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J. Mar. Sci. Eng., Volume 7, Issue 2 (February 2019)

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Cover Story (view full-size image) Modelling is used to study rocky coast development in the past and to predict their response to [...] Read more.
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Open AccessArticle
Oil Spill Scenarios in the Kotor Bay: Results from High Resolution Numerical Simulations
J. Mar. Sci. Eng. 2019, 7(2), 54; https://doi.org/10.3390/jmse7020054
Received: 2 January 2019 / Revised: 15 February 2019 / Accepted: 17 February 2019 / Published: 25 February 2019
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Abstract
A major threat for marine and coastal environment comes from oil spill accidents. Such events have a great impact on both the ecosystem and on the economy, and the risk increases over time due to increasing ship traffic in many sensitive areas. In [...] Read more.
A major threat for marine and coastal environment comes from oil spill accidents. Such events have a great impact on both the ecosystem and on the economy, and the risk increases over time due to increasing ship traffic in many sensitive areas. In recent years, numerical simulation of oil spills has become an affordable tool for the analysis of the risk and for the preparation of contingency plans. However, in coastal areas, the complexity of the bathymetry and of the orography requires an adequate resolution of sea and wind flows. For this reason, we present, to the best of the author’s knowledge, the first study on the subject adopting Large Eddy Simulations for both the low-atmosphere and sea dynamics in order to provide highly-resolved marine surface current and wind stress to the oil slick model, within a one-way coupling procedure. Such approach is applied to the relevant case of Kotor Bay (UNESCO heritage since 1979), in Montenegro, which is a semi-closed basin surrounded by mountains that is subject to an intense ship traffic for touristic purposes. Oil spill spots are tracked along ship paths, in two wind scenarios. Full article
(This article belongs to the Special Issue Marine Oil Spills 2018) Printed Edition available
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Open AccessArticle
Above Water Electric Potential Signatures of Submerged Naval Vessels
J. Mar. Sci. Eng. 2019, 7(2), 53; https://doi.org/10.3390/jmse7020053
Received: 19 December 2018 / Revised: 31 January 2019 / Accepted: 20 February 2019 / Published: 23 February 2019
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Abstract
In this paper, we investigate the fundamental linkage between underwater electric potential (UEP) signatures and their related electric fields above the waterline, which are introduced as above water electric potential (AEP) signatures. As a first step, the field distribution for an underwater point [...] Read more.
In this paper, we investigate the fundamental linkage between underwater electric potential (UEP) signatures and their related electric fields above the waterline, which are introduced as above water electric potential (AEP) signatures. As a first step, the field distribution for an underwater point source excitation (fundamental solution) is derived analytically, using an adjusted method of images. Subsequently a numerical approach is introduced, whereby the calculation of the stationary current density distribution and electrostatic fields are coupled within an FEM simulation. Simulation results are presented for the aforementioned point source, as well as for a submarine model, where the latter includes considering non-linear polarization curves to model the electrochemical behavior at the metal–seawater interface. Finally, the relevance of AEP signatures in the context of anti-submarine warfare (ASW) is discussed. Our results show that AEP signatures inevitably occur along with UEP signatures, and could therefore in principal be used to detect submerged submarines via airborne sensors. However, an estimation of the expectable signal-to-noise-ratio (SNR) suggests that AEP signatures are difficult to exploit and therefore entail a much lower risk compared to other signatures. Full article
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Open AccessArticle
Numerical Simulations of Wave-Induced Soil Erosion in Silty Sand Seabeds
J. Mar. Sci. Eng. 2019, 7(2), 52; https://doi.org/10.3390/jmse7020052
Received: 10 January 2019 / Revised: 17 February 2019 / Accepted: 18 February 2019 / Published: 20 February 2019
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Abstract
Silty sand is a kind of typical marine sediment that is widely distributed in the offshore areas of East China. It has been found that under continuous actions of wave pressure, a mass of fine particles will gradually rise up to the surface [...] Read more.
Silty sand is a kind of typical marine sediment that is widely distributed in the offshore areas of East China. It has been found that under continuous actions of wave pressure, a mass of fine particles will gradually rise up to the surface of silty sand seabeds, i.e., the phenomenon called wave-induced soil erosion. This is thought to be due to the seepage flow caused by the pore-pressure accumulation within the seabed. In this paper, a kind of three-phase soil model (soil skeleton, pore fluid, and fluidized soil particles) is established to simulate the process of wave-induced soil erosion. In the simulations, the analytical solution for wave-induced pore-pressure accumulation was used, and Darcy flow law, mass conservation, and generation equations were coupled. Then, the time characteristics of wave-induced soil erosion in the seabed were studied, especially for the effects of wave height, wave period, and critical concentration of fluidized particles. It can be concluded that the most significant soil erosion under wave actions appears at the shallow seabed. With the increases of wave height and critical concentration of fluidized particles, the soil erosion rate and erosion degree increase obviously, and there exists a particular wave period that will lead to the most severe and the fastest rate of soil erosion in the seabed. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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Open AccessArticle
Analysis of Hydrodynamic Performance of L-Type Podded Propulsion with Oblique Flow Angle
J. Mar. Sci. Eng. 2019, 7(2), 51; https://doi.org/10.3390/jmse7020051
Received: 23 January 2019 / Revised: 16 February 2019 / Accepted: 18 February 2019 / Published: 20 February 2019
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Abstract
In this study, the Reynolds-averaged Navier–Stokes (RANS) method and a model experimental test in a towing tank are used to investigate the unsteady hydrodynamic performance of L-type podded propulsion under different oblique flow angles and advance coefficients. The results show that the [...] Read more.
In this study, the Reynolds-averaged Navier–Stokes (RANS) method and a model experimental test in a towing tank are used to investigate the unsteady hydrodynamic performance of L-type podded propulsion under different oblique flow angles and advance coefficients. The results show that the load of the operative propeller increases with oblique flow angle and the bracket adds resistance to the pod due to the impact of water flow, leading to a reduced propeller thrust coefficient with increased oblique flow angle. Under a high advance coefficient, the speed of increase of the pressure effect is higher than that of the viscosity effect, and the propeller efficiency increases with the oblique flow angle. The nonuniformity of the inflow results in varying degrees of asymmetry in the horizontal and vertical distributions of the propeller blade pressure. Under high oblique flow angle, relatively strong interference effects are seen between venting vortexes and the cabin after blades, leading to a disorderly venting vortex system after the blade. The numerical simulation results are in good agreement with the experimental values. The study findings provide a foundation for further research on L-type podded propulsors. Full article
(This article belongs to the Special Issue Marine Propulsion)
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Open AccessArticle
Exploring Possible Influence of Dust Episodes on Surface Marine Chlorophyll Concentrations
J. Mar. Sci. Eng. 2019, 7(2), 50; https://doi.org/10.3390/jmse7020050
Received: 31 December 2018 / Revised: 11 February 2019 / Accepted: 12 February 2019 / Published: 20 February 2019
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Abstract
Desert dust deposition is thought to act as fertilizer for phytoplankton growth, since it is rich in the required nutrients. The Mediterranean Sea is a nutrient poor marine environment—with its eastern part being the most oligotrophic—which is subject to dust transport. The Hellenic [...] Read more.
