Journal of Marine Science and Engineering

13 pages, 3915 KiB

Open AccessArticle

Variable-Speed Engines on Wind Farm Support Vessels

by Kristian Eikeland Holmefjord, Lars Husdal, Martijn de Jongh and Sverre Torben

J. Mar. Sci. Eng. 2020, 8(3), 229; https://doi.org/10.3390/jmse8030229 - 24 Mar 2020

Cited by 6 | Viewed by 4203

We examine the fuel savings of Edda Passat, a newly constructed wind farm support vessel that utilizes a common direct current (DC) grid. This enables its diesel engines to operate at variable speeds by using frequency converter technology. A detailed investigation of these [...] Read more.

We examine the fuel savings of Edda Passat, a newly constructed wind farm support vessel that utilizes a common direct current (DC) grid. This enables its diesel engines to operate at variable speeds by using frequency converter technology. A detailed investigation of these benefits has been performed based on real-life measurements from three months of operations in the Race Bank wind farm off the east coast of England. The calculated fuel savings of Edda Passat achieved via its variable-speed engines are 21% lower compared to using a conventional alternating current (AC) grid with a fixed frequency. This paper will explain the technology, measurements, and results in detail. Full article

(This article belongs to the Special Issue Modelling and Optimisation of Ship Energy Systems)

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20 pages, 37085 KiB

Open AccessReview

An Overview of the Expected Shoreline Impact of the Marine Energy Farms Operating in Different Coastal Environments

by Alina Raileanu, Florin Onea and Eugen Rusu

J. Mar. Sci. Eng. 2020, 8(3), 228; https://doi.org/10.3390/jmse8030228 - 24 Mar 2020

Cited by 11 | Viewed by 3118

Abstract

The aim of the present work is to provide an overview of the possible implications involving the influence of a generic marine energy farm on the nearshore processes. Several case studies covering various European coastal areas are considered for illustration purposes. These include [...] Read more.

The aim of the present work is to provide an overview of the possible implications involving the influence of a generic marine energy farm on the nearshore processes. Several case studies covering various European coastal areas are considered for illustration purposes. These include different nearshore areas, such as the Portuguese coast, Sardinia Island or a coastal sector close to the Danube Delta in the Black Sea. For the case studies related to the Portuguese coast, it is noted that a marine energy farm may reduce the velocity of the longshore currents, with a complete attenuation of the current velocity for some case studies in the coastal area from Leixoes region being observed. For the area located close to the Danube Delta, it is estimated that in the proposed configuration, a marine energy farm would provide an efficient protection against the wave action, but it will have a relatively negligible impact on the longshore currents. Summarizing the results, we can conclude that a marine energy farm seems to be beneficial for coastal protection, even in the case of the enclosed areas, such as the Mediterranean or Black seas, where the erosion generated by the wave action represents a real problem. Full article

(This article belongs to the Section Coastal Engineering)

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21 pages, 6782 KiB

Open AccessFeature PaperArticle

3D Numerical Simulation of the Interaction between Waves and a T-Head Groin Structure

by Giovanni Cannata, Marco Tamburrino and Francesco Gallerano

J. Mar. Sci. Eng. 2020, 8(3), 227; https://doi.org/10.3390/jmse8030227 - 24 Mar 2020

Cited by 4 | Viewed by 2484

Abstract

The aim of coastal structures for the defense from erosion is to modify the hydrodynamic fields that would naturally occur with the wave motion, to produce zones of sedimentation of solid material, and to combat the recession of the coastline. T-head groin-shaped structures [...] Read more.

The aim of coastal structures for the defense from erosion is to modify the hydrodynamic fields that would naturally occur with the wave motion, to produce zones of sedimentation of solid material, and to combat the recession of the coastline. T-head groin-shaped structures are among the most adopted in coastal engineering. The assessment of the effectiveness of such structures requires hydrodynamic study of the interaction between wave motion and the structure. Hydrodynamic phenomena induced by the interaction between wave motion and T-head groin structures have three-dimensionality features. The aim of the paper is to propose a new three-dimensional numerical model for the simulation of the hydrodynamic fields induced by the interaction between wave fields and coastal structures. The proposed model is designed to represent complex morphologies as well as coastal structures inside the domain. The numerical scheme solves the three-dimensional Navier–Stokes equations in a contravariant formulation, on a time-dependent coordinate system, in which the vertical coordinate varies over time to follow the free-surface elevation. The main innovative element of the paper consists in the proposal of a new numerical scheme that makes it possible to simulate flows around structures with sharp-cornered geometries. The proposed numerical model is validated against a well-known experimental test-case consisting in a wave train approaching a beach (non-parallel with the wave front), with the presence of a T-head groin structure. A detailed comparison between numerical and experimental results is shown. Full article

(This article belongs to the Special Issue Numerical Investigation of Wave-Structure Interaction)

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16 pages, 2279 KiB

Open AccessArticle

Performance Assessment of a Semi-Circular Breakwater through CFD Modelling

by Ana Gomes, José L. S. Pinho, Tiago Valente, José S. Antunes do Carmo and Arkal V. Hegde

J. Mar. Sci. Eng. 2020, 8(3), 226; https://doi.org/10.3390/jmse8030226 - 23 Mar 2020

Cited by 25 | Viewed by 5480

Abstract

Coastal defence works, such as breakwaters, are structures that aim to support the action of waves and dissipate their energy. Therefore, they provide conditions for stabilizing the coast, protecting ports, beaches and other coastal infrastructures and ecosystems. Semicircular breakwaters have been applied in [...] Read more.

Coastal defence works, such as breakwaters, are structures that aim to support the action of waves and dissipate their energy. Therefore, they provide conditions for stabilizing the coast, protecting ports, beaches and other coastal infrastructures and ecosystems. Semicircular breakwaters have been applied in different locations around the world due to their aesthetic advantages and high structural performance. Marine structures are subject to hydrodynamic actions normally estimated through physical models. However, these models are complex to implement, involving high costs and long experimental procedures. Thus, alternative methodologies for studying the hydrodynamic performance of these structures are of great use. This work presents the results of the application of a computational fluid dynamics (CFD) tool to study the stability of a perforated semicircular breakwater, based on a rubble mound foundation. The model was validated against experimental results of the critical weight necessary to resist sliding, taking into account the effects of water depth and different characteristics of the waves. A comparison is made between the perforated and the non-perforated solution in terms of the breakwater’s performance to dissipate wave energy. Dissipation conditions of this energy, in the exposed face, are also evaluated in detail, in order to assess the potential of this structure as a biological refuge for marine species. Both solutions show similar performance in terms of results obtained for the wave reflectivity coefficient. The turbulence dissipation on the exposed face of the perforated breakwater is limited to a region of restricted extension around it, which is advantageous in terms of the passage of species into the breakwater. Full article

(This article belongs to the Special Issue Reefs)

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20 pages, 14609 KiB

Open AccessArticle

Investigation of Blade Tip Shape for Improving VAWT Performance

by Yichen Jiang, Chenlu He, Peidong Zhao and Tiezhi Sun

J. Mar. Sci. Eng. 2020, 8(3), 225; https://doi.org/10.3390/jmse8030225 - 22 Mar 2020

Cited by 16 | Viewed by 4956

Abstract

Vertical axis wind turbine (VAWT) is a competitive power generation device due to structural simplicity, wind direction independence, no yaw mechanism required, easier maintenance, and lower noise emission. However, blade tip vortex will be generated at both ends of the blade during the [...] Read more.

