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Volume 10
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J. Mar. Sci. Eng., Volume 10, Issue 4 (April 2022) – 107 articles

Cover Story (view full-size image): The increase in partial pressure of CO2 in the oceans directly affects the productivity and survival of coastal industries and ecosystems. For marine aquaculture, the decreased alkalinity of seawater results in reduced availability of carbonates for marine organisms to build their shells, leading to decreased aquaculture quality and productivity. The industry has been implementing recirculating aquaculture systems (RASs) to reduce CO2 in feedwaters, but recent interest in ocean-based CO2 capture has led to additional strategies that may be relevant. The new methods in addition to CO2 removal offer capture options for enhanced aquaculture sustainability. View this paper
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22 pages, 48666 KiB  
Article
Multi-Scale Influence of Flexible Submerged Aquatic Vegetation (SAV) on Estuarine Hydrodynamics
by Elizabeth R. Holzenthal, David F. Hill and Meagan E. Wengrove
J. Mar. Sci. Eng. 2022, 10(4), 554; https://doi.org/10.3390/jmse10040554 - 18 Apr 2022
Cited by 3 | Viewed by 2167
Abstract
Bottom friction is an important process in coastal and estuarine environments because it can reduce wave heights and moderate tidal currents. When modeling large systems with spatially varying hydraulic properties, bottom friction values are commonly derived from land use classification products. However, estimation [...] Read more.
Bottom friction is an important process in coastal and estuarine environments because it can reduce wave heights and moderate tidal currents. When modeling large systems with spatially varying hydraulic properties, bottom friction values are commonly derived from land use classification products. However, estimation of bottom friction for vegetated areas can be more challenging due to the complicated and time-varying geometry of the roughness elements. This is particularly true of flexible, buoyant submerged aquatic vegetation (SAV) species, such as seagrasses and kelps, that deform under waves and currents. In this study we incorporate a dynamic friction model that includes the temporal variation in SAV drag forces into a depth-integrated coupled circulation-wave model. In vegetated areas, the bottom friction is continuously updated based on plant geometry, water depth, and combined wave-current velocities. Taking a multi-scale approach, we use the model to investigate the impact of SAV dynamics on both the localized and the integrated bay-wide hydrodynamics of a riverine and tidally influenced estuary. First, we investigate SAV modification of velocity fields and its implications for sediment transport and circulation pathways. Then, we show how SAV can modify tidal behavior throughout the estuary. Full article
(This article belongs to the Section Coastal Engineering)
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8 pages, 1584 KiB  
Article
Enhanced Electroremediation of Metals from Dredged Marine Sediment under Periodic Voltage Using EDDS and Citric Acid
by Mohamed-Tahar Ammami, Ahmed Benamar and Florence Portet-Koltalo
J. Mar. Sci. Eng. 2022, 10(4), 553; https://doi.org/10.3390/jmse10040553 - 18 Apr 2022
Cited by 6 | Viewed by 2029
Abstract
The electrokinetic remediation (EKR) method has been extensively considered for the removal of inorganic pollutants from contaminated dredged sediment. In addition, the use of chelating agents as electrolyte solutions has been beneficial in increasing the mobility of metals. This study investigated the metals’ [...] Read more.
The electrokinetic remediation (EKR) method has been extensively considered for the removal of inorganic pollutants from contaminated dredged sediment. In addition, the use of chelating agents as electrolyte solutions has been beneficial in increasing the mobility of metals. This study investigated the metals’ (Cd, Cr, Cu, Pb, and Zn) mobilities by assessing the effect of two environmentally friendly chelating agents, ethylenediaminedisuccinic acid (EDDS) and citric acid (CA), in enhancing the EKR efficiency under a periodic voltage gradient. The results showed that, for the same concentration (0.1 mol L−1), CA is more suitable for enhancing the removal of Cr (67.83%), Cu (59.77%), and Pb (32.05%) by chelating and desorbing them from the sediment matrix and concentrating them in the electrode compartments. EDDS provided efficiency to improve the Cd extraction percentage (45.87%), whereas CA and EDDS had comparable improvement removal impacts on Zn EKR (39.32% and 41.37%, respectively). From the comparison with previous results obtained with a continuous voltage, applying a periodic voltage gradient associated with a low concentration of chelating agents led to a promising result. Full article
(This article belongs to the Special Issue Sediment Remediation at Harbour)
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24 pages, 8543 KiB  
Article
Natural Convection Induced by Diurnal Heating and Cooling over a Fully Vegetated Slope
by Xiaosheng Ji, Yi-Qi Ye, Bo Wang and Ying-Tien Lin
J. Mar. Sci. Eng. 2022, 10(4), 552; https://doi.org/10.3390/jmse10040552 - 18 Apr 2022
Cited by 3 | Viewed by 1668
Abstract
In this study, by assuming a small bottom slope, asymptotic solutions were developed to discuss natural convection within rooted emergent vegetation in response to different heating and cooling mechanisms. Based upon the maximum water depth in comparison to the penetration depth of solar [...] Read more.
In this study, by assuming a small bottom slope, asymptotic solutions were developed to discuss natural convection within rooted emergent vegetation in response to different heating and cooling mechanisms. Based upon the maximum water depth in comparison to the penetration depth of solar radiation, two scenarios in shallow and deep waters were examined. The temperature structures showed that isotherms in shallows are near vertical but become stable stratified layers (horizontal isotherms) in deep regions. In shallow regions, horizontal velocity profiles perform classic cubic shapes, while the horizontal velocity in deep regions is constant near the surface, and a local upslope flow occurs near the bottom. In shallow water, viscous effects are dominant to shape the velocity profiles, whereas vegetation drag becomes more important in deep regions. By using turbulent parameters, horizontal exchange flowrates and velocities predicted by the asymptotic solutions show good agreements with the existing measurements. Full article
(This article belongs to the Special Issue Recent Development and Application of Hydrodynamics in Marine Environment)
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36 pages, 28138 KiB  
Article
Integration of Node Classification in Storm Surge Surrogate Modeling
by Aikaterini P. Kyprioti, Alexandros A. Taflanidis, Norberto C. Nadal-Caraballo, Madison C. Yawn and Luke A. Aucoin
J. Mar. Sci. Eng. 2022, 10(4), 551; https://doi.org/10.3390/jmse10040551 - 17 Apr 2022
Cited by 4 | Viewed by 2050
Abstract
Surrogate models, also referenced as metamodels, have emerged as attractive data-driven, predictive models for storm surge estimation. They are calibrated based on an existing database of synthetic storm simulations and can provide fast-to-compute approximations of the expected storm surge, replacing the numerical model [...] Read more.
