade root under four different mooring configurations are checked. A well-stabilized configuration (i.e., four vertical lines and 12 diagonal lines with an inclination angle of 30°) is selected to study the coupled dynamic responses of SFOWT with broken mooring lines, and in order to keep the safety of SFOWT under extreme sea-states, the pretension of the vertical mooring line has to increase from 1800–2780 kN. Results show that the optimized mooring system can provide larger restoring force, and the SFOWT has a smaller movement response under extreme sea-states; when the mooring lines in the upwind wave direction are broken, an increased motion response of the platform will be caused. However, there is no slack in the remaining mooring lines, and the SFOWT still has enough stability. Full article
(This article belongs to the Special Issue Offshore Wind Farms)
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Open AccessArticle
Investigation on a Novel Support System for Automatic Ship Berthing in Marine Practice
J. Mar. Sci. Eng. 2019, 7(4), 114; https://doi.org/10.3390/jmse7040114
Received: 13 March 2019 / Revised: 9 April 2019 / Accepted: 13 April 2019 / Published: 22 April 2019
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Abstract
For safe ship berthing, all steps involved, from bringing the ship to the fairway area to directing it to the final wharf position at a desirable speed, need to be performed properly. In this article, a support system is proposed to automatically bring [...] Read more.
For safe ship berthing, all steps involved, from bringing the ship to the fairway area to directing it to the final wharf position at a desirable speed, need to be performed properly. In this article, a support system is proposed to automatically bring the ship into the berth after completing the maneuvering process. This proposed system requires no involvement of a shipmaster, enabling automatic ship berthing in marine practice. Three fuzzy controllers are proposed to conduct different tasks of berthing. The first controller is designed to control the movement of the ship in a longitudinal direction towards the wharf while the second controller stabilizes the relative bearing error with respect to the tugboat. The final controller is responsible for bringing the ship into a wharf according to crabbing motion with bow thruster and tugboat simultaneously. Compared to other approaches, ours has a wider range of adoption, better generalization capability, and is more suitable for marine practice. Comprehensive experiments in numerical simulations are carried out, showing the superior performance of the proposed support system for automatic ship berthing. Full article
(This article belongs to the Special Issue Ship Hydrodynamics)
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Open AccessArticle
A Potential Flow Theory and Boundary Layer Theory Based Hybrid Method for Waterjet Propulsion
J. Mar. Sci. Eng. 2019, 7(4), 113; https://doi.org/10.3390/jmse7040113
Received: 1 April 2019 / Revised: 15 April 2019 / Accepted: 16 April 2019 / Published: 21 April 2019
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Abstract
A hybrid method—coupled with the boundary element method (BEM) for wave-making resistance, the empirical method (EM) for viscous resistance, and the boundary layer theory (BLT) for capture of an area’s physical parameters—was proposed to predict waterjet propulsion performance. The waterjet propulsion iteration process [...] Read more.
A hybrid method—coupled with the boundary element method (BEM) for wave-making resistance, the empirical method (EM) for viscous resistance, and the boundary layer theory (BLT) for capture of an area’s physical parameters—was proposed to predict waterjet propulsion performance. The waterjet propulsion iteration process was established from the force-balanced waterjet–hull system by applying the hybrid approach. Numerical validation of the present method was carried out using the 1/8.556 scale waterjet-propelled ITTC (International Towing Tank Conference) Athena ship model. Resistance, attitudes, wave cut profiles, waterjet thrust, and thrust deduction showed similar tendencies to the experimental curves and were in good agreement with the data. The application of the present hybrid method to the side-hull configuration research of a trimaran indicates that the side-hull arranged at the rear of the main hull contributed to energy-saving and high-efficiency propulsion. In addition, at high Froude numbers, the “fore-body trimaran” showed a local advantage in resistance and thrust deduction. Full article
(This article belongs to the Special Issue Ship Hydrodynamics)
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Open AccessArticle
A Quality Control Method for Broad-Beam HF Radar Current Velocity Measurements
J. Mar. Sci. Eng. 2019, 7(4), 112; https://doi.org/10.3390/jmse7040112
Received: 6 March 2019 / Revised: 14 April 2019 / Accepted: 15 April 2019 / Published: 19 April 2019
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Abstract
This paper describes a method to provide quality control for radial velocity maps derived from radar echo voltage cross spectra measured by broad-beam high frequency radars. The method involves the comparison of voltage cross spectra measured at Doppler frequencies in the Bragg region [...] Read more.
This paper describes a method to provide quality control for radial velocity maps derived from radar echo voltage cross spectra measured by broad-beam high frequency radars. The method involves the comparison of voltage cross spectra measured at Doppler frequencies in the Bragg region with values predicted from basic equations defining the complex voltage cross spectra in terms of the measured antenna patterns and the radar cross section. Poor agreement at a given Doppler frequency indicates contamination of the spectra, usually due to interference; velocity results from that Doppler frequency are then eliminated. Examples are given of its application to broad-beam radars operating at four sites. Full article
(This article belongs to the Special Issue Radar Technology for Coastal Areas and Open Sea Monitoring)
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Open AccessFeature PaperArticle
A Fast Simulation Method for Damaged Ship Dynamics
J. Mar. Sci. Eng. 2019, 7(4), 111; https://doi.org/10.3390/jmse7040111
Received: 27 March 2019 / Revised: 9 April 2019 / Accepted: 16 April 2019 / Published: 19 April 2019
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Abstract
Ship accidents that entail flooding may lead to disastrous consequences which could be avoided or mitigated based on the knowledge of damaged ship dynamics. The dynamic behaviour of a damaged hull is a complex phenomenon involving the interaction of the flooded water and [...] Read more.
