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Volume 8
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J. Mar. Sci. Eng., Volume 8, Issue 4 (April 2020) – 70 articles

Cover Story (view full-size image): Ducted propellers are an unconventional propulsion system usually adopted for ship propulsion. Their functioning has been addressed using medium fidelity (i.e., BEM) approaches with promising results. Despite providing good predictions of forces and moments, these methods are not able to provide accurate insights into the flow peculiarities of such complex systems. On the other hand, modern high-fidelity CFD codes like RANSE could provide a better description of these features. Toward this aim, forces and the wake field around two ducted propellers (one of accelerating and one of decelerating type) are analyzed using RANSE calculations combined with an adaptive mesh refinement process. These predictions are compared to experimental results, including the usual thrust and torque curves as well as LDV measurements to demonstrate the reliability of this method, which is particularly useful for [...] Read more.
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21 pages, 1882 KiB  
Article
Effects of Marine Exhaust Gas Scrubbers on Gas and Particle Emissions
by Hulda Winnes, Erik Fridell and Jana Moldanová
J. Mar. Sci. Eng. 2020, 8(4), 299; https://doi.org/10.3390/jmse8040299 - 24 Apr 2020
Cited by 65 | Viewed by 7217
Abstract
There is an increase in installations of exhaust gas scrubbers on ships following international regulations on sulphur content in marine fuel from 2020. We have conducted emission measurements on a four-stroke marine engine using low sulphur fuel oil (LSFO) and heavy fuel oil [...] Read more.
There is an increase in installations of exhaust gas scrubbers on ships following international regulations on sulphur content in marine fuel from 2020. We have conducted emission measurements on a four-stroke marine engine using low sulphur fuel oil (LSFO) and heavy fuel oil (HFO) at different steady state engine loads. For the HFO the exhaust was probed upstream and downstream of an exhaust gas scrubber. While sulphur dioxide was removed with high efficiency in the scrubber, the measurements of particle emissions indicate lower emissions at the use of LSFO than downstream of the scrubber. The scrubber removes between 32% and 43% of the particle mass from the exhaust at the HFO tests upstream and downstream of the scrubber, but levels equivalent to those in LSFO exhaust are not reached. Decreases in the emissions of polycyclic aromatic hydrocarbons (PAH-16) and particulate matter as black carbon, organic carbon and elemental carbon, over the scrubber were observed for a majority of the trials, although emissions at LSFO use were consistently lower at comparable engine power. Full article
(This article belongs to the Special Issue Marine Engines Performance and Emissions)
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17 pages, 5239 KiB  
Article
Soil Interaction and Grout Behavior for the NREL Reference Monopile Offshore Wind Turbine
by Mário Vieira, Miguel Viana, Elsa Henriques and Luís Reis
J. Mar. Sci. Eng. 2020, 8(4), 298; https://doi.org/10.3390/jmse8040298 - 24 Apr 2020
Cited by 7 | Viewed by 3866
Abstract
Monopiles for offshore wind are the most used foundations by farm operators due to their low production costs, when compared to other bottom-fixed or floating foundations. In this research, a monopile foundation for offshore wind power was evaluated for its soil interaction and [...] Read more.
Monopiles for offshore wind are the most used foundations by farm operators due to their low production costs, when compared to other bottom-fixed or floating foundations. In this research, a monopile foundation for offshore wind power was evaluated for its soil interaction and grout behavior, and an appropriate numerical model for the structural analysis of the foundation and tower was developed. FAST 8, an aero-hydro-servo-elastic numerical code developed by NREL, was used to obtain the loads applied on the supporting structures. These loads were pre-processed before they were inputted on the finite element model, developed using the finite element software ANSYS. The considered conical grout connection, which connects the monopile to the transition piece through friction, was modeled under a changing-status nonlinearity condition. To model the soil–pile interaction, a p-y model was applied using the ANSYS APDL commands. Static, modal, and transient structural analyses were produced to study the structure suitability for its use on offshore environments. Different soil interactions were modeled, and their results were then compared within the transient and modal analysis, indicating that the angle of the grout connection strongly affects the loading conditions on the grout. Moreover, scouring affects the dynamic behavior of the overall supporting structures, thus protection against this phenomenon is suggested. Full article
(This article belongs to the Special Issue Analysis and Design of Offshore Wind Turbine Support Structures)
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26 pages, 12408 KiB  
Article
A DES-SST Based Assessment of Hydrodynamic Performances of the Wetted and Cavitating PPTC Propeller
by Adrian Lungu
J. Mar. Sci. Eng. 2020, 8(4), 297; https://doi.org/10.3390/jmse8040297 - 23 Apr 2020
Cited by 13 | Viewed by 26731
Abstract
The paper describes an investigation of the hydrodynamic performances of a five-bladed controllable pitch propeller, whose geometry was provided by Schiffbau-Versuchsanstalt (SVA) Potsdam GmbH Model Basin. Both cavitating and non-cavitating regimes are numerically simulated for different advance ratio coefficients. The numerical approach is [...] Read more.
The paper describes an investigation of the hydrodynamic performances of a five-bladed controllable pitch propeller, whose geometry was provided by Schiffbau-Versuchsanstalt (SVA) Potsdam GmbH Model Basin. Both cavitating and non-cavitating regimes are numerically simulated for different advance ratio coefficients. The numerical approach is based on a finite volume approach in which closure to the turbulence is achieved through detached eddy simulation (DES). Propeller open water (POW) characteristics are computed, and the numerical solutions are validated through extensive comparisons with experimental data. In addition, the bi-phasic flow for the cavitating regime is simulated, for which comparisons with the cavitation sketches are performed to check the ability of the solver to estimate the cavitation extent. Grid convergence tests are performed for both working regimes together with validation and verification checks, not only to size the level of the numerical errors, but also to prove the robustness of the chosen numerical approach. Finally, a set of final remarks will conclude the present research. Full article
(This article belongs to the Section Ocean Engineering)
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10 pages, 2973 KiB  
Article
Wave Breaker Types on a Smooth and Impermeable 1:10 Slope
by María Victoria Moragues, María Clavero and Miguel Á. Losada
J. Mar. Sci. Eng. 2020, 8(4), 296; https://doi.org/10.3390/jmse8040296 - 23 Apr 2020
Cited by 11 | Viewed by 4164
Abstract
This research identified the types of wave breaker on a non-overtoppable, smooth and impermeable 1:10 slope under regular waves. Experimental tests were carried out in the Atmosphere-Ocean Interaction Flume of the Andalusian Institute for Earth System Research (University of Granada). Using the experimental [...] Read more.
