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J. Mar. Sci. Eng., Volume 9, Issue 8 (August 2021) – 131 articles

Cover Story (view full-size image): The open circulatory system of the shrimp Sicyonia ingentis lacks an endothelium and is lined by three types of acellular matrices. This scanning electron micrograph shows the wrinkled surface of a connective tissue sheath covering the midgut trunk of the shrimp with a pore opening to deeper layers of the sheath and gut wall. The two other matrices include a basal lamina around exposed cells and a fibrillin-like material lining major arteries extending from the heart. View this paper.
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23 pages, 23802 KiB  
Article
Variation and Episodes of Near-Inertial Internal Waves on the Continental Slope of the Southeastern East China Sea
by Bing Yang, Po Hu and Yijun Hou
J. Mar. Sci. Eng. 2021, 9(8), 916; https://doi.org/10.3390/jmse9080916 - 23 Aug 2021
Cited by 6 | Viewed by 3144
Abstract
Based on in situ observations, six episodes of near-inertial internal waves (NIWs) were detected on the East China Sea (ECS) continental slope, and the mechanisms and characteristics of them were examined. The generation mechanisms of the observed NIWs included typhoon, wind burst, lateral [...] Read more.
Based on in situ observations, six episodes of near-inertial internal waves (NIWs) were detected on the East China Sea (ECS) continental slope, and the mechanisms and characteristics of them were examined. The generation mechanisms of the observed NIWs included typhoon, wind burst, lateral propagation, and energy transfer from low-frequency flow. The depth-integrated near-inertial kinetic energy (NIKE) showed no significant seasonal variation, and the annual mean NIKE and near-inertial currents were 400 J/m2 and 3.50 cm/s, respectively. Downward propagation of NIKE was evident in the small wavenumber band according to the rotary vertical wavenumber spectra. The NIKE was subsurface-intensified, and the near-inertial vertical shear reached 0.01 s−1. The vertical phase speeds of the NIWs ranged from 5 to 19 m/h. The frequencies of the NIWs were mostly red-shifted, however, blue-shift also existed. One episode had both blue- and red-shifted frequencies vertically, and had both upward and downward propagating vertical phase speeds. The e-folding times of the observed NIWs ranged from 4 to 11 days, which were influenced by successive wind bursts and background vorticity. On the left-hand side of Kuroshio, the background vorticity is usually positive; however, the NIWs were almost red-shifted, which resulted from the Doppler shift of the Kuroshio. Full article
(This article belongs to the Special Issue Data Modelling for Coastal-Ocean Environments and Disasters)
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17 pages, 56783 KiB  
Article
The Underwater Soundscape at Gulf of Riga Marine-Protected Areas
by Muhammad Saladin Prawirasasra, Mirko Mustonen and Aleksander Klauson
J. Mar. Sci. Eng. 2021, 9(8), 915; https://doi.org/10.3390/jmse9080915 - 23 Aug 2021
Cited by 6 | Viewed by 4116
Abstract
Passive acoustic monitoring (PAM) is widely used as an initial step towards an assessment of environmental status. In the present study, underwater ambient sound recordings from two monitoring locations in marine-protected areas (MPAs) of the Gulf of Riga were analysed. Both locations belong [...] Read more.
Passive acoustic monitoring (PAM) is widely used as an initial step towards an assessment of environmental status. In the present study, underwater ambient sound recordings from two monitoring locations in marine-protected areas (MPAs) of the Gulf of Riga were analysed. Both locations belong to the natural habitat of pinnipeds whose vocalisations were detected and analysed. An increase of vocal activity during the mating period in the late winter was revealed, including percussive signallings of grey seals. The ambient sound spectra showed that in the current shallow sea conditions ship traffic noise contributed more in the higher frequency bands. Thus, a 500 Hz one-third octave band was chosen as an indicator frequency band for anthropogenic noise in the monitoring area. It was shown that changes in the soundscape occurring during the freezing period create favourable conditions for ship noise propagation at larger distances. Based on the monitoring data, the environmental risks related to the anthropogenic sound around the monitoring sites were considered as low. However, further analysis showed that for a small percentage of time the ship traffic can cause auditory masking for the ringed seals. Full article
(This article belongs to the Special Issue Ocean Noise: From Science to Management)
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11 pages, 2468 KiB  
Article
Analysis of Ship Noise Characteristics Generated According to Sailing Conditions of the G/T 1000-ton Stern Fishing Trawler
by Tae-ho Lee, Nam-u Lee, Dae-jae Lee and Bong-kyu Jung
J. Mar. Sci. Eng. 2021, 9(8), 914; https://doi.org/10.3390/jmse9080914 - 23 Aug 2021
Cited by 1 | Viewed by 4309
Abstract
In this study, we conducted onboard noise measurement experiments under the conditions of anchoring, sailing, casting, and hauling to determine whether noise generated in the G/T 1000-ton fishing trawler triggers zone-specific effects upon vessel operation. It was shown that most accommodation areas of [...] Read more.
In this study, we conducted onboard noise measurement experiments under the conditions of anchoring, sailing, casting, and hauling to determine whether noise generated in the G/T 1000-ton fishing trawler triggers zone-specific effects upon vessel operation. It was shown that most accommodation areas of the trawler comfortably met the IMO acceptance criteria regardless of the sailing condition, but most of the stern area, where the fishing actually occurs, exceeded the permitted limit of 75 dB (A). Furthermore, the statistical analysis revealed a significant difference (p < 0.05) only in the bow and the stern, which are both open areas. In the case of the former, improvements were deemed possible due to the influence of the fluid emission noise from the seawater piping in the bow, and the acceptance criteria were also appropriate. However, in the case of the latter, a significant difference was seen in hauling conditions, and on-site analysis confirmed frictional noise from hydraulic oil in the trawl winch and between the chains and the metal hull, leading to the conclusion that various improvements are required, such as the mandatory wearing of safety equipment by workers and stricter legal standards for permitted noise levels. Full article
(This article belongs to the Section Marine Biology)
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20 pages, 7804 KiB  
Review
A Unified Model for Analyzing Comprehensive Behaviors of Deepwater Anchors
by Haixiao Liu, Yancheng Yang and Jinsong Peng
J. Mar. Sci. Eng. 2021, 9(8), 913; https://doi.org/10.3390/jmse9080913 - 23 Aug 2021
Cited by 6 | Viewed by 2767
Abstract
Anchors may exhibit various complicated behaviors in the seabed, especially for deepwater anchors including gravity installed anchors (GIAs) and drag embedment plate anchors (drag anchors), stimulating the development of an efficient analytical tool that applies to a variety of anchors. The present paper [...] Read more.