Ship accidents that entail flooding may lead to disastrous consequences which could be avoided or mitigated based on the knowledge of damaged ship dynamics. The dynamic behaviour of a damaged hull is a complex phenomenon involving the interaction of the flooded water and the ship motions. The presence of a damage opening allows water flow into and out from the compartment, which further complicates the mathematical description of the problem. A fast simulation method, based on the lumped mass approach, is developed and presented. The lumped mass path in space depends on free-surface inclinations that differ from the ship angles of the roll and pitch. The viscous effects in the floodwater dynamics are implemented based on the model for the dissipation of the energy of standing waves in rectangular rooms. The method applies to both the transient stage of flooding and to the dynamic behaviour of a flooded ship in regular waves. In the first case, viscous effects are implemented considering the water in the compartment variable with time. Several case studies are carried out on three different hull models: Transient stage of flooding, roll decay of the damaged hull, and steady state responses in waves are simulated and compared with available experimental data. Full article
(This article belongs to the Special Issue Advances in Marine Dynamic Simulation)
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Open AccessArticle
Analysis and Visualization of Coastal Ocean Model Data in the Cloud
J. Mar. Sci. Eng. 2019, 7(4), 110; https://doi.org/10.3390/jmse7040110
Received: 6 March 2019 / Revised: 29 March 2019 / Accepted: 1 April 2019 / Published: 19 April 2019
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Abstract
The traditional flow of coastal ocean model data is from High-Performance Computing (HPC) centers to the local desktop, or to a file server where just the needed data can be extracted via services such as OPeNDAP. Analysis and visualization are then conducted using [...] Read more.
The traditional flow of coastal ocean model data is from High-Performance Computing (HPC) centers to the local desktop, or to a file server where just the needed data can be extracted via services such as OPeNDAP. Analysis and visualization are then conducted using local hardware and software. This requires moving large amounts of data across the internet as well as acquiring and maintaining local hardware, software, and support personnel. Further, as data sets increase in size, the traditional workflow may not be scalable. Alternatively, recent advances make it possible to move data from HPC to the Cloud and perform interactive, scalable, data-proximate analysis and visualization, with simply a web browser user interface. We use the framework advanced by the NSF-funded Pangeo project, a free, open-source Python system which provides multi-user login via JupyterHub and parallel analysis via Dask, both running in Docker containers orchestrated by Kubernetes. Data are stored in the Zarr format, a Cloud-friendly n-dimensional array format that allows performant extraction of data by anyone without relying on data services like OPeNDAP. Interactive visual exploration of data on complex, large model grids is made possible by new tools in the Python PyViz ecosystem, which can render maps at screen resolution, dynamically updating on pan and zoom operations. Two examples are given: (1) Calculating the maximum water level at each grid cell from a 53-GB, 720-time-step, 9-million-node triangular mesh ADCIRC simulation of Hurricane Ike; (2) Creating a dashboard for visualizing data from a curvilinear orthogonal COAWST/ROMS forecast model. Full article
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Open AccessArticle
A Study of the Maximum Momentum Flux in the Solitary Wave Run-Up Zone over Back-Reef Slopes Based on a Boussinesq Model
J. Mar. Sci. Eng. 2019, 7(4), 109; https://doi.org/10.3390/jmse7040109
Received: 12 March 2019 / Revised: 12 April 2019 / Accepted: 13 April 2019 / Published: 18 April 2019
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Abstract
This study utilized a shock-capturing Boussinesq model FUNWAVE-TVD to investigate the maximum momentum flux in the solitary wave run-up zone over back-reef slopes. Validation results of the present model were compared to the previous version of FUNWAVE using the eddy viscosity breaking model [...] Read more.
This study utilized a shock-capturing Boussinesq model FUNWAVE-TVD to investigate the maximum momentum flux in the solitary wave run-up zone over back-reef slopes. Validation results of the present model were compared to the previous version of FUNWAVE using the eddy viscosity breaking model to demonstrate the advantages of the shock-capturing method in predicting the breaking solitary wave transformation and run-up over fringing reefs. A series of numerical experiments was designed comprehensively and performed then to obtain a new formulation for the envelope of the spatial distribution of the maximum momentum flux within the solitary wave run-up zone over back-reef beaches, which is different from the one used over uniformly-sloping beaches. Finally, the effects of the variation of reef parameters (i.e., the fore-reef slope angle, reef flat width, and water depth over the reef flat) on the maximum momentum flux at the initial shoreline were investigated to better understand the role of fringing reefs in the mitigation of tsunami hazard. Full article
(This article belongs to the Section Coastal Engineering)
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Open AccessArticle
Performance Simulation of the Transportation Process Risk of Bauxite Carriers Based on the Markov Chain and Cloud Model
J. Mar. Sci. Eng. 2019, 7(4), 108; https://doi.org/10.3390/jmse7040108
Received: 4 March 2019 / Revised: 15 April 2019 / Accepted: 16 April 2019 / Published: 18 April 2019
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Abstract
China imports a large quantity of bauxite each year. Bauxite in fine particles with high moisture has a high risk of liquefaction during the maritime transportation process, which is harmful to the stability and safety of the carrier. To ensure safe shipping, it [...] Read more.