Surrogate models, also referenced as metamodels, have emerged as attractive data-driven, predictive models for storm surge estimation. They are calibrated based on an existing database of synthetic storm simulations and can provide fast-to-compute approximations of the expected storm surge, replacing the numerical model that was used to establish this database. This paper discusses specifically the development of a kriging metamodel for the prediction of peak storm surges. For nearshore nodes that have remained dry in some of the synthetic storm simulations, a necessary first step, before the metamodel calibration, is the imputation of the database to address the missing data corresponding to such dry instances to estimate the so-called pseudo-surge. This imputation is typically performed using a geospatial interpolation technique, with the k nearest-neighbor (kNN) interpolation being the one chosen for this purpose in this paper. The pseudo-surge estimates obtained from such an imputation may lead to an erroneous classification for some instances, with nodes classified as inundated (pseudo-surge greater than the node elevation), even though they were actually dry. The integration of a secondary node classification surrogate model was recently proposed to address the challenges associated with such erroneous information. This contribution further examines the above integration and offers several advances. The benefits of implementing the secondary surrogate model are carefully examined across nodes with different characteristics, revealing important trends for the necessity of integrating the classifier in the surge predictions. Additionally, the combination of the two surrogate models using a probabilistic characterization of the node classification, instead of a deterministic one, is considered. The synthetic storm database used to illustrate the surrogate model advances corresponds to 645 synthetic tropical cyclones (TCs) developed for a flood study in the Louisiana region. The fact that various flood protective measures are present in the region creates interesting scenarios with respect to the groups of nodes that remain dry for some storms behind these protected zones. Advances in the kNN interpolation methodology, used for the geospatial imputation, are also presented to address these unique features, considering the connectivity of nodes within the hydrodynamic simulation model. Full article
(This article belongs to the Section Physical Oceanography)
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18 pages, 29551 KiB  
Article
Relationship between the Spatial and Temporal Distribution of Squid-Jigging Vessels Operations and Marine Environment in the North Pacific Ocean
by Yingjie Fei, Shenglong Yang, Wei Fan, Huimin Shi, Han Zhang and Sanling Yuan
J. Mar. Sci. Eng. 2022, 10(4), 550; https://doi.org/10.3390/jmse10040550 - 17 Apr 2022
Cited by 9 | Viewed by 2680
Abstract
Information and understanding of fishing activities at sea is important to fisheries science, public authorities and policy-makers. To understand the spatial–temporal distribution characteristics of squid-jigging vessels and how the marine environment affects the distribution of squid-jigging vessels in the North Pacific Ocean, operation [...] Read more.
Information and understanding of fishing activities at sea is important to fisheries science, public authorities and policy-makers. To understand the spatial–temporal distribution characteristics of squid-jigging vessels and how the marine environment affects the distribution of squid-jigging vessels in the North Pacific Ocean, operation behavior of the squid-jigging vessels was analysed by using spatial–temporal factors and marine environmental factors. The fishing effort (FE) information was calculated based on automatic identification system (AIS) data of squid-jigging fishing vessels in the North Pacific Ocean from July to November in 2017 to 2020, and the overlay maps of the spatial distribution of environmental factors and fishing effort were plotted together with four environmental variables (sea surface temperature (SST), sea surface height (SSH), sea surface salinity (SSS), and concentration of chlorophyll-a (Chla)). A generalized additive model (GAM) was used to investigate the nonlinear influence of the marine environment on squid-jigging fishing vessel activity in the North Pacific Ocean. The results show that fishing effort increased from July to August and then decreased from September to November. The fishing effort was highest in August. The intensity of the fishing effort suggests squid-jigging vessel operations had significant seasonal variations. The overlay maps suggest that the fishing effort of squid-jigging vessels was mainly located in areas where SST was between 10∘C and 20∘C, SSH was between −0.3m and 0.2m, SSS was between 32×10−3 and 34×10−3, and Chla was between 0.1mg·m−3 and 0.4mg·m−3. The generalized additive model indicated evidence of nonlinear relationships between fishing effort and the three environmental factors. The favorable ranges of SST, SSH, SSS and Chla for fishing effort were 15∘C∼18∘C, 0∼0.2m, 33×10−3∼34×10−3 and 0.2mg·m−3∼0.4mg·m−3, respectively. Moreover, the area beneficial to fishing effort was in 41∘N∼44∘N, 152∘E∼165∘E. Full article
(This article belongs to the Section Marine Biology)
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15 pages, 2637 KiB  
Article
Geographic Differentiation of Morphological Characteristics in the Brown Seaweed Sargassum thunbergii along the Korean Coast: A Response to Local Environmental Conditions
by Sangil Kim, Sun Kyeong Choi, Seohyeon Van, Seong Taek Kim, Yun Hee Kang and Sang Rul Park
J. Mar. Sci. Eng. 2022, 10(4), 549; https://doi.org/10.3390/jmse10040549 - 16 Apr 2022
Cited by 9 | Viewed by 3800
Abstract
Intraspecific variation in morphology is widespread among seaweed species in different habitats. We examined the morphological variation in Sargassum thunbergii involving diverse environmental factors. We quantified 16 morphological characteristics on 15 rocky intertidal shores in Korea. A cluster analysis based on morphology identified [...] Read more.
Intraspecific variation in morphology is widespread among seaweed species in different habitats. We examined the morphological variation in Sargassum thunbergii involving diverse environmental factors. We quantified 16 morphological characteristics on 15 rocky intertidal shores in Korea. A cluster analysis based on morphology identified three groups. Group M1 comprised populations on the northern part of the east coast, where the thalli was short and thick, with large leaf and air-vesicle. Group M3 consisted of populations on the west coast exclusively separated from other populations, with short, slender and sparsely branched thalli. Group M2 comprised populations on the southern part of the east coast and on the south coast (including Jeju Island), with longest thalli and lateral branches. Principal coordinate analyses showed that group M1 and M3 were mostly influenced by strong wave action and large tidal amplitudes, respectively. Group M2 were under the influence of warm temperatures and high irradiance. Biota-environment matching analysis showed that the morphology is affected by combinations of different local environmental factors and also that tidal condition is important as a single variable, suggesting that morphology of S. thunbergii reflects and adapts to local environmental conditions. Full article
(This article belongs to the Special Issue Integrated Ecosystem Assessments for Fisheries Management in the Yellow Sea, the East China Sea, and the East/Japan Sea)
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14 pages, 1894 KiB  
Article
Effects of the NaCl Concentration and Montmorillonite Content on Formation Kinetics of Methane Hydrate
by Haopeng Zeng, Yu Zhang, Lei Zhang, Zhaoyang Chen and Xiaosen Li
J. Mar. Sci. Eng. 2022, 10(4), 548; https://doi.org/10.3390/jmse10040548 - 16 Apr 2022
Cited by 7 | Viewed by 2293
Abstract
Most resources of natural gas hydrate (NGH) exist in marine sediments where salts and sea mud are involved. It is of great importance to investigate the effects of salts and sea mud on NGH formation kinetics. In this study, the mixture of silica [...] Read more.
Most resources of natural gas hydrate (NGH) exist in marine sediments where salts and sea mud are involved. It is of great importance to investigate the effects of salts and sea mud on NGH formation kinetics. In this study, the mixture of silica sand and montmorillonite was used to mimic sea mud. The effects of the NaCl concentration of pore water and montmorillonite content on methane hydrate formation were studied. A low NaCl concentration of 0.2 mol/L and a low montmorillonite content range of 10–25 wt% is beneficial to reduce the induction time of hydrate formation. The high NaCl concentration and high content of montmorillonite will significantly increase the induction time. The average induction time for the experiments with the NaCl concentrations of 0, 0.2, 0.6, and 1.2 mol/L is 20.99, 8.11, 15.74, and 30.88 h, respectively. In the pure silica sand, the NaCl concentration of 0.2 mol/L can improve the final water conversion. In the experiments with pure water, the water conversion increases with the increase of the montmorillonite content due to the improvement of the dispersion of montmorillonite to water. The water conversion of the experiments in pure water with the montmorillonite contents of 0, 10, 25 and 40 wt% is 12.14% (±1.06%), 24.68% (±1.49%), 29.59% (±2.30%), and 32.57% (±1.64%), respectively. In the case of both montmorillonite and NaCl existing, there is a complicated change in the water conversion. In general, the increase of the NaCl concentration enhances the inhibition of hydrate formation and reduces the final water conversion, which is the key factor affecting the final water conversion. The average water conversion of the experiments under the NaCl concentrations of 0, 0.2, 0.6 and 1.2 mol/L is 24.74, 15.14, 8.85, and 5.74%, respectively. Full article
(This article belongs to the Special Issue Advances in Gas Hydrate Development: Phase Transition, Multiphase Flow and Heat-Mass Transfer)
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21 pages, 2492 KiB  
Article
An NMR-Based Metabolomics Assessment of the Effect of Combinations of Natural Feed Items on Juvenile Red Drum, Sciaenops ocellatus
by Fabio Casu, David Klett, Justin Yost, Michael R. Denson and Aaron M. Watson
J. Mar. Sci. Eng. 2022, 10(4), 547; https://doi.org/10.3390/jmse10040547 - 15 Apr 2022
Cited by 1 | Viewed by 2681
Abstract
This study evaluated the effects of seven diets composed of natural feed components (chopped fish, shrimp, and squid) alone or in combination on the liver metabolite profile of juvenile red drum (Sciaenops ocellatus) cultured in a 24-tank recirculating aquaculture system over [...] Read more.