Vertical axis wind turbine (VAWT) is a competitive power generation device due to structural simplicity, wind direction independence, no yaw mechanism required, easier maintenance, and lower noise emission. However, blade tip vortex will be generated at both ends of the blade during the rotation, resulting in torque loss and efficiency reduction. In this paper, computational fluid dynamics is used to study blade tip vortex and its reduction technique of a single-blade VAWT rotor in real scale. By monitoring the force and flow field at different heights of the blade, the influence ranges of tip vortex are obtained. The reduction effect of the bulkhead obtained from the blade profile curve is studied, and the size of the bulkhead is optimized. On the basis of adding the optimal bulkhead, the influence of the supporting strut is also explored. The joint action is obtained by changing the location of the supporting strut. The results show that the top supporting strut-bulkhead structure is the optimal position. The power-extraction efficiency of the rotor with this integrated structure is significantly improved at optimal tip speed ratios (TSRs) and higher TSRs. Full article

(This article belongs to the Special Issue Ocean Renewable Energy Systems (ORES); Wave–Structure Interaction Analysis and Design Methods)

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19 pages, 5864 KiB

Open AccessArticle

A Novel Framework of Real-Time Regional Collision Risk Prediction Based on the RNN Approach

by Dapei Liu, Xin Wang, Yao Cai, Zihao Liu and Zheng-Jiang Liu

J. Mar. Sci. Eng. 2020, 8(3), 224; https://doi.org/10.3390/jmse8030224 - 22 Mar 2020

Cited by 25 | Viewed by 4038

Abstract

Regional collision risk identification and prediction is important for traffic surveillance in maritime transportation. This study proposes a framework of real-time prediction for regional collision risk by combining Density-Based Spatial Clustering of Applications with Noise (DBSCAN) technique, Shapley value method and Recurrent Neural [...] Read more.

Regional collision risk identification and prediction is important for traffic surveillance in maritime transportation. This study proposes a framework of real-time prediction for regional collision risk by combining Density-Based Spatial Clustering of Applications with Noise (DBSCAN) technique, Shapley value method and Recurrent Neural Network (RNN). Firstly, the DBSCAN technique is applied to cluster vessels in specific sea area. Then the regional collision risk is quantified by calculating the contribution of each vessel and each cluster with Shapley value method. Afterwards, the optimized RNN method is employed to predict the regional collision risk of specific seas in short time. As a result, the framework is able to determine and forecast the regional collision risk precisely. At last, a case study is carried out with actual Automatic Identification System (AIS) data, the results show that the proposed framework is an effective tool for regional collision risk identification and prediction. Full article

(This article belongs to the Special Issue Maritime Safety)

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16 pages, 4657 KiB

Open AccessArticle

Potential Hydrodynamic Impacts and Performances of Commercial-Scale Turbine Arrays in the Strait of Larantuka, Indonesia

by Kadir Orhan and Roberto Mayerle

J. Mar. Sci. Eng. 2020, 8(3), 223; https://doi.org/10.3390/jmse8030223 - 22 Mar 2020

Cited by 7 | Viewed by 4224

Abstract

The Strait of Larantuka, with highly energetic tidal stream currents reaching speeds of up to 3–4 m/s, is a promising site for renewable electricity production from the ocean. This paper presents the results of an assessment regarding the potential hydrodynamic impacts, wake characteristics, [...] Read more.

The Strait of Larantuka, with highly energetic tidal stream currents reaching speeds of up to 3–4 m/s, is a promising site for renewable electricity production from the ocean. This paper presents the results of an assessment regarding the potential hydrodynamic impacts, wake characteristics, and the performances of large scale turbine arrays in the strait. A high-resolution, three-dimensional baroclinic model is developed using the FLOW module of the Delft3D modeling system to simulate tidal currents. The energy of currents is assumed to be extracted by horizontal-axis tidal turbines, which can harness strong bi-directional flow, positioned on sequential rows and alternating downstream arrangements. Enhanced momentum sinks are used to represent the influence of energy extraction by the tidal turbines. Four different array layouts with rated capacities of up to 35 MW are considered. We find that, in the Strait of Larantuka, array layout significantly affects the flow conditions and the power output, mainly due to the geometric blockage effect of the bounded channel. With respect to undisturbed flow conditions in the strait, decreases in current speeds of up to about 0.6 m/s, alongside increases in the order of 80% near-shore are observed. While operating efficiency rates of turbines reaching around 50%–60% resulted during the spring tide in the arrays with smaller rated capacities, the power output of the devices was negligible during the neap tide. Full article

(This article belongs to the Special Issue Wave and Tidal Energy Resource Characterization and Environment Interactions)

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20 pages, 10885 KiB

Open AccessArticle

A Stereolithographic Model-Based Dense Body Plan Generation Method to Construct a Ship Hydrodynamic Coefficients Database

by Qianfeng Jing, Helong Shen and Yong Yin

J. Mar. Sci. Eng. 2020, 8(3), 222; https://doi.org/10.3390/jmse8030222 - 21 Mar 2020

Cited by 3 | Viewed by 4667

Abstract

A ship’s body plan is a vital data resource of ship hydrodynamics analysis, especially for time-domain simulations. Motivated by 3D printing technology, a novel dense body plan generation method is developed in this study. The slicing algorithm is adopted to generate dense 2D [...] Read more.