Anchors may exhibit various complicated behaviors in the seabed, especially for deepwater anchors including gravity installed anchors (GIAs) and drag embedment plate anchors (drag anchors), stimulating the development of an efficient analytical tool that applies to a variety of anchors. The present paper introduces a unified model for analyzing different anchor behaviors in both clay and sand, consisting of unified concepts, mechanical models, and analytical procedure. The kinematic behaviors of the anchors are classified uniformly as three types, i.e., diving, pulling out, and keying. By utilizing the least-force principle, various anchor properties, such as the ultimate pullout capacity (UPC), failure mode, movement direction, embedment loss, and kinematic trajectory, can all be determined by the combination and analysis of the three behaviors. Applications of the model are demonstrated summarily, by solving the UPC and the failure mode of anchor piles and suction anchors, the kinematic trajectory of drag anchors in a single soil layer or layered soils, the maximum embedment loss (MEL) of suction embedded plate anchors (SEPLAs) and OMNI-Max anchors, and the kinematic behavior of OMNI-Max anchors. Compared to existing theoretical methods, this unified model shows strong applicability and potentiality in solving a variety of behaviors and properties of different anchors under complicated seabed conditions. Full article
(This article belongs to the Special Issue Instability and Failure of Subsea Structures)
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13 pages, 2612 KiB  
Review
Does Sand Beach Nourishment Enhance the Dispersion of Non-Indigenous Species?—The Case of the Common Moon Crab, Matuta victor (Fabricius, 1781), in the Southeastern Mediterranean
by Dov Zviely, Dror Zurel, Dor Edelist, Menashe Bitan and Ehud Spanier
J. Mar. Sci. Eng. 2021, 9(8), 911; https://doi.org/10.3390/jmse9080911 - 23 Aug 2021
Cited by 3 | Viewed by 3031
Abstract
Sand beach nourishment (BN) is one of the commonest “soft solutions” for shore protection and restoration. Yet it may have ecological consequences. Can this practice enhance the introduction and dispersal of non-indigenous species (NIS)? There has been little research on the impacts of [...] Read more.
Sand beach nourishment (BN) is one of the commonest “soft solutions” for shore protection and restoration. Yet it may have ecological consequences. Can this practice enhance the introduction and dispersal of non-indigenous species (NIS)? There has been little research on the impacts of nourishment on NIS, especially in the southeastern Mediterranean, a region considered most affected by invading biota. However, so far only one study referred to the possible interaction between BN and the success of invading species. It reports increasing numbers and densities of the aggressive, omnivorous Indo-Pacific moon crab, Matuta victor (Fabricius, 1781) in Haifa Bay (northern Israel) between 2011 and 2017. This research suggests a possible role of anthropogenic disturbance in the outbreak of M. victor and blames the Israel Ministry of Environmental Protection for authorizing a (rather small scale) BN in Haifa Bay in 2011 as an alleged cause for this outbreak. Circumstantial indirect evidence is not sufficient to establish the role of nourishment in promoting the establishment and dispersal of NIS. There are plenty of examples of successful settlement and rapid and large-scale distribution of NIS (including another member of the genus Matuta), especially in the eastern Mediterranean, without any BN in the region. Furthermore, the location where the M. victor specimens were sampled was exposed to more prevailing and frequent anthropogenic marine stressors than BN, such as eutrophication, pollution, fishing activities and particularly port construction. To firmly establish an assumed role of nourishment in the invasion of NIS, assessments must be based on solid and orderly planned scientific research to be designed well before the beginning of any BN. It is suggested that direct communication between environmental regulators and scientists is crucial for improving both scientific research and environmental management policies. Full article
(This article belongs to the Special Issue Sediment Dynamics in Artificial Nourishments)
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28 pages, 18959 KiB  
Article
Study on Hydrodynamic Characteristics and Environmental Response in Shantou Offshore Area
by Yuezhao Tang, Yang Wang, Enjin Zhao, Jiaji Yi, Kecong Feng, Hongbin Wang and Wanhu Wang
J. Mar. Sci. Eng. 2021, 9(8), 912; https://doi.org/10.3390/jmse9080912 - 22 Aug 2021
Cited by 5 | Viewed by 2592
Abstract
As a coastal trading city in China, Shantou has complex terrain and changeable sea conditions in its coastal waters. In order to better protect the coastal engineering and social property along the coast, based on the numerical simulation method, this paper constructed a [...] Read more.
As a coastal trading city in China, Shantou has complex terrain and changeable sea conditions in its coastal waters. In order to better protect the coastal engineering and social property along the coast, based on the numerical simulation method, this paper constructed a detailed hydrodynamic model of the Shantou sea area, and the measured tide elevation and tidal current were used to verify the accuracy of the model. Based on the simulation results, the tide elevation and current in the study area were analyzed, including the flood and ebb tides of astronomical spring tide, the flood and ebb tides of astronomical neap tide, the high tide, and the low tide. In order to find the main tidal constituent types in this sea, the influence of different tidal constituents on tide elevation and tidal current in the study area was analyzed. At the same time, the storm surge model of the study area was constructed, and the flow field under Typhoon “Mangkhut” in the study area was simulated by using the real recorded data. Typhoon wind fields with different recurrence periods and intensities were constructed to simulate the change in the flow field, the sea water level, and the disaster situation along the coast. The results showed that under normal sea conditions, the sea water flows from southwest to northeast at flood tide and the flow direction is opposite at ebb tide. The tidal range is large in the northwest and small in the southeast of the study area. The tides in the study area are mainly controlled by M2, S2, K1, and O1 tidal constituents, but N2, K2, P1, and Q1 tidal constituents have significant effects on the high water level. The water level caused by typhoons increases significantly along the coast of Shantou City. In the west area of the Rong River estuary, a typhoon with a lower central pressure than 910 hPa may induce a water increase of more than 2 m. Full article
(This article belongs to the Special Issue Monitoring and Modelling of Coastal Environment)
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11 pages, 911 KiB  
Article
Design of an Interactive Cellular System for the Remote Operation of Ocean Sensors: A Pilot Study Integrating Radioactivity Sensors
by Stylianos Alexakis and Christos Tsabaris
J. Mar. Sci. Eng. 2021, 9(8), 910; https://doi.org/10.3390/jmse9080910 - 22 Aug 2021
Cited by 6 | Viewed by 2289
Abstract
Ocean in-situ sensors are crucial for measuring oceanic parameters directly from the sea in a spatial and temporal basis. Real-time operation is used in many applications related to decision support tools and early warning services in case of accidents, incidents and/or disasters. The [...] Read more.