Desert dust deposition is thought to act as fertilizer for phytoplankton growth, since it is rich in the required nutrients. The Mediterranean Sea is a nutrient poor marine environment—with its eastern part being the most oligotrophic—which is subject to dust transport. The Hellenic Seas are part of this low-nutrient, low-chlorophyll environment and they are also affected by dust deposition events. Thus, the dust fertilizing effect can be particularly important, especially during the stratification period, when the nutrients needed for phytoplankton growth are not imported from deeper layers. Some individual dust events are examined here in respect of their possible influence on phytoplankton, through the observed variations of satellite derived chlorophyll concentrations. Two strong dust events that were also extreme weather events and three events in the June–September stratification period are examined for the Hellenic Seas as well as a strong dust event in the Central Mediterranean Sea. The results, only when based on absolute chlorophyll differences above 50%, show that dust events seem to favour phytoplankton abundance mainly during the low productive period; however, these differences are area-limited. The difficulty of reaching safe results through specific dust events and discriminating between other meteorological factors favouring phytoplankton growth are also discussed. Full article
(This article belongs to the Section Physical Oceanography)
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Open AccessArticle
Modeling and Simulation of Planing-Hull Watercraft Outfitted with an Electric Motor Drive and a Surface-Piercing Propeller
J. Mar. Sci. Eng. 2019, 7(2), 49; https://doi.org/10.3390/jmse7020049
Received: 26 December 2018 / Revised: 3 February 2019 / Accepted: 8 February 2019 / Published: 18 February 2019
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Abstract
A simulation model for a prismatic hard-chine planing hull watercraft (V-shaped keel with constant deadrise) with propulsion based on a 3-phase induction motor connected directly to surface-piercing propeller (SPP) and outfitted with a motor rotational speed controller was investigated, tested, and tuned. The [...] Read more.
A simulation model for a prismatic hard-chine planing hull watercraft (V-shaped keel with constant deadrise) with propulsion based on a 3-phase induction motor connected directly to surface-piercing propeller (SPP) and outfitted with a motor rotational speed controller was investigated, tested, and tuned. The modularity of the model developed enables straightforward substitution of diverse and more refined modules, or even attachment of additional ones to obtain greater level of detail or simulate more complicated processes. Industry trends do suggest an increasing interest in all-electric ship development as well as the use of surface-piercing propellers for small or medium-size craft. All-electric drive plants offer distinct advantages due to their flexibility in arrangements, ability to eliminate reduction gears in many cases, low maintenance requirements and wide range of available sizes as well superb load acceptance and dynamic matching to changing operational conditions. Employing electric drives onboard small craft with planing-hulls that achieve significantly higher velocities where arrangements and maneuverability are of critical design issues is a theme that has received increased attention by designers in recent years. Refined speed regulation and tracking compounded by the feature to produce fairly constant torque across a broad speed (rpm) range enables using of unconventional thrusters such as surface-piercing propellers to small craft. By investigating towing tank test data series for a surface-piercing propeller, development of a numerical simulation tool for unconventional thrusters was demonstrated. The surface-piercing propeller simulation model, as an artificial neural network (ANN), was coupled with a 3-phase induction motor as prime mover as well as dynamic propulsion shaft model and proportional-integral-differential (PID) controller. The various sub-models were finally integrated with a sub-model implementing Savitsky’s propulsion resistance method and calculation of equilibrium trim for planing hull modeling. Simulations were conducted using full-scale real-world conditions for a high-speed small craft developed for leisure and sporting activities, rapid close-range transit, reconnaissance and surveying etc. The planing-hull watercraft considered is amenable to minor hull modifications in order to house a 50 kW electric motor and a four bladed surface-piercing propeller. Simulations performed allowed a full assessment of model functionality as well as level of detail. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessFeature PaperArticle
A Hamiltonian Surface-Shaping Approach for Control System Analysis and the Design of Nonlinear Wave Energy Converters
J. Mar. Sci. Eng. 2019, 7(2), 48; https://doi.org/10.3390/jmse7020048
Received: 23 January 2019 / Revised: 7 February 2019 / Accepted: 8 February 2019 / Published: 15 February 2019
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Abstract
The dynamic model of Wave Energy Converters (WECs) may have nonlinearities due to several reasons such as a nonuniform buoy shape and/or nonlinear power takeoff units. This paper presents the Hamiltonian Surface-Shaping (HSS) approach as a tool for the analysis and design of [...] Read more.
The dynamic model of Wave Energy Converters (WECs) may have nonlinearities due to several reasons such as a nonuniform buoy shape and/or nonlinear power takeoff units. This paper presents the Hamiltonian Surface-Shaping (HSS) approach as a tool for the analysis and design of nonlinear control of WECs. The Hamiltonian represents the stored energy in the system and can be constructed as a function of the WEC’s system states, its position, and velocity. The Hamiltonian surface is defined by the energy storage, while the system trajectories are constrained to this surface and determined by the power flows of the applied non-conservative forces. The HSS approach presented in this paper can be used as a tool for the design of nonlinear control systems that are guaranteed to be stable. The optimality of the obtained solutions is not addressed in this paper. The case studies presented here cover regular and irregular waves and demonstrate that a nonlinear control system can result in a multiple fold increase in the harvested energy. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
On the Assessment of Numerical Wave Makers in CFD Simulations
J. Mar. Sci. Eng. 2019, 7(2), 47; https://doi.org/10.3390/jmse7020047
Received: 21 December 2018 / Revised: 3 February 2019 / Accepted: 5 February 2019 / Published: 13 February 2019
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Abstract
A fully non-linear numerical wave tank (NWT), based on Computational Fluid Dynamics (CFD), provides a useful tool for the analysis of coastal and offshore engineering problems. To generate and absorb free surface waves within a NWT, a variety of numerical wave maker (NWM) [...] Read more.