China imports a large quantity of bauxite each year. Bauxite in fine particles with high moisture has a high risk of liquefaction during the maritime transportation process, which is harmful to the stability and safety of the carrier. To ensure safe shipping, it is necessary to pay attention to the effects of the operation of cargo, the ship’s maneuvering and the ocean environment during the whole transportation process. The simulation of the process risk helps to develop measures to intervene with the cargo behavior to keep the risk to an acceptable level. This study examined the transportation process of a bauxite carrier using the Markov Chain method at different stages of loading, unberthing, departure and sea navigation. Based on the risk transfer matrix of the operational status at different stages of transportation, a cloud simulation model was developed to analyze the transportation process risk of a ship carrying bulk bauxite. Results: the research revealed that the risk evolution rule of the solid bulk cargoes with potential liquefaction during the transportation process, especially bauxite. The risk alteration during the prophase of the transportation process conforms to the rule of the “spoon curve”. Conclusions: a simulation model of the process risk based on the Markov Chain Cloud is suitable for the simulation analysis of the transportation risk of the bulk bauxite carrier. The outcomes of this study may contribute to better safety management to prevent the occurrence of ship capsizing. Full article
(This article belongs to the Special Issue Advances in Marine Dynamic Simulation)
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Open AccessArticle
Development of an Image Processing Module for Autonomous Underwater Vehicles through Integration of Visual Recognition with Stereoscopic Image Reconstruction
J. Mar. Sci. Eng. 2019, 7(4), 107; https://doi.org/10.3390/jmse7040107
Received: 8 March 2019 / Revised: 12 April 2019 / Accepted: 13 April 2019 / Published: 18 April 2019
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Abstract
This study investigated the development of visual recognition and stereoscopic imaging technology, applying them to the construction of an image processing system for autonomous underwater vehicles (AUVs). For the proposed visual recognition technology, a Hough transform was combined with an optical flow algorithm [...] Read more.
This study investigated the development of visual recognition and stereoscopic imaging technology, applying them to the construction of an image processing system for autonomous underwater vehicles (AUVs). For the proposed visual recognition technology, a Hough transform was combined with an optical flow algorithm to detect the linear features and movement speeds of dynamic images; the proposed stereoscopic imaging technique employed a Harris corner detector to estimate the distance of the target. A physical AUV was constructed with a wide-angle lens camera and a binocular vision device mounted on the bow to provide image input. Subsequently, a simulation environment was established in Simscape Multibody and used to control the post-driver system of the stern, which contained horizontal and vertical rudder planes as well as the propeller. In static testing at National Cheng Kung University, physical targets were placed in a stability water tank; the study compared the analysis results obtained from various brightness and turbidity conditions in out-of-water and underwater environments. Finally, the dynamic testing results were combined with a fuzzy controller to output the real-time responses of the vehicle regarding the angles, rates of the rudder planes, and the propeller revolution speeds at various distances. Full article
(This article belongs to the Special Issue Underwater Technology—Hydrodynamics and Control System)
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Open AccessArticle
An Investigation into the Suitability of GGBS and OPC as Low Percentage Single-Component Binders for the Stabilisation and Solidification of Harbour Dredge Material Mildly Contaminated with Metals
J. Mar. Sci. Eng. 2019, 7(4), 106; https://doi.org/10.3390/jmse7040106
Received: 20 February 2019 / Revised: 1 April 2019 / Accepted: 13 April 2019 / Published: 18 April 2019
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Abstract
The occurrence of contaminated materials encountered during harbour dredging is becoming increasingly problematic for harbour and port authorities. The risks to human health, wildlife and port infrastructure of exposure to such contaminants necessitates the removal or containment of such risks. As with contaminated [...] Read more.
