Journal of Marine Science and Engineering

23 pages, 6692 KiB

Open AccessArticle

Ensuring the Environmental Friendliness of Drillships during Their Operation in Special Ecological Regions of Northern Europe

by Sergii Sagin, Oleksiy Kuropyatnyk, Arsenii Sagin, Ivan Tkachenko, Oleksij Fomin, Václav Píštěk and Pavel Kučera

J. Mar. Sci. Eng. 2022, 10(9), 1331; https://doi.org/10.3390/jmse10091331 - 19 Sep 2022

Cited by 10 | Viewed by 2833

Abstract

The features of the operation of the drillship-type vessels in special ecological regions of Northern Europe are considered. The main gap in the study of these systems is to determine the optimal degree of recirculation. The requirements of the International Maritime Organization for [...] Read more.

The features of the operation of the drillship-type vessels in special ecological regions of Northern Europe are considered. The main gap in the study of these systems is to determine the optimal degree of recirculation. The requirements of the International Maritime Organization for the emission of nitrogen oxides from the exhaust gases of marine diesel engines are given. The aim of the study is to determine the optimal degree of recirculation of exhaust gases of a 16V32 STX-MAN marine diesel. During the research, the optimal degree of exhaust gas recirculation varied in the range of 0–21%, the load on the diesel—in the range of 35–95% of the rated power. It was established that in this case, the emission of nitrogen oxides decreases up to 7.7–33.6%, the specific fuel consumption increases up to 0.2–3.5%. It was also found that the use of gas recirculation in the range of 18–21% at loads of 35–55% leads to a critical increase in exhaust gas temperature. It is advisable to use exhaust gas recirculation in the range of 6–15% to ensure the environmental friendliness of the operation of the drillships. In these modes, the maximum reduction in nitrogen oxide emissions is ensured with a minimum increase in specific fuel consumption. Future studies should be directed at the development of the criteria for the environmental stability of sea vessels. Full article

(This article belongs to the Special Issue Dynamic Load of Shipping)

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17 pages, 6749 KiB

Open AccessArticle

A Multi-Strategy Framework for Coastal Waste Detection

by Chengjuan Ren, Sukhoon Lee, Dae-Kyoo Kim, Guangnan Zhang and Dongwon Jeong

J. Mar. Sci. Eng. 2022, 10(9), 1330; https://doi.org/10.3390/jmse10091330 - 19 Sep 2022

Cited by 1 | Viewed by 1781

Abstract

In recent years, deep learning has been widely used in the field of coastal waste detection, with excellent results. However, there are difficulties in coastal waste detection such as, for example, detecting small objects and the low performance of the object detection model. [...] Read more.

In recent years, deep learning has been widely used in the field of coastal waste detection, with excellent results. However, there are difficulties in coastal waste detection such as, for example, detecting small objects and the low performance of the object detection model. To address these issues, we propose the Multi-Strategy Deconvolution Single Shot Multibox Detector (MS-DSSD) based on DSSD. The method combines feature fusion, dense blocks, and focal loss into a state-of-the-art feed-forward network with an end-to-end training style. In the network, we employ feature fusion to import contextual information to boost the accuracy of small object detection. The dense blocks are constructed by a complex function of three concurrent operations, which can yield better feature descriptions. Then, focal loss is applied to address the class imbalance. Due to the lack of coastal waste datasets, data augmentation is designed to increase the amount of data, prevent overfitting of the model, and speed up convergence. Experimental results show that MS-DSSD513 obtains a higher mAP, of 82.2% and 84.1%, compared to the state-of-the-art object detection algorithms on PASCAL VOC2007 and our coastal waste dataset. The proposed new model is shown to be effective for small object detection and can facilitate the automatic detection of coastal waste management. Full article

(This article belongs to the Section Coastal Engineering)

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26 pages, 9600 KiB

Open AccessArticle

An Improved Sea Spray-Induced Heat Flux Algorithm and Its Application in the Case Study of Typhoon Mangkhut (2018)

by Yunjie Lan, Hongze Leng, Difu Sun, Junqiang Song and Xiaoqun Cao

J. Mar. Sci. Eng. 2022, 10(9), 1329; https://doi.org/10.3390/jmse10091329 - 19 Sep 2022

Cited by 3 | Viewed by 1737

Abstract

The prediction of tropical cyclone (TC) intensity has been a lasting challenge. Numerical models often underestimate the intensity of strong TCs. Accurately describing the air–sea heat flux is essential for improving the simulation of TCs. It is widely accepted that sea spray has [...] Read more.

The prediction of tropical cyclone (TC) intensity has been a lasting challenge. Numerical models often underestimate the intensity of strong TCs. Accurately describing the air–sea heat flux is essential for improving the simulation of TCs. It is widely accepted that sea spray has a nonnegligible effect on the heat transfer between the atmosphere and the ocean. However, the commonly used sea spray-induced heat flux algorithms have poor applicability under high wind speeds, and it is difficult to apply these algorithms to models to forecast TCs. In this study, we proposed an improved sea spray-induced heat flux algorithm based on the FASTEX dataset. This improved algorithm performs much better under high wind speed conditions than the commonly used algorithms and can be used in a coupled numerical model. The addition of sea spray-induced heat fluxes noticeably enhances the total air–sea heat fluxes and allows more energy to be transferred from the ocean to the lower atmosphere. In the simulation of TCs, the addition of sea spray-induced heat fluxes significantly improves the simulation of TC intensity and makes the low-pressure structure and wind field structure more fully developed in the horizontal direction. Full article

(This article belongs to the Special Issue Numerical Modelling of Atmospheres and Oceans)

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23 pages, 1747 KiB

Open AccessReview

Review of the Scientific Literature on Biology, Ecology, and Aspects Related to the Fishing Sector of the Striped Venus (Chamelea gallina) in Northern Adriatic Sea

by Eleonora Grazioli, Cristiana Guerranti, Paolo Pastorino, Giuseppe Esposito, Emanuele Bianco, Emilio Simonetti, Simona Rainis, Monia Renzi and Antonio Terlizzi

J. Mar. Sci. Eng. 2022, 10(9), 1328; https://doi.org/10.3390/jmse10091328 - 19 Sep 2022

Cited by 9 | Viewed by 2826

Abstract

Striped venus (Chamelea gallina) is one of the most important fish resources on the west coast of the Adriatic Sea. Recently, there has been a widespread die-off of C. gallina populations in Friuli-Venezia Giulia (northern Adriatic Sea, Italy), probably due to [...] Read more.