A fully non-linear numerical wave tank (NWT), based on Computational Fluid Dynamics (CFD), provides a useful tool for the analysis of coastal and offshore engineering problems. To generate and absorb free surface waves within a NWT, a variety of numerical wave maker (NWM) methodologies have been suggested in the literature. Therefore, when setting up a CFD-based NWT, the user is faced with the task of selecting the most appropriate NWM, which should be driven by a rigorous assessment of the available methods. To provide a consistent framework for the quantitative assessment of different NWMs, this paper presents a suite of metrics and methodologies, considering three key performance parameters: accuracy, computational requirements and available features. An illustrative example is presented to exemplify the proposed evaluation metrics, applied to the main NWMs available for the open source CFD software, OpenFOAM. The considered NWMs are found to reproduce waves with an accuracy comparable to real wave makers in physical wave tank experiments. However, the paper shows that significant differences are found between the various NWMs, and no single method performed best in all aspects of the assessment across the different test cases. Full article
(This article belongs to the Special Issue Computational Fluid Dynamics for Ocean Surface Waves)
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Open AccessFeature PaperArticle
On Tidal Current Velocity Vector Time Series Prediction: A Comparative Study for a French High Tidal Energy Potential Site
J. Mar. Sci. Eng. 2019, 7(2), 46; https://doi.org/10.3390/jmse7020046
Received: 13 December 2018 / Revised: 26 January 2019 / Accepted: 8 February 2019 / Published: 13 February 2019
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Abstract
Estimating the energy potential of tidal stream site is a key feature for tidal energy system deployment. This paper aims to compare two methods of prediction of tidal current velocities. The first one is based on the use of a fully three-dimensional (3D) [...] Read more.
Estimating the energy potential of tidal stream site is a key feature for tidal energy system deployment. This paper aims to compare two methods of prediction of tidal current velocities. The first one is based on the use of a fully three-dimensional (3D) numerical approach. However, while being accurate, the numerical model is highly time-consuming. The second method is based on a linear approximation of the tidal current, which only requires preliminary knowledge of local current velocities time series during two typical tidal cycles. This second method allows a very quick evaluation of the tidal stream resource during a long time period. The proposed comparison is done in three different locations of a high potential tidal energy site in west of France. It is carried out in terms of current velocity and energy harnessing for several turbines technology options (with and without yaw). The achieved results show that the linear approximation gives satisfactory evaluation of the tidal stream potential and can be a very interesting tool for preliminary site evaluation and first technology options selection. However, the fully 3D numerical model can obviously be very useful in more advanced steps of a project. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessArticle
Automatic Shoreline Position and Intertidal Foreshore Slope Detection from X-Band Radar Images Using Modified Temporal Waterline Method with Corrected Wave Run-up
J. Mar. Sci. Eng. 2019, 7(2), 45; https://doi.org/10.3390/jmse7020045
Received: 22 December 2018 / Revised: 7 February 2019 / Accepted: 8 February 2019 / Published: 12 February 2019
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Abstract
Automatic and accurate shoreline position and intertidal foreshore slope detection are challenging and significantly important for coastal dynamics. In the present study, a time series shoreline position and intertidal foreshore slope have been automatically detected using modified Temporal Waterline Method (mTWM) from time-averaged [...] Read more.
Automatic and accurate shoreline position and intertidal foreshore slope detection are challenging and significantly important for coastal dynamics. In the present study, a time series shoreline position and intertidal foreshore slope have been automatically detected using modified Temporal Waterline Method (mTWM) from time-averaged X-band radar images captured throughout the course of two-week tidal cycle variation over an area spanning 5.6 km on the Hasaki coast between 12 April 2005 and 31 December 2008. The methodology is based on the correlation map between the pixel intensity variation of the time-averaged X-band radar images and the binary signal of the tide level ranging from −0.8 m to 0.8 m. In order to ensure the binary signal represented each of the water levels in the intertidal shore profile, determining the water level direction-wise bottom elevation is considered as the modification. Random gaps were detected in the captured images owing to the unclear or oversaturation of the waterline signal. A horizontal shift in the detected shoreline positions was observed compared to the survey data previously collected at Hasaki Oceanographical Research Station (HORS). This horizontal shift can be attributed to wave breaking and high wave conditions. Wave set-up and run-up are the effects of wave breaking and high wave conditions, respectively. The correction of the wave set-up and run-up is considered to allow the upward shift of the water level position, as well as shoreline position, to the landward direction. The findings indicate that the shoreline positions derived by mTWM with the corrected wave run-up reasonably agree with the survey data. The mean absolute bias (MAB) between the survey data and the shoreline positions detected using mTWM with the corrected wave run-up is approximately 5.9 m, which is theoretically smaller than the spatial resolution of the radar measurements. The random gaps in the mTWM-derived shoreline positions are filled by Garcia’s data filling algorithm which is a Penalized Least Squares regression method by means of the Discrete Cosine Transform (PLS-DCT). The MAB between survey data and the gap filled shoreline positions detected using TWM with corrected wave run-up is approximately 5.9 m. The obtained results indicate the accuracy of the mTWM with corrected wave run-up integrated with Garcia’s method compared to the survey observations. The executed approach in this study is considered as an efficient and robust tool to automatically detect shoreline positions and intertidal foreshore slopes extracted from X-band radar images with the consideration of wave run-up correction. Full article
(This article belongs to the Special Issue Radar Technology for Coastal Areas and Open Sea Monitoring)
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Open AccessArticle
Modeling Tidal Datums and Spatially Varying Uncertainty in the Texas and Western Louisiana Coastal Waters
J. Mar. Sci. Eng. 2019, 7(2), 44; https://doi.org/10.3390/jmse7020044
Received: 30 September 2018 / Revised: 22 December 2018 / Accepted: 22 December 2018 / Published: 9 February 2019
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Abstract
Tidal datums are key components in NOAA’s Vertical Datum transformation project (VDatum), which enables effective vertical transformation of the water level between tidal, orthometric, and ellipsoid -based three-dimensional reference systems. An initial application of modeling tidal datums was developed for the coastal waters [...] Read more.