The occurrence of contaminated materials encountered during harbour dredging is becoming increasingly problematic for harbour and port authorities. The risks to human health, wildlife and port infrastructure of exposure to such contaminants necessitates the removal or containment of such risks. As with contaminated terrestrial sites the solidification and stabilization (S/S) of this material has been proven to be an effective alternative to disposing of contaminants off-site, typically via dumping at sea or in a landfill. Research, to date, on S/S has been focused on heavily contaminated sediments in large industrial ports. However, with tightening environmental regulations, the limits of acceptable contamination are generally decreasing. This means the number of port dredging projects requiring contaminant remediation is increasing. There is now a need to examine the effectiveness of S/S on harbour sites that are mildly contaminated from both an environmental and project feasibility viewpoint. To that end, this study examines the effectiveness of various S/S mix percentages of ordinary Portland cement (OPC) and ground granulated blast furnace slag (GGBS) in retarding the leaching of contaminants from a mildly contaminated harbour site. Full article
(This article belongs to the Special Issue Marine Dredging Engineering: Environmental Dredging)
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Open AccessArticle
Fish Hybridization Leads to Uncertainty Regarding Ciguatera Fish Poisoning Risk; Confirmation of Hybridization and Ciguatoxin Accumulation with Implications for Stakeholders
J. Mar. Sci. Eng. 2019, 7(4), 105; https://doi.org/10.3390/jmse7040105
Received: 13 March 2019 / Revised: 12 April 2019 / Accepted: 13 April 2019 / Published: 17 April 2019
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Abstract
Globally, ciguatera fish poisoning (CFP) avoidance efforts rely primarily on local knowledge of the fish being consumed, its collection location, and association with illnesses. In 2016, several fish that appeared to be hybrids between a local commercially prized species, Ocyurus chrysurus, and [...] Read more.
Globally, ciguatera fish poisoning (CFP) avoidance efforts rely primarily on local knowledge of the fish being consumed, its collection location, and association with illnesses. In 2016, several fish that appeared to be hybrids between a local commercially prized species, Ocyurus chrysurus, and a regionally prohibited species Lutjanus apodus (due to CFP concerns), were caught nearshore in United States Virgin Islands waters, leading to confusion regarding the safety of consuming the fish. The hybrid status of the fish was verified as O. chrysurus (male) × L. apodus (female) by comparing two sets of gene sequences (mitochondrial CO1 and nuclear S7). Using an in vitro mouse neuroblastoma (N2a) assay, one of the hybrid fish exhibited a composite cytotoxicity of 0.038 ppb Caribbean ciguatoxin-1 (C-CTX-1) equivalents (Eq.); a concentration below the US Food and Drug Administration (FDA) guidance level for safety in fish products for CFP (0.1 ppb C-CTX-1 Eq.) but approximately 2× above the maximum described in the commercially prized parent species (0.019 ppb C-CTX-1 Eq./g). C-CTX-1 was confirmed in the hybrid sample by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The second hybrid fish tested negative for CTXs. This research confirms hybridization between two species with contrasting commercial statuses, discusses CTX accumulation implications for hybridization, and provides a methodology for future studies into novel CFP vectors, with the goal of providing critical information for fishermen and consumers regarding CFP risk management. Full article
(This article belongs to the Special Issue Advances and Current Challenges in Marine Biotoxins Monitoring)
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Open AccessArticle
Second Path Planning for Unmanned Surface Vehicle Considering the Constraint of Motion Performance
J. Mar. Sci. Eng. 2019, 7(4), 104; https://doi.org/10.3390/jmse7040104
Received: 11 March 2019 / Revised: 10 April 2019 / Accepted: 11 April 2019 / Published: 17 April 2019
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Abstract
When utilizing the traditional path planning method for unmanned surface vehicles (USVs), ‘planning-failure’ is a common phenomenon caused by the inflection points of large curvatures in the planned path, which exceed the performances of USVs. This paper presents a second path planning method [...] Read more.
When utilizing the traditional path planning method for unmanned surface vehicles (USVs), ‘planning-failure’ is a common phenomenon caused by the inflection points of large curvatures in the planned path, which exceed the performances of USVs. This paper presents a second path planning method (SPP), which is an initial planning path optimization method based on the geometric relationship of the three-point path. First, to describe the motion performance of a USV in conjunction with the limited test data, a method of integral nonlinear least squares identification is proposed to rapidly obtain the motion constraint of the USV merely by employing a zig zag test. It is different from maneuverability identification, which is performed in combination with various tests. Second, the curvature of the planned path is limited according to the motion performance of the USV based on the traditional path planning, and SPP is proposed to make the maximum curvature radius of the optimized path smaller than the rotation curvature radius of the USV. Finally, based on the ‘Dolphin 1’ prototype USV, comparative simulation experiments were carried out. In the experiment, the path directly obtained by the initial path planning and the path optimized by the SPP method were considered as the tracking target path. The artificial potential field method was used as an example for the initial path planning. The experimental results demonstrate that the tracking accuracy of the USV significantly improved after the path optimization using the SPP method. Full article
(This article belongs to the Special Issue Intelligent Marine Robotics Modelling, Simulation and Applications)
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Open AccessArticle
A Comprehensive Study of the Wave Impact Loads on an Inclined Plate
J. Mar. Sci. Eng. 2019, 7(4), 103; https://doi.org/10.3390/jmse7040103
Received: 8 March 2019 / Revised: 9 April 2019 / Accepted: 10 April 2019 / Published: 16 April 2019
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Abstract
Water wave impact on a wet deck is an important issue in ocean engineering, and the plate-shaped structure in the splash zone tends to suffer tremendous impact loads. This work presents a method for predicting the wave slamming uplift force on a fixed [...] Read more.