This study evaluated the effects of seven diets composed of natural feed components (chopped fish, shrimp, and squid) alone or in combination on the liver metabolite profile of juvenile red drum (Sciaenops ocellatus) cultured in a 24-tank recirculating aquaculture system over the course of 12 weeks using Nuclear Magnetic Resonance (NMR)-based metabolomics. Experimental diets included fish (F), shrimp (SH), squid (SQ), fish and shrimp (FSH), fish and squid (FSQ), shrimp and squid (SHSQ), fish, shrimp, and squid (FSHSQ). A commercial fishmeal-based pelleted diet was used as a control. Fish were fed isocalorically. Red drum liver samples were collected at five different time points: T0, before the start of the trial (n = 12), and subsequently every 3 weeks over the course of 12 weeks (T3, T6, T9, T12), with n = 9 fish/diet/time point. Polar liver extracts were analyzed by NMR-based metabolomics. Multivariate statistical analyses (PCA, PLS-DA) revealed that red drum fed the F diet had a distinct liver metabolite profile from fish fed the other diets, with those fed SH, SQ and the combination diets displaying greater similarities in their metabolome. Results show that 19 metabolites changed significantly among the different dietary treatments, including amino acids and amino acid derivatives, quaternary amines and methylamines, carbohydrates and phospholipids. Specifically, γ-butyrobetaine, N-formimino-L-glutamate (FIGLU), sarcosine and beta-alanine were among the most discriminating metabolites. Significant correlations were found between metabolites and six growth performance parameters (final body weight, total length, condition factor, liver weight, hepatosomatic index, and eviscerated weight). Metabolites identified in this study constitute potential candidates for supplementation in fish feeds for aquaculture and optimization of existing formulations. Additionally, we identified a quaternary amine, γ-butyrobetaine as a potential biomarker of shrimp consumption in red drum. These results warrant further investigation and biomarker validation and have the potential for broader applicability outside of the aquaculture field in future investigations in wild red drum populations and potentially other carnivorous marine fishes. Full article
(This article belongs to the Special Issue New Insights into Fish Physiology-Applications Focus: Challenges and Mitigations)
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14 pages, 6585 KiB  
Article
Numerical Investigation on the Effect of Asymmetry of Flow Velocity on the Wake Vortex of Hydrofoils
by Xiang Xia, Liangcheng Ge, Lingjiu Zhou, Yingyao Feng, Haiyan Zeng and Zhengwei Wang
J. Mar. Sci. Eng. 2022, 10(4), 546; https://doi.org/10.3390/jmse10040546 - 15 Apr 2022
Cited by 1 | Viewed by 2049
Abstract
The Karman vortex street is a common flow phenomenon. In hydraulic machinery, it is usually located downstream of the guide vanes and the runner blades, which reduces hydraulic performance and may also cause fatigue damage to the structure. The latest research suggested that [...] Read more.
The Karman vortex street is a common flow phenomenon. In hydraulic machinery, it is usually located downstream of the guide vanes and the runner blades, which reduces hydraulic performance and may also cause fatigue damage to the structure. The latest research suggested that the difference in velocity gradient on each side of the blade trailing edge may have a significant impact on the strength of the wake vortex. The current work aims to verify the above conclusion and further explore the influence of asymmetry of flow velocity on the wake vortex. A numerical model with the velocity ratio, α, between the two sides of the hydrofoil as the only variable was designed, and the wake characteristics were solved by a computational fluid dynamics (CFD) method based on the finite volume. The unsteady Reynolds-average Navier–Stokes (URANS) equations were numerically solved by coupling with a transitional shear-stress transport (SST) turbulence model. The results showed that with the increase of α, the vortex shedding frequency decreased first, and then increased after reaching the critical velocity ratio αc1 ≈ 1.4. The vortex intensity first gradually decreased, and the vortex street suddenly disappeared after reaching the critical velocity ratio αc2 ≈ 2.2. The value of αc1 was affected by the thickness of the trailing edge, and αc2 was affected by the thickness and the Reynolds number. Besides, the asymmetry of the flow velocity also affected the effectiveness of the trailing-edge trimming. This research can provide references for the design of hydraulic machinery and other submerged structures. Full article
(This article belongs to the Section Ocean Engineering)
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15 pages, 2763 KiB  
Article
Prediction of Aerosol Extinction Coefficient in Coastal Areas of South China Based on Attention-BiLSTM
by Zhou Ye, Shengcheng Cui, Zhi Qiao, Zihan Zhang, Wenyue Zhu, Xuebin Li and Xianmei Qian
J. Mar. Sci. Eng. 2022, 10(4), 545; https://doi.org/10.3390/jmse10040545 - 15 Apr 2022
Viewed by 2063
Abstract
The aerosol extinction coefficient (AEC) characterises the attenuation of the light propagating in a turbid medium with suspended particles. Therefore, it is of great significance to carry out AEC prediction research using state-of-art neural network (NN) methods. The attention mechanism (AM) has become [...] Read more.
The aerosol extinction coefficient (AEC) characterises the attenuation of the light propagating in a turbid medium with suspended particles. Therefore, it is of great significance to carry out AEC prediction research using state-of-art neural network (NN) methods. The attention mechanism (AM) has become an indispensable part of NNs that focuses on input weight assignment. Traditional AM is used in time steps to help generate the outputs. To select important features of meteorological parameters (MP) that are helpful for forecasting, in this study, we apply AM to features instead of time steps. Then we propose a bidirectional long short-term memory (BiLSTM) NN based on AM to predict the AEC. The proposed method can remember information twice (i.e., forward and backward), which can provide more context for AEC forecasting. Finally, an in situ measured MP dataset is applied in the proposed model, which presents Maoming coastal area’s atmospheric conditions in November 2020. The experimental results show that the model proposed in this paper has higher accuracy compared with traditional NN, providing a novel solution to the AEC prediction problem for the current studies of marine aerosol. Full article
(This article belongs to the Special Issue Decision Support Systems and Tools in Coastal Areas)
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22 pages, 12052 KiB  
Article
Effects of the Parameter C4ε in the Extended k-ε Turbulence Model for Wind Farm Wake Simulation Using an Actuator Disc
by Ning Li, Li Li, Yongqian Liu, Yulu Wu, Hang Meng, Jie Yan and Shuang Han
J. Mar. Sci. Eng. 2022, 10(4), 544; https://doi.org/10.3390/jmse10040544 - 15 Apr 2022
Cited by 4 | Viewed by 2217
Abstract
The actuator disc model (ADM) incorporated into the k-ε turbulence model of EI Kasmi is able to simulate the wind farm wakes with high fidelity, which is essential for layout optimization and the evaluation of power production in modern wind farms. However, the [...] Read more.