Tidal datums are key components in NOAA’s Vertical Datum transformation project (VDatum), which enables effective vertical transformation of the water level between tidal, orthometric, and ellipsoid -based three-dimensional reference systems. An initial application of modeling tidal datums was developed for the coastal waters of Texas and western Louisiana in 2013. The goals of the current work include: (1) updating the tidal model by using the best available shoreline, bathymetry, and tide station data; (2) implementing a recently developed statistical interpolation method for interpolating modeled tidal datums and computing tidal datum uncertainties; and (3) using modeled tidal datums to upgrade non-tidal polygons for enhancing the quality of the VDatum marine grid population. The updated tidal model outperformed the previous tidal model in most cases. The statistical interpolation method is able to limit the interpolated tidal datums to within a user-defined model error (0.01 m in this work) and produce a spatially varying uncertainty field for each interpolated tidal datum field. The upgraded non-tidal polygons enhanced the quality of the VDatum marine grid population. This paper will introduce the detailed procedures of this modeling work, present and discuss the obtained results, share the effective methods used for improving model performance and lessons learned in the model assessments, and analyze the improvement of the current tidal model in comparison with the previous tidal model. Full article
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Open AccessArticle
An Evaluation of the Wind and Wave Dynamics along the European Coasts
J. Mar. Sci. Eng. 2019, 7(2), 43; https://doi.org/10.3390/jmse7020043
Received: 9 December 2018 / Revised: 2 February 2019 / Accepted: 4 February 2019 / Published: 8 February 2019
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Abstract
The objective of this work is to analyze the wind and wave conditions along the coasts of the European seas. The emphasis is put on the mean and maximum values. The areas studied are characterized by intense maritime activities, including traffic, as well [...] Read more.
The objective of this work is to analyze the wind and wave conditions along the coasts of the European seas. The emphasis is put on the mean and maximum values. The areas studied are characterized by intense maritime activities, including traffic, as well as various harbor and offshore operations. In the present study, 35 years of data (1983–2017) coming from the European Centre for Medium-Range Weather Forecasts (ECMWF) were processed, corresponding to 40 different geographical locations. Thus, these 40 reference points are defined for some of the most relevant offshore locations in the coastal environments targeted. As regards the data considered in the analysis, two different sets were used. The first corresponds to the wave model, while the second to the atmospheric model, both operated by ECMWF. Finally, it can be concluded that the proposed work provides a global perspective related to the average and maximum wind and wave conditions and to a further extent on the climate dynamics along the coasts of the European seas. Full article
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Open AccessArticle
Mapping Heavy Metal Concentrations in Beach Sands Using GIS and Portable XRF Data
J. Mar. Sci. Eng. 2019, 7(2), 42; https://doi.org/10.3390/jmse7020042
Received: 16 January 2019 / Revised: 2 February 2019 / Accepted: 4 February 2019 / Published: 8 February 2019
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Abstract
It is necessary to investigate the contamination of beach sands to ensure water safety, as they may contain potentially toxic trace elements. Tourists, oil spills, or replenishing sands can cause beach sand contamination. In this study, heavy metal contamination maps of lead (Pb) [...] Read more.
It is necessary to investigate the contamination of beach sands to ensure water safety, as they may contain potentially toxic trace elements. Tourists, oil spills, or replenishing sands can cause beach sand contamination. In this study, heavy metal contamination maps of lead (Pb) and zinc (Zn) were created for Wolpo Beach, on the eastern coast of Korea, using portable X-ray fluorescence and geographic information systems (GIS). Interpolation methods, such as kriging and inverse distance weighting, were used in this study and their results were compared. Understanding the spatial variation of potentially toxic trace elements in beach sand is necessary to determine suitable measures for preventing contamination. Sufficient sand data for understanding spatial patterns can be acquired by using rapid portable X-ray fluorescence analysis. As a result, we could create heavy metal concentration maps for the sand of Wolpo Beach. It was confirmed that the southern part of the target area is more contaminated than the northern part. However, there are no sand areas with highly concentrated heavy metal levels. In addition, no sample data exceed the soil contamination standards. This study demonstrates that portable X-ray fluorescence and geographic information systems can be utilized for investigating and preventing the contamination of beach sands by creating heavy metal concentration maps. Full article
(This article belongs to the Section Coastal Engineering)
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Open AccessArticle
An Improved Method to Estimate the Probability of Oil Spill Contact to Environmental Resources in the Gulf of Mexico
J. Mar. Sci. Eng. 2019, 7(2), 41; https://doi.org/10.3390/jmse7020041
Received: 30 November 2018 / Revised: 2 February 2019 / Accepted: 3 February 2019 / Published: 8 February 2019
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Abstract
The oil spill risk analysis (OSRA) model is a tool used by the Bureau of Ocean Energy Management (BOEM) to evaluate oil spill risks to biological, physical, and socioeconomic resources that could be exposed to oil spill contact from oil and gas leasing, [...] Read more.
The oil spill risk analysis (OSRA) model is a tool used by the Bureau of Ocean Energy Management (BOEM) to evaluate oil spill risks to biological, physical, and socioeconomic resources that could be exposed to oil spill contact from oil and gas leasing, exploration, or development on the U.S. Outer Continental Shelf (OCS). Using long-term hindcast winds and ocean currents, the OSRA model generates hundreds of thousands of trajectories from hypothetical oil spill locations and derives the probability of contact to these environmental resources in the U.S. OCS. This study generates probability of oil spill contact maps by initiating trajectories from hypothetical oil spill points over the entire planning areas in the U.S. Gulf of Mexico (GOM) OCS and tabulating the contacts over the entire waters in the GOM. Therefore, a probability of oil spill contact database that stores information of the spill points and contacts can be created for a given set of wind and current data such that the probability of oil spill contact to any environmental resources from future leasing areas can be estimated without a rerun of the OSRA model. The method can be applied to other OCS regions and help improve BOEM’s decision-making process. Full article
(This article belongs to the Special Issue Marine Oil Spills 2018) Printed Edition available
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Open AccessArticle
Modeling Sediment Bypassing around Idealized Rocky Headlands
J. Mar. Sci. Eng. 2019, 7(2), 40; https://doi.org/10.3390/jmse7020040
Received: 20 December 2018 / Revised: 22 January 2019 / Accepted: 24 January 2019 / Published: 7 February 2019
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Abstract
Alongshore sediment bypassing rocky headlands remains understudied despite the importance of characterizing littoral processes for erosion abatement, beach management, and climate change adaptation. To address this gap, a numerical model sediment transport study was developed to identify controlling factors and mechanisms for sediment [...] Read more.