This research identified the types of wave breaker on a non-overtoppable, smooth and impermeable 1:10 slope under regular waves. Experimental tests were carried out in the Atmosphere-Ocean Interaction Flume of the Andalusian Institute for Earth System Research (University of Granada). Using the experimental space [log(h/L)–log(H/L)] and the alternate slope similarity parameter [χ = log (h/L H/L)], a complete set of breaker types was identified. Four types of wave breaker were then added to Galvin’s classification. Our results showed that the value of the Iribarren number was not sufficient to predict the expected type of wave breaker on the slope. Except for spilling and early plunging breakers, no biunivocal relationship was found between Ir and the type of breaker. The data obtained in the physical model were further enriched with the results of the flow characteristics and the wave energy transformation coefficients obtained with the IH-2VOF numerical model on a 1:10 impermeable slope. This research study, presented in this paper, showed that the Iribarren number is not a convenient wave breaking similarity parameter. Full article
(This article belongs to the Special Issue Selected Papers from the Spanish Days of Ports and Coasts)
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24 pages, 5834 KiB  
Article
Application of STORMTOOLS Coastal Environmental Risk Index (CERI) to Inform State and Local Planning and Decision Making along the Southern RI Shoreline
by Malcolm L. Spaulding, Annette Grilli, Chris Damon, Teresa Crean and Grover Fugate
J. Mar. Sci. Eng. 2020, 8(4), 295; https://doi.org/10.3390/jmse8040295 - 21 Apr 2020
Cited by 4 | Viewed by 2794
Abstract
STORMTOOLS coastal environmental risk index (CERI) was applied to communities located along the southern coast of Rhode Island (RI) to determine the risk to structures located in the flood plain. CERI uses estimates of the base flood elevation (BFE), explicitly including the effects [...] Read more.
STORMTOOLS coastal environmental risk index (CERI) was applied to communities located along the southern coast of Rhode Island (RI) to determine the risk to structures located in the flood plain. CERI uses estimates of the base flood elevation (BFE), explicitly including the effects of sea level rise (SLR); details on the structure types, from the E911 emergency data base/parcel data, and associated first floor elevation (FFE); and damage curves from the US Army Corp of Engineers North Atlantic Coast Comprehensive Study (NACCS) to determine the damages to structures for the study area. Surge levels and associated offshore waves used to determine BFEs were obtained from the NACCS hydrodynamic and wave model predictions. The impacts of sea level rise and coastal erosion on flooding were modeled using XBeach and STWAVE and validated by observations at selected locations along the coastline. CERI estimated the structural damage to each structure in the coastal flood plain for 100 yr flooding with SLR ranging from 0 to 10 ft. The number of structures at risk was estimated to increase approximate linearly from 3700 for no SLR to about 8000 for 10 ft SLR, with about equal percentages for each of the four coastal communities (Narragansett, South Kingstown, Charlestown, and Westerly, Rhode Island (RI)). The majority of the structures in the flood plain are single/story residences without (41%) and with (46%) basements (total 87%; structures with basements are the most vulnerable). Less vulnerable are structures elevated on piles with 8.8% of the total. The remaining are commercial structures principally located either in the Port of Galilee and or Watch Hill. The analysis showed that about 20% of the structures in the 100 yr flood plain are estimated to be damaged at 50% or greater. This increases to 55% of structures as SLR rises to 5 ft. At higher SLR values the percent damaged at 50% or greater slowly declines to 45% at 10 ft SLR. This behavior is a result of the number of homes below MSL increasing dramatically as SLR values moves higher than 5 ft and thus being removed from the structures damaged pool. Generalized CERI risk maps have developed to allow the managers to determine the broad risk of siting structures at any location in their communities. CERI has recently become available as a mobile phone App, facilitating the ability of state and local decision makers and the public to determine the risk of locating a selected building type at any location in their communities. Full article
(This article belongs to the Section Ocean Engineering)
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17 pages, 2941 KiB  
Article
Data Driven In-Cylinder Pressure Diagram Based Optimization Procedure
by Mina Tadros, Manuel Ventura and C. Guedes Soares
J. Mar. Sci. Eng. 2020, 8(4), 294; https://doi.org/10.3390/jmse8040294 - 21 Apr 2020
Cited by 19 | Viewed by 4377
Abstract
An engine optimization model is developed to fit the calculated in-cylinder pressure diagram to the experimental data by finding the optimal values of the start angle of injection and the amount of injected fuel for different engine loads. Firstly, the engine model is [...] Read more.
An engine optimization model is developed to fit the calculated in-cylinder pressure diagram to the experimental data by finding the optimal values of the start angle of injection and the amount of injected fuel for different engine loads. Firstly, the engine model is built in Ricardo Wave software and some parts are calibrated using data collected from the manufacturer. Then, an optimization process is performed based on the fitness function that includes the objective of the study and the penalty functions to express constraints. This optimization environment simulates the performance of a marine generator system for three different loads by minimizing the mean absolute percentage error (MAPE) between the in-cylinder pressure simulated data and the measured data along 40 degrees of the combustion process and by verifying the firing pressure and the engine brake power. The percentage of error between the calculated and the real thermodynamic data does not exceed 3.4% and the MAPE between the calculated and the real in-cylinder pressure diagram along the combustion process does not exceed 5.7% for the different loads. The proposed method can be further used to find the optimal value of different input parameters during the calibration process of different engine numerical models. Full article
(This article belongs to the Special Issue Green Shipping)
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8 pages, 807 KiB  
Technical Note
Modelling of Waves for the Design of Offshore Structures
by Ove Tobias Gudmestad
J. Mar. Sci. Eng. 2020, 8(4), 293; https://doi.org/10.3390/jmse8040293 - 19 Apr 2020
Cited by 8 | Viewed by 3959
Abstract
For the design of structures we need to select design safety levels to ensure structures shall safely operate and not collapse. These levels are given in relevant safety standards. For these levels we need to identify the actions and ensure that we design [...] Read more.
For the design of structures we need to select design safety levels to ensure structures shall safely operate and not collapse. These levels are given in relevant safety standards. For these levels we need to identify the actions and ensure that we design according to recognized codes. The objective of this technical note is to shed light on the identification of the design action due to waves to ensure that the design action events be incorporated in the design phase of the structures. The approach used in this technical note is to give a description of an actual extreme event, discuss the efforts and research that was undertaken to explain the event, investigate wave conditions which possibly could have been present at the day of the event, and present a challenge and suggestion for wave tanks to ensure that design action events really are identified during wave tank experiments. We will, in particular, discuss the need for modelling of nonlinear waves to ensure that the action effects from waves are properly identified. Full article
(This article belongs to the Special Issue Selected Papers from the Future Paths and Needs in Wave Modelling Workshop)
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18 pages, 2313 KiB  
Article
Stormtools Design Elevation (SDE) Maps: Including Impact of Sea Level Rise
by Malcolm L. Spaulding, Annette Grilli, Chris Damon, Reza Hashemi, Soroush Kouhi and Grover Fugate
J. Mar. Sci. Eng. 2020, 8(4), 292; https://doi.org/10.3390/jmse8040292 - 18 Apr 2020
Cited by 7 | Viewed by 3516
Abstract
Many coastal communities in the US use base flood elevation (BFE) maps for the 100-year return period, specified on Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps (FIRMs), to design structures and infrastructure. The FIRMs are increasingly known to have serious problems [...] Read more.