Ocean in-situ sensors are crucial for measuring oceanic parameters directly from the sea in a spatial and temporal basis. Real-time operation is used in many applications related to decision support tools and early warning services in case of accidents, incidents and/or disasters. The design of the proposed system is described as a rapid-response detection system, which aims to measure natural and artificial radioactive contaminants or other crucial ocean parameters, to replace the traditional method of sampling. The development of an interactive cellular system is undertaken using a commercial router that is programmed according to sensor specifications. A radioactivity sensor is integrated in a communication box enabling self-powered operation with a solar panel. The proposed system operates in (near) real-time mode and provides gamma-ray spectra by integrating the sensor and the appropriate electronic modules in it. Additionally, an on-site experiment was conducted to test the operability of the system in a real environment close to the sea, for monitoring fallout due to rainfall and snowfall events. The main intense radionuclides that were observed by different energy lines, were radon progenies (214Bi, 214Pb). The continuous operation of the whole system was controlled by operating the system during the winter period. Full article
(This article belongs to the Special Issue Application of Coastal/Ocean Sensors and Systems)
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27 pages, 7346 KiB  
Article
The Effects of Tidal Translation on Wave and Current Dynamics on a Barred Macrotidal Beach, Northern France
by Arnaud Héquette, Adrien Cartier and François G. Schmitt
J. Mar. Sci. Eng. 2021, 9(8), 909; https://doi.org/10.3390/jmse9080909 - 22 Aug 2021
Cited by 1 | Viewed by 2722
Abstract
Barred macrotidal beaches are affected by continuous horizontal displacements of different hydrodynamic zones associated with wave transformation (shoaling, breaker and surf zones) due to significant tide-induced water level changes. A series of wave and current meters, complemented by a video imagery system, were [...] Read more.
Barred macrotidal beaches are affected by continuous horizontal displacements of different hydrodynamic zones associated with wave transformation (shoaling, breaker and surf zones) due to significant tide-induced water level changes. A series of wave and current meters, complemented by a video imagery system, were deployed on a barred beach of northern France during a 6-day experiment in order to characterize the spatial and temporal variability of wave-induced processes across the beach. Wave and current spectral analyses and analyses of cross-shore current direction and asymmetry resulted in the identification of distinct hydrodynamic processes, including the development of infragravity waves and offshore-directed flows in the breaker and surf zones. Our results revealed a high spatial variability in the hydrodynamic processes across the beach, related to the bar-trough topography, as well as significant variations in the directions and intensity of cross-shore currents at fixed locations due to the horizontal translation of the different hydrodynamic zones resulting from continuous changes in water level due to tides. Full article
(This article belongs to the Special Issue Observational and Numerical Approaches in Coastal Sediment Dynamics and Hydrodynamics)
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14 pages, 3776 KiB  
Article
Ship Target Detection Algorithm Based on Improved YOLOv5
by Junchi Zhou, Ping Jiang, Airu Zou, Xinglin Chen and Wenwu Hu
J. Mar. Sci. Eng. 2021, 9(8), 908; https://doi.org/10.3390/jmse9080908 - 22 Aug 2021
Cited by 57 | Viewed by 6474
Abstract
In order to realize the real-time detection of an unmanned fishing speedboat near a ship ahead, a perception platform based on a target visual detection system was established. By controlling the depth and width of the model to analyze and compare training, it [...] Read more.
In order to realize the real-time detection of an unmanned fishing speedboat near a ship ahead, a perception platform based on a target visual detection system was established. By controlling the depth and width of the model to analyze and compare training, it was found that the 5S model had a fast detection speed but low accuracy, which was judged to be insufficient for detecting small targets. In this regard, this study improved the YOLOv5s algorithm, in which the initial frame of the target is re-clustered by K-means at the data input end, the receptive field area is expanded at the output end, and the loss function is optimized. The results show that the precision of the improved model’s detection for ship images was 98.0%, and the recall rate was 96.2%. Mean average precision (mAP) reached 98.6%, an increase of 4.4% compared to before the improvements, which shows that the improved model can realize the detection and identification of multiple types of ships, laying the foundation for subsequent path planning and automatic obstacle avoidance of unmanned ships. Full article
(This article belongs to the Special Issue Maritime Autonomous Vessels)
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10 pages, 1789 KiB  
Article
An Exact Algorithm for Task Allocation of Multiple Unmanned Surface Vehicles with Minimum Task Time
by Kai Xue, Zhiqin Huang, Ping Wang and Zeyu Xu
J. Mar. Sci. Eng. 2021, 9(8), 907; https://doi.org/10.3390/jmse9080907 - 22 Aug 2021
Cited by 13 | Viewed by 2734
Abstract
Task allocation of unmanned surface vehicles (USVs) with low task cost is an important research area which assigns USVs from starting points to different target points to complete tasks. Most of the research lines of task allocation are using heuristic algorithms to obtain [...] Read more.
Task allocation of unmanned surface vehicles (USVs) with low task cost is an important research area which assigns USVs from starting points to different target points to complete tasks. Most of the research lines of task allocation are using heuristic algorithms to obtain suboptimal solutions to reduce both the max task cost and total task cost. In practice, reducing the maximum is more important to task time, which is from the departure of USVs to the last USV arriving at the designated position. In this paper, an exact algorithm is proposed to minimize the max task time and reduce the total task time based on the Hungarian algorithm. In this algorithm, task time is composed of the travel time along the planned path and the turning time at initial and target points. The fast marching square method (FMS) is used to plan the travel path with obstacle avoidance. The effectiveness and practicability of the proposed algorithm are verified by comparing it with the Hungarian algorithm (HA), the auction algorithm (AA), the genetic algorithm (GA) and the ant colony optimization algorithm (ACO). The results of path planning and task allocation are displayed in the simulation. Full article
(This article belongs to the Special Issue Manoeuvring and Control of Ships and Other Marine Vehicles)
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25 pages, 24058 KiB  
Article
Using Cloud-Based Array Electromagnetics on the Path to Zero Carbon Footprint during the Energy Transition
by Kurt Strack, Sofia Davydycheva, Herminio Passalacqua, Maxim Smirnov and Xiayu Xu
J. Mar. Sci. Eng. 2021, 9(8), 906; https://doi.org/10.3390/jmse9080906 - 22 Aug 2021
Cited by 3 | Viewed by 2577
Abstract
Fluid imaging is one of the key geophysical technologies for the energy industry during energy transition to zero footprint. We propose better Cloud-based fluid distribution imaging to allow better, more optimized production, thus reducing carbon dioxide (CO2) footprint per barrel produced. [...] Read more.
Fluid imaging is one of the key geophysical technologies for the energy industry during energy transition to zero footprint. We propose better Cloud-based fluid distribution imaging to allow better, more optimized production, thus reducing carbon dioxide (CO2) footprint per barrel produced. For CO2 storage, the location knowledge of the stored fluids is mandatory. Electromagnetics is the preferred way to image reservoir fluids due to its strong coupling to the fluid resistivity. Unfortunately, acquiring and interpreting the data takes too long to contribute significantly to cost optimization of field operations. Using artificial intelligence and Cloud based data acquisition we can reduce the operational feedback to near real time and even, for the interpretation, to close to 24 h. This then opens new doors for the breakthrough of this technology from exploration to production and monitoring. It allows the application envelope to be enlarged to much noisier environments where real time acquisition can be optimized based on the acquired data. Once all components are commercialized, the full implementation could become a real game changer by providing near real time 3-dimensional subsurface images in support of the energy transition. Full article
(This article belongs to the Section Geological Oceanography)
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19 pages, 5939 KiB  
Article
Experimental Study on the Influence of Bulbous Bow Form on the Velocity Field around the Bow of a Trimaran Using Towed Underwater 2D-3C SPIV
by Rui Deng, Shigang Wang, Wanzhen Luo and Tiecheng Wu
J. Mar. Sci. Eng. 2021, 9(8), 905; https://doi.org/10.3390/jmse9080905 - 21 Aug 2021
Cited by 4 | Viewed by 2908
Abstract
In this study, particle image velocimetry was applied to measure the flow field around the bow region of a trimaran with different appendages. The dimensionless axial velocity u/U in test planes 1 and 2 of the testing model was measured by [...] Read more.