A ship’s body plan is a vital data resource of ship hydrodynamics analysis, especially for time-domain simulations. Motivated by 3D printing technology, a novel dense body plan generation method is developed in this study. The slicing algorithm is adopted to generate dense 2D body plans from ship stereolithographic models. The dense body plan can be produced automatically under arbitrary rotational angles and slices. Moreover, a section redistribution algorithm is integrated to eliminate the non-uniform distribution features in sliced data inherited from the stereolithographic models. The benchmark ship models are selected to validate the accuracy of the method. The hull volumes of three ship models are calculated based on the produced data. The calculated results show satisfactory agreement with the published values. Furthermore, the estimation formulas of wetted surface area (WSA) are reviewed and utilized for validation. The calculated WSAs by slice integration turn out to be adaptive and accurate. The time costs of different slices are provided to illustrate the computational efficiency. A ship hydrodynamic coefficients database is constructed based on a 2D strip method and the produced data. The proposed method aims to improve the generation process of the body plan, which could meet the accuracy requirements of the strip method. As a result, hydrodynamic coefficients utilized in time-domain simulations could be obtained smoothly from the database. Full article

(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)

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21 pages, 1253 KiB

Open AccessArticle

Optimization of the Emissions Profile of a Marine Propulsion System Using a Shaft Generator with Optimum Tracking-Based Control Scheme

by Joel R. Perez and Carlos A. Reusser

J. Mar. Sci. Eng. 2020, 8(3), 221; https://doi.org/10.3390/jmse8030221 - 20 Mar 2020

Cited by 13 | Viewed by 4491

Abstract

Nowadays, marine propulsion systems based on thermal machines that operate under the diesel cycle have positioned themselves as one of the main options for this type of applications. The main comparative advantages of diesel engines, compared to other propulsion systems based on thermal [...] Read more.

Nowadays, marine propulsion systems based on thermal machines that operate under the diesel cycle have positioned themselves as one of the main options for this type of applications. The main comparative advantages of diesel engines, compared to other propulsion systems based on thermal cycle engines, are the low specific fuel consumption of residual fuels, and their higher thermal efficiency. However, its main disadvantage lies in the emissions produced by the combustion of the residual fuels, such as carbon dioxide (CO₂), sulfur oxide (SO_x), and nitrogen oxide (NO_x). These emissions are directly related to the operating conditions of the propulsion system. Over the last decade, the International Maritime Organization (IMO) has adopted a series of regulations to reduce CO₂ emissions based on the introduction of an Energy Efficiency Design Index (EEDI) and an Energy Efficiency Operational Indicator (EEOI). In this context, adding a Shaft Generator (SG) to the propulsion system favoring lower EEDI and EEOI values. The present work proposes a selective control system and optimization scheme that allows operating the shaft generator in Power Take Off (PTO) or Power Take In (PTI) mode, ensuring that the main engine operates, always, at the optimum fuel efficiency point, thus ensuring minimum CO₂ emissions. Full article

(This article belongs to the Special Issue Marine Engines Performance and Emissions)

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27 pages, 34134 KiB

Open AccessArticle

Model Structures and Identification for Fully Embedded Thrusters: 360-Degrees-Steerable Steering-Grid and Four-Channel Thrusters

by Gerben Peeters, Muhammad Raheel Afzal, Maarten Vanierschot, René Boonen and Peter Slaets

J. Mar. Sci. Eng. 2020, 8(3), 220; https://doi.org/10.3390/jmse8030220 - 20 Mar 2020

Cited by 9 | Viewed by 4885

Abstract

The European

{Watertruck}^{+}

project introduced a new fleet of self-propelled inland cargo barges to the European waters, in order to induce more sustainable freight transport in the European hinterland. An augmentation of the automation level of this fleet could further advance their [...] Read more.

The European

{Watertruck}^{+}

project introduced a new fleet of self-propelled inland cargo barges to the European waters, in order to induce more sustainable freight transport in the European hinterland. An augmentation of the automation level of this fleet could further advance their competitiveness and potentially pave the way for unmanned inland cargo vessels. The motion control of such a vessel forms a key component in this envisaged automation chain and benefits from the knowledge of the capabilities of the propulsion system, which here envelops a 360-degrees-steerable steering-grid thruster in conjunction with a 360-degrees-steerable four-channel thruster. Therefore, this study details the mechanical design of both thrusters and lists their experimental towing-tank data. Furthermore, two different modelling methods are offered, one theoretically based and one using a multilayer neural network. A model structure comparison, based on a bias-variance trade-off, verifies the adequacy of the theoretical model which got expended with an angle-dependent thrust deduction coefficient. In addition, several multilayer feedforward neural network architectures exemplify their inherent capability to model the complex, nonlinear, flow phenomena inside the thrusters. These identified model structures can additionally improve thrust allocation algorithms and offer better plant models to study more advanced control strategies. Full article

(This article belongs to the Section Ocean Engineering)

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14 pages, 4379 KiB

Open AccessArticle

Numerical Investigation on Nonlinear Dynamic Responses of a Towed Vessel in Calm Water

by Bo Woo Nam

J. Mar. Sci. Eng. 2020, 8(3), 219; https://doi.org/10.3390/jmse8030219 - 20 Mar 2020

Cited by 8 | Viewed by 2994

Abstract

In this study, we numerically investigated the nonlinear dynamic responses of an autonomous towing system where a vessel is passively towed by a tug via a towline. A three-degrees-of-freedom maneuvering mathematical model is utilized to describe the nonlinear dynamics of the towed vessel [...] Read more.

In this study, we numerically investigated the nonlinear dynamic responses of an autonomous towing system where a vessel is passively towed by a tug via a towline. A three-degrees-of-freedom maneuvering mathematical model is utilized to describe the nonlinear dynamics of the towed vessel in calm sea. The hydrodynamic force acting on the towed vessel is modelled as a modular-type hull force model, which includes linear and nonlinear (third order) damping forces in sway and yawing directions. The towline force is simply modeled as a linear spring. First, the motion responses of a towing system, showing large sway-yaw coupled motions due to unstable towing characteristics, are studied by applying phase plane analysis. For the validation of the present numerical method, the simulation results are directly compared with the model test data. Then, simulation parameters, such as towing speed, initial positions and hull force coefficients, are changed and their resulting limit cycles are investigated. Finally, the effects of towline and tug motion are discussed based on the simulation results. It is found that the dynamic characteristics of the towed vessel come closer to being chaotic due to the nonlinear stiffness effect of the towline and tug motion effect. Full article

(This article belongs to the Special Issue Ship Dynamics for Performance Based Design and Risk Averse Operations)

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11 pages, 929 KiB

Open AccessArticle

Density and Abundance of Delphinus delphis in Waters South of Samos Island, Greece (Eastern Mediterranean Sea)

by Guido Pietroluongo, Giulia Cipriano, Karthik Ashok, Simone Antichi, Heloise Carlier, Anastasia Miliou, Rosalia Maglietta, Carmelo Fanizza and Roberto Carlucci

J. Mar. Sci. Eng. 2020, 8(3), 218; https://doi.org/10.3390/jmse8030218 - 20 Mar 2020

Cited by 10 | Viewed by 3919

Abstract

The Mediterranean subpopulation of short-beaked common dolphin Delphinus delphis is ranked as endangered on the IUCN (International Union for Conservation of Nature) Red List because it has sharply declined during the last decades, resulting in sparse and decreasing populations. Monitoring the conservation status [...] Read more.