Many coastal communities in the US use base flood elevation (BFE) maps for the 100-year return period, specified on Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps (FIRMs), to design structures and infrastructure. The FIRMs are increasingly known to have serious problems in accurately specifying the risk coastal communities face, as most recently evidenced during hurricanes Harvey and Irma in 2017 and Florence and Michael in 2018. The FIRM BFE maps also do not include the impact of sea level rise, which clearly needs to be considered in the design of coastal structures over the next several decades given recent National Oceanic and Atmospheric Administration (NOAA) sea level rise (SLR) projections. Here, we generate alternative BFE maps (STORMTOOLS Design Elevation (SDE) maps) for coastal waters of Rhode Island (RI) using surge predictions from tropical and extratropical storms of the coupled surge-wave models from the US Army Corp of Engineers, North Atlantic Comprehensive Coast Study (NACCS). Wave predictions are based on application of a steady state, spectral wave model (STWAVE), while impacts of coastal erosion/accretion and changes of geomorphology are modeled using XBeach. The high-resolution application of XBeach to the southern RI shoreline has dramatically increased the ability to represent the details of dune erosion and overtopping and the associated development of surge channels and over-wash fans and the resulting landward impact on inundation and waves. All methods used were consistent with FEMA guidelines for the study area and used FEMA-approved models. Maps were generated for 0, 2 ft (0.6 m), 5 ft (1.5 m), 7 ft (2.1 m), and 10 ft (3.1 m) of sea level rise, reflecting NOAA high estimates at various times for the study area through 2100. Results of the simulations are shown for both the southern RI shoreline (South Coast) and Narragansett Bay, to facilitate communication of projected BFEs to the general public. The maps are hosted on the STORMTOOLS ESRI Hub to facilitate access to the data. They are also now part of the RI Coastal Resources Management Council (CRMC) risk-based permitting system. The user interface allows access to all supporting data including grade elevation, inundation depth, and wave crest heights as well as corresponding FEMA FIRM BFEs and associated zones. Full article
(This article belongs to the Section Ocean Engineering)
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17 pages, 8529 KiB  
Article
Study on the Influence of Mud Properties on the Stability of Excavated Face of Slurry Shield and the Quality of Filter Cake Formation
by Hu Wang, Jian Chen, Hongjun Liu, Lei Guo, Yao Lu, Xiuting Su, Yongmao Zhu and Tao Liu
J. Mar. Sci. Eng. 2020, 8(4), 291; https://doi.org/10.3390/jmse8040291 - 18 Apr 2020
Cited by 10 | Viewed by 2775
Abstract
In the construction of subsea tunnels, the stability and control of the excavation surface are the main concerns of the engineering community. In this paper, the Xiamen Metro Line 2 is used as the study case. The filter cake formation of mud shields [...] Read more.
In the construction of subsea tunnels, the stability and control of the excavation surface are the main concerns of the engineering community. In this paper, the Xiamen Metro Line 2 is used as the study case. The filter cake formation of mud shields is experimentally studied, and the excavation surface is numerically simulated. It is found that the formation of filter cake does not require a large pressure difference, and can be formed under 0.06 MPa. With the increase of pressure, the quality of filter cake is further improved, and a small amount of seawater (volume ratio less than 3%) also has a significant effect on the viscosity of mud. Under different cross-section geological conditions, with the decrease of the support pressure of the excavation face, the vertical displacement and vertical (Y-direction) displacement of the excavation face dome gradually increase, the maximum longitudinal displacement is 9.7 mm, the maximum longitudinal displacement can reach 23.9 mm, and the growth trend is nonlinear. According to different stratum conditions, during the excavation of the tunnel, the plastic area of the excavation face is different. Full article
(This article belongs to the Section Ocean Engineering)
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12 pages, 1395 KiB  
Article
Long-Term Durability of Marine Reinforced Concrete Structures
by Robert E Melchers
J. Mar. Sci. Eng. 2020, 8(4), 290; https://doi.org/10.3390/jmse8040290 - 18 Apr 2020
Cited by 33 | Viewed by 8689
Abstract
The sustainability of reinforced concrete is critical, particularly for structures exposed to marine environments. Chlorides are implicated in causing or accelerating reinforcement corrosion and potentially earlier expensive repairs, yet there are many older reinforced concrete structures in good condition for many decades despite [...] Read more.
The sustainability of reinforced concrete is critical, particularly for structures exposed to marine environments. Chlorides are implicated in causing or accelerating reinforcement corrosion and potentially earlier expensive repairs, yet there are many older reinforced concrete structures in good condition for many decades despite very high chloride levels at the reinforcement. The reasons for this are reviewed briefly, together with recent experimental work that better defines the role of chlorides. One is initiation of reinforcement corrosion but only through localized pitting at air-voids in concrete at the interface with the steel reinforcement. These tend to be small or negligible for high quality well-compacted concretes. The other role for chlorides has been shown, in experimental work, to accelerate the long-term loss of concrete alkali material. On the other hand, a review of practical experience shows that what has been termed chloride-induced reinforcement corrosion often is not that at all, but is the end-product of factors that impair the protective nature of the concrete. As reviewed herein, these include poor compaction, physical damage to concrete cover, concrete shrinkage, and alkali-aggregate reactions. The various observations presented are important for the proper understanding, analysis, and design of durable reinforced concrete structures exposed to chloride-rich environments. Full article
(This article belongs to the Special Issue Sustainable Concrete in the Marine Environment)
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19 pages, 4038 KiB  
Article
Characterization of Extreme Wave Conditions for Wave Energy Converter Design and Project Risk Assessment
by Vincent S. Neary, Seongho Ahn, Bibiana E. Seng, Mohammad Nabi Allahdadi, Taiping Wang, Zhaoqing Yang and Ruoying He
J. Mar. Sci. Eng. 2020, 8(4), 289; https://doi.org/10.3390/jmse8040289 - 18 Apr 2020
Cited by 33 | Viewed by 4489
Abstract
Best practices and international standards for determining n-year return period extreme wave (sea states) conditions allow wave energy converter designers and project developers the option to apply simple univariate or more complex bivariate extreme value analysis methods. The present study compares extreme [...] Read more.