The actuator disc model (ADM) incorporated into the k-ε turbulence model of EI Kasmi is able to simulate the wind farm wakes with high fidelity, which is essential for layout optimization and the evaluation of power production in modern wind farms. However, the effects of the parameter C4ε in the k-ε model of EI Kasmi on turbulent kinetic energy (TKE) in the superposition areas and the recovery of wind farm wake velocity have rarely been studied. To this end, the k-ε model of EI Kasmi is coupled with the advanced ADM in PHOENICS to investigate the influence of the parameter C4ε on the wake simulation of wind farms (e.g., two offshore wind farms, one onshore wind farm). It is concluded that a decreased parameter C4ε makes the generation range of TKE in the vicinity of the rotor smaller, but the TKE near the rotor becomes larger, and the wake recovery rate of the downstream turbine is less affected by the near wake. As the interwind turbine spacing increases, the influence area of TKE in the wake region of each downstream machine gradually reduces, and atmospheric turbulence plays a dominant role in wake recovery. A decreased parameter C4ε can effectively promote the inflow wind velocity and power output of downstream turbines. The power output simulated compares well with the measured power value when the parameter C4ε = 0.15. Full article
(This article belongs to the Section Ocean Engineering)
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15 pages, 11544 KiB  
Article
On the Response of Zhejiang Coastal Waters to 12 Typhoons from 2011 to 2015
by Yunhe Pan, Anzhou Cao, Yuqian Wu, Shiming Lu, Luteng Fan and Peiliang Li
J. Mar. Sci. Eng. 2022, 10(4), 543; https://doi.org/10.3390/jmse10040543 - 14 Apr 2022
Cited by 2 | Viewed by 1919
Abstract
Based on the hybrid coordinate ocean model (HYCOM) reanalysis data, the dynamical and thermal response of Zhejiang coastal waters to 12 typhoons from 2011 to 2015 was studied, and the relationship between the oceanic response and typhoon characteristics was analyzed. The HYCOM reanalysis [...] Read more.
Based on the hybrid coordinate ocean model (HYCOM) reanalysis data, the dynamical and thermal response of Zhejiang coastal waters to 12 typhoons from 2011 to 2015 was studied, and the relationship between the oceanic response and typhoon characteristics was analyzed. The HYCOM reanalysis data were validated by satellite-observed sea surface temperature data. Results show that all the 12 typhoons caused near-inertial waves, sea surface cooling and seafloor warming, but significant differences existed among them. Based on statistics, it was found that the domain-averaged near-inertial kinetic energy and seafloor warming are significantly correlated with the typhoon’s maximum wind speed, both of which show a positive relationship. The domain-averaged seafloor warming also decreases with the typhoon’s translation speed. Moreover, there exists a positive correlation between the domain-averaged sea surface cooling and seafloor warming. The different mechanisms that caused the seafloor warming for the 12 typhoons were also investigated in this study. Full article
(This article belongs to the Special Issue Advance in Circulation and Internal Wave Dynamics)
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18 pages, 13030 KiB  
Article
Integrated Dynamics Response Analysis for IEA 10-MW Spar Floating Offshore Wind Turbine
by Xiaojiang Guo, Yu Zhang, Jiatao Yan, Yiming Zhou, Shu Yan, Wei Shi and Xin Li
J. Mar. Sci. Eng. 2022, 10(4), 542; https://doi.org/10.3390/jmse10040542 - 14 Apr 2022
Cited by 10 | Viewed by 3930
Abstract
Wind energy in the deep-sea area is more abundant and the capacity of wind turbines can be made larger. Therefore, the research on deep-sea floating offshore wind turbines will be the primary strategy for wind energy exploitation in the future. The spar-type platform [...] Read more.
Wind energy in the deep-sea area is more abundant and the capacity of wind turbines can be made larger. Therefore, the research on deep-sea floating offshore wind turbines will be the primary strategy for wind energy exploitation in the future. The spar-type platform depends on the characteristics of a small water plane, deep draft, and good stability, which has been applied to the commercial development of deep-sea wind energy. In the next ten years, the 10-MW wind turbine will become the mainstream class installed in the floating offshore wind turbine farm. Thus, it is very necessary to conduct a comprehensive and in-depth study on the 10-MW spar type floating offshore wind turbine. The direct-drive 10-MW offshore wind turbine was proposed by the International Energy Agency (IEA) in Wind Task 37 in 2019. In this paper, a spar-type platform is designed to support the IEA 10-MW reference wind turbines, and a nonlinear aero-hydro-servo-elastic numerical model is established using the FAST tool (which is developed by the National Renewable Energy Laboratory, NREL). Then, the accuracy of the wind turbine and the sensitivity of the controller are verified, and the natural periods of the floating offshore wind turbine are obtained by free-decay tests. The natural periods of the platform in six degrees-of-freedom are found to be within the range recommended by the design standard. The measured wind and wave data of the target site close to Fujian Province of China are used to evaluate the performance of the floating offshore wind turbine under the 100-, 50-, 5-, and 2-year-return stochastic weather conditions. The results indicate that the design of the spar platform is reasonable and has excellent hydrodynamic performance. Full article
(This article belongs to the Special Issue Offshore Wind Energy)
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17 pages, 3130 KiB  
Article
Long-Term Benefits of Coastline Ecological Restoration in China
by Yaowen Zhang, Haoli Lin and Guanqiong Ye
J. Mar. Sci. Eng. 2022, 10(4), 541; https://doi.org/10.3390/jmse10040541 - 14 Apr 2022
Cited by 7 | Viewed by 2867
Abstract
Coastline ecological restoration is a critical approach for improving the coastal ecological environment and natural disaster mitigation capacity. Zhejiang Province, with the longest coastline in China, has carried out a three-year action of coastline remediation and restoration, expecting to complete the 300-km coastline [...] Read more.
Coastline ecological restoration is a critical approach for improving the coastal ecological environment and natural disaster mitigation capacity. Zhejiang Province, with the longest coastline in China, has carried out a three-year action of coastline remediation and restoration, expecting to complete the 300-km coastline restoration by 2020 as part of China’s coastline restoration project. We developed a cost–benefit framework synthesizing the ecosystem services (ES) analysis pattern and input-output approach to evaluate Zhejiang’s coastline ecological restoration projects. The results showed that the average value of ecosystem services (VES) of coastline restoration in Zhejiang was approximately 11,829 yuan/m, which was lower than the average VES of natural coastline. Obviously, damaged natural coastline could cause VES degradation, which cannot make up for the loss in a short time. In an optimistic scenario, coastline ecological restoration projects would deliver enormous well-being to Zhejiang and even China. Our results suggested that making decisions should be based on the net value after accounting for costs (NES), because ignoring costs might mislead planners to overstate the perceived benefits. The study provided a realistic data basis and method for coastline restoration projects in terms of the design, implementation and effectiveness evaluation to achieve sustainable development. Full article
(This article belongs to the Special Issue Monitoring and Assessing the Changing Coastal Ecosystem in Response to Global Change)
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16 pages, 4792 KiB  
Article
Experimental Investigation of Wave-Induced Forces on a Large Quasi-Elliptical Cylinder during Extreme Events
by Zhiying Yang, Hao Ding, Ke Li, Liang Cheng, Bo Huang and Qingyang Ren
J. Mar. Sci. Eng. 2022, 10(4), 540; https://doi.org/10.3390/jmse10040540 - 14 Apr 2022
Cited by 5 | Viewed by 1960
Abstract
Large quasi-elliptical cylinders are extensively used in ocean engineering. To enhance a better understanding of the hydrodynamic wave force on such quasi-elliptical cylinders during extreme events, a series of experiments on extreme wave interaction with a quasi-elliptical cylinder were conducted. A series of [...] Read more.