Water wave impact on a wet deck is an important issue in ocean engineering, and the plate-shaped structure in the splash zone tends to suffer tremendous impact loads. This work presents a method for predicting the wave slamming uplift force on a fixed plate with different inclined angles. Both numerical simulation and the scale model test of the wave impact loads on an inclined plate were performed, and a good agreement was obtained. In addition, the influence of three important wave parameters on the slamming uplift force was systematically investigated: relative deck width B/LS, relative wave height Δh/H1/3, and the plate’s inclined angle α. The results indicate that the three parameters can significantly influence the wave slamming uplift force. Finally, a developed empirical equation is proposed for estimating the wave slamming uplift force on the inclined plate. Full article
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Open AccessArticle
Stability Analysis of Near-Wellbore Reservoirs Considering the Damage of Hydrate-Bearing Sediments
J. Mar. Sci. Eng. 2019, 7(4), 102; https://doi.org/10.3390/jmse7040102
Received: 4 March 2019 / Revised: 31 March 2019 / Accepted: 9 April 2019 / Published: 13 April 2019
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Abstract
The stability of hydrate-bearing near-wellbore reservoirs is one of the key issues in gas hydrate exploitation. In most previous investigations, the damage evolution process of the sediment structure and its effect on near-wellbore reservoir stability have been neglected. Therefore, the damage variable is [...] Read more.
The stability of hydrate-bearing near-wellbore reservoirs is one of the key issues in gas hydrate exploitation. In most previous investigations, the damage evolution process of the sediment structure and its effect on near-wellbore reservoir stability have been neglected. Therefore, the damage variable is introduced into a multi-field coupled model based on continuous damage theory and multi-field coupling theory. A thermo-hydro-mechanical-chemical (THMC) multi-field coupling mathematical model considering damage of hydrate-bearing sediments is established. The effects of damage of hydrate-bearing sediments on the thermal field, seepage field, and mechanical field are considered. Finally, the distributions of hydrate saturation, pore pressure, damage variable, and effective stress of a near-wellbore reservoir in gas hydrate exploitation by depressurization are calculated, and the stability of a hydrate-bearing near-wellbore reservoir is analyzed using the model. Through calculation and analysis, it is found that structural damage of hydrate-bearing sediments has an adverse effect on the stability of hydrate-bearing near-wellbore reservoirs. The closer to the wellbore, the worse the reservoir stability, and the near-wellbore reservoir stability is the worst in the direction of minimum horizontal ground stress. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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Open AccessArticle
A Novel Segmented Structure and Control Method for a Permanent-Magnet Linear Generator to Broaden the Range of Efficient Energy Capture
J. Mar. Sci. Eng. 2019, 7(4), 101; https://doi.org/10.3390/jmse7040101
Received: 20 February 2019 / Revised: 20 March 2019 / Accepted: 1 April 2019 / Published: 12 April 2019
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Abstract
Wave energy, a high-quality renewable energy, is abundant in reserves and relatively stable. However, the wave energy power of the same sea area varies greatly in different seasons. The traditional linear generator cannot work efficiently in such a wide power range. This paper [...] Read more.
Wave energy, a high-quality renewable energy, is abundant in reserves and relatively stable. However, the wave energy power of the same sea area varies greatly in different seasons. The traditional linear generator cannot work efficiently in such a wide power range. This paper presents a segmented permanent-magnet linear generator structure, which is especially designed for the wave energy converter. This type of linear generator can match the wave energy power by increasing or decreasing the specific primary unit, making the generator more efficient over a wider range of wave power than the traditional type. This paper verifies the correctness by finite element analysis. Full article
(This article belongs to the Special Issue Selected Papers from the 4th Asian Wave and Tidal Energy Conference)
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Open AccessArticle
Development of Upwelling during the Sedimentary Period of the Organic-Rich Shales in the Wufeng and Longmaxi Formations of the Upper Yangtze Region and Its Impact on Organic Matter Enrichment
J. Mar. Sci. Eng. 2019, 7(4), 99; https://doi.org/10.3390/jmse7040099
Received: 3 March 2019 / Revised: 6 April 2019 / Accepted: 7 April 2019 / Published: 11 April 2019
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Abstract
This study uses logging data, mineral component content, total organic carbon (TOC) content, and microscopic characteristics of the organic-rich shales in the Wufeng and Longmaxi Formations, as well as data reported by other researchers, to demonstrate that upwelling has played an important role [...] Read more.