In this study, particle image velocimetry was applied to measure the flow field around the bow region of a trimaran with different appendages. The dimensionless axial velocity u/U in test planes 1 and 2 of the testing model was measured by using a towed underwater stereoscopic particle image velocimetry (SPIV) system. Based on the measured flow field data, the local sinkage values in test planes 1 and 2 of the testing model with different appendages at speeds of 1.766 and 2.943 m/s were presented. In addition, the effects of speed, bulbous bow type, T foils, and bow wave on the axial velocity u/U were studied in detail. The acquired experimental data help in understanding the distribution of the flow field around the ship bow, and the data can also act as a reference to verify computational fluid dynamics (CFD) results. Full article
(This article belongs to the Section Ocean Engineering)
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36 pages, 1740 KiB  
Review
Review on Ship Manoeuvrability Criteria and Standards
by Serge Sutulo and C. Guedes Soares
J. Mar. Sci. Eng. 2021, 9(8), 904; https://doi.org/10.3390/jmse9080904 - 21 Aug 2021
Cited by 17 | Viewed by 4637
Abstract
Possible reduction of the installed power on newly designed merchant ships triggered by requirements of the Energy Efficiency Design Indices (EEDI) raised concern in possible safety degradation and revived interest in manoeuvrability standards to make them capable to compensate for negative effects of [...] Read more.
Possible reduction of the installed power on newly designed merchant ships triggered by requirements of the Energy Efficiency Design Indices (EEDI) raised concern in possible safety degradation and revived interest in manoeuvrability standards to make them capable to compensate for negative effects of underpowering. A substantial part of the present article presents a detailed analytical review of general principles laid in the foundation of consistent safety standards in the naval architecture and analysis of the existing IMO manoeuvrability criteria and standards. Possible ways of extension of the existing standards to embrace situations associated with adverse sea and wind conditions are discussed and modification of the present standards related to the directional stability is considered as one of the possible solutions. At the same time, it was found that introduction of additional standards for the ship controllability in wind is justified, and the second part of the contribution is dedicated to developing a theoretical basis useful for devising such standards. This includes obtaining a set of analytical solutions related to the steady motion in wind and analysis of wind-tunnel data which resulted in simple equations for conservative generalized envelopes for the aerodynamic forces which are especially convenient for standardizing purposes. Possible design decisions aimed at augmentation of the ship’s capacity to resist adverse environmental factors are outlined. Full article
(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)
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25 pages, 15593 KiB  
Article
Rainfall Investigation by Means of Marine In Situ Gamma-ray Spectrometry in Ligurian Sea, Mediterranean Sea, Italy
by Dionisis L. Patiris, Sara Pensieri, Christos Tsabaris, Roberto Bozzano, Effrossyni G. Androulakaki, Marios N. Anagnostou and Stylianos Alexakis
J. Mar. Sci. Eng. 2021, 9(8), 903; https://doi.org/10.3390/jmse9080903 - 21 Aug 2021
Cited by 4 | Viewed by 2880
Abstract
Marine in situ gamma-ray spectrometry was utilized for a rainfall study at the W1M3A observing system in Ligurian Sea, Mediterranean Sea, Italy. From 7 June to 10 October 2016, underwater total gamma-ray counting rate (TCR) and the activity concentration of radon daughters 214 [...] Read more.
Marine in situ gamma-ray spectrometry was utilized for a rainfall study at the W1M3A observing system in Ligurian Sea, Mediterranean Sea, Italy. From 7 June to 10 October 2016, underwater total gamma-ray counting rate (TCR) and the activity concentration of radon daughters 214Pb, 214Bi and potassium 40K were continuously monitored along with ambient noise and meteorological parameters. TCR was proven as a good rainfall indicator as radon daughters’ fallout resulted in increased levels of marine radioactivity during and 2–3 h after the rainfall events. Cloud origin significantly affects TCR and radon progenies variations, as aerial mass trajectories, which extend upon terrestrial areas, result in higher increments. TCR and radon progenies concentrations revealed an increasing non-linear trend with rainfall height and intensity. 40K was proven to be an additional radio-tracer as its dilution was associated with rainfall height. 40K variations combined with 214Bi measurements can be used to investigate the mixing of rain- and seawater. In comparison with measurements in the atmosphere, the application of marine in situ gamma-ray spectrometry for precipitation investigation provided important advantages: allows quantitative measurement of the radionuclides; 40K can be used, along with radon daughters, as a radio-tracer; the mixing of rain- and seawater can be associated with meteorological parameters. Full article
(This article belongs to the Special Issue Application of Coastal/Ocean Sensors and Systems)
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13 pages, 2543 KiB  
Article
An Agent-Based Ship Firefighting Model
by Dean Sumic, Lada Males and Marko Rosic
J. Mar. Sci. Eng. 2021, 9(8), 902; https://doi.org/10.3390/jmse9080902 - 20 Aug 2021
Cited by 9 | Viewed by 2451
Abstract
Maritime safety is an ongoing process in shipping that is constantly being improved by the modernization of equipment and constant improvements in operators’ safety procedures and training. However, human error remains a significant factor in maritime accidents, as it contributes to 75% of [...] Read more.
Maritime safety is an ongoing process in shipping that is constantly being improved by the modernization of equipment and constant improvements in operators’ safety procedures and training. However, human error remains a significant factor in maritime accidents, as it contributes to 75% of incidents. Addressing this problem, the current paper shows a proof of principal for on-board fire monitoring and extinguishing software agents that may be used to upgrade present systems and contribute to an autonomous ship design. Agent technology that engages fire detection and firefighting equipment while minimizing human intervention will reduce the risks of human error and increase maritime safety. Full article
(This article belongs to the Section Ocean Engineering)
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16 pages, 4708 KiB  
Article
Research on Optimization and Verification of the Number of Stator Blades of kW Ammonia Working Medium Radial Flow Turbine in Ocean Thermal Energy Conversion
by Yun Chen, Yanjun Liu, Wei Yang, Yiming Wang, Li Zhang and Yongpeng Wu
J. Mar. Sci. Eng. 2021, 9(8), 901; https://doi.org/10.3390/jmse9080901 - 20 Aug 2021
Cited by 5 | Viewed by 2053
Abstract
Ocean Thermal Energy Conversion (OTEC) is one of the emerging industries of ocean energy and an important link in carbon neutrality. Turbine is a key component of ocean thermal energy conversion, which has an important impact on the performance and energy conversion efficiency [...] Read more.