Striped venus (Chamelea gallina) is one of the most important fish resources on the west coast of the Adriatic Sea. Recently, there has been a widespread die-off of C. gallina populations in Friuli-Venezia Giulia (northern Adriatic Sea, Italy), probably due to unfavorable climatic events. Overall, wild populations have become increasingly rare due to many factors affecting the ecological balance of the species. In this study, the available literature was reviewed to determine the current state of knowledge on the biology, ecology, fisheries, and status of C. gallina populations with reference to populations in Friuli-Venezia Giulia. However, few data are available in terms of peer-reviewed articles; much of it can be found in the gray literature (e.g., project reports, ministerial reports, institutional websites, etc.). However, a critical review of the sources reveals that the species is as endangered as the habitats it inhabits. As a result, conservation and restoration efforts have been undertaken to date as part of some larger project to protect the species. Therefore, considering the ecological and economic importance of this species, the results of the new studies will be useful for the scientific community and will be a key element in the conservation of this species. Full article

(This article belongs to the Special Issue Environmental Stressors and Pathology of Marine Molluscs)

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22 pages, 7577 KiB

Open AccessArticle

Design and Control of an Underwater Robot Based on Hybrid Propulsion of Quadrotor and Bionic Undulating Fin

by Xiaofeng Zeng, Minghai Xia, Zirong Luo, Jianzhong Shang, Yuze Xu and Qian Yin

J. Mar. Sci. Eng. 2022, 10(9), 1327; https://doi.org/10.3390/jmse10091327 - 19 Sep 2022

Cited by 12 | Viewed by 6004

Abstract

Stable, quiet, and efficient propulsion methods are essential for underwater robots to complete their tasks in a complex marine environment. However, with a single propulsion method, such as propeller propulsion and bionic propulsion, it is difficult to achieve high efficiency and high mobility [...] Read more.

Stable, quiet, and efficient propulsion methods are essential for underwater robots to complete their tasks in a complex marine environment. However, with a single propulsion method, such as propeller propulsion and bionic propulsion, it is difficult to achieve high efficiency and high mobility at the same time. Based on the advantages of the high-efficiency propulsion of a bionic undulating fin and the stable control of the propeller, an underwater robot based on the hybrid propulsion of a quadrotor and undulating fin is proposed in this paper. This paper first introduces the mechanical implementation of the underwater robot. Then, based on kinematic modeling and theoretical derivation, the underwater motion and attitude of the robot are analyzed and the 6-DOF dynamic equation of the robot is established. Finally, the underwater motion performance of the robot is verified through field experiments. The experimental results show that the robot can realize the heave motion, surge motion, and in-situ steering motion independently and can hover stably. When the undulating frequency is 6 Hz, the maximum propulsion speed of the robot can reach up to 1.2 m/s (1.5 BL/s). Full article

(This article belongs to the Special Issue Advances in Marine Vehicles, Automation and Robotics)

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11 pages, 2117 KiB

Open AccessArticle

Reproductive Characteristics of the Flat Oyster Ostrea denselamellosa (Bivalvia, Ostreidae) Found on the Southern Coast of South Korea

by Jeonghoon Han, Han-Jun Kim, Sung-Yong Oh and Young-Ung Choi

J. Mar. Sci. Eng. 2022, 10(9), 1326; https://doi.org/10.3390/jmse10091326 - 19 Sep 2022

Cited by 3 | Viewed by 2044

Abstract

In this study, we investigated the reproductive pattern of the commercially and ecologically important species, Ostrea denelamellosa, to inform stock management strategies in South Korea. Prior to the reproduction experiment, the complete mitochondrial (mt) genome of the flat oyster, Ostrea denselamellosa, [...] Read more.

In this study, we investigated the reproductive pattern of the commercially and ecologically important species, Ostrea denelamellosa, to inform stock management strategies in South Korea. Prior to the reproduction experiment, the complete mitochondrial (mt) genome of the flat oyster, Ostrea denselamellosa, was analyzed using next-generation sequencing technology. Then, to determine the reproductive pattern of Ostrea denselamellosa, we investigated monthly changes in the gametogenesis, reproductive cycle, and sex ratio from January to October 2021 in females. The total length of the mt genome sequence of O. denselamellosa was 16,225 bp and contained 37 genes (13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes). Molecular phylogenetic comparison with 20 known species of Pteriomorphia showed that O. denselamellosa belongs to the family Ostreidae. In addition, O. denselamellosa clustered together with the O. denselamellosa Chinese strain, with a bootstrap value of 100%. Histological analysis indicated a discrepancy in gamete development of O. denselamellosa with synchronous maturation of oocytes and asynchronous development of spermatozoa in gonads. The spawning activity occurred between May and September with a temperature range gap of 6.5 °C. The spawning activity occurred from May when the temperature reached 16.7 °C until September when the temperature dropped below 23.2 °C. Furthermore, sex ratio bias was observed. This is the first study to report the complete mt genome sequence and examine the reproductive pattern in native O. denselamellosa in South Korea. Overall, these findings will help enhance the knowledge for the management and sustainable fishery of endangered oyster species including O. denselamellosa in the South Sea of Korea. Full article

(This article belongs to the Section Marine Aquaculture)

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17 pages, 7670 KiB

Open AccessArticle

Test System Development and Experimental Study on the Fatigue of a Full-Scale Steel Catenary Riser

by Jianxing Yu, Fucheng Wang, Yang Yu, Xin Liu, Pengfei Liu and Yefan Su

J. Mar. Sci. Eng. 2022, 10(9), 1325; https://doi.org/10.3390/jmse10091325 - 19 Sep 2022

Cited by 5 | Viewed by 1919

Abstract

This paper presents a full-scale deep-water steel catenary riser fatigue test system. The proposed system can carry out fatigue tests on steel catenary risers, hoses, and subsea pipelines up to 21 m in length, ranging from 8 to 24 inches in diameter. The [...] Read more.

This paper presents a full-scale deep-water steel catenary riser fatigue test system. The proposed system can carry out fatigue tests on steel catenary risers, hoses, and subsea pipelines up to 21 m in length, ranging from 8 to 24 inches in diameter. The test system was realized by mechanical loading with loading control systems, and could carry out axial tension and compression, bending moment, torsion, and internal pressure to simulate all load types on deep-water steel catenary risers or subsea pipelines. The counterforce was sustained by a counterforce frame. Through mechanical simulation analysis, the authors determined the size of the counterforce frame and designed the connection form of the counterforce frame and loading system. According to the required loading capacity, the appropriate cylinder thickness and diameter were obtained through calculation. After the design and construction of the test system, the authors designed a fatigue test to confirm the loading capacity and accuracy of the test system. The authors performed full-scale testing to assess the fatigue performance of pipe-to-pipe mainline 5G girth welds fabricated to BS 7608. This test was designed according to the stress level of pipelines in the Lingshui 17-2 gas field, and the test results were compared with the calculation results of the S–N curve. Full article

(This article belongs to the Special Issue Subsea Pipelines)

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19 pages, 5964 KiB

Open AccessArticle

A Frequency-Dependent Assimilation Algorithm: Ensemble Optimal Smoothing

by Zhongjie He, Yueqi Zhao, Xiachuan Fu, Xin Sheng and Siwen Xu

J. Mar. Sci. Eng. 2022, 10(9), 1324; https://doi.org/10.3390/jmse10091324 - 19 Sep 2022

Viewed by 1453

Abstract

Motivated by the need for a simple and effective assimilation scheme that could be used in a relocatable ocean model, a new assimilation algorithm called ensemble optimal smoothing (EnOS) was developed. This scheme was a straightforward extension of the ensemble optimal interpolation (EnOI) [...] Read more.