This study uses logging data, mineral component content, total organic carbon (TOC) content, and microscopic characteristics of the organic-rich shales in the Wufeng and Longmaxi Formations, as well as data reported by other researchers, to demonstrate that upwelling has played an important role in the organic matter enrichment. The results show that (1) the organic-rich shales of Well N211 in the Upper Yangtze region are located in the Wufeng Formation and the lower Longmaxi Formation, with a burial depth between 2308–2357 m. (2) The organic-rich shales are enriched in biogenic silica. (3) Based on paleogeographic location and characteristics of organisms, this study determines that upwelling occurred during the deposition of the organic-rich shales in the Wufeng and Longmaxi Formations, promoting the enrichment of organic matter in the shales. (4) The upwelling intensity gradually increased from the sedimentary period of the organic-rich shales in the mid-lower Wufeng Formation to the sedimentary period of the Guanyinqiao Member, and then decreased gradually from the sedimentary period of the Guanyinqiao Member to the sedimentary period of the organic-rich shales in the Longmaxi Formation, and leads to the different enrichment of organic matter in the vertical direction. The different developments of upwelling led to the coexistence of both high and low TOC contents in the Guanyinqiao Member along the vertical direction. Full article
(This article belongs to the Special Issue Marine Mineral Resource Mining)
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Open AccessArticle
Towing Operation Methods of Offshore Integrated Meteorological Mast for Offshore Wind Farms
J. Mar. Sci. Eng. 2019, 7(4), 100; https://doi.org/10.3390/jmse7040100
Received: 22 January 2019 / Revised: 30 March 2019 / Accepted: 3 April 2019 / Published: 11 April 2019
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Abstract
An offshore integrated meteorological mast (OIMM) is introduced which has great application potential for the development of offshore wind turbine power. This innovative OIMM features in two aspects: the integrated construction and the integrated transportation. Its integrated techniques enable this OIMM to be [...] Read more.
An offshore integrated meteorological mast (OIMM) is introduced which has great application potential for the development of offshore wind turbine power. This innovative OIMM features in two aspects: the integrated construction and the integrated transportation. Its integrated techniques enable this OIMM to be prefabricated onshore and transported by a relatively small tugboat to the installation site. It is efficient in construction, rapid in transportation and saving in cost. The towing process is an important section for the integrated transportation, which makes the towing operation necessary to investigate. With the numerical simulation software MOSES, the hydrodynamic behavior of the towing operation is investigated. Two special wet towing methods (surface towing and submerged towing) are adopted and analyzed in terms of the towing resistance, towing speed, fairlead position and the motion response. The results show that for both towing methods, to obtain a higher speed by increasing the towing force is uneconomic since the towing resistance increases a much higher percentage than the towing speed dose. Surface towing has a smaller resistance but larger motion response compared to submerged towing. The submerged towing shows a clear descending heave motion. The heave and pitch motions are smaller with the lower fairlead position and fluctuate less with deeper submerged depth. Full article
(This article belongs to the Special Issue Marine Structures)
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Open AccessArticle
Seagrass Resource Assessment Using WorldView-2 Imagery in the Redfish Bay, Texas
J. Mar. Sci. Eng. 2019, 7(4), 98; https://doi.org/10.3390/jmse7040098
Received: 25 March 2019 / Revised: 25 March 2019 / Accepted: 4 April 2019 / Published: 10 April 2019
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Abstract
Seagrass meadows play important roles as habitats for many marine organisms, traps for sediment, and buffers against wave actions. The objective of this paper is to map seagrass meadows in the Redfish Bay, Texas from WorldView-2 imagery. Seagrass meadows grow in shallow and [...] Read more.
Seagrass meadows play important roles as habitats for many marine organisms, traps for sediment, and buffers against wave actions. The objective of this paper is to map seagrass meadows in the Redfish Bay, Texas from WorldView-2 imagery. Seagrass meadows grow in shallow and clear water areas in the Redfish Bay. The WorldView-2 satellite can acquire multispectral imagery from the bay bottom with 2 m spatial resolution 8 multispectral bands and 0.46 m panchromatic imagery. The top of atmosphere radiance was transformed to the bottom reflectance through the atmospheric correction and the water column correction. The object based image analysis was used to identify seagrass meadows distributions in the Redfish Bay. This investigation demonstrated that seagrass can be identified with 94% accuracy, although seagrass species cannot be satisfactorily recognized. The results implied that the WorldView-2 satellite imagery is a suitable data source for seagrass distribution mapping. Full article
(This article belongs to the Special Issue Application of Remote Sensing Methods to Monitor Coastal Zones)
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Open AccessArticle
High Resolution Shoreline and Shelly Ridge Monitoring over Stormy Winter Events: A Case Study in the Megatidal Bay of Mont-Saint-Michel (France)
J. Mar. Sci. Eng. 2019, 7(4), 97; https://doi.org/10.3390/jmse7040097
Received: 18 March 2019 / Revised: 29 March 2019 / Accepted: 2 April 2019 / Published: 4 April 2019
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Abstract
In the current context of decadal global changes and predicted sea level rise, annual erosion is one of the most obvious indicators of threats to coastal systems. Shoreline monitoring during high energy events is therefore a crucial action to prevent and alleviate future [...] Read more.