Alongshore sediment bypassing rocky headlands remains understudied despite the importance of characterizing littoral processes for erosion abatement, beach management, and climate change adaptation. To address this gap, a numerical model sediment transport study was developed to identify controlling factors and mechanisms for sediment headland bypassing potential. Four idealized headlands were designed to investigate sediment flux around the headlands using the process-based hydrodynamic model Delft-3D and spectral wave model SWAN. The 120 simulations explored morphologies, substrate compositions, sediment grain sizes, and physical forcings (i.e., tides, currents, and waves) commonly observed in natural settings. A generalized analytical framework based on flow disruption and sediment volume was used to refine which factors and conditions were more useful to address sediment bypassing. A bypassing parameter was developed for alongshore sediment flux between upstream and downstream cross-shore transects to determine the degree of blockage by a headland. The shape of the headland heavily influenced the fate of the sediment by changing the local angle between the shore and the incident waves, with oblique large waves generating the most flux. All headlands may allow sediment flux, although larger ones blocked sediment more effectively, promoting their ability to be littoral cell boundaries. The controlling factors on sediment bypassing were determined to be wave angle, size, and shape of the headland, and sediment grain size. Full article
(This article belongs to the Section Physical Oceanography)
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Open AccessArticle
Separation of Long-Crested Nonlinear Bichromatic Waves into Incident and Reflected Components
J. Mar. Sci. Eng. 2019, 7(2), 39; https://doi.org/10.3390/jmse7020039
Received: 11 December 2018 / Revised: 29 January 2019 / Accepted: 31 January 2019 / Published: 7 February 2019
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Abstract
Methods for the separation of long-crested linear waves into incident and reflected waves have existed for more than 40 years. The present paper presents a new method for the separation of nonlinear bichromatic long-crested waves into incident and reflected components, as well as [...] Read more.
Methods for the separation of long-crested linear waves into incident and reflected waves have existed for more than 40 years. The present paper presents a new method for the separation of nonlinear bichromatic long-crested waves into incident and reflected components, as well as into free and bound components. The new method is an extension of a recently proposed method for the separation of nonlinear regular waves. The new methods include both bound and free higher harmonics, which is important for nonlinear waves. The applied separation method covers interactions to the third order, but can easily be extended to a higher orders. Synthetic tests, as well as physical model tests, showed that the method accurately predict the bound amplitudes and incident and reflected surface elevations of nonlinear bichromatic waves. The new method is important in order to be able to describe the detailed characteristics of nonlinear bichromatic waves and their reflection. Full article
(This article belongs to the Special Issue Selected Papers from Coastlab18 Conference)
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Open AccessArticle
Numerical Simulations of the Hydraulic Performance of a Breakwater-Integrated Overtopping Wave Energy Converter
J. Mar. Sci. Eng. 2019, 7(2), 38; https://doi.org/10.3390/jmse7020038
Received: 18 December 2018 / Revised: 2 February 2019 / Accepted: 3 February 2019 / Published: 7 February 2019
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Abstract
OBREC is the acronym that stands for Overtopping Breakwater for Energy Conversion. It is a multifunctional device aimed to produce energy from the waves, while keeping the harbour area protected from flooding. In this paper, the inclusions of a berm to reduce wave [...] Read more.
OBREC is the acronym that stands for Overtopping Breakwater for Energy Conversion. It is a multifunctional device aimed to produce energy from the waves, while keeping the harbour area protected from flooding. In this paper, the inclusions of a berm to reduce wave reflection, the shape of the sloping plate to maximise wave overtopping and the reservoir width and the crown wall shape to maximise wave energy capture while keeping the harbour safety were analysed to optimize the hydraulic and structural performances of the device. Several configurations were numerically investigated by means of a 2DV RANS-VOF code to extend the results already obtained during previous experimental campaigns. The wave reflection coefficient, the average wave overtopping flows and the wave loadings along the structure are computed, compared with existing formulae and discussed with reference to the OBREC prototype installed in the Port of Naples. Full article
(This article belongs to the Section Coastal Engineering)
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Open AccessArticle
Continuous Coastal Monitoring with an Automated Terrestrial Lidar Scanner
J. Mar. Sci. Eng. 2019, 7(2), 37; https://doi.org/10.3390/jmse7020037
Received: 3 January 2019 / Revised: 26 January 2019 / Accepted: 29 January 2019 / Published: 7 February 2019
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Abstract
This paper details the collection, geo-referencing, and data processing algorithms for a fully-automated, permanently deployed terrestrial lidar system for coastal monitoring. The lidar is fixed on a 4-m structure located on a shore-backing dune in Duck, North Carolina. Each hour, the lidar collects [...] Read more.
This paper details the collection, geo-referencing, and data processing algorithms for a fully-automated, permanently deployed terrestrial lidar system for coastal monitoring. The lidar is fixed on a 4-m structure located on a shore-backing dune in Duck, North Carolina. Each hour, the lidar collects a three-dimensional framescan of the nearshore region along with a 30-min two-dimensional linescan time series oriented directly offshore, with a linescan repetition rate of approximately 7 Hz. The data are geo-referenced each hour using a rigorous co-registration process that fits 11 fixed planes to a baseline scan to account for small platform movements, and the residual errors from the fit are used to assess the accuracy of the rectification. This process decreased the mean error (defined as the magnitude of the offset in three planes) over a two-year period by 24.41 cm relative to using a fixed rectification matrix. The automated data processing algorithm then filters and grids the data to generate a dry-beach digital elevation model (DEM) from the framescan along with hourly wave runup, hydrodynamic, and morphologic statistics from the linescan time series. The lidar has collected data semi-continuously since January 2015 (with gaps occurring while the lidar was malfunctioning or being serviced), resulting in an hourly data set spanning four years as of January 2019. Examples of data products and potential applications spanning a range of spatial and temporal scales relevant to coastal processes are discussed. Full article
(This article belongs to the Special Issue Application of Remote Sensing Methods to Monitor Coastal Zones)
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Open AccessArticle
Oil Slick Characterization Using a Statistical Region-Based Classifier Applied to UAVSAR Data
J. Mar. Sci. Eng. 2019, 7(2), 36; https://doi.org/10.3390/jmse7020036
Received: 31 October 2018 / Revised: 20 December 2018 / Accepted: 25 December 2018 / Published: 6 February 2019
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Abstract
During emergency responses to oil spills on the sea surface, quick detection and characterization of an oil slick is essential. The use of Synthetic Aperture Radar (SAR) in general and polarimetric SAR (PolSAR) in particular to detect and discriminate mineral oils from look-alikes [...] Read more.