Motivated by the need for a simple and effective assimilation scheme that could be used in a relocatable ocean model, a new assimilation algorithm called ensemble optimal smoothing (EnOS) was developed. This scheme was a straightforward extension of the ensemble optimal interpolation (EnOI) by involving time correlation information in the Kalman gain. The main advantage of this scheme was the ability to estimate the present state from the time history of observation. We first examined the new scheme in an ideal ocean model using simulated observations. Further applying these two assimilation schemes to the Chinese offshore and adjacent waters, the root-mean-square error (RMSE) of the EnOS scheme was reduced by 6.4% relative to EnOI. The results showed that the EnOS was more efficient and effective in eliminating model errors when compared to the EnOI scheme. Full article

(This article belongs to the Section Ocean Engineering)

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16 pages, 4985 KiB

Open AccessArticle

Organic Geochemical Signatures of the Upper Miocene (Tortonian—Messinian) Sedimentary Succession Onshore Crete Island, Greece: Implications for Hydrocarbon Prospectivity

by Angelos G. Maravelis, George Kontakiotis, Spyridon Bellas, Assimina Antonarakou, Chrysanthos Botziolis, Hammad Tariq Janjuhah, Panayota Makri, Pierre Moissette, Jean-Jacques Cornée, Nikolaos Pasadakis, Emmanouil Manoutsoglou, Avraam Zelilidis and Vasileios Karakitsios

J. Mar. Sci. Eng. 2022, 10(9), 1323; https://doi.org/10.3390/jmse10091323 - 18 Sep 2022

Cited by 6 | Viewed by 2425

Abstract

The definition of pre-Messinian source rocks in the eastern Mediterranean is of paramount importance for hydrocarbon exploration because of the ability of salt to act as a high-quality seal rock. This research evaluates the organic geochemical features of the Upper Miocene (Tortonian—Messinian) sedimentary [...] Read more.

The definition of pre-Messinian source rocks in the eastern Mediterranean is of paramount importance for hydrocarbon exploration because of the ability of salt to act as a high-quality seal rock. This research evaluates the organic geochemical features of the Upper Miocene (Tortonian—Messinian) sedimentary succession onshore Crete Island, Greece. The study employs original (Messinian, Agios Myron Fm) and published (Tortonian, Viannos Fm, Skinias Fm, Moulia Fm, and Messinian Ploutis section) results from organic geochemical analyses of mudstone samples. One hundred and one samples were examined using standard organic geochemistry methodology (Rock-Eval II and VI-TOC) to define the origin, type, and degree of organic matter maturity. The data indicate that the studied samples have poor to fair gas-prone source rock potential. These possible source rock units have not experienced great temperatures during burial, and, thus, their organic matter is thermally immature. The sub-salt (Tortonian—Messinian) source rock units are likely to be of higher thermal maturity in the western and eastern south Cretan trenches because of tectonic subsidence and a thicker sedimentary overburden. Several traps can grow in these regions, associated with normal faults, rotated blocks and unconformities (both below and above the unconformities). This research provides a basis for the further evaluation of the hydrocarbon potential in Crete Island. It is an area that shares geological similarities with the surrounding regions that contain proven reserves and is of crucial economic and strategic importance. Full article

(This article belongs to the Special Issue Recent Advances in Geological Oceanography)

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26 pages, 14264 KiB

Open AccessArticle

An Integrated Monitoring System for Coastal and Riparian Areas Based on Remote Sensing and Machine Learning

by Anastasios Tzepkenlis, Nikos Grammalidis, Christos Kontopoulos, Vasiliki Charalampopoulou, Dimitra Kitsiou, Zoi Pataki, Anastasia Patera and Theodoros Nitis

J. Mar. Sci. Eng. 2022, 10(9), 1322; https://doi.org/10.3390/jmse10091322 - 18 Sep 2022

Cited by 7 | Viewed by 2807

Abstract

Nowadays, coastal areas are exposed to multiple hazards of increasing severity, such as coastal floods, erosion, subsidence due to a combination of natural and anthropogenic factors, including climate change and urbanisation. In order to cope with these challenges, new remote sensing monitoring solutions [...] Read more.

Nowadays, coastal areas are exposed to multiple hazards of increasing severity, such as coastal floods, erosion, subsidence due to a combination of natural and anthropogenic factors, including climate change and urbanisation. In order to cope with these challenges, new remote sensing monitoring solutions are required that are based on knowledge extraction and state of the art machine learning solutions that provide insights into the related physical mechanisms and allow the creation of innovative Decision Support Tools for managing authorities. In this paper, a novel user-friendly monitoring system is presented, based on state-of-the-art remote sensing and machine learning approaches. It uses processes for collecting and analysing data from various heterogeneous sources (satellite, in-situ, and other auxiliary data) for monitoring land cover and land use changes, coastline changes soil erosion, land deformations, and sea/ground water level. A rule-based Decision Support System (DSS) will be developed to evaluate changes over time and create alerts when needed. Finally, a WebGIS interface allows end-users to access and visualize information from the system. Experimental results deriving from various datasets are provided to assess the performance of the proposed system, which is implemented within the EPIPELAGIC bilateral Greece-China project. The system is currently being installed in the Greek case study area, namely Thermaikos Gulf in Thessaloniki, Greece. Full article

(This article belongs to the Special Issue Decision Support Systems and Tools in Coastal Areas)

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25 pages, 8726 KiB

Open AccessArticle

Hydraulic Performance of Geotextile Sand Containers for Coastal Defenses

by Sara Corvaro, Carlo Lorenzoni, Alessandro Mancinelli, Francesco Marini and Stefania Rocchi

J. Mar. Sci. Eng. 2022, 10(9), 1321; https://doi.org/10.3390/jmse10091321 - 18 Sep 2022

Viewed by 2205

Abstract

Laboratory experiments were performed in the wave flume of the Laboratorio di Idraulica e Costruzioni Marittime of the Università Politecnica delle Marche (Ancona, Italy) to study the hydrodynamic performance of coastal protection structures made of a new type of geotextile sand containers (GSCs). [...] Read more.

Laboratory experiments were performed in the wave flume of the Laboratorio di Idraulica e Costruzioni Marittime of the Università Politecnica delle Marche (Ancona, Italy) to study the hydrodynamic performance of coastal protection structures made of a new type of geotextile sand containers (GSCs). Such structures are used as softer and flexible alternatives to traditional hard coastal defenses made of concrete or rubble mound material. The GSC structures can also be used as temporary coastal protections during the winter period. The physical model reproduced two main configurations: in the former one, the GSCs were used as coastal revetments with three different slopes. In the latter one, the GSCs were applied to make detached submerged breakwaters with different submergences and berm widths. The geometric scale of the models was 1:10, and the weight of each GSC in the prototype was 5 t. The geotextile material of the containers and the wave characteristics were reproduced by using the Reynolds and the Froude similarity criteria, respectively. Reflection coefficients and hydraulic stability behaviors for the revetments, as well as transmission coefficients and piling-up amount for breakwaters, were obtained. Full article

(This article belongs to the Special Issue Non-conventional Coastal Protection Solutions)

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23 pages, 4936 KiB

Open AccessArticle

Impact of Design Parameters on the Dynamic Response and Fatigue of Offshore Jacket Foundations

by Ali Marjan and Phil Hart

J. Mar. Sci. Eng. 2022, 10(9), 1320; https://doi.org/10.3390/jmse10091320 - 18 Sep 2022

Cited by 4 | Viewed by 2826

Abstract

The lifetime of offshore foundations is governed by a combination of harsh environmental conditions and complex service loads. The fatigue limit state (FLS) analysis needs to be performed in the time domain to capture the complex phenomenon. This study aims to investigate different [...] Read more.