Ocean Thermal Energy Conversion (OTEC) is one of the emerging industries of ocean energy and an important link in carbon neutrality. Turbine is a key component of ocean thermal energy conversion, which has an important impact on the performance and energy conversion efficiency of the system. This paper fully considers the application characteristics of ocean thermal energy conversion and the state conversion characteristics of ammonia working fluid. Taking the 100 kW radial inflow turbine in the OTEC application system as an example, based on the design, the turbine is optimized for the key parameters of the turbine stator and the influence of different geometric parameters is analyzed. Subsequently, the optimization results are verified by CFD numerical simulation analysis under different conditions. The results show that the number of stator blades has an important influence on the performance of the turbine. Further optimization studies have shown that through optimization, when the number of stator blades is 33, the internal flow field performance is the best, and the working conditions of the inlet and outlet working fluids are in accordance with the design points without obvious shock wave and reverse flow phenomenon, the efficiency is 89.46%, 3.94% higher than the design value. Full article
(This article belongs to the Special Issue Ocean Engineering and Oceanography for Carbon Neutralization)
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18 pages, 4742 KiB  
Article
A Universal Simulation Framework of Shipborne Inertial Sensors Based on the Ship Motion Model and Robot Operating System
by Qianfeng Jing, Haichao Wang, Bin Hu, Xiuwen Liu and Yong Yin
J. Mar. Sci. Eng. 2021, 9(8), 900; https://doi.org/10.3390/jmse9080900 - 20 Aug 2021
Cited by 7 | Viewed by 2985
Abstract
A complete virtual test environment is a powerful tool for Autonomous Surface Vessels (ASVs) research, and the simulation of ship motion and shipborne sensors is one of the prerequisites for constructing such an environment. This paper proposed a universal simulation framework of shipborne [...] Read more.
A complete virtual test environment is a powerful tool for Autonomous Surface Vessels (ASVs) research, and the simulation of ship motion and shipborne sensors is one of the prerequisites for constructing such an environment. This paper proposed a universal simulation framework of shipborne inertial sensors. A ship motion model considering environmental disturbances is proposed to simulate the six-degrees-of-freedom motion of ships. The discrete form of the inertial sensor stochastic error model is derived. The inertial measurement data are simulated by adding artificial errors to a simulated motion status. In addition, the ship motion simulation, inertial measurement simulation, and environment simulation nodes are implemented based on the computational graph architecture of the Robot Operating System (ROS). The benefit from the versatility of the ROS messages, the format of simulated inertial measurement is exactly the same as that of real sensors, which provides a research basis for the fusion perception algorithm based on visual–inertial and laser–inertial sensors in the research field of ASVs. Full article
(This article belongs to the Special Issue Explainable AI and Evaluation of Algorithms for Autonomous Marine Vehicles)
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17 pages, 2788 KiB  
Article
Contamination Evaluation of Heavy Metals in a Sediment Core from the Al-Salam Lagoon, Jeddah Coast, Saudi Arabia
by Ammar A. Mannaa, Athar Ali Khan, Rabea Haredy and Aaid G. Al-Zubieri
J. Mar. Sci. Eng. 2021, 9(8), 899; https://doi.org/10.3390/jmse9080899 - 20 Aug 2021
Cited by 12 | Viewed by 3212
Abstract
The Al-Salam Lagoon is one of the recreational sites along the Jeddah coast, showing the environmental impacts of urbanization along the coast. A sediment core (220 cm) was collected from the intertidal zone to evaluate the heavy metals (Fe, Mn, Cr, Ni, Cu, [...] Read more.
The Al-Salam Lagoon is one of the recreational sites along the Jeddah coast, showing the environmental impacts of urbanization along the coast. A sediment core (220 cm) was collected from the intertidal zone to evaluate the heavy metals (Fe, Mn, Cr, Ni, Cu, Zn, and Pb) and geochemical indices (contamination factor, geo-accumulation index, and pollution load index). In the organ-ic-rich muddy sediments (0–100 cm), there is a high metals content and a pollution load index of ~3, indicting anthropogenic impacts with high Cu contamination (CF:12) and moderate Fe, Mn, Cr, Ni, Zn, and Pb contamination (CF: <3). The organic matter and heavy metals washed through surface run-off from the land and deposited as urban waste. Down the core, consistent metals concentration, CF, and Igeo trends indicate a common pollutant source and pollution load variations over time. In the sediment section (70–40 cm), a high organic matter, metal concentration, CF, Igeo, and PLI value (≥5) suggest an uncontrolled pollution load. The decreased and stable trends of environmental indicators toward surface sediments suggest measures taken to control the pollution along the Jeddah coast. Below 110 cm, the carbonate-rich sediments have low organic matter and metals, showing an unpolluted depositional environment. The negative geo-accumulation index implies a geogenic source and indicates no anthropogenic impacts as inferred from low (~1.0) CF and PLI. Full article
(This article belongs to the Section Marine Environmental Science)
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31 pages, 14184 KiB  
Article
Hydrodynamic Climate of Port Phillip Bay
by Huy Quang Tran, David Provis and Alexander V. Babanin
J. Mar. Sci. Eng. 2021, 9(8), 898; https://doi.org/10.3390/jmse9080898 - 20 Aug 2021
Cited by 11 | Viewed by 5461
Abstract
This study is dedicated to the hydrodynamic climate of Port Phillip Bay (PPB)—a largest coastal lagoon system in Victoria, Australia. Novelty of the present study includes long-term hydrodynamic hindcast simulations integrated with a spectral wave model. Specifically, a coupled unstructured grid wave–current modelling [...] Read more.