During emergency responses to oil spills on the sea surface, quick detection and characterization of an oil slick is essential. The use of Synthetic Aperture Radar (SAR) in general and polarimetric SAR (PolSAR) in particular to detect and discriminate mineral oils from look-alikes is known. However, research exploring its potential to detect oil slick characteristics, e.g., thickness variations, is relatively new. Here a Multi-Source Image Processing System capable of processing optical, SAR and PolSAR data with proper statistical models was tested for the first time for oil slick characterization. An oil seep detected by NASA`s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) in the Gulf of Mexico was used as a study case. This classifier uses a supervised approach to compare stochastic distances between different statistical distributions (fx) and hypothesis tests to associate confidence levels to the classification results. The classifier was able to detect zoning regions within the slick with high global accuracies and low uncertainties. Two different classes, likely associated with the thicker and thinner oil layers, were recognized. The best results, statistically equivalent, were obtained using different data formats: polarimetric, intensity pair and intensity single-channel. The presence of oceanic features in the form of oceanic fronts and internal waves created convergence zones that defined the shape, spreading and concentration of the thickest layers of oil. The statistical classifier was able to detect the thicker oil layers accumulated along these features. Identification of the relative thickness of spilled oils can increase the oil recovery efficiency, allowing better positioning of barriers and skimmers over the thickest layers. Decision makers can use this information to guide aerial surveillance, in situ oil samples collection and clean-up operations in order to minimize environmental impacts. Full article
(This article belongs to the Special Issue Marine Oil Spills 2018) Printed Edition available
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Open AccessArticle
New Equations to Evaluate Lateral Displacement Caused by Liquefaction Using the Response Surface Method
J. Mar. Sci. Eng. 2019, 7(2), 35; https://doi.org/10.3390/jmse7020035
Received: 8 January 2019 / Revised: 30 January 2019 / Accepted: 31 January 2019 / Published: 4 February 2019
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Abstract
Few empirical and semi-empirical approaches have considered the influence of the geology, tectonic source, causative fault type, and frequency content of earthquake motion on lateral displacement caused by liquefaction (DH). This paper aims to address this gap in the literature [...] Read more.
Few empirical and semi-empirical approaches have considered the influence of the geology, tectonic source, causative fault type, and frequency content of earthquake motion on lateral displacement caused by liquefaction (DH). This paper aims to address this gap in the literature by adding an earthquake parameter of the standardized cumulative absolute velocity (CAV5) to the original dataset for analyzing. Furthermore, the complex influence of fine content in the liquefiable layer (F15) is analyzed by deriving two different equations: the first one is for the whole range of parameters, and the second one is for a limited range of F15 values under 28% in order to the F15’s critical value presented in literature. The new response surface method (RSM) approach is applied on the basis of the artificial neural network (ANN) model to develop two new equations. Moreover, to illustrate the capability and efficiency of the developed models, the results of the RSM models are examined by comparing them with an additional three available models using data from the Chi-Chi earthquake sites that were not used for developing the models in this study. In conclusion, the RSM provides a capable tool to evaluate the liquefaction phenomenon, and the results fully justify the complex effect of different values of F15. Full article
(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)
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Open AccessFeature PaperReview
Hard-Rock Coastal Modelling: Past Practice and Future Prospects in a Changing World
J. Mar. Sci. Eng. 2019, 7(2), 34; https://doi.org/10.3390/jmse7020034
Received: 12 January 2019 / Revised: 26 January 2019 / Accepted: 30 January 2019 / Published: 3 February 2019
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Abstract
This paper reviews the history of conceptual and numerical modelling of hard rock coasts (mean annual cliff erosion typically < 1 mm up to 1 cm) and its use in studying coastal evolution in the past and predicting the impact of the changing [...] Read more.
This paper reviews the history of conceptual and numerical modelling of hard rock coasts (mean annual cliff erosion typically < 1 mm up to 1 cm) and its use in studying coastal evolution in the past and predicting the impact of the changing climate, and especially rising sea level, in the future. Most of the models developed during the last century were concerned with the development and morphology of shore-normal coastal profiles, lacking any sediment cover, in non-tidal environments. Some newer models now consider the plan shape of rock coasts, and models often incorporate elements, such as the tidally controlled expenditure of wave energy within the intertidal zone, beach morphodynamics, weathering, changes in relative sea level, and the role of wave refraction and sediment accumulation. Despite these advances, the lack of field data, combined with the inherent complexity of rock coasts and uncertainty over their age, continue to inhibit attempts to develop more reliable models and to verify their results. Full article
(This article belongs to the Special Issue Coastal Morphodynamics II)
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Open AccessArticle
Experimental Study of a Hybrid Wave Energy Converter Integrated in a Harbor Breakwater
J. Mar. Sci. Eng. 2019, 7(2), 33; https://doi.org/10.3390/jmse7020033
Received: 31 December 2018 / Revised: 19 January 2019 / Accepted: 23 January 2019 / Published: 3 February 2019
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Abstract
Sea ports are infrastructures with substantial energy demands and often responsible for air pollution and other environmental problems, which may be minimized by using renewable energy, namely electricity harvested from ocean waves. In this regard, a wide variety of concepts to harvest wave [...] Read more.
Sea ports are infrastructures with substantial energy demands and often responsible for air pollution and other environmental problems, which may be minimized by using renewable energy, namely electricity harvested from ocean waves. In this regard, a wide variety of concepts to harvest wave energy are available and some shoreline technologies are already in an advanced development phase. The [email protected] project aims to assess the suitability and viability of existing wave energy conversion technologies to be integrated in harbor breakwaters, in order to take advantage of their high exposure to ocean waves. This paper describes the experimental study carried out to assess the performance of a hybrid wave energy converter (WEC) integrated in the rubble-mound structure that was proposed for the extension of the North breakwater of the Port of Leixões, Portugal. The hybrid concept combines the overtopping and the oscillating water column principles and was tested on a geometric scale of 1/50. This paper is focused on the assessment of the effects of the hybrid WEC integration on the case-study breakwater, both in terms of its stability and functionality. The 2D physical model included the reproduction of the seabed bathymetry in front of the breakwater and the generation of a wide range of irregular sea states, including extreme wave conditions. The experimental results shown that the integration of the hybrid WEC in the breakwater does not worsens the stability of its toe berm blocks and reduces the magnitude of the overtopping events. The conclusions obtained are therefore favorable to the integration of this type of devices on harbor breakwaters. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
An Operational Wave System within the Monitoring Program of a Mediterranean Beach
J. Mar. Sci. Eng. 2019, 7(2), 32; https://doi.org/10.3390/jmse7020032
Received: 20 December 2018 / Revised: 26 January 2019 / Accepted: 30 January 2019 / Published: 2 February 2019
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Abstract
This work assesses the performance of an operational wave system in the Mediterranean Sea by comparing computed data with measurements collected at different water depths. Nearshore data measurements were collected through a field experiment carried out at Poetto beach (Southern Sardinia, Italy) during [...] Read more.