The lifetime of offshore foundations is governed by a combination of harsh environmental conditions and complex service loads. The fatigue limit state (FLS) analysis needs to be performed in the time domain to capture the complex phenomenon. This study aims to investigate different parameters and design modifications that can impact the design life of an offshore jacket foundation. An OC4 jacket foundation is designed in industrial software from DNV and reduced to a super-element model. The super-element model is connected to an NREL 5-MW wind turbine designed in Bladed. The time-series loads are used to compute the fatigue damages faced by the foundation during the service life. The impact of soil non-linearity, marine growth, scour size, the mass of the transition piece, and the grouted connection’s design on the dynamic response and fatigue damages are compared. A 30% increase in life was observed by replacing the concrete transition piece with a lightweight steel configuration. The fatigue damages were considerably greater for the inclined pile in the leg grouted connection than for the leg in the pile concept. The study provides a different perspective by analysing the effect of design parameters and design changes in the complex and computationally expensive time-series domain. Full article

(This article belongs to the Topic Advances in Wind Energy Technology)

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24 pages, 22080 KiB

Open AccessArticle

Incorporation of Deep Kernel Convolution into Density Clustering for Shipping AIS Data Denoising and Reconstruction

by Jufu Zhang, Xujie Ren, Huanhuan Li and Zaili Yang

J. Mar. Sci. Eng. 2022, 10(9), 1319; https://doi.org/10.3390/jmse10091319 - 18 Sep 2022

Cited by 2 | Viewed by 2277

Abstract

Automatic Identification System (AIS) equipment can aid in identifying ships, reducing ship collision risks and ensuring maritime safety. However, the explosion of massive AIS data has caused increasing data processing challenges affecting their practical applications. Specifically, mistakes, noise, and missing data are presented [...] Read more.

Automatic Identification System (AIS) equipment can aid in identifying ships, reducing ship collision risks and ensuring maritime safety. However, the explosion of massive AIS data has caused increasing data processing challenges affecting their practical applications. Specifically, mistakes, noise, and missing data are presented during AIS data transmission and encoding, resulting in poor data quality and inaccurate data sources that negatively impact maritime safety research. To address this issue, a robust AIS data denoising and reconstruction methodology was proposed to realise the data preprocessing for different applications in maritime transportation. It includes two parts: Density-Based Spatial Clustering of Applications with Noise based on Deep Kernel Convolution (DBSCANDKC) and the reconstruction method, which can extract high-quality AIS data to guarantee the accuracy of the related maritime research. Firstly, the kinematics feature was employed to remove apparent noise from the AIS data. The square deep kernel convolution was then incorporated into density clustering to find and remove possibly anomalous data. Finally, a piecewise cubic spline interpolation approach was applied to construct the missing denoised trajectory data. The experiments were implemented in the Arctic Ocean and Strait of Dover to demonstrate the effectiveness and performance of the proposed methodology in different shipping environments. This methodology makes significant contributions to future maritime situational awareness, collision avoidance, and robust trajectory development for safety at sea. Full article

(This article belongs to the Section Ocean Engineering)

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13 pages, 4773 KiB

Open AccessArticle

Dependence of Convective Cloud Properties and Their Transport on Cloud Fraction and GCM Resolution Diagnosed from a Cloud-Resolving Model Simulation

by Zhanjie Zhang and Guang J. Zhang

J. Mar. Sci. Eng. 2022, 10(9), 1318; https://doi.org/10.3390/jmse10091318 - 17 Sep 2022

Cited by 2 | Viewed by 1554

Abstract

The scale-aware convective parameterization for high resolution global climate models must satisfy the requirement that the parameterized subgrid convective transport diminishes as the model resolution increases to convection-resolving resolutions. A major assumption in current scale-aware convection schemes is that the differences between convective [...] Read more.

The scale-aware convective parameterization for high resolution global climate models must satisfy the requirement that the parameterized subgrid convective transport diminishes as the model resolution increases to convection-resolving resolutions. A major assumption in current scale-aware convection schemes is that the differences between convective cloud properties and their environmental counterparts are independent of cloud fraction. This study examines convective cloud vertical velocity, moist static energy (MSE), moisture, and the vertical eddy transport of MSE and moisture for different averaging subdomain sizes and fractional convective cloudiness using a cloud resolving model simulation of a midlatitude mesoscale convective system. Results show that convective cloud fraction, mass flux, and vertical transport of MSE and moisture increase with decreasing subdomain size. The differences between convective cloud properties in both updrafts and downdrafts and their environment depend on both cloud fraction and the averaging subdomain size. For a given subdomain size, the differences increase with cloud fraction, in contrast to the assumption used in current scale-aware convection parameterization schemes. A consequence of this is that the parameterized convective eddy transport reaches maximum at a higher cloud fraction than believed in previous studies. This has implications on how fast the subgrid convective transport should diminish as GCM resolution increases. Full article

(This article belongs to the Special Issue Numerical Modelling of Atmospheres and Oceans)

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22 pages, 6692 KiB

Open AccessArticle

An Investigation of the Effect of Utilizing Solidified Soil as Scour Protection for Offshore Wind Turbine Foundations via a Simplified Scour Resistance Test

by Jing Wang, Jinbo Xie, Yingjie Wu, Chen Wang and Fayun Liang

J. Mar. Sci. Eng. 2022, 10(9), 1317; https://doi.org/10.3390/jmse10091317 - 17 Sep 2022

Cited by 8 | Viewed by 2268

Abstract

Offshore wind power is rapidly developing as a source of clean energy. However, as local scour of the foundation of an offshore wind turbine can create serious safety risks to the normal operation of the turbine, it is necessary to protect the foundation [...] Read more.

Offshore wind power is rapidly developing as a source of clean energy. However, as local scour of the foundation of an offshore wind turbine can create serious safety risks to the normal operation of the turbine, it is necessary to protect the foundation from scour. In this paper, a new scour protection countermeasure using solidified soil has been investigated via an updated apparatus for a simplified scour resistance test (SSRT). Two types of tests were carried out: an unconfined compressive test to determine geotechnical parameters and an SSRT test to reflect the scour resistance of the soil samples. The results show that unconfined strength is approximately related to the critical flow velocity of the scour resistance as a power function. Soil samples having an unconfined compressive strength of 300 kPa can resist erosion under flow conditions above 3.14 m/s after solidification. In addition, the solidification state of the solidified soil has a great impact on the scour resistance of the soil sample, and the critical scour velocity of the final solidified soil is increased by 80–150% as compared to an initial solidified soil having the same final unconfined strength. These results suggest that attention should be paid to the state of the solidified soil during the construction process. The engineers should control the ratio of cement, water, and soil of the solidified soil according to the hydraulic parameters at the time of construction so that no great loss of solidified soil will occur during the construction process. Full article

(This article belongs to the Special Issue Advances in Offshore Geotechnics)

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22 pages, 1864 KiB

Open AccessArticle

Downsizing the Linear PM Generator in Wave Energy Conversion for Improved Economic Feasibility

by Jian Tan, Xuezhou Wang, Henk Polinder, Antonio Jarquin Laguna and Sape A. Miedema

J. Mar. Sci. Eng. 2022, 10(9), 1316; https://doi.org/10.3390/jmse10091316 - 17 Sep 2022

Cited by 9 | Viewed by 2010

Abstract

A crucial part of wave energy converters (WECs) is the power take-off (PTO) mechanism, and PTO sizing has been shown to have a considerable impact on the levelized cost of energy (LCOE). However, as a dominating type of PTO system in WECs, previous [...] Read more.