Best practices and international standards for determining n-year return period extreme wave (sea states) conditions allow wave energy converter designers and project developers the option to apply simple univariate or more complex bivariate extreme value analysis methods. The present study compares extreme sea state estimates derived from univariate and bivariate methods and investigates the performance of spectral wave models for predicting extreme sea states at buoy locations within several regional wave climates along the US East and West Coasts. Two common third-generation spectral wave models are evaluated, a WAVEWATCH III® model with a grid resolution of 4 arc-minutes (6–7 km), and a Simulating WAves Nearshore model, with a coastal resolution of 200–300 m. Both models are used to generate multi-year hindcasts, from which extreme sea state statistics used for wave conditions characterization can be derived and compared to those based on in-situ observations at National Data Buoy Center stations. Comparison of results using different univariate and bivariate methods from the same data source indicates reasonable agreement on average. Discrepancies are predominantly random. Large discrepancies are common and increase with return period. There is a systematic underbias for extreme significant wave heights derived from model hindcasts compared to those derived from buoy measurements. This underbias is dependent on model spatial resolution. However, simple linear corrections can effectively compensate for this bias. A similar approach is not possible for correcting model-derived environmental contours, but other methods, e.g., machine learning, should be explored. Full article
(This article belongs to the Special Issue Wave and Tidal Energy Resource Characterization and Environment Interactions)
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16 pages, 1598 KiB  
Article
Anomalous Oceanic Conditions in the Central and Eastern North Pacific Ocean during the 2014 Hurricane Season and Relationships to Three Major Hurricanes
by Victoria L. Ford, Nan D. Walker and Iam-Fei Pun
J. Mar. Sci. Eng. 2020, 8(4), 288; https://doi.org/10.3390/jmse8040288 - 17 Apr 2020
Cited by 2 | Viewed by 4028
Abstract
The 2014 Northeast Pacific hurricane season was highly active, with above-average intensity and frequency events, and a rare landfalling Hawaiian hurricane. We show that the anomalous northern extent of sea surface temperatures and anomalous vertical extent of upper ocean heat content above 26 [...] Read more.
The 2014 Northeast Pacific hurricane season was highly active, with above-average intensity and frequency events, and a rare landfalling Hawaiian hurricane. We show that the anomalous northern extent of sea surface temperatures and anomalous vertical extent of upper ocean heat content above 26 °C throughout the Northeast and Central Pacific Ocean may have influenced three long-lived tropical cyclones in July and August. Using a variety of satellite-observed and -derived products, we assess genesis conditions, along-track intensity, and basin-wide anomalous upper ocean heat content during Hurricanes Genevieve, Iselle, and Julio. The anomalously northern surface position of the 26 °C isotherm beyond 30° N to the north and east of the Hawaiian Islands in 2014 created very high sea surface temperatures throughout much of the Central Pacific. Analysis of basin-wide mean conditions confirm higher-than-average storm activity during strong positive oceanic thermal anomalies. Positive anomalies of 15–50 kJ cm−2 in the along-track upper ocean heat content for these three storms were observed during the intensification phase prior to peak intensity, advocating for greater understanding of the ocean thermal profile during tropical cyclone genesis and development. Full article
(This article belongs to the Special Issue Sea Surface Temperature: From Observation to Applications)
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16 pages, 5527 KiB  
Article
Experimental and Estimation Studies of Resilient Modulus of Marine Coral Sand under Cyclic Loading
by Shao-Heng He, Qiong-Fang Zhang, Zhi Ding, Tang-Dai Xia and Xiao-Lu Gan
J. Mar. Sci. Eng. 2020, 8(4), 287; https://doi.org/10.3390/jmse8040287 - 16 Apr 2020
Cited by 21 | Viewed by 3008
Abstract
Coral sand is an important filler resource that can solve the shortage of terrestrial fillers in coastal areas. Recently, the foundations of many infrastructures in the South China Sea have been built with coral sand as fillers, which have been subjected to wave [...] Read more.
Coral sand is an important filler resource that can solve the shortage of terrestrial fillers in coastal areas. Recently, the foundations of many infrastructures in the South China Sea have been built with coral sand as fillers, which have been subjected to wave and traffic cyclic loads. Resilient modulus (Mr) is an important design parameter in marine engineering, but there are few studies on the resilient modulus response of coral sand under cyclic loading. A series of drained cyclic triaxial tests were carried out to investigate the effects of the initial mean effective stress (p0) and cyclic stress ratio (ζ) on the resilient modulus response of the coral sand from the South China Sea. The change of fractal dimension (αc) can reflect the rule of particle breakage evolution. The αc of coral sand shows a tendency of almost maintaining stable and then increasing rapidly with the increase of mean effective stress p0 under each cyclic stress ratio ζ. There is a threshold of p0, when the p0 exceeds this threshold, αc will increase significantly with the increase of p0. The increase of p0 has a beneficial effect on the improvement of the Mr, while the increase of ζ has both beneficial and detrimental effects on the improvement of the Mr. A new prediction model of the Mr considering particle breakage was established, which can better predict the Mr of coral sand in the whole stress interval. The research results can provide guidance for the design of marine transportation infrastructures, which can promote the development of marine transportation industry and energy utilization. Full article
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18 pages, 5937 KiB  
Article
Dynamic Behavior of the Deepwater Flexible Pipeline during Pipe Laying Process
by Liquan Wang, Ming Ju, Xiaodong Xing, Feihong Yun and Xiangyu Wang
J. Mar. Sci. Eng. 2020, 8(4), 286; https://doi.org/10.3390/jmse8040286 - 16 Apr 2020
Cited by 9 | Viewed by 4932
Abstract
The dynamic behavior of the flexible pipeline during deepwater Flex-lay directly determines the structures of laying facilities and the actual installation process. A coupled dynamic model considering the effects of different factors was established in this paper. Based on the model, the initial [...] Read more.
The dynamic behavior of the flexible pipeline during deepwater Flex-lay directly determines the structures of laying facilities and the actual installation process. A coupled dynamic model considering the effects of different factors was established in this paper. Based on the model, the initial attitude of the flexible pipeline during the laying process was determined by using the natural catenary theory and Morison equation. The hydrodynamic analysis of the HYSY201 pipelaying vessel was carried out by using the finite element software AQWA. Under the specific sea condition, a flexible pipeline with outer-diameter of 352.42 mm being laid onto the 3000 m deep seabed was simulated by using the software OrcaFlex to study the pipeline dynamic behaviors including axial tension, bending moment and stress-strain in the laying process, and the factors affecting the dynamic behavior of the pipeline were analyzed. The results show a significant correlation between the marine loads, vessel motion and the dynamic response of the pipeline. Compared with the static state case, the maximum axial tension, bending moment and stress-strain of the pipeline under the interaction of the marine loads and the vessel motion increased by 42.7%, 220%, 52% and 18.7%, separately. Among the marine loads, the surface wave had the most significant effect on the dynamic performance of the pipeline. When the wave direction acts on the width of the ship, the wave height is greater than 2 m and the spectrum period is eight seconds, the wave has the greatest influence on the dynamic response of the pipeline. Full article
(This article belongs to the Section Ocean Engineering)
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16 pages, 4832 KiB  
Article
Relationship between the Persian Gulf Sea-Level Fluctuations and Meteorological Forcing
by Naghmeh Afshar-Kaveh, Mostafa Nazarali and Charitha Pattiaratchi
J. Mar. Sci. Eng. 2020, 8(4), 285; https://doi.org/10.3390/jmse8040285 - 16 Apr 2020
Cited by 9 | Viewed by 4135
Abstract
Sea-level data from six tide gauge stations along the northern coast of the Persian Gulf were analyzed both in time and frequency domain to evaluate meteorological forcing. Spectral analyses indicated that mixed, predominantly semi-diurnal tides were dominant at all stations, but low-frequency fluctuations [...] Read more.