The Mediterranean subpopulation of short-beaked common dolphin Delphinus delphis is ranked as endangered on the IUCN (International Union for Conservation of Nature) Red List because it has sharply declined during the last decades, resulting in sparse and decreasing populations. Monitoring the conservation status of this endangered dolphin species is particularly relevant to fulfil targets under the range of several international agreements. Moreover, estimating the abundance of D. delphis is essential to verify the effectiveness of conservation action to maintain safe population levels in the Mediterranean Sea and to suggest appropriate modifications to limit potential threats. In this regard, a monitoring program of the short-beaked common dolphin in Samos Island (Greece) was carried out from 2016 to 2019, adopting a random line transect sampling method. The overall density and abundance estimates of D. delphis, obtained by applying conventional distance sampling (CDS) on sighting data, were 0.15 individuals/km² (CV = 13.27%; 95% CI = 0.11–0.19 individuals/km²) and 51 individuals (CV = 13.27%; 95% CI = 40-66 individuals), respectively. Although, a longer time series of sighting data should be collected and a larger area should be investigated to better understand the population trend of D. delphis and its residency pattern, the results contribute to setting up a baseline reference for future assessment of its population in the Eastern Aegean Sea. Full article

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21 pages, 39893 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Numerical Simulation of Large Wave Heights from Super Typhoon Nepartak (2016) in the Eastern Waters of Taiwan

by Shih-Chun Hsiao, Hongey Chen, Han-Lun Wu, Wei-Bo Chen, Chih-Hsin Chang, Wen-Dar Guo, Yung-Ming Chen and Lee-Yaw Lin

J. Mar. Sci. Eng. 2020, 8(3), 217; https://doi.org/10.3390/jmse8030217 - 20 Mar 2020

Cited by 56 | Viewed by 5725

Abstract

Super Typhoon Nepartak (2016) was used for this case study because it is the most intense typhoon that made landfall in Taiwan in the past decade. Winds extracted from the Climate Forecast System version 2 (CFSV2) and ERA5 datasets and merged with a [...] Read more.

Super Typhoon Nepartak (2016) was used for this case study because it is the most intense typhoon that made landfall in Taiwan in the past decade. Winds extracted from the Climate Forecast System version 2 (CFSV2) and ERA5 datasets and merged with a parametric typhoon model using two hybrid techniques served as the meteorological conditions for driving a coupled wave-circulation model. The computed significant wave heights were compared with the observations recorded at three wave buoys in the eastern waters of Taiwan. Model performance in terms of significant wave height was also investigated by employing the CFSV2 winds under varying spatial and temporal resolutions. The results of the numerical experiments reveal that the simulated storm wave heights tended to decrease significantly due to the lower spatial resolution of the hourly winds from the CFSV2 dataset; however, the variations in the storm wave height simulations were less sensitive to the temporal resolution of the wind field. Introducing the combination of the CFSV2 and the parametric typhoon winds greatly improved the storm wave simulations, and similar phenomena can be found in the exploitation of the ERA5 dataset blended into the parametric wind field. The overall performance of the hybrid winds derived from ERA5 was better than that from the CFSV2, especially in the outer region of Super Typhoon Nepartak (2016). Full article

(This article belongs to the Special Issue Storm Tide and Wave Simulations and Assessment)

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Graphical abstract

12 pages, 676 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Knowledge about Microplastic in Mediterranean Tributary River Ecosystems: Lack of Data and Research Needs on Such a Crucial Marine Pollution Source

by Cristiana Guerranti, Guido Perra, Tania Martellini, Luisa Giari and Alessandra Cincinelli

J. Mar. Sci. Eng. 2020, 8(3), 216; https://doi.org/10.3390/jmse8030216 - 20 Mar 2020

Cited by 32 | Viewed by 5379

Abstract

Plastic debris occurring in freshwater environments, which can either come from the surrounding terrestrial areas or transported from upstream, has been identified as one of the main sources and routes of plastic pollution in marine systems. The ocean is the final destination of [...] Read more.

Plastic debris occurring in freshwater environments, which can either come from the surrounding terrestrial areas or transported from upstream, has been identified as one of the main sources and routes of plastic pollution in marine systems. The ocean is the final destination of land- based microplastic sources, but compared to marine environments, the occurrence and effects of microplastics in freshwater ecosystems remain largely unknown. A thorough examination of scientific literature on abundance, distribution patterns, and characteristics of microplastics in freshwater environments in Mediterranean tributary rivers has shown a substantial lack of information and the need to apply adequate and uniform measurement methods. Full article

(This article belongs to the Special Issue Marine Litter)

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19 pages, 5434 KiB

Open AccessArticle

Analysis of Piled Concrete Foundation for a 3-MW Class Offshore Wind Turbine along the Southwest Coast in Korea

by Hyun-Gi Kim, Bum-Joon Kim and Kwang-Ho Lee

J. Mar. Sci. Eng. 2020, 8(3), 215; https://doi.org/10.3390/jmse8030215 - 20 Mar 2020

Cited by 5 | Viewed by 3673

Abstract

Concrete foundations have received attention as offshore wind turbine support structures because of their various advantages. However, because of the lack of information on structural analysis and the design method of complex marine environmental loads, concrete foundations cannot be applied on actual sites. [...] Read more.

Concrete foundations have received attention as offshore wind turbine support structures because of their various advantages. However, because of the lack of information on structural analysis and the design method of complex marine environmental loads, concrete foundations cannot be applied on actual sites. Therefore, the structure behavior mechanism and concrete reinforcement design need to be evaluated based on soil-structure interactions. Herein, an efficient method for analysis of piled concrete foundations (PCFs) is presented, and the stability of PCF structures is evaluated under environmental conditions of the coast in Korea for a 3-MW wind turbine. Three analytical parameters for PCF models were defined to consider soil-structure interaction. The results of each model were compared with the displacement, stresses, and natural frequencies. Using the analysis results, a prestressing reinforcement design for concrete foundations was proposed. Quasi-static analysis showed that maximum displacement was sufficiently small and the maximum stresses did not exceed the allowable stresses. PCF showed excellent dynamic performance and structural stability. In addition, stiffness of the soil spring model influenced the natural frequency rather than the stiffness of the pile type. Detailed analysis of the connections between piles and concrete need to be studied in the future. Full article

(This article belongs to the Special Issue Ocean Renewable Energy Systems (ORES); Wave–Structure Interaction Analysis and Design Methods)

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19 pages, 9834 KiB

Open AccessArticle

Performance Assessment of ERA5 Wave Data in a Swell Dominated Region

by Maria Francesca Bruno, Matteo Gianluca Molfetta, Vincenzo Totaro and Michele Mossa

J. Mar. Sci. Eng. 2020, 8(3), 214; https://doi.org/10.3390/jmse8030214 - 19 Mar 2020

Cited by 48 | Viewed by 5842

Abstract

The present paper deals with a performance assessment of the ERA5 wave dataset in an ocean basin where local wind waves superimpose on swell waves. The evaluation framework relies on observed wave data collected during a coastal experimental campaign carried out offshore of [...] Read more.