A crucial part of wave energy converters (WECs) is the power take-off (PTO) mechanism, and PTO sizing has been shown to have a considerable impact on the levelized cost of energy (LCOE). However, as a dominating type of PTO system in WECs, previous research pertinent to PTO sizing did not take modeling and optimization of the linear permanent magnet (PM) generator into consideration. To fill this gap, this paper provides an insight into how PTO sizing affects the performance of linear permanent magnet (PM) generators, and further the techno-economic performance of WECs. To thoroughly reveal the power production of the WEC, both hydrodynamic modeling and generator modeling are incorporated. In addition, three different methods for sizing the linear generator are applied and compared. The effect of the selection of the sizing method on the techno-economic performance of the WEC is identified. Furthermore, to realistically reflect the relevance of PTO sizing, wave resources from three European sea sites are considered in the techno-economic analysis. The dependence of PTO sizing on wave resources is demonstrated. Full article

(This article belongs to the Special Issue Optimization and Energy Maximizing Control Systems for Wave Energy Converters II)

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29 pages, 15398 KiB

Open AccessArticle

Simulated Short- and Long-Term Deformation in Coastal Karst Caves

by Chunxiu Lin, Chang Xia, Hong Zhang, Zhen Liu and Cuiying Zhou

J. Mar. Sci. Eng. 2022, 10(9), 1315; https://doi.org/10.3390/jmse10091315 - 17 Sep 2022

Cited by 4 | Viewed by 1980

Abstract

The self-balanced pressure arch theory is an important basis for excavation support in karst caves, but it is difficult to quantify the empirical theory in coastal areas. In addition, the rheological effects of karst strata could pose a hazard to engineering. Therefore, this [...] Read more.

The self-balanced pressure arch theory is an important basis for excavation support in karst caves, but it is difficult to quantify the empirical theory in coastal areas. In addition, the rheological effects of karst strata could pose a hazard to engineering. Therefore, this study investigated the rheological mechanism under the self-balanced pressure arch effect, and we proposed a mesoscopic unit rheological model for clay minerals in a water-rich environment. With the discrete element method (DEM), we realized the numerical modeling of the rheological model. Then, the proposed model is validated by a case study of foundation excavation in the coastal karst area of China. The mesoscopic mechanical characteristics of caves considering the influence of pressure arch are analyzed. The results show that the self-balance of the caverns mainly lies in the mesoscopic mineral strength and local stress. With the rheological controlled model, the final predicted convergent deformation of the foundation has an error of less than 10% compared with the field monitoring data. In this study, we can quantitively describe the self-balance effect of the pressure arch surrounding the caves and reveal the rheological mechanism. The proposed model can be applied to similar engineering with careful calibration and provide safety guidance. Full article

(This article belongs to the Section Coastal Engineering)

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12 pages, 1819 KiB

Open AccessArticle

Automatic Identification System (AIS) Data Supported Ship Trajectory Prediction and Analysis via a Deep Learning Model

by Xinqiang Chen, Chenxin Wei, Guiliang Zhou, Huafeng Wu, Zhongyu Wang and Salvatore Antonio Biancardo

J. Mar. Sci. Eng. 2022, 10(9), 1314; https://doi.org/10.3390/jmse10091314 - 16 Sep 2022

Cited by 17 | Viewed by 4598

Abstract

Automatic Identification System (AIS) data-supported ship trajectory analysis consistently helps maritime regulations and practitioners make reasonable traffic controlling and management decisions. Significant attentions are paid to obtain an accurate ship trajectory by learning data feature patterns in a feedforward manner. A ship may [...] Read more.

Automatic Identification System (AIS) data-supported ship trajectory analysis consistently helps maritime regulations and practitioners make reasonable traffic controlling and management decisions. Significant attentions are paid to obtain an accurate ship trajectory by learning data feature patterns in a feedforward manner. A ship may change her moving status to avoid potential traffic accident in inland waterways, and thus, the ship trajectory variation pattern may differ from previous data samples. The study proposes a novel ship trajectory exploitation and prediction framework with the help of the bidirectional long short-term memory (LSTM) (Bi-LSTM) model, which extracts intrinsic ship trajectory features with feedforward and backward manners. We have evaluated the proposed ship trajectory performance with single and multiple ship scenarios. The indicators of mean absolute error (MAE), mean absolute percentage error (MAPE) and mean square error (MSE) suggest that the proposed Bi-LSTM model can obtained satisfied ship trajectory prediction performance. Full article

(This article belongs to the Special Issue Marine Intelligent Transportation Systems: Data Mining and Control Optimization)

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30 pages, 671 KiB

Open AccessReview

Review of Hollow Fiber (HF) Membrane Filtration Technology for the Treatment of Oily Wastewater: Applications and Challenges

by Mahsa Keyvan Hosseini, Lei Liu, Parisa Keyvan Hosseini, Anisha Bhattacharyya, Kenneth Lee, Jiahe Miao and Bing Chen

J. Mar. Sci. Eng. 2022, 10(9), 1313; https://doi.org/10.3390/jmse10091313 - 16 Sep 2022

Cited by 12 | Viewed by 5120

Abstract

Oily wastewater has been recognized as a threat to the environment due to its hazardous nature and it can negatively affect the ecosystem, and threaten wildlife and human health. Physical, chemical, and biological technologies demonstrated a mixed performance in oily wastewater treatment, and, [...] Read more.

Oily wastewater has been recognized as a threat to the environment due to its hazardous nature and it can negatively affect the ecosystem, and threaten wildlife and human health. Physical, chemical, and biological technologies demonstrated a mixed performance in oily wastewater treatment, and, therefore, a proper treatment technology for oily wastewater needs to be addressed. Membrane filtration using a hollow fiber (HF) membrane is a promising alternative to remove emulsified oil from oily wastewater. This review discusses different sources of oily wastewater, various treatment methods, and membrane technology. The assessment has been focused on the parameters affecting HF membrane performance and applications of HF membrane-based technology to treat oily wastewater. This review paper reveals that HF membrane filtration systems have been previously used for the treatment of oily wastewater in bench-scale studies and few pilot-scale applications, which proved to be favorable in the treatment of recalcitrant wastewater containing oil and high salinity. Limitations associated with membrane fouling and the reduction of membrane permeability and membrane lifespan can be tackled and alleviated through modifying membrane chemistry and adjusting operational parameters. The compilation of studies showed that a low food/microorganism (F/M) ratio, long solid retention time (SRT) with high sludge age, long hydraulic retention time (HRT), and moderate aeration were the preferred operational parameters when treating oily wastewater. Based on this review, future studies should focus on optimizing the hydrodynamic conditions of the HF system, the commercialization of modified HF membranes, and the utilization of green technology in HF membrane construction to broaden HF membrane technology applications. Full article

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

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15 pages, 3453 KiB

Open AccessReview

A Review on Genus Halichondria (Demospongiae, Porifera)

by Josephine Goldstein and Peter Funch

J. Mar. Sci. Eng. 2022, 10(9), 1312; https://doi.org/10.3390/jmse10091312 - 16 Sep 2022

Cited by 6 | Viewed by 3541

Abstract

Demosponges of the genus Halichondria Fleming (1828) are common in coastal marine ecosystems worldwide and have been well-studied over the last decades. As ecologically important filter feeders, Halichondria species represent potentially suitable model organisms to link and fill in existing knowledge gaps in [...] Read more.