In the current context of decadal global changes and predicted sea level rise, annual erosion is one of the most obvious indicators of threats to coastal systems. Shoreline monitoring during high energy events is therefore a crucial action to prevent and alleviate future coastal risks. However, most studies look at this on a regional issue basis with limited resolution, and with limited support from field observations. This study addresses this lack by focusing on high resolution (HR) shoreline surveys, combined with wave measurements, in the megatidal Bay of Mont-Saint-Michel. The salt marsh vegetation line and the inner margin of shelly ridges were selected as markers of the stabilized shoreline, to follow its evolution during two high energy winter events, from February 18 to 24, 2015 and from March 19 to 24, 2015, in two different study sites. A transdisciplinary methodology was adopted which included: (1) in situ wave measurements with pressure sensors, (2) topographical data acquisition using a differential GPS, and (3) in silico observations of the shoreline movements through HR aerial and satellite imageries. Our findings highlighted the positive linkage between significant wave height and erosion rate (ranging from 0 to 60.9 m), as well as the variability of coastline responses depending on the geomorphic features. Full article
(This article belongs to the Special Issue Storm Erosion)
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Open AccessArticle
Path Analysis of Causal Factors Influencing Marine Traffic Accident via Structural Equation Numerical Modeling
J. Mar. Sci. Eng. 2019, 7(4), 96; https://doi.org/10.3390/jmse7040096
Received: 24 February 2019 / Revised: 22 March 2019 / Accepted: 26 March 2019 / Published: 4 April 2019
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Abstract
Many causal factors to marine traffic accidents (MTAs) influence each other and have associated effects. It is necessary to quantify the correlation path mode of these factors to improve accident prevention measures and their effects. In the application of human factors to accident [...] Read more.
Many causal factors to marine traffic accidents (MTAs) influence each other and have associated effects. It is necessary to quantify the correlation path mode of these factors to improve accident prevention measures and their effects. In the application of human factors to accident mechanisms, the complex structural chains on causes to MTA systems were analyzed by combining the human failure analysis and classification system (HFACS) with theoretical structural equation modeling (SEM). First, the accident causation model was established as a human error analysis classification in sight of a MTA, and the constituent elements of the causes of the accident were conducted. Second, a hypothetical model of human factors classification was proposed by applying the practice of the structural model. Third, with the data resources from ship accident cases, this hypothetical model was discussed and simulated, and as a result, the relationship path dependency mode between the latent independent variable of the accident was quantitatively analyzed based on the observed dependent variable of human behavior. Application examples show that relationships in the HFACS are verified and in line with the path developing mode, and resource management factors have a pronounced influence and a strong relevance to the causal chain of the accidents. Appropriate algorithms for the theoretical model can be used to numerically understand the safety performance of marine traffic systems under different parameters through mathematical analysis. Hierarchical assumptions in the HFACS model are quantitatively verified. Full article
(This article belongs to the Special Issue Advances in Marine Dynamic Simulation)
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Open AccessArticle
Investigation of Lumped-Mass Method on Coupled Torsional-longitudinal Vibrations for a Marine Propulsion Shaft with Impact Factors
J. Mar. Sci. Eng. 2019, 7(4), 95; https://doi.org/10.3390/jmse7040095
Received: 15 February 2019 / Revised: 22 March 2019 / Accepted: 28 March 2019 / Published: 4 April 2019
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Abstract
Severe vibrations of the marine propulsion shaft can evidently affect the dynamical response of the propulsion system and degrade the performance of a ship. As the vibration forms couples which interact with each other, a better understanding of the coupled vibrations is essential [...] Read more.
Severe vibrations of the marine propulsion shaft can evidently affect the dynamical response of the propulsion system and degrade the performance of a ship. As the vibration forms couples which interact with each other, a better understanding of the coupled vibrations is essential for dynamic prediction to improve the efficiency and reliability of the marine propulsion system. Thus, an investigation of the lumped-mass method for coupled torsional-longitudinal vibrations of the shaft is proposed. First, a theoretical solution for the coupled ordinary differential equations demonstrates the accuracy of the proposed lumped-mass model. This model allows for the bifurcation diagram and the Poincare surface, and transient accelerations of the coupled vibrations are numerically calculated. Furthermore, the impact factors including various length-diameter ratios, coupling stiffness coefficients, and damping coefficients are respectively discussed. These impact factors are found to affect the coupled vibrations to different extents through the comparison of the transient accelerations. Finally, an accurate and applicative lumped-mass method for the coupled torsional-longitudinal vibrations of the marine propulsion shaft has been obtained. An optimal design and vibration reduction of the shaft, considering the above-mentioned impact factors, can be achieved. Full article
(This article belongs to the Special Issue Marine Propellers and Ship Propulsion)
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Open AccessArticle
Numerical Investigation into the Two-Phase Convective Heat Transfer within the Hold of an Oil Tanker Subjected to a Rolling Motion
J. Mar. Sci. Eng. 2019, 7(4), 94; https://doi.org/10.3390/jmse7040094
Received: 20 March 2019 / Revised: 28 March 2019 / Accepted: 1 April 2019 / Published: 3 April 2019
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Abstract
A crude oil tanker usually encounters a rolling motion during sea transportation, which leads to rotational movement and sometimes a sloshing of the liquid hold. This rolling-induced body motion seriously affects the thermal and hydraulic behavior of the liquid hold, which then affects [...] Read more.