The present paper deals with a performance assessment of the ERA5 wave dataset in an ocean basin where local wind waves superimpose on swell waves. The evaluation framework relies on observed wave data collected during a coastal experimental campaign carried out offshore of the southern Oman coast in the Western Arabian Sea. The applied procedure requires a detailed investigation on the observed waves, and aims at classifying wave regimes: observed wave spectra have been split using a 2D partition scheme and wave characteristics have been evaluated for each wave component. Once the wave climate was defined, a detailed wave model assessment was performed. The results revealed that during the analyzed time span the ERA5 wave model overestimates the swell wave heights, whereas the wind waves’ height prediction is highly influenced by the wave developing conditions. The collected field dataset is also useful for a discussion on spectral wave characteristics during monsoon and post-monsoon season in the examined region; the recorded wave data do not suffice yet to adequately describe wave fields generated by the interaction of monsoon and local winds. Full article

(This article belongs to the Section Ocean Engineering)

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12 pages, 3524 KiB

Open AccessArticle

Effects of Temperature on the Survival and Larval Development of Deiratonotus Japonicus (Brachyura, Camptandriidae) as a Biological Indicator

by Il-Kweun Oh and Seung-Woo Lee

J. Mar. Sci. Eng. 2020, 8(3), 213; https://doi.org/10.3390/jmse8030213 - 19 Mar 2020

Cited by 5 | Viewed by 2590

Abstract

Deiratonotus japonicus (D. japonicus) inhabits isolated locations and upstream brackish waters from Kanagawa Prefecture to Okinawa Prefecture in Japan. This species faces the threat of extinction because of changing habitat conditions. Our previous studies have shown that its complete larval development [...] Read more.

Deiratonotus japonicus (D. japonicus) inhabits isolated locations and upstream brackish waters from Kanagawa Prefecture to Okinawa Prefecture in Japan. This species faces the threat of extinction because of changing habitat conditions. Our previous studies have shown that its complete larval development from hatching to metamorphosis consists of five zoeal stages and one megalopal stage. In this study, the effect of temperature on the survival and growth of larval development in D. japonicus under controlled laboratory conditions of 13, 18, 23, 24, 25, and 26 °C was investigated by rearing larvae (30 PSU; 12:12 h light/dark cycle; fed a diet of Brachionus plicatilis rotundiformis and Artemia sp. nauplii). The survival rates and developmental periods were measured for each larval stage. The highest survival rates were obtained at 18–24 °C. Metamorphosis to megalopa occurred at 23–25 °C. There were rapid and synchronous developments at 25–26 °C but delayed and extended developments at 13 °C. The molting period decreased with increasing temperature. With decreasing temperature, the beginning of the development and duration of molting was prolonged. In addition, there were very low survival rates at 13 °C and 26 °C in all zoeal stages. Our results indicate that the early larval stages of D. japonicus are well adapted to 18–24 °C, the range observed in the estuarine marine environment of the Kita River during the breeding season. Optimum larval survival and growth were obtained at 23 °C. Temperature significantly affected the survival rate, developmental period, and molting of the larvae. The relationship between the cumulative periods of development from hatching through individual larval stages (y) and temperatures (T) was described as a power function (y = a × Tb). Full article

(This article belongs to the Section Marine Biology)

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18 pages, 6952 KiB

Open AccessFeature PaperArticle

Wall-Resolved LES Modeling of a Wind Turbine Airfoil at Different Angles of Attack

by Irene Solís-Gallego, Katia María Argüelles Díaz, Jesús Manuel Fernández Oro and Sandra Velarde-Suárez

J. Mar. Sci. Eng. 2020, 8(3), 212; https://doi.org/10.3390/jmse8030212 - 19 Mar 2020

Cited by 8 | Viewed by 3863

Abstract

Noise has arisen as one of the main restrictions for the deployment of wind turbines in urban environments or in sensitive ecosystems like oceans for offshore and coastal applications. An LES model, adequately planned and resolved, is useful to describe the noise generation [...] Read more.

Noise has arisen as one of the main restrictions for the deployment of wind turbines in urban environments or in sensitive ecosystems like oceans for offshore and coastal applications. An LES model, adequately planned and resolved, is useful to describe the noise generation mechanisms in wind turbine airfoils. In this work, a wall-resolved LES model of the turbulent flow around a typical wind turbine airfoil is presented and described in detail. The numerical results obtained have been validated with hot wire measurements in a wind tunnel. The description of the boundary layer over the airfoil provides an insight into the main noise generation mechanism, which is known to be the scattering of the vortical disturbances in the boundary layer into acoustic waves at the airfoil trailing edge. In the present case, 2D wave instabilities are observed in both suction and pressure sides, but these perturbations are diffused into a turbulent boundary layer prior to the airfoil trailing edge, so tonal noise components are not expected in the far-field noise propagation. The results obtained can be used as input data for the prediction of noise propagation to the far-field using a hybrid aeroacoustic model. Full article

(This article belongs to the Special Issue Large Eddy Simulation and Turbulence Modeling)

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63 pages, 31072 KiB

Open AccessArticle

Surprising Behaviour of the Wageningen B-Screw Series Polynomials

by Stephan Helma

J. Mar. Sci. Eng. 2020, 8(3), 211; https://doi.org/10.3390/jmse8030211 - 18 Mar 2020

Cited by 8 | Viewed by 6318

Abstract

Undoubtedly, the Wageningen B-screw Series is the most widely used systematic propeller series. It is very popular to preselect propeller dimensions during the preliminary design stage before performing a more thorough optimisation, but in the smaller end of the market it is often [...] Read more.