Demosponges of the genus Halichondria Fleming (1828) are common in coastal marine ecosystems worldwide and have been well-studied over the last decades. As ecologically important filter feeders, Halichondria species represent potentially suitable model organisms to link and fill in existing knowledge gaps in sponge biology, providing important novel insights into the physiology and evolution of the sponge holobiont. Here we review studies on the morphology, taxonomy, geographic distribution, associated fauna, life history, hydrodynamic characteristics, and coordinated behavior of Halichondria species. Full article

(This article belongs to the Special Issue Filter-Feeding in Marine Invertebrates)

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21 pages, 8894 KiB

Open AccessArticle

Underwater Anthropogenic Noise Pollution Assessment in Shallow Waters on the South-Eastern Coast of Spain

by Francisco Javier Rodrigo, Jaime Ramis, Jesus Carbajo and Pedro Poveda

J. Mar. Sci. Eng. 2022, 10(9), 1311; https://doi.org/10.3390/jmse10091311 - 16 Sep 2022

Cited by 3 | Viewed by 2815

Abstract

Anthropogenic noise is a growing threat to marine life due to the incrementation of human activity in the marine environment. In Europe, the Directive 2008/56/EC of the European Parliament and of the Council was published with the aim of establishing a framework for [...] Read more.

Anthropogenic noise is a growing threat to marine life due to the incrementation of human activity in the marine environment. In Europe, the Directive 2008/56/EC of the European Parliament and of the Council was published with the aim of establishing a framework for community action in the field of marine environmental policy. The directive introduces underwater acoustic energy, as detailed in Descriptor 11, and stipulates that the member states should set the threshold levels at which a good environmental status can be achieved by means of long-term monitoring campaigns. This research presents the results of a long-term underwater noise monitoring campaign with a duration of three years in the port of Cartagena located on the south-eastern coast of Spain, focusing on the monthly and annual variation patterns of low-frequency continuous noise. The acquired data are classified according to the source of the acoustic noise into shipping, other anthropogenic, and natural noise measurements. These three groups of measurements are processed in order to obtain one-third octave band levels centered at 63 and 125 Hz, as well as the overall bandwidth of unweighted Sound Pressure Level (SPL). The analysis of the measurements shows an increase in the annual average overall band of 4 and 3 dB of the natural and shipping noise, respectively, from 2013 to 2015. This monitoring campaign provides accurate acoustic values to establish threshold levels to achieve good environmental status and recommendations to conduct monitoring programs and regulations to control underwater noise pollution. Full article

(This article belongs to the Section Ocean Engineering)

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20 pages, 949 KiB

Open AccessFeature PaperReview

A Comprehensive Review of Canadian Marine Oil Spill Response System through the Lens of Decanting Regulations and Practices

by Naznin Sultana Daisy, Mohammad Hesam Hafezi, Lei Liu and Kenneth Lee

J. Mar. Sci. Eng. 2022, 10(9), 1310; https://doi.org/10.3390/jmse10091310 - 16 Sep 2022

Cited by 6 | Viewed by 3908

Abstract

Marine oil spill response operations could generate a large volume of liquid oily wastes (e.g., emulsified oil, non-emulsified oil, and wastewater) that can be up to 30 to 40 times greater than the original volume of spilled oil. Oil decanting technologies are used [...] Read more.

Marine oil spill response operations could generate a large volume of liquid oily wastes (e.g., emulsified oil, non-emulsified oil, and wastewater) that can be up to 30 to 40 times greater than the original volume of spilled oil. Oil decanting technologies are used globally for recovering spilled oil and handling liquid wastes. Canada follows the standards set out in the MARPOL 73/78 Annex 1 International regulations in most areas, with more strict discharge requirements in certain locations. For instance, inland waters discharge should not exceed 5 ppm, and in special areas, such as the Great Lakes, the discharge standard is under 0 ppm. In the event of an oil spill, decanted seawater should be barged to shore for disposal, which significantly constrains the response capacity and efficiency of oil recovery by skimmers due to limited temporary storage space in barges and the long time and high cost of transportation. This has become one of the greatest challenges the Canadian governments and oil spill response industries are facing in Canada. Moreover, when the spill response team decides that decanting is an appropriate way to handle the spilled oil, the approval process may take a long time, which negatively impacts the spill that has already occurred. Moreover, Canada uses a 10,000-tonne planning standard for oil spill preparedness, whereas the United States uses a worst-case scenario, and Europe uses a 60,000 m³ planning standard. The existing planning threshold in Canada can cause the country to be not fully prepared when it comes to responding to a very large oil spill if one should occur. This study conducted a comprehensive review of the current Canadian oil spill response system and framework, regulations, roles and responsibilities of federal and provincial governments, existing decanting capabilities, and capacities of Canadian oil spill responders. More importantly, this study identified the gaps in the current oil spill response system and regulatory and technological barriers to oil decanting. Marine oil decanting regulations and practices in the US and selected European countries have also been reviewed to support addressing the challenges and improving the Canadian experience. It is expected that this study would help the stakeholders and professionals to better understand the oil spill response system and oil decanting status quo in Canada and facilitate Canadian governments and industries to better address the challenges in oil spill regulations and practices. Full article

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

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18 pages, 12888 KiB

Open AccessArticle

Side-Scan Sonar Coupled with Scuba Diving Observation for Enhanced Monitoring of Benthic Artificial Reefs along the Coast of Terengganu, Peninsular Malaysia

by Azizi Ali, Muhammad Ruzi Abdullah, Che Din Mohd Safuan, Aminudin Muhammad Afiq-Firdaus, Zainudin Bachok, Mohd Fadzil Mohd Akhir, Roslan Latif, Azri Muhamad, Tan Hock Seng, Adina Roslee and Khaira Ismail

J. Mar. Sci. Eng. 2022, 10(9), 1309; https://doi.org/10.3390/jmse10091309 - 16 Sep 2022

Cited by 4 | Viewed by 2655

Abstract

Since the 1970s, artificial reef (AR) deployment has been one of the common approaches to augment the local production of coastal fish in Malaysia. However, there is a lack of strategy to assess and evaluate the success of pre-deployed AR. Realizing the need [...] Read more.