A crude oil tanker usually encounters a rolling motion during sea transportation, which leads to rotational movement and sometimes a sloshing of the liquid hold. This rolling-induced body motion seriously affects the thermal and hydraulic behavior of the liquid hold, which then affects the heating process and heat preservation of the tanker. Clarification of the involved thermal and hydraulic characteristics is the basic requirement for establishment of a scientific heating scheme and heat preservation method. A two-phase 3D model considering the free liquid surface and non-Newtonian behavior of the fluid was established for the thermal calculation of the liquid holds in oil tankers. The thermal and hydraulic characteristics of the liquid hold were investigated under different combinations of dimensionless parameters, and the combined effect of rolling and fluid non-Newtonian behavior was investigated. It was found that rolling intensifies the heat transfer based on the combination of the Richardson number ( R i ) and the rotation-strength number ( ω * ), and non-Newtonian behavior of the fluid effectively affects the heat transfer in a rolling motion. This research is expected to provide a reference for design and optimization of the heating and heat preservation method for oil tanker operation. Full article
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Open AccessArticle
Seasonal Changes in the Intertidal and Subtidal Algal Communities of Extremely and Moderately Polluted Coastal Regions of Sanya Bay (Hainan Island, China)
J. Mar. Sci. Eng. 2019, 7(4), 93; https://doi.org/10.3390/jmse7040093
Received: 1 March 2019 / Revised: 22 March 2019 / Accepted: 26 March 2019 / Published: 3 April 2019
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Abstract
At the end of the rainy season in 2016 and at the end of the dry season in 2017, we conducted a floristic study of marine macrophytic algae in the intertidal and subtidal zones in moderately and heavily polluted areas at Luhuitou reef, [...] Read more.
At the end of the rainy season in 2016 and at the end of the dry season in 2017, we conducted a floristic study of marine macrophytic algae in the intertidal and subtidal zones in moderately and heavily polluted areas at Luhuitou reef, Sanya Bay, Hainan Island, China. A total of 109 species of marine macrophytes were found during these samplings. At the end of the rainy season, 72 species of macrophytes (50% reds, 19% browns, and 31% greens) were found. At the end of the dry season, we found and identified 92 species of macrophytes (46% reds, 20% browns, and 34% greens). Seasonal changes in species diversity, species composition, and the structure of algal communities at differently polluted sites exhibited common features as well as specific characteristics. By the end of the dry season, the diversity of macroalgal species was increased, and the composition of dominant and accompanying species of macrophytes in polydominant communities was changed in moderately and heavily polluted areas. Seasonal changes in the marine flora of differently polluted areas were characterized by specific features as follows: Less changes in species diversity of heavily polluted area compared with moderately polluted area during the change from the rainy season to the dry season; significant increase in the biomass of green algae and their projective coverage in the middle and low intertidal zones of heavily polluted sites in the dry season; and the increase in the numbers of mono- and bidominant communities in the middle and low intertidal zones of heavily polluted sites by the end of the dry season. Full article
(This article belongs to the Section Marine Biology)
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Open AccessArticle
Kelvin-Helmholtz Billows Induced by Shear Instability along the North Passage of the Yangtze River Estuary, China
J. Mar. Sci. Eng. 2019, 7(4), 92; https://doi.org/10.3390/jmse7040092
Received: 14 February 2019 / Revised: 17 March 2019 / Accepted: 27 March 2019 / Published: 2 April 2019
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Abstract
Kelvin-Helmholtz (K-H) instability plays a significant role in mixing. To investigate the existence of K-H instability along the North Passage of the Yangtze River Estuary, the non-hydrostatic model NHWAVE is utilized to simulate the fresh-salt water mixing process along the North Passage of [...] Read more.
Kelvin-Helmholtz (K-H) instability plays a significant role in mixing. To investigate the existence of K-H instability along the North Passage of the Yangtze River Estuary, the non-hydrostatic model NHWAVE is utilized to simulate the fresh-salt water mixing process along the North Passage of the Yangtze River Estuary. Using high horizontal resolution, the structure of K-H billows have been successfully captured within the Lower Reach of the North Passage. The K-H instability occurs between the max flood and high-water slack. The duration and length scale of the K-H billows highly depends on the local interaction between fresh-water discharge and tide. The horizontal length scale of the instability is about 60 m, similar to the observations in other estuaries. In the vertical direction, the K-H billows exist within the pycnocline with length scale ranging from 6 to 7 m. The timescale of the billows is approximate 6 min. By analyzing the changes of potential energy during the mixing process, results show that the existence of K-H instability induces intense vertical mixing, which can greatly increase mixing efficiency in the North Passage of the Yangtze River Estuary. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessEditorial
Announcing the 2019 JMSE Travel Awards for Postdoctoral Researchers and Ph.D. Students
J. Mar. Sci. Eng. 2019, 7(4), 91; https://doi.org/10.3390/jmse7040091
Received: 29 March 2019 / Accepted: 29 March 2019 / Published: 1 April 2019
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Abstract
Following the successful launch of the JMSE travel awards last year, this year’s competition attracted over 40 applications [...] Full article
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J. Mar. Sci. Eng. EISSN 2077-1312 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
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