Large quasi-elliptical cylinders are extensively used in ocean engineering. To enhance a better understanding of the hydrodynamic wave force on such quasi-elliptical cylinders during extreme events, a series of experiments on extreme wave interaction with a quasi-elliptical cylinder were conducted. A series of waves with various wave heights, wave periods, and wave incident directions were tested to investigate the wave parameter effect and wave directionality effect on the wave forces on the quasi-elliptical structure. The experimental results indicate that the extreme wave-induced forces on the quasi-elliptical cylinder are strongly correlated to the wave period and wave incident direction. The peak forces on the quasi-elliptical model do not vary monotonically with the increasing wave period but show an increase followed by a decrease. Both the longitudinal and transversal forces are significantly increased when the wave incident direction changes from 0° to 45° and the wave directionality effect is enhanced when the wave period is decreased. Additionally, the inertial force equation was applied to the wave force estimation for such quasi-elliptical cylinders, and the inertia coefficient CM was fitted based on the experimental results of α = 0°. Full article
(This article belongs to the Special Issue Performance of Transportation Systems Subjected to Extreme Hydrodynamic Events)
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12 pages, 4418 KiB  
Article
A Simplified Approach to Modeling the Dispersion of Mercury from Precipitation to Surface Waters—The Bay of Kaštela Case Study
by Igor Živković, Jan Gačnik, Slaven Jozić, Jože Kotnik, Mladen Šolić and Milena Horvat
J. Mar. Sci. Eng. 2022, 10(4), 539; https://doi.org/10.3390/jmse10040539 - 14 Apr 2022
Cited by 1 | Viewed by 2011
Abstract
Wet deposition is the main source of mercury (Hg) from the atmosphere to the Earth’s surface. However, the processes that govern the dispersion of deposited Hg in seawater are currently not well understood. To address this issue, total mercury (THg) concentrations in surface [...] Read more.
Wet deposition is the main source of mercury (Hg) from the atmosphere to the Earth’s surface. However, the processes that govern the dispersion of deposited Hg in seawater are currently not well understood. To address this issue, total mercury (THg) concentrations in surface seawaters and precipitation were determined on a monthly basis in the Bay of Kaštela (Central Adriatic Sea). Following the assumption that deposited THg is diluted in the seawater bulk due to mixing processes, an exponential decay-like model was developed and the wet deposition of THg was normalized based on periods between precipitation events and seawater sampling. Normalized wet deposition of THg showed significant correlation with the THg gradient in surface seawater after removal of an outlier. To explain the observed outlier, further data normalization included wind data to account for enhanced seawater mixing due to strong winds. Wind-normalized THg deposition of all datapoints showed significant correlation with the THg gradient in surface seawater. The correlation showed that the THg gradient in surface seawater of 0.378 pg L−1 m−1 corresponds to THg wet deposition of 1 ng m−2 after including the influence of wind speed on seawater mixing. Full article
(This article belongs to the Special Issue Water Pollution under Climate Change in Coastal Areas)
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30 pages, 5488 KiB  
Article
Design and Dynamic Stability Analysis of a Submersible Ocean Current Generator Platform Mooring System under Typhoon Irregular Wave
by Shueei-Muh Lin, Chihng-Tsung Liauh and Didi-Widya Utama
J. Mar. Sci. Eng. 2022, 10(4), 538; https://doi.org/10.3390/jmse10040538 - 14 Apr 2022
Cited by 3 | Viewed by 2404
Abstract
This research proposes a mooring system for an ocean current generator that is working under the impact of typhoon waves. The turbine and the platform are kept stable at a designed water depth to ensure that the generator remains undamaged and continuously generates [...] Read more.
This research proposes a mooring system for an ocean current generator that is working under the impact of typhoon waves. The turbine and the platform are kept stable at a designed water depth to ensure that the generator remains undamaged and continuously generates electricity under excessive water pressure. In this design, the turbine generator is mounted in front of the floating platform by ropes and withstands the force of ocean currents, while the platform is anchored to the deep seabed with lightweight, high-strength PE ropes. In addition, two pontoons are used to connect the generator and the platform with ropes. When the balance is reached, the depth of the generator and the depth of the platform’s dive can be determined by the length of the ropes. In this study, typhoon irregular wave is represented by the Jonswap wave spectrum. The irregular wave is simulated by six regular waves. The equation of motion of the mooring system is derived. The theoretical solution of the dynamic system is presented to determine the dynamic displacements of the platform, pontoon, turbine and the dynamic tensions of the ropes. The dynamic tensions of the ropes increase with the cross-sectional area of pontoon. The natural frequency of the mooring system depends on the parameters, including the mases of elements, the lengths of ropes and the cross-sectional area of pontoons. In the proposed mooring configuration, the dynamic tension of the rope is far less than the breaking strength of the rope; thus, the ocean turbine is stable, and no water that flows through will be disturbed by the floating platform. Full article
(This article belongs to the Topic Marine Renewable Energy)
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15 pages, 5602 KiB  
Article
Design and Experimental Research on a Bionic Robot Fish with Tri-Dimensional Soft Pectoral Fins Inspired by Cownose Ray
by Lingkun Chen, Shusheng Bi, Yueri Cai, Yong Cao and Guang Pan
J. Mar. Sci. Eng. 2022, 10(4), 537; https://doi.org/10.3390/jmse10040537 - 14 Apr 2022
Cited by 21 | Viewed by 3979
Abstract
Bionic propulsion has advantages over traditional blade propellers, such as efficiency and noise control. Existing research on ray-inspired robot fish has mainly focused on a single type of pectoral fin as bionic propeller, which only performed well in terms of pure speed or [...] Read more.
Bionic propulsion has advantages over traditional blade propellers, such as efficiency and noise control. Existing research on ray-inspired robot fish has mainly focused on a single type of pectoral fin as bionic propeller, which only performed well in terms of pure speed or maneuverability. Rarely has the performance of different fin types been compared on the same platform to find an optimal solution. In this paper, a modularized robot fish with high-fidelity biomimetic pectoral fins and novel multi-DOF propelling mechanism is presented. A kinematic model of the pectoral fin based on motion analysis of a cownose ray is introduced as guidance for the propelling mechanism design. A high-fidelity parametric geo-model is established and evaluated based on statistical data. The design and fabrication process of the 3D soft bionic fins, as well as the robot platform, is also elaborated. Through experiments comparing the performance of different fin types constructed with different materials and approaches, it was found that the new soft fins made of silicon rubber have better performance than traditional fins constructed with a flexible inner skeleton and a permeable outer skin as a result of better 3D profile preservation and hydrodynamic force interaction. The robot ray prototype also acquires a better combination of high speed and maneuverability compared to results of previous research. Full article
(This article belongs to the Special Issue Frontiers in Deep-Sea Equipment and Technology)
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14 pages, 2856 KiB  
Article
A Block Sparse-Based Dynamic Compressed Sensing Channel Estimator for Underwater Acoustic Communication
by Lingji Xu, Lixing Chen, Yaan Li and Weihua Jiang
J. Mar. Sci. Eng. 2022, 10(4), 536; https://doi.org/10.3390/jmse10040536 - 14 Apr 2022
Cited by 4 | Viewed by 2364
Abstract
Due to the complex ocean propagation environments, the underwater acoustic (UWA) multipath channel often exhibits block sparse time-varying features, and while dynamic compressed sensing (DCS) can mitigate the time-varying effects of the UWA channel, DCS-based algorithms have limited performance for the UWA channel [...] Read more.