This study is dedicated to the hydrodynamic climate of Port Phillip Bay (PPB)—a largest coastal lagoon system in Victoria, Australia. Novelty of the present study includes long-term hydrodynamic hindcast simulations integrated with a spectral wave model. Specifically, a coupled unstructured grid wave–current modelling system (SCHISM + WWM) was built upon a high resolution and advanced wave physics (ST6). This coupling system was thoroughly calibrated and validated against field observations prior to applying for 27-year hindcast and case scenarios. Data from these simulations were then used to investigate the hydrodynamic climate of PPB focusing on three main aspects: water levels, waves and currents. For sea levels, this study shows that tidal and extreme sea levels (storm tides) across a large part of PPB have a similar magnitude. The highest storm tide level is found along eastern coasts of the bay in line with the wind pattern. In the vicinity of the entrance, the extreme sea level slightly reduced, in line with wave decay due to coupling effects. This extreme level is lower than results reported by previous studies, which were not built on a wave–current coupled system. For the wave field, the mean wave direction inside PPB is strongly affected by seasonality, in line with wind patterns. The 100-year return significant wave height is above 2 m along the eastern coasts. At PPH, waves get refracted after passing the narrow entrance. For currents, this study shows that both mean variations and high percentile currents are not affected by seasonality. This highlights the fact that tidal currents dominate flow movements in PPB. However, in extreme conditions, the circulation in PPB is also driven by wind patterns, forming two gyre systems. Based on case scenarios simulations, the strongest magnitude of wind-driven currents is above 0.5 m/s and found in the confined shallow region in the southern portion of PPB. Full article
(This article belongs to the Special Issue Sea Level Rise: Drivers, Variability and Impacts)
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21 pages, 14501 KiB  
Article
Investigations of Hydraulic Power Take-Off Unit Parameters Effects on the Performance of the WAB-WECs in the Different Irregular Sea States
by Mohd Afifi Jusoh, Zulkifli Mohd Yusop, Aliashim Albani, Muhamad Zalani Daud and Mohd Zamri Ibrahim
J. Mar. Sci. Eng. 2021, 9(8), 897; https://doi.org/10.3390/jmse9080897 - 20 Aug 2021
Cited by 4 | Viewed by 2341
Abstract
Hydraulic power take-off (HPTO) is considered to be one of the most effective power take-off schemes for wave energy conversion systems (WECs). The HPTO unit can be constructed using standard hydraulic components that are readily available from the hydraulic industry market. However, the [...] Read more.
Hydraulic power take-off (HPTO) is considered to be one of the most effective power take-off schemes for wave energy conversion systems (WECs). The HPTO unit can be constructed using standard hydraulic components that are readily available from the hydraulic industry market. However, the construction and operation of the HPTO unit are more complex rather than other types of power take-off, as many components parameters need to be considered during the optimization. Generator damping, hydraulic motor displacement, hydraulic cylinder and accumulator size are among the important parameters that influence the HPTO performance in generating usable electricity. Therefore, the influence of these parameters on the amount of generated electrical power from the HPTO unit was investigated in the present study. A simulation study was conducted using MATLAB/Simulink software, in which a complete model of WECs was developed using the Simscape fluids toolbox. During the simulation, each parameters study of the HPTO unit were separately manipulated to investigate its effects on the WECs performance in five different sea states. Finally, the simulated result of the effect of HPTO parameters on the amount of generated electrical power from the HPTO unit in different sea states is given and discussed. Full article
(This article belongs to the Topic Marine Renewable Energy)
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20 pages, 25025 KiB  
Article
Verification and Validation of a Methodology to Numerically Generate Waves Using Transient Discrete Data as Prescribed Velocity Boundary Condition
by Rafael P. Maciel, Cristiano Fragassa, Bianca N. Machado, Luiz A. O. Rocha, Elizaldo D. dos Santos, Mateus N. Gomes and Liércio A. Isoldi
J. Mar. Sci. Eng. 2021, 9(8), 896; https://doi.org/10.3390/jmse9080896 - 19 Aug 2021
Cited by 10 | Viewed by 2798
Abstract
This work presents a two-dimensional numerical analysis of a wave channel and a oscillating water column (OWC) device. The main goal is to validate a methodology which uses transient velocity data as a means to impose velocity boundary condition for the generation of [...] Read more.
This work presents a two-dimensional numerical analysis of a wave channel and a oscillating water column (OWC) device. The main goal is to validate a methodology which uses transient velocity data as a means to impose velocity boundary condition for the generation of numerical waves. To achieve this, a numerical wave channel was simulated using regular waves with the same parameters as those used in a laboratory experiment. First, these waves were imposed as prescribed velocity boundary condition and compared with the analytical solution; then, the OWC device was inserted into the computational domain, aiming to validate this methodology. For the numerical analysis, computational fluid dynamics ANSYS Fluent software was employed, and to tackle with water–air interaction, the nonlinear multiphase model volume of fluid (VOF) was applied. Although the results obtained through the use of discrete data as velocity boundary condition presented a little disparity; in general, they showed a good agreement with laboratory experiment results. Since many studies use regular waves, there is a lack of analysis with ocean waves realistic data; thus, the proposed methodology stands out for its capacity of using realistic sea state data in numerical simulations regarding wave energy converters (WECs). Full article
(This article belongs to the Special Issue Wind and Wave Climate)
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15 pages, 4282 KiB  
Article
Additive Manufacturing and Maritime Spare Parts: Benefits and Obstacles for the End-Users
by Evanthia Kostidi, Nikitas Nikitakos and Iosif Progoulakis
J. Mar. Sci. Eng. 2021, 9(8), 895; https://doi.org/10.3390/jmse9080895 - 19 Aug 2021
Cited by 23 | Viewed by 4667
Abstract
3D printing or additive manufacturing (AM) (in the industrial context) is an innovative, as opposed to subtractive, technology, bringing new opportunities and benefits to the spare part supply chain (SPSC). The aim of this work is to capture the views of the stakeholders [...] Read more.
3D printing or additive manufacturing (AM) (in the industrial context) is an innovative, as opposed to subtractive, technology, bringing new opportunities and benefits to the spare part supply chain (SPSC). The aim of this work is to capture the views of the stakeholders at the end of the chain, extruding factors that will benefit the end-user and the factors that are likely to be an obstacle, by employing the questionnaire method. Company objectives regarding spares (cost reductions, improvement of services, space reduction) have been prioritized differently by the stakeholders. The most important barriers according to the participants are the quality assurance of the spare parts made by the new technology followed by the know-how and skills of staff. Other views such as suitable parts are suggested. The practical value of this work, in addition to assessing the readiness of the industry, is that it provides guidance for the successful implementation of AM in the maritime industry. Full article
(This article belongs to the Special Issue Advanced Research in Shipping Informatics and Communications)
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19 pages, 7826 KiB  
Article
An Experimental Analysis of Active Pitch Control for an Assault Amphibious Vehicle Considering Waterjet-Hydrofoil Interaction Effect
by Daehan Lee, Sanggi Ko, Jongyeol Park, Yong Cheol Kwon, Shin Hyung Rhee, Myungjun Jeon and Tae Hyung Kim
J. Mar. Sci. Eng. 2021, 9(8), 894; https://doi.org/10.3390/jmse9080894 - 19 Aug 2021
Cited by 8 | Viewed by 2485
Abstract
The present study aims to reduce the pitch motion of an assault amphibious vehicle system in seaways by waterjet impeller revolution rate control. A series of seakeeping tests were performed in a towing tank with a 1/4.5-scale model. This vehicle is manufactured as [...] Read more.