Undoubtedly, the Wageningen B-screw Series is the most widely used systematic propeller series. It is very popular to preselect propeller dimensions during the preliminary design stage before performing a more thorough optimisation, but in the smaller end of the market it is often used to merely select the final propeller. Over time, the originally measured data sets were faired and scaled to a uniform Reynolds number of 2 · 10⁶ to increase the reliability of the series. With the advent of the computer, polynomials for the thrust and torque values were calculated based on the available data sets. The measured data are typically presented in the well-known open-water curves of thrust and torque coefficients

K_{T}

and

K_{Q}

versus the advance coefficient

J

. Changing the presentation from these diagrams to efficiency maps reveals some unsuspected and surprising behaviours, such as multiple extrema when optimising for efficiency or even no optimum at all for certain conditions, where an optimum could be expected. These artefacts get more pronounced at higher pitch to diameter ratios and low blade numbers. The present work builds upon the paper presented by the author at the AMT’17 and smp’19 conferences and now includes the extended efficiency maps, as suggested by Danckwardt, for all propellers of the Wageningen B-screw Series. Full article

(This article belongs to the Special Issue Selected Papers from the Sixth International Symposium on Marine Propulsors)

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13 pages, 1533 KiB

Open AccessArticle

Optimized Radial Basis Function Neural Network Based Intelligent Control Algorithm of Unmanned Surface Vehicles

by Renqiang Wang, Donglou Li and Keyin Miao

J. Mar. Sci. Eng. 2020, 8(3), 210; https://doi.org/10.3390/jmse8030210 - 18 Mar 2020

Cited by 31 | Viewed by 3821

Abstract

To improve the tracking stability control of unmanned surface vehicles (USVs), an intelligent control algorithm was proposed on the basis of an optimized radial basis function (RBF) neural network. The design process was as follows. First, the adaptation value and mutation probability were [...] Read more.

To improve the tracking stability control of unmanned surface vehicles (USVs), an intelligent control algorithm was proposed on the basis of an optimized radial basis function (RBF) neural network. The design process was as follows. First, the adaptation value and mutation probability were modified to improve the traditional optimization algorithm. Then, the improved genetic algorithms (GA) were used to optimize the network parameters online to improve their approximation performance. Additionally, the RBF neural network was used to approximate the function uncertainties of the USV motion system to eliminate the chattering caused by the uninterrupted switching of the sliding surface. Finally, an intelligent control law was introduced based on the sliding mode control with the Lyapunov stability theory. The simulation tests showed that the intelligent control algorithm can effectively guarantee the control accuracy of USVs. In addition, a comparative study with the sliding mode control algorithm based on an RBF network and fuzzy neural network showed that, under the same conditions, the stabilization time of the intelligent control system was 33.33% faster, the average overshoot was reduced by 20%, the control input was smoother, and less chattering occurred compared to the previous two attempts. Full article

(This article belongs to the Special Issue Unmanned Marine Vehicles)

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14 pages, 7196 KiB

Open AccessArticle

Worldwide Availability of Maritime Medium-Frequency Radio Infrastructure for R-Mode-Supported Navigation

by Paul Koch and Stefan Gewies

J. Mar. Sci. Eng. 2020, 8(3), 209; https://doi.org/10.3390/jmse8030209 - 18 Mar 2020

Cited by 10 | Viewed by 3640

Abstract

The Ranging Mode (R-Mode), a maritime terrestrial navigation system under development, is a promising approach to increase the resilient provision of position, navigation and timing (PNT) information for bridge instruments, which rely on Global Navigation Satellite Systems (GNSS). The R-Mode utilizes existing maritime [...] Read more.

The Ranging Mode (R-Mode), a maritime terrestrial navigation system under development, is a promising approach to increase the resilient provision of position, navigation and timing (PNT) information for bridge instruments, which rely on Global Navigation Satellite Systems (GNSS). The R-Mode utilizes existing maritime radio infrastructure such as marine radio beacons, which support maritime traffic with more reliable and accurate PNT data in areas with challenging conditions. This paper analyzes the potential service, which the R-Mode could provide to the mariner if worldwide radio beacons were upgraded to broadcast R-Mode signals. The authors assumed for this study that the R-Mode is available in the service area of the 357 operational radio beacons. The comparison with the maritime traffic, which was generated from a one-day worldwide Automatic Identification System (AIS) Class A dataset, showed that on average, 67% of ships would operate in a global R-Mode service area, 40% of ships would see at least three and 25% of ships would see at least four radio beacons at a time. This means that R-Mode would support 25% to 40% of all ships with position and 67% of all ships with PNT integrity information. The relatively high number of supported ships compared to the total radio beacon coverage of about 9% of the earth’s surface is caused by the good coverage of busy ports and areas such as the coast of China, North Sea and Baltic Sea. These numbers emphasize the importance of marine radio beacons for the R-Mode system. Full article

(This article belongs to the Special Issue Maritime Traffic Engineering and International Symposium Information on Ships Conference MTE-ISIS 2019)

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8 pages, 1281 KiB

Open AccessTechnical Note

A Time-Extended (24 h) Baited Remote Underwater Video (BRUV) for Monitoring Pelagic and Nocturnal Marine Species

by Agusti Torres, Ana-Maria Abril and Eric E. G. Clua

J. Mar. Sci. Eng. 2020, 8(3), 208; https://doi.org/10.3390/jmse8030208 - 18 Mar 2020

Cited by 11 | Viewed by 5641

Abstract

Baited remote underwater video systems (BRUVs) are efficient devices for remotely characterising the assemblage and relative density of fishes and other marine organisms. However, technological constraints (e.g., battery life and limited storage memory) typically limit deployment times to <2 h making it very [...] Read more.

Baited remote underwater video systems (BRUVs) are efficient devices for remotely characterising the assemblage and relative density of fishes and other marine organisms. However, technological constraints (e.g., battery life and limited storage memory) typically limit deployment times to <2 h making it very difficult to capture the presence of marine species, including rare and elusive ones. We developed an extended duration (24 h) BRUV to enable fisheries-independent surveying of a pelagic shark population in the western Mediterranean. Video data revealed seven visits (three nocturnal, four diurnal) by blue sharks (Prionace glauca) over a period of 1355 h. In the future, this cost-effective device could be fitted with a wireless video transmitter to provide real-time observations of marine animals for scientific or ecotourism purposes. Full article

(This article belongs to the Section Marine Biology)

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11 pages, 1437 KiB

Open AccessArticle

Feeding Whole Thraustochytrid Biomass to Cultured Atlantic Salmon (Salmo salar) Fingerlings: Culture Performance and Fatty Acid Incorporation

by Kim Jye Lee Chang, Christopher C. Parrish, Cedric J. Simon, Andrew T. Revill and Peter D. Nichols

J. Mar. Sci. Eng. 2020, 8(3), 207; https://doi.org/10.3390/jmse8030207 - 17 Mar 2020

Cited by 16 | Viewed by 3948

Abstract

Replacement of fish oil by 5% thraustochytrid whole cell biomass in diets for Atlantic salmon had no ill effect on fish growth performance, carcass total lipid and total fatty acid content. Carcass fatty acid composition indicated incorporation of the dietary thraustochytrid-derived fatty acids. [...] Read more.