Due to the complex ocean propagation environments, the underwater acoustic (UWA) multipath channel often exhibits block sparse time-varying features, and while dynamic compressed sensing (DCS) can mitigate the time-varying effects of the UWA channel, DCS-based algorithms have limited performance for the UWA channel with block sparsity. In this study, by formulating the UWA channel with blocks concatenation, a block sparse-based DCS approach (BS-CS) is proposed to explore the block and time-varying sparsity of UWA channel simultaneously. In detail, we firstly adopt a block sparse recovery algorithm, block orthogonal matching pursuit (BOMP), to compute the temporary estimate. Then, the CS approach is applied to compute the support additions, which are caused by the time-varying components of the UWA channel. Next, we use the selected support to perform the BOMP estimate, and obtain the estimated channel response. Finally, the numerical simulation and the sea experiment were carried out to verify the superior performance of the proposed BS-CS algorithm in the block sparse time-varying UWA channels. Full article
(This article belongs to the Special Issue Advanced Marine Electronic Applications in Smart Ocean)
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21 pages, 9251 KiB  
Article
Storm Surge Forecasting along Korea Strait Using Artificial Neural Network
by Youngmin Park, Euihyun Kim, Youngjin Choi, Gwangho Seo, Youngtaeg Kim and Hokyun Kim
J. Mar. Sci. Eng. 2022, 10(4), 535; https://doi.org/10.3390/jmse10040535 - 14 Apr 2022
Cited by 6 | Viewed by 2912
Abstract
Typhoon attacks on the Korean Peninsula have recently become more frequent, and the strength of these typhoons is also gradually increasing because of climate change. Typhoon attacks cause storm surges in coastal regions; therefore, forecasts that enable advanced preparation for these storm surges [...] Read more.
Typhoon attacks on the Korean Peninsula have recently become more frequent, and the strength of these typhoons is also gradually increasing because of climate change. Typhoon attacks cause storm surges in coastal regions; therefore, forecasts that enable advanced preparation for these storm surges are important. Because storm surge forecasts require both accuracy and speed, this study uses an artificial neural network algorithm suitable for nonlinear modeling and rapid computation. A storm surge forecast model was created for five tidal stations on the Korea Strait (southern coast of the Korean Peninsula), and the accuracy of its forecasts was verified. The model consisted of a deep neural network and convolutional neural network that represent the two-dimensional spatial characteristics. Data from the Global Forecast System numerical weather model were used as input to represent the spatial characteristics. The verification of the forecast accuracy revealed an absolute relative error of ≤5% for the five tidal stations. Therefore, it appears that the proposed method can be used for forecasts for other locations in the Korea Strait. Furthermore, because accurate forecasts can be computed quickly, the method is expected to provide rapid information for use in the field to support advance preparation for storm surges. Full article
(This article belongs to the Section Coastal Engineering)
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24 pages, 2710 KiB  
Review
Recent Advances in Functional Materials for Wastewater Treatment: From Materials to Technological Innovations
by Nadia Khan, Zahra A. Tabasi, Jiabin Liu, Baiyu H. Zhang and Yuming Zhao
J. Mar. Sci. Eng. 2022, 10(4), 534; https://doi.org/10.3390/jmse10040534 - 14 Apr 2022
Cited by 14 | Viewed by 4797
Abstract
The growing concerns about climate changes and environmental pollution have galvanized considerable research efforts in recent years to develop effective and innovative remediation technologies for contaminated soils and water caused by industrial and domestic activities. In this context, the establishment of effective treatment [...] Read more.
The growing concerns about climate changes and environmental pollution have galvanized considerable research efforts in recent years to develop effective and innovative remediation technologies for contaminated soils and water caused by industrial and domestic activities. In this context, the establishment of effective treatment methods for wastewater has been critically important and urgent, since water pollution can take place on a very large scale (e.g., oceanic oil spills) and have massive impacts on ecosystems and human lives. Functional materials play a central role in the advancement of these technologies due to their highly tunable properties and functions. This article focuses on reviewing the recent progress in the application of various functional materials for wastewater treatment. Our literature survey is first concentrated on new modification methods and outcomes for a range of functional materials which have been actively investigated in recent years, including biofilm carriers, sand filters, biomass, biopolymers, and functional inorganic materials. Apart from the development of modified functional materials, our literature survey also covers the technological applications of superhydrophilic/superhydrophobic meshes, hybrid membranes, and reusable sponges in oil–water separation. These devices have gained significantly enhanced performance by using new functional materials as the key components (e.g., coating materials), and are therefore highly useful for treatment of oily wastewater, such as contaminated water collected from an oil spill site or oil–water emulsions resulting from industrial pollution. Based on our state-of-the-art literature review, future directions in the development and application of functional materials for wastewater treatment are suggested. Full article
(This article belongs to the Special Issue Reviews in Marine Environmental Science and Engineering)
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18 pages, 10522 KiB  
Article
GPU-Accelerated Multi-Objective Optimal Planning in Stochastic Dynamic Environments
by Rohit Chowdhury, Atharva Navsalkar and Deepak Subramani
J. Mar. Sci. Eng. 2022, 10(4), 533; https://doi.org/10.3390/jmse10040533 - 13 Apr 2022
Cited by 5 | Viewed by 2255
Abstract
The importance of autonomous marine vehicles is increasing in a wide range of ocean science and engineering applications. Multi-objective optimization, where trade-offs between multiple conflicting objectives are achieved (such as minimizing expected mission time, energy consumption, and environmental energy harvesting), is crucial for [...] Read more.
The importance of autonomous marine vehicles is increasing in a wide range of ocean science and engineering applications. Multi-objective optimization, where trade-offs between multiple conflicting objectives are achieved (such as minimizing expected mission time, energy consumption, and environmental energy harvesting), is crucial for planning optimal routes in stochastic dynamic ocean environments. We develop a multi-objective path planner in stochastic dynamic flows by further developing and improving our recently developed end-to-end GPU-accelerated single-objective Markov Decision Process path planner. MDPs with scalarized rewards for multiple objectives are formulated and solved in idealized stochastic dynamic ocean environments with dynamic obstacles. Three simulated mission scenarios are completed to elucidate our approach and capabilities: (i) an agent moving from a start to target by minimizing travel time and net-energy consumption when harvesting solar energy in an uncertain flow; (ii) an agent moving from a start to target by minimizing travel time and-energy consumption with uncertainties in obstacle initial positions; (iii) an agent attempting to cross a shipping channel while avoiding multiple fast moving ships in an uncertain flow. Optimal operating curves are computed in a fraction of the time that would be required for existing solvers and algorithms. Crucially, our solution can serve as the benchmark for other approximate AI algorithms such as Reinforcement Learning and help improve explainability of those models. Full article
(This article belongs to the Special Issue Explainable AI and Evaluation of Algorithms for Autonomous Marine Vehicles)
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24 pages, 10524 KiB  
Article
Explosion Characteristics of Hydrogen Gas in Varying Ship Ventilation Tunnel Geometries: An Experimental Study
by Soung Woo Park, Jeong Hwan Kim and Jung Kwan Seo
J. Mar. Sci. Eng. 2022, 10(4), 532; https://doi.org/10.3390/jmse10040532 - 12 Apr 2022
Cited by 12 | Viewed by 4284
Abstract
Hydrogen is widely regarded as a key element of prospective energy solutions for alleviating environmental emission problems. However, hydrogen is classified as a high-risk gas because of its wide explosive range, high overpressure, low ignition energy, and fast flame propagation speed compared with [...] Read more.