Since the 1970s, artificial reef (AR) deployment has been one of the common approaches to augment the local production of coastal fish in Malaysia. However, there is a lack of strategy to assess and evaluate the success of pre-deployed AR. Realizing the need for an effective qualitative and quantitative monitoring and evaluation of AR, this study proposes side-scan sonar coupled with scuba diving observation for the enhanced monitoring of pre-deployed Bioceramic Korean (BK) AR along the coast of Terengganu, Peninsular Malaysia. This method employs an integrated side-scan sonar with a data acquisition system for the detection of the precise location of the BK AR which were deployed at Tukun Telaga Batin off the Terengganu coastline in 2003 by the Fisheries Development Authority of Malaysia (FDAM). Following the determination of the exact location of three BK AR areas, a scuba diving team was sent to survey the physical conditions of the AR and assess the feasibility of the AR as an artificial habitat for marine life. The scan sonar images were compared with the captured photographs and videos acquired during the scuba diving session for a comprehensive value-added assessment. The collected data from the scuba diving session were also processed to measure the fish diversity, the fish biomass, and identify the fish community surrounding the AR. Based on the results, the BK AR remained in extremely good condition, physically intact, without significant breakage or damage, and with no major subsidence into the sediment after 19 years of deployment. A total of 108 BK AR modules were detected in three large groups using the mosaicked sonar images. Following cross-examination to validate the AR measurements using the AR’s shadows on the seafloor, the height of the BK AR consistently ranged from 1.7 m to 1.8 m. In addition, 34 species of fish from 14 families and 26 genera were identified, with most species classified as reef-associated (RA) fish with a biomass value of 1173.31 ± 1136.69 kg m⁻³, indicating the successfulness of the BK AR as fish-aggregating devices (FADs). The growth of hard corals on top of the bioceramic plate of the AR module further supported the diversified community of marine life surrounding the BK AR. In conclusion, the side-scan sonar coupled with scuba diving observation demonstrates an effective qualitative and quantitative technique for the monitoring and evaluation of pre-deployed AR. This strategy is recommended to be utilized to determine the success of pre-deployment AR. Full article

(This article belongs to the Special Issue Artificial Reefs Research)

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17 pages, 1782 KiB

Open AccessArticle

Formation Control of Unmanned Surface Vehicles Using Fixed-Time Non-Singular Terminal Sliding Mode Strategy

by Meng Joo Er and Zhongkun Li

J. Mar. Sci. Eng. 2022, 10(9), 1308; https://doi.org/10.3390/jmse10091308 - 15 Sep 2022

Cited by 5 | Viewed by 1981

Abstract

Unmanned surface vehicles (USVs) have been widely applied in the fields of marine hydrological exploration, marine resource exploration, area search, target detection, and military operations. In order to meet the demand of a complex ocean environment, USVs are frequently grouped together to improve [...] Read more.

Unmanned surface vehicles (USVs) have been widely applied in the fields of marine hydrological exploration, marine resource exploration, area search, target detection, and military operations. In order to meet the demand of a complex ocean environment, USVs are frequently grouped together to improve the reliability of mission accomplishment. In this paper, a fixed-time control strategy, combined with a non-singular terminal sliding mode, is proposed for the formation control of USVs under complex external disturbances and system uncertainties. The main contributions of this paper are: (1) the leader–follower formation control framework is divided into a tracking control subsystem and a formation control subsystem. A new fixed-time non-singular terminal sliding mode (FTNTSM) strategy is developed for the tracking control subsystem, which dramatically increases the convergence rate and ensures closed-loop fixed-time stability; (2) a finite-time uncertain observer (FUO) is designed to observe lumped uncertainty items, which greatly increase the stability and robustness of the formation system; (3) the FUO-based fixed-time formation control (FUOFT-FC) strategy is designed for the formation control subsystem, which ensures the fast and stable formation of USVs. Fixed-time convergence of the formation system is established by Lyapunov stability analysis. Rigorous simulation and comparative studies demonstrate that the proposed method is superior to the state-of-the-art methods. Full article

(This article belongs to the Special Issue Advanced Studies in the Autonomy and Control of Marine Vehicle Systems)

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13 pages, 5204 KiB

Open AccessArticle

Power Tracking Control of Marine Boiler-Turbine System Based on Fractional Order Model Predictive Control Algorithm

by Shiquan Zhao, Sizhe Wang, Ricardo Cajo, Weijie Ren and Bing Li

J. Mar. Sci. Eng. 2022, 10(9), 1307; https://doi.org/10.3390/jmse10091307 - 15 Sep 2022

Cited by 4 | Viewed by 2127

Abstract

The marine boiler-turbine system is the core part for the steam-powered ships with complicated dynamics. To improve the power tracking performance and fulfill the requirement of high utilization rate of fossil energy, the control performance of the system should be improved. In this [...] Read more.

The marine boiler-turbine system is the core part for the steam-powered ships with complicated dynamics. To improve the power tracking performance and fulfill the requirement of high utilization rate of fossil energy, the control performance of the system should be improved. In this paper, a nonlinear model predictive control method is proposed for the boiler-turbine system with fractional order cost functions. Firstly, a nonlinear model of the boiler-turbine system is introduced. Secondly, a nonlinear extended predictive self adaptive control(EPSAC) method is designed to the system. Then, integer order cost function is replaced with a fractional order cost function to improve the control performance, and also the configuration of the cost function is simplified. Finally, the superiority of the proposed method is proved accordring to the comparison experiments between the fractional order model predictive control and the traditional model predictive control. Full article

(This article belongs to the Special Issue Smart Control of Ship Propulsion System)

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19 pages, 13477 KiB

Open AccessArticle

Fragmentation Characteristics of Seafloor Massive Sulfides: A Coupled Fluid-Particle Flow Simulation

by Huan Dai, Hao Li and Yan Li

J. Mar. Sci. Eng. 2022, 10(9), 1306; https://doi.org/10.3390/jmse10091306 - 15 Sep 2022

Cited by 6 | Viewed by 1673

Abstract

The research on the fragmentation mechanism of seabed minerals under high ambient pressure significantly contributes to the exploitation of seafloor massive sulfides (SMS). In this paper, the uniaxial compressive strength (UCS) test and triaxial compressive strength (TCS) test were carried out on two [...] Read more.

The research on the fragmentation mechanism of seabed minerals under high ambient pressure significantly contributes to the exploitation of seafloor massive sulfides (SMS). In this paper, the uniaxial compressive strength (UCS) test and triaxial compressive strength (TCS) test were carried out on two kinds of SMS samples to obtain the key mechanical properties of minerals, including cohesion, internal friction angle, compressive strength, and elastic modulus. Then, based on these mechanical parameters, the fluid-solid coupling cutting model of two SMS samples at high ambient pressure is established by using the coupling method of discrete elements and smooth particles. A mixed-bond model is selected, and the microscopic parameters are determined by a repeated calibration process. Meanwhile, the cutting force and debris information are monitored and collected in real time during the whole cutting process. The results show that under different confining pressure environments, the model shows the transformation of minerals from brittleness to ductility. The cutting force increases with the increasing ambient pressure. Due to the fluid pressure, the crushing mechanism tends to shear failure, which is more likely to produce mud and finer fragments. Full article

(This article belongs to the Special Issue Recent Advances in Geological Oceanography)

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20 pages, 4010 KiB

Open AccessArticle

A Novel Discrete Group Teaching Optimization Algorithm for TSP Path Planning with Unmanned Surface Vehicles

by Shaolong Yang, Jin Huang, Weichao Li and Xianbo Xiang

J. Mar. Sci. Eng. 2022, 10(9), 1305; https://doi.org/10.3390/jmse10091305 - 15 Sep 2022

Cited by 8 | Viewed by 2045

Abstract

A growing number of researchers are interested in deploying unmanned surface vehicles (USVs) in support of ocean environmental monitoring. To accomplish these missions efficiently, multiple-waypoint path planning strategies for survey USVs are still a key challenge. The multiple-waypoint path planning problem, mathematically equivalent [...] Read more.