This work assesses the performance of an operational wave system in the Mediterranean Sea by comparing computed data with measurements collected at different water depths. Nearshore data measurements were collected through a field experiment carried out at Poetto beach (Southern Sardinia, Italy) during spring 2017. In addition to coastal observations, we use intermediate and deep water wave data measured by two buoys: one situated North-West of Corsica and the other in the Gulf of Lion. The operational wave system runs once a day to predict the wave evolution up to five days in advance. We use a multi-grid approach in which a large grid extends over the entire Mediterranean basin and a fine grid covers the coastal seas surrounding the islands of Sardinia and Corsica. The comparison with measurements shows that the operational wave system is able to satisfactorily reproduce the wave evolution in deep and intermediate waters where the relative error of the significant wave height is 17%. The error exceeding 25% in coastal waters suggests that the use of a finer grid and the coupling with an atmospheric model able to catch local effects is advisable to accurately address nearshore wave processes driven by coastal wind forcing. Full article
(This article belongs to the Special Issue Selected Papers from Coastlab18 Conference)
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Open AccessArticle
Interaction of Swell and Sea Waves with Partially Reflective Structures for Possible Engineering Applications
J. Mar. Sci. Eng. 2019, 7(2), 31; https://doi.org/10.3390/jmse7020031
Received: 22 January 2019 / Revised: 29 January 2019 / Accepted: 30 January 2019 / Published: 2 February 2019
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Abstract
In this work, we investigate the interaction between the combination of wind-driven and regular waves and a chamber defined by a rigid wall and a thin vertical semi-submerged barrier. A series of laboratory experiments were performed with different values of incident wave height, [...] Read more.
In this work, we investigate the interaction between the combination of wind-driven and regular waves and a chamber defined by a rigid wall and a thin vertical semi-submerged barrier. A series of laboratory experiments were performed with different values of incident wave height, wave period, and wind speed. The analysis focuses on the effect of the geometry of the system characterized in terms of its relative submergence d/h and relative width B/L. Results show that for the case of d/h = 0.58 a resonant effect takes place inside the chamber regardless of the wind speed. Wind-driven waves have a higher influence on the variation of the wave period of the waves seaward and leeward of the plate, as well as on the phase lag. Results show that the amplification or reduction of the wave energy inside the chamber is closely related to the wave period as compared to the 1st order natural period of the chamber. Full article
(This article belongs to the Special Issue Selected Papers from Coastlab18 Conference)
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Open AccessArticle
Spatial and Temporal Variability of Dense Shelf Water Cascades along the Rottnest Continental Shelf in Southwest Australia
J. Mar. Sci. Eng. 2019, 7(2), 30; https://doi.org/10.3390/jmse7020030
Received: 21 December 2018 / Revised: 25 January 2019 / Accepted: 27 January 2019 / Published: 1 February 2019
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Abstract
Along the majority of Australian shallow coastal regions, summer evaporation increases the salinity of shallow waters, and subsequently in autumn/winter, the nearshore waters become cooler due to heat loss. This results in the formation of horizontal density gradients with density increasing toward the [...] Read more.
Along the majority of Australian shallow coastal regions, summer evaporation increases the salinity of shallow waters, and subsequently in autumn/winter, the nearshore waters become cooler due to heat loss. This results in the formation of horizontal density gradients with density increasing toward the coast that generates gravity currents known as dense shelf water cascades (DSWCs) flowing offshore along the sea bed. DSWCs play important role in ecological and biogeochemical processes in Australian waters through the transport of dissolved and suspended materials offshore. In this study a numerical ocean circulation model of Rottnest continental shelf, validated using simultaneous ocean glider and mooring data, indicated that the passage of cold fronts associated with winter storms resulted in rapid heat loss through evaporative cooling. These conditions resulted in enhancement of the DSWCs due to modifications of the cross-shelf density gradient and wind effects. Specifically, onshore (offshore) directed winds resulted in an enhancement (inhibition) of DSWCs due to downwelling (vertical mixing). Consequently, the largest DSWC events occurred during the cold fronts when atmospheric temperatures reinforced density gradients and onshore winds promoted downwelling that enhanced DSWCs. Advection of DSWCs was also strongly influenced by the wind conditions, with significantly more transport occurring along-shelf compared to cross-shelf. Full article
(This article belongs to the Section Physical Oceanography)
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Open AccessArticle
KNSwing—On the Mooring Loads of a Ship-Like Wave Energy Converter
J. Mar. Sci. Eng. 2019, 7(2), 29; https://doi.org/10.3390/jmse7020029
Received: 10 January 2019 / Revised: 23 January 2019 / Accepted: 26 January 2019 / Published: 1 February 2019
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Abstract
The critical function of keeping a floating Wave Energy Converter in position is done by a mooring system. Several WECs have been lost due to failed moorings, indicating that extreme loads, reliability and durability are very important aspects. An understanding of the interaction [...] Read more.
The critical function of keeping a floating Wave Energy Converter in position is done by a mooring system. Several WECs have been lost due to failed moorings, indicating that extreme loads, reliability and durability are very important aspects. An understanding of the interaction between the WEC’s motion in large waves and the maximum mooring loads can be gained by investigating the system at model scale supported by numerical models. This paper describes the testing of a novel attenuator WEC design called KNSwing. It is shaped like a ship facing the waves with its bow, which results in low mooring loads and small motions in most wave conditions when the structure is longer than the waves. The concept is tested using an experimental model at scale 1:80 in regular and irregular waves, moored using rubber bands to simulate synthetic moorings. The experimental results are compared to numerical simulations done using the OrcaFlex software. The experimental results show that the WEC and the mooring system survives well, even under extreme and breaking waves. The numerical model coefficient concerning the nonlinear drag term for the surge motion is validated using decay tests. The numerical results compare well to the experiments and, thereby, the numerical model can be further used to optimize the mooring system. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
The Role of Latent Heat Flux in Tropical Cyclogenesis over the Western North Pacific: Comparison of Developing versus Non-Developing Disturbances
J. Mar. Sci. Eng. 2019, 7(2), 28; https://doi.org/10.3390/jmse7020028
Received: 25 December 2018 / Revised: 19 January 2019 / Accepted: 23 January 2019 / Published: 28 January 2019
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Abstract
The possible role of air–sea latent heat flux (LHF) in tropical cyclone (TC) genesis over the western North Pacific (WNP) is investigated using state-of-the-art satellite and analysis datasets. The authors conducted composite analyses of several meteorological variables after identifying developing and non-developing tropical [...] Read more.