Hydrogen is widely regarded as a key element of prospective energy solutions for alleviating environmental emission problems. However, hydrogen is classified as a high-risk gas because of its wide explosive range, high overpressure, low ignition energy, and fast flame propagation speed compared with those of hydrocarbon-based gases. In addition, deflagration can develop into detonation in ventilation or explosion guide tunnels if explosion overpressure occurs, leading to the explosion of all combustible gases. However, quantitative evidence of an increase in the explosion overpressure of ventilation tunnels is unavailable because the explosive characteristics of hydrogen gas are insufficiently understood. Therefore, this study investigated an explosion chamber with the shape of a ventilation pipe in a ship compartment. The effect of tunnel length on explosion overpressure was examined experimentally. For quantitative verification, the size of the hydrogen gas explosion overpressure was analyzed and compared with experimental values of hydrocarbon-based combustible gases (butane and LPG (propane 98%)). The experimental database can be used for explosion risk analyses of ships when designing ventilation holes and piping systems and developing new safety guidelines for hydrogen carriers and hydrogen-fueled ships. Full article
(This article belongs to the Special Issue Marine Alternative Fuels and Environmental Protection II)
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24 pages, 1647 KiB  
Article
Vertical Motion Control of an Underwater Glider with a Command Filtered Adaptive Algorithm
by Mingjie Li, Baoheng Yao, Caoyang Yu and Lian Lian
J. Mar. Sci. Eng. 2022, 10(4), 531; https://doi.org/10.3390/jmse10040531 - 12 Apr 2022
Cited by 2 | Viewed by 2008
Abstract
Underwater gliders are widely used in oceanic observation, which are driven by a hydraulic buoyancy regulating system and a movable mass. Better motion performance can help us to accomplish observation tasks better. Therefore, a command filtered adaptive algorithm with a detailed system dynamic [...] Read more.
Underwater gliders are widely used in oceanic observation, which are driven by a hydraulic buoyancy regulating system and a movable mass. Better motion performance can help us to accomplish observation tasks better. Therefore, a command filtered adaptive algorithm with a detailed system dynamic model is proposed for underwater gliders in this paper. The dynamic model considers seawater density variation, temperature variation and hull deformation according to dive depth. The hydraulic pump model and the movable mass dynamic are also taken into account. An adaptive nonlinear control strategy based on backstepping technique is developed to compensate the uncertainties and disturbances in the control system. To deal with the command saturation and calculation of derivatives in the backstepping process, command filtered method is employed. The stability of the whole system is proved through the Lyapunov theory. Comparative simulations are conducted to verify the effectiveness of the proposed controller. The results demonstrate that the proposed algorithm can improve the motion control performance for underwater gliders under uncertainties and disturbances. Full article
(This article belongs to the Special Issue Frontiers in Deep-Sea Equipment and Technology)
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18 pages, 4266 KiB  
Article
Addressing the Directionality Challenge through RSSI-Based Multilateration Technique, to Localize Nodes in Underwater WSNs by Using Magneto-Inductive Communication
by Gang Qiao, Aman Muhammad, Muhammad Muzzammil, Muhammad Shoaib Khan, Muhammad Owais Tariq and Muhammad Shahbaz Khan
J. Mar. Sci. Eng. 2022, 10(4), 530; https://doi.org/10.3390/jmse10040530 - 12 Apr 2022
Cited by 16 | Viewed by 2400
Abstract
The deployment and efficient use of wireless sensor networks (WSNs) in underwater and underground environments persists to be a difficult task. In addition, the localization of a sensor Rx node in WSNs is an important aspect for the successful communication with the aforementioned [...] Read more.
The deployment and efficient use of wireless sensor networks (WSNs) in underwater and underground environments persists to be a difficult task. In addition, the localization of a sensor Rx node in WSNs is an important aspect for the successful communication with the aforementioned environments. To overcome the limitations of electromagnetic, acoustic, and optical communication in underwater and underground wireless sensor networks (UWSNs), magneto-inductive (MI) communication technology emerged as a promising alternative for usage in UWSNs with a wide range of applications. To make the magneto-inductive underwater wireless sensor networks (MI-UWSNs) more efficient, recently, various research studies focused on the optimization of the physical layer, MAC layer, and routing layer, but none of them has taken into account the effect of directionality. Despite the directionality issue posed by the physical nature of a magnetic field, the unique qualities of MI communication open up a gateway for several applications. The directionality issue of MI sensors is a critical challenge that must be taken into account while developing any WSN protocol or localization algorithm. This paper highlights and discusses the severity and impact of the directionality issue in designing a localization algorithm for magneto-inductive wireless sensor networks (MI-WSNs). A received signal strength indicator (RSSI)-based multilateration localization algorithm is presented in this paper, where a minimum of 2 and maximum of 10 anchor Tx nodes are used to estimate the position of the sensor Rx nodes, which are deployed randomly in a 15 m × 15 m simulation environment. This RSSI-based multilateration technique is the most suitable option that can be used to quantify the impact of directionality on the localization of a sensor Rx node. Full article
(This article belongs to the Section Ocean Engineering)
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17 pages, 1647 KiB  
Article
DCA-Based Collision Avoidance Path Planning for Marine Vehicles in Presence of the Multi-Ship Encounter Situation
by Jiagen Yu, Zhengjiang Liu and Xianku Zhang
J. Mar. Sci. Eng. 2022, 10(4), 529; https://doi.org/10.3390/jmse10040529 - 12 Apr 2022
Cited by 7 | Viewed by 2350
Abstract
The problem of ship collision avoidance path planning is one of the key problems in the ship motion control field. Aiming at the high computational time problem of path planning in multi-ship encounter situations and the impact of the target ship’s action changes [...] Read more.
The problem of ship collision avoidance path planning is one of the key problems in the ship motion control field. Aiming at the high computational time problem of path planning in multi-ship encounter situations and the impact of the target ship’s action changes on path planning, this paper proposes a dynamic path-planning method based on dynamic cluster analysis (DCA), which is used to dynamically cluster target ships with similar attributes into a group ship, reducing the number of calculated targets and improving the efficiency of path planning. Taking into full consideration the action requirements of the International Regulations for Preventing Collisions at Sea (COLREGs), the course alteration action matrix (CAAM) for collision avoidance is established to limit the space of candidate solutions. On the basis of the rapid optimization capability of the deterministic optimization algorithm (DOA), a dynamic monitoring mechanism is introduced to establish a multi-ship encounter intelligent collision avoidance decision-making model that meets the needs of real-time collision avoidance. The simulation results showed that the method can obtain a dynamic collision avoidance path that is safe and feasible. Full article
(This article belongs to the Special Issue Control Theory and Applications in Marine Autonomous Vehicles)
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16 pages, 5312 KiB  
Article
Influence of End Wall Clearance on Guide Vane Self-Excited Vibrations at Small Openings during Pump Mode’s Starting Up Process of a Reversible Pump Turbine
by Quanwei Liang, Wenzhe Kang, Lingjiu Zhou and Zhengwei Wang
J. Mar. Sci. Eng. 2022, 10(4), 528; https://doi.org/10.3390/jmse10040528 - 12 Apr 2022
Cited by 3 | Viewed by 1929
Abstract
Unstable guide vane torsional mode self-excited vibrations that occur at small guide vane openings during the transient operations with pump flow, such as the starting and closing of the pump mode, are considered to have potentially severe consequences, such as guide vane slippage [...] Read more.