Sea-level data from six tide gauge stations along the northern coast of the Persian Gulf were analyzed both in time and frequency domain to evaluate meteorological forcing. Spectral analyses indicated that mixed, predominantly semi-diurnal tides were dominant at all stations, but low-frequency fluctuations correlated well with atmospheric pressure and wind components. Non-tidal sea-level fluctuations up to 0.75 m were observed along the northern coasts of the Gulf due to the combined action of lower atmospheric pressure and cross-shore wind. Coherency between low-frequency sea-level records and mean sea-level pressure indicated that the latter usually leads to sea-level fluctuations between 1 and 6.4 days. In contrast, the same analysis on the wind velocity and sea level revealed that the former lags between 3 and 13 days. The effect of wind stress on coastal sea-level variations was higher compared with the effect of atmospheric pressure. Concurrent analysis of low-pass-filtered sea-level records proved that the non-tidal wave moves from west to east along the northern coasts of the Persian Gulf. Full article
(This article belongs to the Section Physical Oceanography)
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24 pages, 7826 KiB  
Article
Study of Current- and Wave-Induced Sediment Transport in the Nowshahr Port Entrance Channel by Using Numerical Modeling and Field Measurements
by Ayyuob Mahmoodi, Mir Ahmad Lashteh Neshaei, Abbas Mansouri and Mahmood Shafai Bejestan
J. Mar. Sci. Eng. 2020, 8(4), 284; https://doi.org/10.3390/jmse8040284 - 15 Apr 2020
Cited by 10 | Viewed by 3449
Abstract
The Nowshahr port in the southern coastlines of the Caspian Sea is among the oldest northern ports of Iran, first commissioned in the year 1939. In recent years, this port has been faced with severe sedimentation issues in and around its entrance that [...] Read more.
The Nowshahr port in the southern coastlines of the Caspian Sea is among the oldest northern ports of Iran, first commissioned in the year 1939. In recent years, this port has been faced with severe sedimentation issues in and around its entrance that has had negative impacts on the operability of the port. The present study aims at identifying major reasons for severe sedimentation in the port entrance. First, field measurements were evaluated to gain an in-depth view of the hydrodynamics of the study area. Numerical models then were calibrated and validated against existing field measurements. Results of numerical modeling indicated that wind-induced current is dominant in the Caspian Sea. The numerical results also indicated that in the case of an eastward current direction, the interaction between current and the western breakwater arm would lead to the formation of a separation zone and a recirculation zone to the east of the port entrance region. This eddying circulation could transport suspend settled sediments from eastern shoreline towards the port entrance and its access channel. The results of this paper are mostly based on the study of current patterns around the port in the storm conditions incorporate with the identification of sediment sources. Full article
(This article belongs to the Special Issue Modelling of Harbour and Coastal Structures)
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16 pages, 6281 KiB  
Article
Design and Performance of Permeable Groins on a Low-Energy Natural Beach
by Alec Torres-Freyermuth, Anne Hofman, José Clemente Tuz-Pech, Gabriela Medellín and Pieter C. Roos
J. Mar. Sci. Eng. 2020, 8(4), 283; https://doi.org/10.3390/jmse8040283 - 15 Apr 2020
Cited by 4 | Viewed by 3150
Abstract
Beach erosion, ubiquitous of sandy coasts around the world, can be exacerbated or mitigated with the use of hard engineering solutions including groins. The use of groins has been discouraged in many countries despite its capability to reduce sand losses. This study aims [...] Read more.
Beach erosion, ubiquitous of sandy coasts around the world, can be exacerbated or mitigated with the use of hard engineering solutions including groins. The use of groins has been discouraged in many countries despite its capability to reduce sand losses. This study aims to design a 15 m permeable groin that allows sediment bypassing. Field experiments were conducted on a low-energy, sea-breeze dominated micro-tidal beach at the northern Yucatan peninsula during both mean and extreme wave conditions. Firstly, a short-term experiment consisted in monitoring the structure performance for 24 h during typical sea breeze conditions and the subsequent beach recovery after the structure removal. Secondly, a multi-day (60 days) experiment was conducted to investigate the performance of a single- and double-groin system during both mean and local storm conditions. Beach surveys were conducted to evaluate the beach response. Shoreline variability shows sediment accretion on the east side of the structure during sea breezes, whereas during NNW storm events, the accretion occurred on the west side. Importantly, on a scale of days, sediment bypassing occurs, and hence a net accretion was measured at both sides of the structure. During this time, a second structure was deployed 30 m apart to test the performance of a double-groin system, finding a net shoreline advance at all beach transects. Thus, low-crested short-length permeable groins are found to be a suitable emergency mitigation measure against beach erosion in micro-tidal environments causing moderate shoreline change. Full article
(This article belongs to the Section Coastal Engineering)
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12 pages, 1825 KiB  
Article
Assessment of Halamphora coffeaeformis Growth and Biochemical Composition for Aquaculture Purposes
by Paola G. Scodelaro Bilbao, Lucas A. Martín, Cecilia A. Popovich, María Delfina Almeyda, Verónica Chamorro and Patricia I. Leonardi
J. Mar. Sci. Eng. 2020, 8(4), 282; https://doi.org/10.3390/jmse8040282 - 15 Apr 2020
Cited by 11 | Viewed by 2997
Abstract
The vast majority of the world’s fishery by-products are utilized in the fish farming industry. However, due to the high cost and unsustainability of these by-products, alternative sources must be found. Marine diatoms produce important amounts of fatty acids, sterols, proteins and carbohydrates. [...] Read more.
The vast majority of the world’s fishery by-products are utilized in the fish farming industry. However, due to the high cost and unsustainability of these by-products, alternative sources must be found. Marine diatoms produce important amounts of fatty acids, sterols, proteins and carbohydrates. In this work, we assessed the nutritional value of Halamphora coffeaeformis at the exponential growth phase, to determine its suitability for aquafeed. The strain was grown in a photobioreactor at 20 °C for 6 days. The production of proteins, lipids and carbohydrates was determined, and essential fatty acid, sterol and amino acid composition was assessed. The highest values of triacylglycerides (TAG), free and esterified sterols, proteins and carbohydrates were found after 6 days of growth in the photobioreactor. Fatty acid analysis by gas chromatography showed the presence of eicosapentaenoic (EPA) and arachidonic (ARA) in amounts similar to those for fish oils. In terms of sterols, a predominance of stigmasterol was observed, followed by cholesterol. The amino acid composition revealed 50% of them to be among those essential for fish and other aquatic animals. Finally, a suitable amount of carbohydrates was found in H. coffeaeformis cultures. Together, these findings support the use of H. coffeaeformis as an alternative and sustainable source for aquafeed to partially replace the use of fishery by-products. Full article
(This article belongs to the Special Issue Marine Diatoms from Physiology to Ecology and Biotechnology)
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22 pages, 2112 KiB  
Article
Shoaling Waves Interacting with an Orthogonal Current
by Massimiliano Marino, Carla Faraci and Rosaria Ester Musumeci
J. Mar. Sci. Eng. 2020, 8(4), 281; https://doi.org/10.3390/jmse8040281 - 14 Apr 2020
Cited by 10 | Viewed by 2725
Abstract
In the present work, an experimental investigation on the hydrodynamics of shoaling waves superposed on a steady orthogonal current is carried out. An experimental campaign in a wave tank has been performed, with waves and current interacting at a right angle over a [...] Read more.