The possible role of air–sea latent heat flux (LHF) in tropical cyclone (TC) genesis over the western North Pacific (WNP) is investigated using state-of-the-art satellite and analysis datasets. The authors conducted composite analyses of several meteorological variables after identifying developing and non-developing tropical disturbances from June to October of the period 2000 to 2009. Compared to the non-developing disturbances, increased LHF underlying the developing disturbances enhances boundary–layer specific humidity. The secondary circulation then transports more boundary–layer moisture inward and upward and, thus, induces a stronger moist core in the middle troposphere. Accordingly, the air in the core region ascends following a warmer moist adiabat than that in the environment and results in a stronger upper-level warm core, which is associated with a stronger near-surface tangential wind based on the thermal wind balance. This enlarges the magnitude and negative radial gradient of LHF and, thereby, further increases boundary–layer specific humidity. A tropical depression forms when the near-surface tangential wind increases to a certain extent as a result of the continuing positive feedback between near-surface wind and LHF. The results suggest an important role of wind-driven LHF in TC genesis over the WNP. Full article
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Open AccessArticle
Integrating Three-Dimensional Benthic Habitat Characterization Techniques into Ecological Monitoring of Coral Reefs
J. Mar. Sci. Eng. 2019, 7(2), 27; https://doi.org/10.3390/jmse7020027
Received: 4 January 2019 / Revised: 18 January 2019 / Accepted: 22 January 2019 / Published: 28 January 2019
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Abstract
Long-term ecological monitoring of reef fish populations often requires the simultaneous collection of data on benthic habitats in order to account for the effects of these variables on fish assemblage structure. Here, we described an approach to benthic surveys that uses photogrammetric techniques [...] Read more.
Long-term ecological monitoring of reef fish populations often requires the simultaneous collection of data on benthic habitats in order to account for the effects of these variables on fish assemblage structure. Here, we described an approach to benthic surveys that uses photogrammetric techniques to facilitate the extraction of quantitative metrics for characterization of benthic habitats from the resulting three-dimensional (3D) reconstruction of coral reefs. Out of 92 sites surveyed in the Northwestern Hawaiian Islands, photographs from 85 sites achieved complete alignment and successfully produced 3D reconstructions and digital elevation models (DEMs). Habitat metrics extracted from the DEMs were generally correlated with one another, with the exception of curvature measures, indicating that complexity and curvature measures should be treated separately when quantifying the habitat structure. Fractal dimension D64, calculated by changing resolutions of the DEMs from 1 cm to 64 cm, had the best correlations with other habitat metrics. Fractal dimension was also less affected by changes in orientations of the models compared to surface complexity or slope. These results showed that fractal dimension can be used as a single measure of complexity for the characterization of coral reef habitats. Further investigations into metrics for 3D characterization of habitats should consider relevant spatial scales and focus on obtaining variables that can complement fractal dimension in the characterization of reef habitats. Full article
(This article belongs to the Special Issue Underwater Imaging)
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Open AccessArticle
Rogue Wave Formation in Adverse Ocean Current Gradients
J. Mar. Sci. Eng. 2019, 7(2), 26; https://doi.org/10.3390/jmse7020026
Received: 19 November 2018 / Revised: 12 January 2019 / Accepted: 18 January 2019 / Published: 24 January 2019
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Abstract
Studies of the nonlinear Schrödinger (NLS) equation indicate that surface gravity waves traveling against currents of increasing strength gain energy and steepness in the process, and this can be a mechanism for rogue wave formation. Likewise, experimental studies have shown that stable wavetrains [...] Read more.
Studies of the nonlinear Schrödinger (NLS) equation indicate that surface gravity waves traveling against currents of increasing strength gain energy and steepness in the process, and this can be a mechanism for rogue wave formation. Likewise, experimental studies have shown that stable wavetrains traveling against adverse currents can give rise to extreme waves. We studied this phenomenon by using computational fluid dynamics (CFD) tools, whereby the non-hydrostatic Euler equations were solved utilizing the finite volume method. Waveforms based on a JONSWAP spectrum were generated in a numerical wave tank and were made to travel against current gradients of known strength, and wave characteristics were monitored in the process. We verified that waves gain energy from the underlying flow field as they travel against current gradients, and the simulated level of energy increase was comparable to that predicted by earlier studies of the NLS equation. The computed significant wave height, H s , increased substantially, and there were strong indications that the current gradients induced nonlinear wave instabilities. The simulations were used to determine a new empirical relationship that correlates changes in the current velocity to changes in the Benjamin–Feir Index (BFI). The empirical relationship allows for seafaring entities to predict increased risk of rogue waves ahead, based on wave and current conditions. Full article
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Open AccessArticle
Energetic Potential Assessment of Wind-Driven Waves on the South-Southeastern Brazilian Shelf
J. Mar. Sci. Eng. 2019, 7(2), 25; https://doi.org/10.3390/jmse7020025
Received: 30 November 2018 / Revised: 14 January 2019 / Accepted: 21 January 2019 / Published: 23 January 2019
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Abstract
Global electric energy demand is constantly growing, consequently leading towards the usage of renewable energy sources reducing pollution and increasing sustainability. The ocean is a poorly explored renewable energy source; thus, to evaluate the Brazilian wave energy budget, this study investigated the mean [...] Read more.
Global electric energy demand is constantly growing, consequently leading towards the usage of renewable energy sources reducing pollution and increasing sustainability. The ocean is a poorly explored renewable energy source; thus, to evaluate the Brazilian wave energy budget, this study investigated the mean behaviour of the wave power rate on the south-southeastern Brazilian Shelf as well as analysed the temporal variability of the wave power rate at the most energetic locations near the coast. Three locations were examined, namely Laguna, Ilhabela and Farol Island, based on the criteria of high means and small standard deviations. The mean wave power rate was approximately 9.08 kW / m on Laguna, 10.01 kW / m on Ilhabela and 15.93 kW / m on Farol Island. The standard deviation identified in the three locations reached values of 6.47 kW / m on Laguna, 7.59 kW / m on Ilhabela and 13.51 kW / m on Farol Island. Temporal variability analysis was conducted through wavelet analysis. The results show a dominant yearly cycle with a background presence of synoptic cycles, with little deviation between the locations. The El Niño southern oscillation plays a minor role on the energy spectrum of Laguna and does not have a significant influence on Ilhabela and Farol Island. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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