The present study aims to reduce the pitch motion of an assault amphibious vehicle system in seaways by waterjet impeller revolution rate control. A series of seakeeping tests were performed in a towing tank with a 1/4.5-scale model. This vehicle is manufactured as a box-shaped hull, and since an appendage that generates lift force is attached, the amount of change in pitch motion is large according to the forward speed. For pitch motion reduction, the impeller revolution rate and resultant pitch moment were controlled through a proportional-integral-derivative controller. Improvements in seakeeping performance were examined in both regular and irregular conditions by the model tests in terms of root mean square of pitch motion. The tuned controller decreased pitch motion by more than 60%. Full article
(This article belongs to the Section Ocean Engineering)
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25 pages, 11546 KiB  
Article
A Modelling Approach for the Assessment of Wave-Currents Interaction in the Black Sea
by Salvatore Causio, Stefania A. Ciliberti, Emanuela Clementi, Giovanni Coppini and Piero Lionello
J. Mar. Sci. Eng. 2021, 9(8), 893; https://doi.org/10.3390/jmse9080893 - 19 Aug 2021
Cited by 8 | Viewed by 3216
Abstract
In this study, we investigate wave-currents interaction for the first time in the Black Sea, implementing a coupled numerical system based on the ocean circulation model NEMO v4.0 and the third-generation wave model WaveWatchIII v5.16. The scope is to evaluate how the waves [...] Read more.
In this study, we investigate wave-currents interaction for the first time in the Black Sea, implementing a coupled numerical system based on the ocean circulation model NEMO v4.0 and the third-generation wave model WaveWatchIII v5.16. The scope is to evaluate how the waves impact the surface ocean dynamics, through assessment of temperature, salinity and surface currents. We provide also some evidence on the way currents may impact on sea-state. The physical processes considered here are Stokes–Coriolis force, sea-state dependent momentum flux, wave-induced vertical mixing, Doppler shift effect, and stability parameter for computation of effective wind speed. The numerical system is implemented for the Black Sea basin (the Azov Sea is not included) at a horizontal resolution of about 3 km and at 31 vertical levels for the hydrodynamics. Wave spectrum has been discretised into 30 frequencies and 24 directional bins. Extensive validation was conducted using in-situ and satellite observations over a five-year period (2015–2019). The largest positive impact of wave-currents interaction is found during Winter while the smallest is in Summer. In the uppermost 200 m of the Black Sea, the average reductions of temperature and salinity error are about −3% and −6%, respectively. Regarding waves, the coupling enhanced the model skill, reducing the simulation error, about −2%. Full article
(This article belongs to the Special Issue Ocean Modelling in Support of Operational Ocean and Coastal Services)
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19 pages, 21875 KiB  
Article
A Spectral Method for Two-Dimensional Ocean Acoustic Propagation
by Xian Ma, Yongxian Wang, Xiaoqian Zhu, Wei Liu, Qiang Lan and Wenbin Xiao
J. Mar. Sci. Eng. 2021, 9(8), 892; https://doi.org/10.3390/jmse9080892 - 19 Aug 2021
Cited by 12 | Viewed by 2840
Abstract
The accurate calculation of the sound field is one of the most concerning issues in hydroacoustics. The one-dimensional spectral method has been used to correctly solve simplified underwater acoustic propagation models, but it is difficult to solve actual ocean acoustic fields using this [...] Read more.
The accurate calculation of the sound field is one of the most concerning issues in hydroacoustics. The one-dimensional spectral method has been used to correctly solve simplified underwater acoustic propagation models, but it is difficult to solve actual ocean acoustic fields using this model due to its application conditions and approximation error. Therefore, it is necessary to develop a direct solution method for the two-dimensional Helmholtz equation of ocean acoustic propagation without using simplified models. Here, two commonly used spectral methods, Chebyshev–Galerkin and Chebyshev–collocation, are used to correctly solve the two-dimensional Helmholtz model equation. Since Chebyshev–collocation does not require harsh boundary conditions for the equation, it is then used to solve ocean acoustic propagation. The numerical calculation results are compared with analytical solutions to verify the correctness of the method. Compared with the mature Kraken program, the Chebyshev–collocation method exhibits higher numerical calculation accuracy. Therefore, the Chebyshev–collocation method can be used to directly solve the representative two-dimensional ocean acoustic propagation equation. Because there are no model constraints, the Chebyshev–collocation method has a wide range of applications and provides results with high accuracy, which is of great significance in the calculation of realistic ocean sound fields. Full article
(This article belongs to the Special Issue Technological Oceanography)
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20 pages, 81283 KiB  
Article
Analysis of the Makran Coastline of Iran’s Vulnerability to Global Sea-Level Rise
by Ezatollah Ghanavati, Majid Shah-Hosseini and Nick Marriner
J. Mar. Sci. Eng. 2021, 9(8), 891; https://doi.org/10.3390/jmse9080891 - 18 Aug 2021
Cited by 7 | Viewed by 6888
Abstract
The SE coast of Iran is of great economic and environmental importance. Global climate change affects this coastline through sea level rise (SLR), compounded by a decrease in sediment budgets in coastal areas. This study developed a Coastal Vulnerability Index (CVI) for the [...] Read more.
The SE coast of Iran is of great economic and environmental importance. Global climate change affects this coastline through sea level rise (SLR), compounded by a decrease in sediment budgets in coastal areas. This study developed a Coastal Vulnerability Index (CVI) for the SE coast of Iran using satellite, instrumental and field data. Eight risk variables were defined: coastal slope, regional coastal elevation, mean tidal range, mean significant wave height, rate of relative sea-level change, rate of shoreline change, environmental sensitivity and socio-economic sensitivity. The coast was divided into 27 segments based on geomorphic, environmental and socioeconomic traits. Coastal segments were categorized based on their vulnerability to each risk factor using a CVI. The resulting maps highlighted the vulnerability of each coastal segment to SLR. Approximately 50% of the coast is comprised of mostly rocky shores, which are less vulnerable to SLR. Approximately 33% of the coastal length, including sandy beaches, tidal flats and mangrove forests, were determined to be highly vulnerable to SLR. Approximately 12% of the coastline was determined to be moderately vulnerable. Population centers and infrastructure were ranked as highly-to-moderately vulnerable to SLR. This study highlighted the high vulnerability of low-lying areas, such as lagoons and mangroves, in the western part of the Iranian coast of Makran. Proper coastal management and mitigation plans are essential in the future to protect coastal societies and environments. Full article
(This article belongs to the Section Coastal Engineering)
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19 pages, 62076 KiB  
Article
Real-Time Nonlinear Model Predictive Controller for Multiple Degrees of Freedom Wave Energy Converters with Non-Ideal Power Take-Off
by Ali S. Haider, Ted K. A. Brekken and Alan McCall
J. Mar. Sci. Eng. 2021, 9(8), 890; https://doi.org/10.3390/jmse9080890 - 18 Aug 2021
Cited by 16 | Viewed by 3151
Abstract
An increase in wave energy converter (WEC) efficiency requires not only consideration of the nonlinear effects in the WEC dynamics and the power take-off (PTO) mechanisms, but also more integrated treatment of the whole system, i.e., the buoy dynamics, the PTO system, and [...] Read more.