Replacement of fish oil by 5% thraustochytrid whole cell biomass in diets for Atlantic salmon had no ill effect on fish growth performance, carcass total lipid and total fatty acid content. Carcass fatty acid composition indicated incorporation of the dietary thraustochytrid-derived fatty acids. This was confirmed by compound specific stable isotope analysis (CSIA) which revealed significantly ¹³C-depleted (δ¹³C value of −24‰) ω3 long-chain (≥C₂₀) polyunsaturated fatty acids (ω3 LC-PUFAs) in the fingerlings fed the thraustochytrid biomass containing diet, reflecting the highly ¹³C-depleted glycerol used to grow the thraustochytrid cultures. This finding demonstrates the bioavailability of the ω3 LC-PUFA of the Australian strain thraustochytrid culture (TC) 20 from the whole cell biomass that was partly cultivated on crude glycerol produced during biodiesel manufacturing. This paper demonstrates the value of Australian thraustochytrid strains grown heterotrophically for their wider biotechnological potential including as a source of higher value lipids, in particular the health-benefitting ω3 LC-PUFA, for use in aquaculture and other applications. Full article

(This article belongs to the Special Issue Selected Papers from the 3rd Australian New Zealand Marine Biotechnology (ANZMBS) Conference)

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21 pages, 9427 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Wave and Hydrodynamic Processes in the Vicinity of a Rubble-Mound, Permeable, Zero-Freeboard Breakwater

by Theofano I. Koutrouveli and Athanassios A. Dimas

J. Mar. Sci. Eng. 2020, 8(3), 206; https://doi.org/10.3390/jmse8030206 - 17 Mar 2020

Cited by 8 | Viewed by 3496

Abstract

A numerical study for the effect of crest width, breaking parameter, and trunk permeability on hydrodynamics and flow behavior in the vicinity of rubble-mound, permeable, zero-freeboard breakwaters (ZFBs) is presented. The modified two-dimensional Navier-Stokes equations for two-phase flows in porous media with a [...] Read more.

A numerical study for the effect of crest width, breaking parameter, and trunk permeability on hydrodynamics and flow behavior in the vicinity of rubble-mound, permeable, zero-freeboard breakwaters (ZFBs) is presented. The modified two-dimensional Navier-Stokes equations for two-phase flows in porous media with a Smagorinsky model for the subgrid scale stresses were solved numerically. An immersed-boundary/level-set method was used. The numerical model was validated for the cases of wave propagation over a submerged impermeable trapezoidal bar and a low-crested permeable breakwater. Five cases of breakwaters were examined, and the main results are: (a) The size of the crest width, B, does not notably affect the wave reflection, vorticity, and currents in the seaward region of ZFBs, while wave transmission, currents in the leeward side, and mean overtopping discharge all decrease with increasing B. A non-monotonic behavior of the wave setup is also observed. (b) As the breaking parameter decreases, wave reflection, transmission, currents, mean overtopping discharge, and wave setup decrease. This observation is also verified by relevant empirical formulas. (c) As the ZFB trunk permeability decreases, an increase of the wave reflection, currents, wave setup, and a decrease of wave transmission and mean overtopping discharge is observed. Full article

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

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22 pages, 1052 KiB

Open AccessArticle

Dead Reckoning for Trajectory Estimation of Underwater Drifters under Water Currents ^†

by Itzik Klein and Roee Diamant

J. Mar. Sci. Eng. 2020, 8(3), 205; https://doi.org/10.3390/jmse8030205 - 16 Mar 2020

Cited by 15 | Viewed by 4419

Abstract

Between external position updates, the most useful technique for trajectory estimation of a submerged drifter is dead reckoning (DR). These devices drift with the water current to measure the current’s velocity or to observe physical phenomena. We focus on the specific but important [...] Read more.

Between external position updates, the most useful technique for trajectory estimation of a submerged drifter is dead reckoning (DR). These devices drift with the water current to measure the current’s velocity or to observe physical phenomena. We focus on the specific but important case of when the drifter, due to its size and shape, experiences acceleration by the water current, an effect that must be taken into account during the DR. The force induced by the water current over the drifter is translated into a shift in the heading direction, thus creating a horizontal (sideslip) and a vertical (angle of attack) directional angles between the drifter’s moving direction and its body frame. In this paper, we extend and modify techniques used for pedestrian DR and propose PCA-DR: a principle component analysis-based DR algorithm to estimate the directional angles. Used for cases where the water current is significant such that its force induces acceleration over the drifter and used only for short time periods of a few seconds between navigation fixes, PCA-DR uses acceleration measurements only and does not assume knowledge of the drifter’s dynamics. Instead, as part of the DR process, PCA-DR estimates the directional angles induced by the water current. Compared to the traditional DR approach, our results demonstrate good navigation performance. A designated sea experiment demonstrates the applicability of PCA-DR in a realistic sea environment. Full article

(This article belongs to the Section Ocean Engineering)

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33 pages, 68713 KiB

Open AccessArticle

Development of a Marine Two-Stroke Diesel Engine MVEM with In-Cylinder Pressure Trace Predictive Capability and a Novel Compressor Model

by Haosheng Shen, Jundong Zhang, Baicheng Yang and Baozhu Jia

J. Mar. Sci. Eng. 2020, 8(3), 204; https://doi.org/10.3390/jmse8030204 - 16 Mar 2020

Cited by 12 | Viewed by 5982

Abstract

In this article, to meet the requirements of marine engine room simulator on both the simulation speed and simulation accuracy, a mean value engine model (MVEM) for the 7S80ME-C9.2 marine two-stroke diesel engine was developed and validated in the MATLAB/Simulink environment. In consideration [...] Read more.

In this article, to meet the requirements of marine engine room simulator on both the simulation speed and simulation accuracy, a mean value engine model (MVEM) for the 7S80ME-C9.2 marine two-stroke diesel engine was developed and validated in the MATLAB/Simulink environment. In consideration of the significant influence of turbocharger compressor on both the engine steady state performance and transient response, a novel compressor model (mass flow rate and isentropic efficiency model) based on a previous study carried out by the first author was proposed with the aim of achieving satisfactory simulation accuracy within the whole engine operating envelope. The predictive and extrapolative capability of the proposed compressor model was validated by carrying out simulation experiments and analyzing the simulation results under steady state condition and during transient process. To make the traditional MVEM capable of predicting in-cylinder pressure trace, the cylinder pressure analytic model proposed by Eriksson and Andersson for the four-stroke SI (spark ignition) engine was adapted to the 7S80ME-C9.2 marine two-stroke diesel engine based on the characteristic of in-cylinder pressure trace of this type of engine and then coupled to the MVEM developed in this paper. Since there is no need to solve any differential equation as it is done in the 0-D model, the advantage of MVEM in running speed is not impaired. For achieving satisfactory simulation accuracy by using the analytic model, the model parameters were calibrated elaborately by using engine measured data and a 0-D model and the relevant tuning procedure was discussed in detail. Full article

(This article belongs to the Special Issue Marine Engines Performance and Emissions)

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25 pages, 7288 KiB

Open AccessArticle

Surface Currents Derived from SAR Doppler Processing: An Analysis over the Naples Coastal Region in South Italy

by Virginia Zamparelli, Francesca De Santi, Andrea Cucco, Stefano Zecchetto, Giacomo De Carolis and Gianfranco Fornaro

J. Mar. Sci. Eng. 2020, 8(3), 203; https://doi.org/10.3390/jmse8030203 - 15 Mar 2020

Cited by 13 | Viewed by 3420

Abstract

Several studies have shown the capabilities of Synthetic Aperture Radar to map sea currents in ocean regions mainly characterized by large flows. We consider the well known method based on the analysis of the Doppler Centroid. The Doppler, as, in general, the scattering [...] Read more.