In the present work, an experimental investigation on the hydrodynamics of shoaling waves superposed on a steady orthogonal current is carried out. An experimental campaign in a wave tank has been performed, with waves and current interacting at a right angle over a sloping planar beach. Velocity data have been gathered during the experiments in order to investigate mean, phase and turbulent flow. A detailed preliminary analysis of the time- and space-variability of the experiments is presented. Results show that a complex interaction between waves and current occurs as the wave shoals, in terms of sheer production, momentum transfer and turbulent mixing. Superposition of waves determines a shear increase at the bottom due to an enhanced turbulence mixing, nonetheless as depth decreases and the current velocity consequently increases, shoaling waves may be less efficient in enhancing shear at the bottom. Moreover, the superposition of waves determines the current to oscillate around its mean velocity value. Nevertheless, as wave shoals and simultaneously current velocity increases with decreasing depth, waves and current oscillatory motion experience a phase lag, as a response of the larger momentum of the current to the changing of the shoaling waves acceleration distribution along the wave phase. Moreover, the turbulent bursting events of the combined flow in proximity of the bed have been investigated by means of quadrant analysis, showing an increase of the turbulent ejections and sweeps due to the superposition of the shoaling waves. Full article
(This article belongs to the Special Issue Hydro-Morphodynamics of Coastal Areas)
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19 pages, 1742 KiB  
Article
“Are You Planning to Follow Your Route?” The Effect of Route Exchange on Decision Making, Trust, and Safety
by Katie Aylward, Reto Weber, Yemao Man, Monica Lundh and Scott N. MacKinnon
J. Mar. Sci. Eng. 2020, 8(4), 280; https://doi.org/10.3390/jmse8040280 - 13 Apr 2020
Cited by 8 | Viewed by 3266
Abstract
The Sea Traffic Management (STM) Validation project is a European based initiative which focuses on connecting and updating the maritime world in real time, with efficient information exchange. The purpose of this paper is to evaluate two functions developed during the project: a [...] Read more.
The Sea Traffic Management (STM) Validation project is a European based initiative which focuses on connecting and updating the maritime world in real time, with efficient information exchange. The purpose of this paper is to evaluate two functions developed during the project: a ship to ship route exchange (S2SREX) function and rendezvous (RDV) information layer, collectively referred to as S2SREX/RDV. S2SREX displays the route segment consisting of the next seven waypoints of the monitored route of a collaborating ship and the RDV layer that predicts a meeting point. S2SREX/RDV provides supplementary information to data acquired by existing navigation systems and is intended to improve situational awareness and safety through a more comprehensive understanding of the surrounding traffic. Chalmers University of Technology and Solent University completed an experiment using twenty-four experienced navigators in bridge simulators. Six traffic scenarios were developed by subject matter experts and tested with and without S2SREX/RDV functionalities. Qualitative data were collected using post-test questionnaires and group debriefs to evaluate the participants’ perceptions of S2SREX/RDV in the various traffic scenarios, and quantitative data were collected to assess the ship distances and behavior in relation to the International Regulations for Preventing Collisions at Sea (COLREGs). The results revealed that participants generally trusted the S2SREX/RDV information, and most used S2SREX/RDV for decision support. The quantitative assessment revealed that the COLREGs were breached more often when S2SREX/RDV was used. Experimental findings are discussed in relation to safety, trust, reliance, situational awareness, and human-automation interaction constructs. Full article
(This article belongs to the Special Issue Human-Automation Integration in the Maritime Sector)
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15 pages, 6288 KiB  
Article
Challenges in Description of Nonlinear Waves Due to Sampling Variability
by Elzbieta M. Bitner-Gregersen, Odin Gramstad, Anne Karin Magnusson and Mika Malila
J. Mar. Sci. Eng. 2020, 8(4), 279; https://doi.org/10.3390/jmse8040279 - 13 Apr 2020
Cited by 11 | Viewed by 2864
Abstract
Wave description is affected by several uncertainties, with sampling variability due to limited number of observations being one of them. Ideally, temporal/spatial wave registrations should be as large as possible to eliminate this uncertainty. This is difficult to reach in nature, where stationarity [...] Read more.
Wave description is affected by several uncertainties, with sampling variability due to limited number of observations being one of them. Ideally, temporal/spatial wave registrations should be as large as possible to eliminate this uncertainty. This is difficult to reach in nature, where stationarity of sea states is an issue, but it can in principle be obtained in laboratory tests and numerical simulations, where initial wave conditions can be kept constant and intrinsic variability can be accounted for by changing random seeds for each run. Using linear, second-order, and third-order unidirectional numerical simulations, we compare temporal and spatial statistics of selected wave parameters and show how sampling variability affects their estimators. The JONSWAP spectrum with gamma peakedness parameters γ = 1, 3.3, and 6 is used in the analysis. The third-order wave data are simulated by a numerical solver based on the higher-order spectral method which includes the leading-order nonlinear dynamical effects. Field data support the analysis. We demonstrate that the nonlinear wave field including dynamical effects is more sensitive to sampling variability than the second-order and linear ones. Furthermore, we show that the mean values of temporal and spatial wave parameters can be equal if the number of simulations is sufficiently large. Consequences for design work are discussed. Full article
(This article belongs to the Special Issue Selected Papers from the Future Paths and Needs in Wave Modelling Workshop)
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16 pages, 7946 KiB  
Article
Long-Term Strength of Alkali-Activated Mortars with Steel Fibres Cured in Various Conditions
by Minhao Dong, Mohamed Elchalakani, Ali Karrech and Bo Yang
J. Mar. Sci. Eng. 2020, 8(4), 278; https://doi.org/10.3390/jmse8040278 - 13 Apr 2020
Cited by 8 | Viewed by 2379
Abstract
The long-term effect of extreme conditions, such as high concentrations of CO2, a combination of chloride and air, and sulfuric acid, on the performance of steel fibre reinforced alkali-activated fly ash and slag (AAFS) mortars was investigated. The selected conditions simulated [...] Read more.