An increase in wave energy converter (WEC) efficiency requires not only consideration of the nonlinear effects in the WEC dynamics and the power take-off (PTO) mechanisms, but also more integrated treatment of the whole system, i.e., the buoy dynamics, the PTO system, and the control strategy. It results in an optimization formulation that has a nonquadratic and nonstandard cost functional. This article presents the application of real-time nonlinear model predictive controller (NMPC) to two degrees of freedom point absorber type WEC with highly nonlinear PTO characteristics. The nonlinear effects, such as the fluid viscous drag, are also included in the plant dynamics. The controller is implemented on a real-time target machine, and the WEC device is emulated in real-time using the WECSIM toolbox. The results for the successful performance of the design are presented for irregular waves under linear and nonlinear hydrodynamic conditions. Full article
(This article belongs to the Special Issue Optimization and Energy Maximizing Control Systems for Wave Energy Converters)
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26 pages, 9161 KiB  
Article
Coupled Flow-Seepage-Elastoplastic Modeling for Competition Mechanism between Lateral Instability and Tunnel Erosion of a Submarine Pipeline
by Yumin Shi, Fuping Gao, Ning Wang and Zhenyu Yin
J. Mar. Sci. Eng. 2021, 9(8), 889; https://doi.org/10.3390/jmse9080889 - 18 Aug 2021
Cited by 9 | Viewed by 2947
Abstract
The instability of a partially embedded pipeline under ocean currents involves complex fluid–pipe–soil interactions, which may induce two typical instability modes; i.e., the lateral instability of the pipe and the tunnel erosion of the underlying soil. In previous studies, such two instability modes [...] Read more.
The instability of a partially embedded pipeline under ocean currents involves complex fluid–pipe–soil interactions, which may induce two typical instability modes; i.e., the lateral instability of the pipe and the tunnel erosion of the underlying soil. In previous studies, such two instability modes were widely investigated, but separately. To reveal the competition mechanism between the lateral instability and the tunnel erosion, a coupled flow-seepage-elastoplastic modeling approach was proposed that could realize the synchronous simulation of the pipe hydrodynamics, the seepage flow, and elastoplastic behavior of the seabed soil beneath the pipe. The coupling algorithm was provided for flow-seepage-elastoplastic simulations. The proposed model was verified through experimental and numerical results. Based on the instability criteria for the lateral instability and tunnel erosion, the two instability modes and their corresponding critical flow velocities could be determined. The instability envelope for the flow–pipe–soil interaction was established eventually, and could be described by three parameters; i.e., the critical flow velocity (Ucr), the embedment-to-diameter ratio (e/D), and the non-dimensional submerged weight of the pipe (G). There existed a transition line on the envelope when switching from one instability mode to the other. If the flow velocity of ocean currents gets beyond the instability envelope, either tunnel erosion or lateral instability could be triggered. With increasing e/D or concurrently decreasing G, the lateral instability was more prone to being triggered than the tunnel erosion. The present analyses may provide a physical insight into the dual-mode competition mechanism for the current-induced instability of submarine pipelines. Full article
(This article belongs to the Special Issue Instability and Failure of Subsea Structures)
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18 pages, 2151 KiB  
Article
Classification of Reservoir Recovery Factor for Oil and Gas Reservoirs: A Multi-Objective Feature Selection Approach
by Qasem Al-Tashi, Emelia Akashah Patah Akhir, Said Jadid Abdulkadir, Seyedali Mirjalili, Tareq M. Shami, Hitham Alhusssian, Alawi Alqushaibi, Ayed Alwadain, Abdullateef O. Balogun and Nasser Al-Zidi
J. Mar. Sci. Eng. 2021, 9(8), 888; https://doi.org/10.3390/jmse9080888 - 18 Aug 2021
Cited by 9 | Viewed by 3440
Abstract
The accurate classification of reservoir recovery factor is dampened by irregularities such as noisy and high-dimensional features associated with the reservoir measurements or characterization. These irregularities, especially a larger number of features, make it difficult to perform accurate classification of reservoir recovery factor, [...] Read more.
The accurate classification of reservoir recovery factor is dampened by irregularities such as noisy and high-dimensional features associated with the reservoir measurements or characterization. These irregularities, especially a larger number of features, make it difficult to perform accurate classification of reservoir recovery factor, as the generated reservoir features are usually heterogeneous. Consequently, it is imperative to select relevant reservoir features while preserving or amplifying reservoir recovery accuracy. This phenomenon can be treated as a multi-objective optimization problem, since there are two conflicting objectives: minimizing the number of measurements and preserving high recovery classification accuracy. In this study, wrapper-based multi-objective feature selection approaches are proposed to estimate the set of Pareto optimal solutions that represents the optimum trade-off between these two objectives. Specifically, three multi-objective optimization algorithms—Non-dominated Sorting Genetic Algorithm II (NSGA-II), Multi-Objective Grey Wolf Optimizer (MOGWO) and Multi-Objective Particle Swarm Optimization (MOPSO)—are investigated in selecting relevant features from the reservoir dataset. To the best of our knowledge, this is the first time multi-objective optimization has been used for reservoir recovery factor classification. The Artificial Neural Network (ANN) classification algorithm is used to evaluate the selected reservoir features. Findings from the experimental results show that the proposed MOGWO-ANN outperforms the other two approaches (MOPSO and NSGA-II) in terms of producing non-dominated solutions with a small subset of features and reduced classification error rate. Full article
(This article belongs to the Special Issue Applications of AI Tools in Petroleum Industry from Geosciences to Engineering)
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18 pages, 4977 KiB  
Article
Functionality Investigation of the UAV Arranged FMCW Solid-State Marine Radar
by Saulius Rudys, Andrius Laučys, Dainius Udris, Raimondas Pomarnacki and Domantas Bručas
J. Mar. Sci. Eng. 2021, 9(8), 887; https://doi.org/10.3390/jmse9080887 - 18 Aug 2021
Cited by 5 | Viewed by 2972
Abstract
Some models of marine radars are light-weight enough and thus are attractive for potential applications when arranged on UAVs. Elevating a marine radar to high altitudes provides a much wider field of view, however, this could lead to a higher radio interference level. [...] Read more.
Some models of marine radars are light-weight enough and thus are attractive for potential applications when arranged on UAVs. Elevating a marine radar to high altitudes provides a much wider field of view, however, this could lead to a higher radio interference level. The practical estimation of the radio interferences affecting the solid-state FMCW marine radar at altitudes up to 120 m was the main objective of this contribution. A rotary-wing octocopter UAV was developed and built for the experiments. Two different kinds of interferences were observed at higher altitudes. Ray-like interferences were caused by signals, which are received by the radar’s antenna. Circle-like interferences appear due to the low frequency interfering signal directly penetrating the detector due to insufficient receiver screening. Full article
(This article belongs to the Section Ocean Engineering)
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