Unstable guide vane torsional mode self-excited vibrations that occur at small guide vane openings during the transient operations with pump flow, such as the starting and closing of the pump mode, are considered to have potentially severe consequences, such as guide vane slippage or damage to the link and lever mechanism. Related site tests have indicated that the end wall clearance of a guide vane may have important influences on torsional mode self-excited vibrations. In this paper, numerical investigations, which were based on computational fluid dynamics (CFD) with a single degree of freedom (1DOF) mass-spring oscillator, were carried out on a prototype high-head reversible pump turbine. The results showed that the guide vane self-excited vibrations are unstable under steady-state conditions and during the pump mode’s starting up process for cases with small end wall clearances. In addition, the critical conditions of self-excitation instability under steady-state conditions have larger safety margins than those during the pump mode’s starting up process. After further discussion, it was concluded that increasing the end wall clearance to suppress unstable guide vane self-excited vibration is unreliable due to the complexity and randomness of the initial vibration excitations. Full article
(This article belongs to the Section Ocean Engineering)
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23 pages, 7419 KiB  
Article
Assessment of Sea Level and Morphological Changes along the Eastern Coast of Bangladesh
by Md. Shibly Anwar, Kalimur Rahman, Md Abul Ehsan Bhuiyan and Rupayan Saha
J. Mar. Sci. Eng. 2022, 10(4), 527; https://doi.org/10.3390/jmse10040527 - 11 Apr 2022
Cited by 12 | Viewed by 4331
Abstract
Bangladesh is one of the climate risk-prone countries in South Asia facing tremendous challenges to combat sea-level rise and its associated coastal morphological changes. This study aimed to determine the interaction of the sea-level rise and morphological changes, particularly at Cox’s Bazar and [...] Read more.
Bangladesh is one of the climate risk-prone countries in South Asia facing tremendous challenges to combat sea-level rise and its associated coastal morphological changes. This study aimed to determine the interaction of the sea-level rise and morphological changes, particularly at Cox’s Bazar and Kutubdia Island along the eastern coast of Bangladesh. Available hourly tide gauge data, daily temperature, daily rainfall data, and 15 LANDSAT satellite images for the period of 1983–2016 were analyzed to examine the sea level shore morphological change and associated climate change phenomenon. First, we identified the historical nonlinear sea-level trend using Hilbert-Huang Transformation (HHT) based on the complete ensemble empirical mode decomposition (CEEMD) technique. We divided the study period into three distinct sea-level change periods of 1983–1993, 1993–2003, and 2003–2014 based on nonlinear sea-level trend analysis. The study revealed that the sea level on the east coast of Bangladesh had a moderate rising trend during 1983–1993, slight decrease during 1993–2003, and steep rising trend during 2003–2014. We also observed that a sea-level change within a particular period impacted the shore morphological change after approximately two years, such that the average sea-level change during the period of 1993–2003 might have affected the shore morphology for 1996–2005. Alarming shore erosion was found for the period of 2005–2016 compared to the previous periods of 1989–1996 and 1996–2005 for both Cox’s Bazar and Kutubdia Island. The shore morphology of some segments was also substantially affected due to the geometric shape of the land, significant waves, and shore protection works. This study encourages policymakers to minimize the threats of sea-level rise and ensure sustainable coastal management strategies are introduced to sustain the vital eastern coast of Bangladesh. Full article
(This article belongs to the Special Issue Sea Level Rise: Drivers, Variability and Impacts)
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13 pages, 2289 KiB  
Communication
Autonomous Water Sampler for Oil Spill Response
by Daniel Gomez-Ibanez, Amy L. Kukulya, Abhimanyu Belani, Robyn N. Conmy, Devi Sundaravadivelu and Lisa DiPinto
J. Mar. Sci. Eng. 2022, 10(4), 526; https://doi.org/10.3390/jmse10040526 - 11 Apr 2022
Cited by 4 | Viewed by 2502
Abstract
A newly developed water sampling system enables autonomous detection and sampling of underwater oil plumes. The Midwater Oil Sampler collects multiple 1-L samples of seawater when preset criteria are met. The sampler has a hydrocarbon-free sample path and can be configured with several [...] Read more.
A newly developed water sampling system enables autonomous detection and sampling of underwater oil plumes. The Midwater Oil Sampler collects multiple 1-L samples of seawater when preset criteria are met. The sampler has a hydrocarbon-free sample path and can be configured with several modules of six glass sample bottles. In August 2019, the sampler was deployed on an autonomous underwater vehicle and captured targeted water samples in natural oil seeps offshore Santa Barbara, CA, USA. Full article
(This article belongs to the Special Issue Autonomous Underwater Vehicle Technology Advances in Ocean Observation)
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24 pages, 4484 KiB  
Article
Measuring Organization of Large Surficial Clasts in Heterogeneous Gravel Beach Sediments
by Dennis C. Lees, Christopher J. Hein and Duncan M. FitzGerald
J. Mar. Sci. Eng. 2022, 10(4), 525; https://doi.org/10.3390/jmse10040525 - 11 Apr 2022
Viewed by 2522
Abstract
The natural stratification and interlocking “organization” of armored sediments in heterogeneous, coarse-grained, beaches provides protection and enhances habitat for borrowing sedentary megafauna and macrofauna such as hard-shelled clams. Here, we develop a novel metric for quantifying sediment organization of large surficial beach clasts [...] Read more.
The natural stratification and interlocking “organization” of armored sediments in heterogeneous, coarse-grained, beaches provides protection and enhances habitat for borrowing sedentary megafauna and macrofauna such as hard-shelled clams. Here, we develop a novel metric for quantifying sediment organization of large surficial beach clasts through sedimentologic and photogrammetric analyses of 37 lower intertidal heterogeneous gravel beaches in western Prince William Sound, Alaska (USA). Grain size, photogrammetric, and Wolman Pebble Count clast-size data from 64, ~1-m2 study plots are combined into a clast-size-independent “Organization Metric” to quantify the degree of organization in the meshed arrangement of larger surficial sediments. This metric was validated through field manipulation experiments and comparisons of adjacent plots characterized by different clast sizes. Application of this metric to subsets of Prince William Sound beaches that underwent differential treatment following the Exxon Valdez oil spill reveals persistent physical effects of artificial beach disturbance even 21 years after the cleanup. This has important implications for beach management (e.g., cleaning or dredging) and for the diverse and productive sedentary megafaunal assemblages that live within these sediments. Overall, this study provides a new approach for quantifying organization of heterogenous coarse sediments in diverse natural settings; in particular, heterogenous gravel beaches. Full article
(This article belongs to the Special Issue Learning from Geomorphological Adaptation of Coasts at Different Time Scales)
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