The long-term effect of extreme conditions, such as high concentrations of CO2, a combination of chloride and air, and sulfuric acid, on the performance of steel fibre reinforced alkali-activated fly ash and slag (AAFS) mortars was investigated. The selected conditions simulated the long-term exposure to the marine environment and had an influence on both the matrix and the fibres. Four AAFS mixes were analysed alongside a control ordinary Portland cement (OPC) mix. Mechanical properties such as the compressive strength, elastic moduli and ductility indices, as well as microscopic analyses were carried out. It was found that the AAFS was stable in most of the conditions. The primary way for its reduction in strength was through the neutralisation of pore fluids and the leaching of sodium cations. The addition of the short fibres could reduce the ingress of deleterious materials by limiting the development of cracks and allowing for the efficient use of higher activator ratios. The fibres were susceptible to corrosion by chloride and acid attacks. The relatively chemically stable environment of the AAFS provided protection to the embedded fibres. Based on this study, in a very aggressive environment, a combination of 1%–2% fibre by volume, with a high activator content in the AAFS mortar, could be the most suitable. Full article
(This article belongs to the Special Issue Sustainable Concrete in the Marine Environment)
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14 pages, 5052 KiB  
Article
Environmental Management System for the Analysis of Oil Spill Risk Using Probabilistic Simulations. Application at Tarragona Monobuoy
by Mariano Morell Villalonga, Manuel Espino Infantes, Manel Grifoll Colls and Marc Mestres Ridge
J. Mar. Sci. Eng. 2020, 8(4), 277; https://doi.org/10.3390/jmse8040277 - 12 Apr 2020
Cited by 14 | Viewed by 3890
Abstract
Oil spill accidents during port operations are one of the main hydrocarbon pollution threats for coastal waters. Appropriate environmental risk assessment and pollution events management tools are needed to achieve sustainability and environmental protection in port activity. Recent developments in monitoring techniques and [...] Read more.
Oil spill accidents during port operations are one of the main hydrocarbon pollution threats for coastal waters. Appropriate environmental risk assessment and pollution events management tools are needed to achieve sustainability and environmental protection in port activity. Recent developments in monitoring techniques and accurate meteo-oceanographic prediction systems have been implemented in many ports, providing tools for environmental management. A novel method based on meteo-oceanographic operational services, in conjunction with Monte Carlo experiments using an oil spill model, is implemented to perform probabilistic maps of potential pollution events. Tarragona port area was chosen as the study case for three reasons: it accommodates a hub of petrochemical industry, the availability of high-resolution wind and water current data, and previous studies at the area offer the possibility to check the results’ accuracy. The interpretation of the impact probability maps reveals a specific pattern explained by the mean hydrodynamic conditions and the energetic north-westerly wind conditions. The impact probability maps may enhance efficiency in the environmental management of port waters and nearby coastal areas, reducing the negative impact of pollutant discharges. Full article
(This article belongs to the Special Issue Selected Papers from the Spanish Days of Ports and Coasts)
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15 pages, 9245 KiB  
Article
Numerical Study of Wave Forces on Crown Walls of Mound Breakwaters with Parapets
by Jorge Molines, Arnau Bayón, M. Esther Gómez-Martín and Josep R. Medina
J. Mar. Sci. Eng. 2020, 8(4), 276; https://doi.org/10.3390/jmse8040276 - 11 Apr 2020
Cited by 21 | Viewed by 3820
Abstract
The influence of parapets on crown walls of mound breakwaters on wave forces has not been extensively analyzed in the literature. In this study, numerical experiments were carried out using the open-source platform OpenFOAM® to evaluate the influence of nine crown wall [...] Read more.
The influence of parapets on crown walls of mound breakwaters on wave forces has not been extensively analyzed in the literature. In this study, numerical experiments were carried out using the open-source platform OpenFOAM® to evaluate the influence of nine crown wall geometries with and without parapets. The OpenFOAM® model was validated with laboratory experiments. Dimensionless horizontal forces and overturning moments due to horizontal forces increase when there is a parapet. Dimensionless up-lift forces provide similar results, regardless of the existence of a parapet. Crown walls with parapets increase the horizontal wave forces and overturning moments due to horizontal wave forces by a factor of two. Full article
(This article belongs to the Special Issue Selected Papers from the Spanish Days of Ports and Coasts)
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19 pages, 2133 KiB  
Article
Robust Output Path-Following Control of Marine Surface Vessels with Finite-Time LOS Guidance
by Lu Wang, Changkui Xu and Jianhua Cheng
J. Mar. Sci. Eng. 2020, 8(4), 275; https://doi.org/10.3390/jmse8040275 - 11 Apr 2020
Cited by 4 | Viewed by 3296
Abstract
This paper proposes a finite-time output feedback methodology for the path-following task of marine surface vessels. First, a horizontal path-following model is established with unknown sideslip angle, unmeasured system state and system uncertainties. A hierarchical control structure is adopted to deal with the [...] Read more.
This paper proposes a finite-time output feedback methodology for the path-following task of marine surface vessels. First, a horizontal path-following model is established with unknown sideslip angle, unmeasured system state and system uncertainties. A hierarchical control structure is adopted to deal with the cascade property. For kinematics system design, a finite-time sideslip angle observer is first proposed, and thus the sideslip angle estimation is compensated in a nonlinear line-of-sight (LOS) guidance strategy to acquire finite-time convergence. For the heading control design, an extended state observer is introduced for the unmeasured state and equivalent disturbance estimation, based on which an output feedback backstepping approach is proposed for the desired tracking of command course angle. The global stability of the cascade system is analyzed. Simulation results validate the effectiveness of the proposed methodology. Full article
(This article belongs to the Special Issue Unmanned Marine Vehicles)
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16 pages, 7354 KiB  
Article
A New Method for Extracting Laver Culture Carriers Based on Inaccurate Supervised Classification with FCN-CRF
by Xinliang Pan, Tao Jiang, Zhen Zhang, Baikai Sui, Chenxi Liu and Linjing Zhang
J. Mar. Sci. Eng. 2020, 8(4), 274; https://doi.org/10.3390/jmse8040274 - 11 Apr 2020
Cited by 10 | Viewed by 2726
Abstract
Timely monitoring of marine aquaculture has considerable significance for marine ecological protection and maritime safety and security. Considering that supervised learning needs to rely on a large number of training samples and the characteristics of intensive and regular distribution of the laver aquaculture [...] Read more.
Timely monitoring of marine aquaculture has considerable significance for marine ecological protection and maritime safety and security. Considering that supervised learning needs to rely on a large number of training samples and the characteristics of intensive and regular distribution of the laver aquaculture zone, in this paper, an inaccurate supervised classification model based on fully convolutional neural network and conditional random filed (FCN-CRF) is designed for the study of a laver aquaculture zone in Lianyungang, Jiangsu Province. The proposed model can extract the aquaculture zone and calculate the area and quantity of laver aquaculture net simultaneously. The FCN is used to extract the laver aquaculture zone by roughly making the training label. Then, the CRF is used to extract the isolated laver aquaculture net with high precision. The results show that the k a p p a coefficient of the proposed model is 0.984, the F 1 is 0.99, and the recognition effect is outstanding. For label production, the fault tolerance rate is high and does not affect the final classification accuracy, thereby saving more label production time. The findings provide a data basis for future aquaculture yield estimation and offshore resource planning as well as technical support for marine ecological supervision and marine traffic management. Full article
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18 pages, 7890 KiB  
Article
Sand Beach Nourishment: Experience from the Mediterranean Coast of Israel
by Menashe Bitan and Dov Zviely
J. Mar. Sci. Eng. 2020, 8(4), 273; https://doi.org/10.3390/jmse8040273 - 10 Apr 2020
Cited by 32 | Viewed by 6947
Abstract
Beach nourishment along the Mediterranean coast of Israel represents a new approach to mitigate coastal erosion by adding suitable sand to threatened beaches. This ‘soft’ solution has become more environmentally and economically acceptable than traditional ‘hard’ solutions, such as seawalls, revetments, detached breakwaters [...] Read more.