A growing number of researchers are interested in deploying unmanned surface vehicles (USVs) in support of ocean environmental monitoring. To accomplish these missions efficiently, multiple-waypoint path planning strategies for survey USVs are still a key challenge. The multiple-waypoint path planning problem, mathematically equivalent to the traveling salesman problem (TSP), is addressed in this paper using a discrete group teaching optimization algorithm (DGTOA). Generally, the algorithm consists of three phases. In the initialization phase, the DGTOA generates the initial sequence for students through greedy initialization. In the crossover phase, a new greedy crossover algorithm is introduced to increase diversity. In the mutation phase, to balance the exploration and exploitation, this paper proposes a dynamic adaptive neighborhood radius based on triangular probability selection to apply in the shift mutation algorithm, the inversion mutation algorithm, and the 3-opt mutation algorithm. To verify the performance of the DGTOA, fifteen benchmark cases from TSPLIB are implemented to compare the DGTOA with the discrete tree seed algorithm, discrete Jaya algorithm, artificial bee colony optimization, particle swarm optimization-ant colony optimization, and discrete shuffled frog-leaping algorithm. The results demonstrate that the DGTOA is a robust and competitive algorithm, especially for large-scale TSP problems. Meanwhile, the USV simulation results indicate that the DGTOA performs well in terms of exploration and exploitation. Full article

(This article belongs to the Section Marine Environmental Science)

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19 pages, 6862 KiB

Open AccessArticle

CFD Aided Ship Design and Helicopter Operation

by Weixing Yuan, Alanna Wall, Eric Thornhill, Chris Sideroff, Mahmoud Mamou and Richard Lee

J. Mar. Sci. Eng. 2022, 10(9), 1304; https://doi.org/10.3390/jmse10091304 - 15 Sep 2022

Cited by 3 | Viewed by 2223

Abstract

In support of Canadian industrial and defence ship design and offshore helicopter operations, a series of Ship–Helicopter Operational Limits Analysis and Simulation (SHOLAS) projects are being conducted at the National Research Council Canada (NRC) in collaboration with Defence Research and Development Canada (DRDC). [...] Read more.

In support of Canadian industrial and defence ship design and offshore helicopter operations, a series of Ship–Helicopter Operational Limits Analysis and Simulation (SHOLAS) projects are being conducted at the National Research Council Canada (NRC) in collaboration with Defence Research and Development Canada (DRDC). This study presents a brief overview of a Canadian in-house ship airwake simulation capability combining in-house high-fidelity wind-tunnel tests, full-scale sea trials, high-order computational fluid dynamics (CFD) tools, and realistic engineering-oriented flight simulators. This paper reports challenges and lessons learned during the course of the study, discusses the current capabilities and limitations of the CFD tools and the infrastructure required, and evaluates the gaps and barriers in industry adoption by focusing on how they could be overcome based on our current practice. After validating the CFD results of an updated version of a simplified frigate shape (SFS2) and the real-world Canadian Patrol Frigate (CPF), which are in reasonable agreement with the available in-house wind-tunnel and sea-trial data, the developed approach was recently applied to the design of an undisclosed Canadian ship. Among other applications, CFD airwake results were used with confidence as input to produce representative airwake features in industrial high-fidelity piloted flight simulators. Full article

(This article belongs to the Section Ocean Engineering)

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19 pages, 1073 KiB

Open AccessArticle

On the Non-Gaussianity of Sea Surface Elevations

by Alicia Nieto-Reyes

J. Mar. Sci. Eng. 2022, 10(9), 1303; https://doi.org/10.3390/jmse10091303 - 15 Sep 2022

Viewed by 1262

Abstract

The sea surface elevations are generally stated as non-Gaussian processes in the current literature, being considered Gaussian for short periods of relatively low wave heights. The objective here is to study the evolution of the distribution of the sea surface elevation from Gaussian [...] Read more.

The sea surface elevations are generally stated as non-Gaussian processes in the current literature, being considered Gaussian for short periods of relatively low wave heights. The objective here is to study the evolution of the distribution of the sea surface elevation from Gaussian to non-Gaussian as the period of time in which the associated time series is recorded increases. To do this, an empirical study based on the measurements of the buoys in the US coast downloaded at a casual day is performed. This study results in rejecting the null hypothesis of Gaussianity in below 25% of the cases for short periods of time and in over 95% of the cases for long periods of time. The analysis pursued relates to a recent one by the author in which the heights of sea waves are proved to be non-Gaussian. It is similar in that the Gaussianity of the process is studied as a whole and not just of its one-dimensional marginal, as it is common in the literature. It differs, however, in that the analysis of the sea surface elevations is harder from a statistical point of view, as the one-dimensional marginals can be Gaussian, which is observed throughout the study and in that a longitudinal study is performed here. Full article

(This article belongs to the Special Issue Challenges and Perspectives for Marine Data Science)

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17 pages, 7079 KiB

Open AccessArticle

Ice-Water-Gas Interaction during Icebreaking by an Airgun Bubble

by Qi-Gang Wu, Zuo-Cheng Wang, Bao-Yu Ni, Guang-Yu Yuan, Yuriy A. Semenov, Zhi-Yuan Li and Yan-Zhuo Xue

J. Mar. Sci. Eng. 2022, 10(9), 1302; https://doi.org/10.3390/jmse10091302 - 15 Sep 2022

Cited by 8 | Viewed by 1859

Abstract

When an airgun releases high-pressure gas underwater below an ice plate, it is observed that a bubble is formed rapidly while the ice plate is broken fiercely. In order to study the ice-water-gas interaction during this transient and violent phenomenon, a set of [...] Read more.

When an airgun releases high-pressure gas underwater below an ice plate, it is observed that a bubble is formed rapidly while the ice plate is broken fiercely. In order to study the ice-water-gas interaction during this transient and violent phenomenon, a set of laboratory-scale devices was designed and a series of icebreaking experiments were carried out. High-speed photography was used to capture the evolution of the bubble and the ice plate. It was found that the airgun bubble had a unique ‘pear’ shape compared with the spherical bubble generated by electric sparking. The pressure induced by the pulsation of the airgun bubble near a rigid wall was measured by the pressure sensor. The initial shockwave, oscillatory pressure peaks caused by the directional fast air injection, secondary shockwave, and pressure peak caused by the bubble jet impact were clearly recorded. Three damage patterns of ice plates were observed and corresponding reasons were analyzed. The influence of dimensionless parameters, such as airgun-ice distance

H

and ice thickness

T

, was also investigated. The physical mechanism of ice-water-gas interaction was summarized. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions II)

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J. Mar. Sci. Eng., Volume 10, Issue 9 (September 2022) – 167 articles

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