Several studies have shown the capabilities of Synthetic Aperture Radar to map sea currents in ocean regions mainly characterized by large flows. We consider the well known method based on the analysis of the Doppler Centroid. The Doppler, as, in general, the scattering from the sea, is sensitive to several phenomena, occurring between the upper ocean and atmospheric boundary layers. To investigate such phenomena, we considered the combined use of both ENVISAT calibrated amplitude and Doppler data in conjunction with hindcast wind information provided by atmospheric models as well as Wind and Doppler Geophysical Model Functions (W/D-GMF) developed, in the literature, for C-Band systems. This integrated analysis for the interpretation of the Doppler surface currents measurements was carried out on a case study located in the Mediterranean Sea which is characterized by a general low circulation regime: specifically, the coastal region around the city of Naples. In this case study, we show that generally, wind plays a direct significant role in the observed Doppler surface current. The availability of an oceanographic numerical model for one of the analyzed cases also allowed us to attempt to interpret the effect of the typical thermohaline circulation pattern on the Doppler anomaly. Full article

(This article belongs to the Special Issue Radar Technology for Coastal Areas and Open Sea Monitoring)

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17 pages, 879 KiB

Open AccessArticle

Analysis of the Discrete Theory of Radiative Transfer in the Coupled “Ocean–Atmosphere” System: Current Status, Problems and Development Prospects

by Viktor P. Afanas’ev, Alexander Yu. Basov, Vladimir P. Budak, Dmitry S. Efremenko and Alexander A. Kokhanovsky

J. Mar. Sci. Eng. 2020, 8(3), 202; https://doi.org/10.3390/jmse8030202 - 15 Mar 2020

Cited by 12 | Viewed by 2533

Abstract

In this paper, we analyze the current state of the discrete theory of radiative transfer. One-dimensional, three-dimensional and stochastic radiative transfer models are considered. It is shown that the discrete theory provides a unique solution to the one-dimensional radiative transfer equation. All approximate [...] Read more.

In this paper, we analyze the current state of the discrete theory of radiative transfer. One-dimensional, three-dimensional and stochastic radiative transfer models are considered. It is shown that the discrete theory provides a unique solution to the one-dimensional radiative transfer equation. All approximate solution techniques based on the discrete ordinate formalism can be derived based on the synthetic iterations, the small-angle approximation, and the matrix operator method. The possible directions for the perspective development of radiative transfer are outlined. Full article

(This article belongs to the Special Issue Light Fields in the Ocean from Natural and Artificial Sources)

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9 pages, 1153 KiB

Open AccessArticle

Use of Artificial Intelligence as a Problem Solution for Maritime Transport

by Irena Jurdana, Artem Krylov and Julia Yamnenko

J. Mar. Sci. Eng. 2020, 8(3), 201; https://doi.org/10.3390/jmse8030201 - 14 Mar 2020

Cited by 10 | Viewed by 3703

Abstract

The purpose of this article is to propose a solution for the transport problem in sea freight using machine learning algorithms. An important aspect of sea transport is the organization of freight. In particular, the maritime freight network is a large complex system [...] Read more.

The purpose of this article is to propose a solution for the transport problem in sea freight using machine learning algorithms. An important aspect of sea transport is the organization of freight. In particular, the maritime freight network is a large complex system whose complexity of route maps and the variety of ship traffic render it difficult to model. When investigating the characteristics of the sea freight system, it is generally advisable to use rough models in which only significant approximations are introduced and a number of details are not taken into account. At the same time, an exact model is used in a detailed study of isolated areas of the network wherein it is the area which is explored in detail and not the connections between the said areas. By so doing, one should be careful not to overlook the deviations of the model from the real network in the first case and the connections between areas in the second.Building a model that accurately takes into account and describes all the details results in excessive complications in the design process, so, in practice, a number of assumptions are always used in the simulation which are basically approximations of the real characteristics related to ship movement, depending on the specific task. Four models are used in order to build an optimal cargo transportation system: Transnational cargo model; model of cargo transportation with a dedicated initial port of cargo departure; model of cargo transportation with dedicated initial ports of departure and final port of cargo distribution; model of cargo transportation on a circular chain of ports. The route conditions are given by the traveling wave equation and on the basis of these calculations the optimal route of cargo ship movement is put forth whereby conditions affecting freight traffic include: Number of ports, fuel quantity, port of cargo destination, as well as distances between ports and intermediate ports of call. The scientific contribution lies in the fact that the human role is reduced only to that of the system observer, which, in turn, simplifies the freight calculations, as well as helps reduce the cost of fuel and human resources. Full article

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29 pages, 4160 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Towards Marine Dual Fuel Engines Digital Twins—Integrated Modelling of Thermodynamic Processes and Control System Functions

by Sokratis Stoumpos, Gerasimos Theotokatos, Christoforos Mavrelos and Evangelos Boulougouris

J. Mar. Sci. Eng. 2020, 8(3), 200; https://doi.org/10.3390/jmse8030200 - 14 Mar 2020

Cited by 35 | Viewed by 6350

Abstract

This study aims at developing an integrated model that combines detailed engine thermodynamic modelling and the control system functional modelling paving the way towards the development of high-fidelity digital twins. To sufficiently represent the combustion process, a multi-Wiebe function approach was employed, whereas [...] Read more.

This study aims at developing an integrated model that combines detailed engine thermodynamic modelling and the control system functional modelling paving the way towards the development of high-fidelity digital twins. To sufficiently represent the combustion process, a multi-Wiebe function approach was employed, whereas a database for storing the combustion model parameters was developed. The developed model was employed for the systematic investigation of a marine four-stroke dual fuel engine response during demanding transient operation with mode switching and load changes. The derived results were analysed to identify the critical engine components and their effect on the engine operational limitations. The results demonstrate that the developed model can sufficiently represent the engine and its subsystems/components behaviour and effectively capture the engine control system’s functionality. The appropriate turbocharger matching along with the sufficient design of the exhaust gas waste gate valve and fuel control systems are crucial for ensuring the smooth engine operation of dual fuel engines. Full article

(This article belongs to the Special Issue Modelling and Optimisation of Ship Energy Systems)

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