Beach nourishment along the Mediterranean coast of Israel represents a new approach to mitigate coastal erosion by adding suitable sand to threatened beaches. This ‘soft’ solution has become more environmentally and economically acceptable than traditional ‘hard’ solutions, such as seawalls, revetments, detached breakwaters and groins. Beach nourishment projects have been implemented on the Israeli coast north of Ashdod Port (2011), north of Ashkelon Marina (2015) and in the south of Haifa Bay (2016–2017). The performance of these projects was analyzed and compared with nourishment projects along the Mediterranean beaches of Italy, France and Spain. Despite a lack of detailed documentation on most of the European nourishment projects, they proved more durable than the Israeli projects, which were compromised when the imported sand eventually washed offshore. Key factor for the Israeli projects’ failure include the unsuitable morphology of the beaches; insufficient unit sand volume (m3/m—volume of nourished sand per meter of the beach length); and imported sand that was too fine versus native sand. The unique physical conditions of the Israeli coast specifically, its open shelf and straight coastline subject to relatively high waves with a very long fetch—also contributed to the poor durability of the nourishment. To improve durability on future projects: imported grain size should be at least 1.5–2.0 times the native sand; unit sand volume should be 400–500 m3/m; and supporting measures should be utilized as appropriate. Full article
(This article belongs to the Special Issue Mitigating Coastal Erosion and Climate Change Impacts)
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17 pages, 3833 KiB  
Article
Numerical Simulation and Validation in Scrubber Wash Water Discharge from Ships
by Yong-Seok Choi and Tae-Woo Lim
J. Mar. Sci. Eng. 2020, 8(4), 272; https://doi.org/10.3390/jmse8040272 - 10 Apr 2020
Cited by 8 | Viewed by 3346
Abstract
A regulation on the sulfur emissions of ships sailing in global sea areas has been enforced since 1 January 2020. In this new regulation, ships are required to use low-sulfur fuel oils or to install an after-treatment equipment, such as a scrubber. Open [...] Read more.
A regulation on the sulfur emissions of ships sailing in global sea areas has been enforced since 1 January 2020. In this new regulation, ships are required to use low-sulfur fuel oils or to install an after-treatment equipment, such as a scrubber. Open and hybrid scrubbers wash the exhaust gas using seawater and then discharge the wash water overboard. According to the regulation promulgated by the International Maritime Organization (IMO) Marine Environment Protection Committee (MEPC), the wash water must have a pH of 6.5 or higher at 4 m from the discharge point. Wash water is generally acidic, with a pH of 2.5–3.5, whereas seawater is alkaline, with a pH of approximately 8.2. The wash water is dispersed after being discharged overboard through a nozzle, and its pH is restored through dilution with the surrounding seawater. In this study, the pH was calculated by using a theoretical chemical reaction model, and then the dispersion of wash water was analyzed using CFD simulation. This study describes the process of selecting the appropriate turbulent Schmidt number in a wide range of nozzle diameters. Finally, the appropriate nozzle diameter was determined based on the initial pH of the discharged scrubber wash. Full article
(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)
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14 pages, 24623 KiB  
Article
The Impact of Storm-Induced Breaches on Barrier Coast Systems Subject to Climate Change—A Stochastic Modelling Study
by Koen R. G. Reef, Pieter C. Roos, Tessa E. Andringa, Ali Dastgheib and Suzanne J. M. H. Hulscher
J. Mar. Sci. Eng. 2020, 8(4), 271; https://doi.org/10.3390/jmse8040271 - 10 Apr 2020
Cited by 3 | Viewed by 2647
Abstract
Storms can have devastating impacts on barrier coasts causing coastal erosion, partial inundation, and possibly the breaching of barrier islands. The breaching of barrier islands provides a mechanism for the creation of new tidal inlets that connect the backbarrier basin (or lagoon) and [...] Read more.
Storms can have devastating impacts on barrier coasts causing coastal erosion, partial inundation, and possibly the breaching of barrier islands. The breaching of barrier islands provides a mechanism for the creation of new tidal inlets that connect the backbarrier basin (or lagoon) and the outer sea. As a new tidal inlet affects both the basin and the hydrodynamics of existing inlets, it is important to understand why an initial breach either closes or may evolve into a new tidal inlet. To this end, we performed a Monte Carlo analysis using an idealized model capable of simulating the long-term morphological evolution of multiple tidal inlets connected to a single backbarrier basin. To do so required the creation of a stochastic shell, as a new element around this existing barrier coast model. Our results demonstrate that barrier coast systems tend towards an equilibrium value for the number of inlets per kilometer of barrier coast and total inlet cross section. This even holds with the continuous stochastic forcing of storm-induced breaches. This finding implies that if a new breach opens in a coast that is already in equilibrium, existing inlets will shrink and may close if the new breach remains open. Furthermore, we find that climate-driven changes in storm frequency will modify the timescales in which barrier coasts reach their equilibrium state. Finally, we find that the distance between a new breach and its nearest neighbor is more important for its survival than the size of the breach or the degree of saturation of the barrier coast. Full article
(This article belongs to the Special Issue Future Coasts and Estuaries)
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16 pages, 8113 KiB  
Article
Development of a New Ship Adaptive Weather Routing Model Based on Seakeeping Analysis and Optimization
by Silvia Pennino, Salvatore Gaglione, Anna Innac, Vincenzo Piscopo and Antonio Scamardella
J. Mar. Sci. Eng. 2020, 8(4), 270; https://doi.org/10.3390/jmse8040270 - 10 Apr 2020
Cited by 33 | Viewed by 4928
Abstract
This paper provides a new adaptive weather routing model, based on the Dijkstra shortest path algorithm, aiming to select the optimal route that maximizes the ship performances in a seaway. The model is based on a set of ship motion-limiting criteria and on [...] Read more.
This paper provides a new adaptive weather routing model, based on the Dijkstra shortest path algorithm, aiming to select the optimal route that maximizes the ship performances in a seaway. The model is based on a set of ship motion-limiting criteria and on the weather forecast maps, providing the sea state conditions the ship is expected to encounter along the scheduled route. The new adaptive weather routing model is applied to optimize the scheduled route in the Northern Atlantic Ocean of the S175 containership, assumed as a reference vessel, based on the weather forecast data provided by the Global WAve Model (GWAM). In the analysis, both wave and combined wind/swell wave conditions are embodied to investigate the incidence on the optimum route assessment. Furthermore, the effect of the vessel speed on the optimum route detection is also investigated. Current results clearly show that it is possible to achieve appreciable improvements, up to 50% of the ship seakeeping performances, without excessively increasing the route length and the voyage duration. Full article
(This article belongs to the Special Issue Stability and Seakeeping of Marine Vessels)
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