Journal of Marine Science and Engineering

15 pages, 4708 KiB

Open AccessArticle

Prediction of Self-Propulsion Performance of Ship Model with Double L-Type Podded Propulsors and Conversion Method for Full-Scale Ship

by Dagang Zhao, Chunyu Guo, Jianfeng Lin, Zuotian Zhang and Xue Bai

J. Mar. Sci. Eng. 2019, 7(5), 162; https://doi.org/10.3390/jmse7050162 - 27 May 2019

Cited by 8 | Viewed by 3333

Abstract

In this study, the self-propulsion performance of a ship model with double-L-type podded propulsors was predicted. Additionally, a conversion method for the performance of a full-scale ship was established based on the correction method published by the International Towing Tank Conference (ITTC) for [...] Read more.

In this study, the self-propulsion performance of a ship model with double-L-type podded propulsors was predicted. Additionally, a conversion method for the performance of a full-scale ship was established based on the correction method published by the International Towing Tank Conference (ITTC) for the scaling effect of a single podded propeller and research reports on pod tests conducted by different ship research institutes. The thrust deduction and wake fraction of the ship were also analyzed. Furthermore, the self-propulsion performance of a full-scale ship with double L-type pods was determined, the full- and model-scale ships compared in terms of their flow fields and pressure charts, and the influence of the scaling effect analyzed. In addition, the calculation results were compared with the conversion results of a full-scale ship, and the reliability of the method adopted for the performance estimation of a full-scale ship with double podded propulsors was verified. The findings reported herein can provide statistics and technical support for the design of L-type podded propulsors and their application in full-scale ships, which are of theoretical significance and practical value in the engineering domain. Full article

(This article belongs to the Special Issue Marine Propulsion)

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12 pages, 7567 KiB

Open AccessArticle

A Numerical Study on the Impact of High-Frequency Winds on the Peru Upwelling System during 2014–2016

by Linhui Wang, Huiwang Gao, Jie Shi and Lian Xie

J. Mar. Sci. Eng. 2019, 7(5), 161; https://doi.org/10.3390/jmse7050161 - 25 May 2019

Viewed by 2247

Abstract

The contribution of high-frequency wind to the Peruvian upwelling system during 2014–2016 was studied using the Regional Ocean Modeling System (ROMS), forced by four different temporal resolution (six-hourly, daily, weekly, and monthly) wind forcing. A major effect of the high-frequency wind is its [...] Read more.

The contribution of high-frequency wind to the Peruvian upwelling system during 2014–2016 was studied using the Regional Ocean Modeling System (ROMS), forced by four different temporal resolution (six-hourly, daily, weekly, and monthly) wind forcing. A major effect of the high-frequency wind is its warming of the water at all depths along the Peruvian coast. The mechanism for the temperature changes induced by high-frequency wind forcing was analyzed through heat budget analysis, which indicated a three-layer structure. Vertical advection plays a leading role in the warming of the mixed layer (0–25 m), and enhanced vertical mixing balances the warming effect. Analysis suggests that around the depths of 25–60 m, vertical mixing warms the water by bringing heat from the surface to deeper depths. In waters deeper than 60 m, the effect of vertical mixing is negligible. The differences among the oceanic responses in the sensitivity experiments suggest that wind forcing containing variabilities at higher than synoptic frequencies must be included in the atmospheric forcing in order to properly simulate the Peru upwelling system. Full article

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22 pages, 3461 KiB

Open AccessArticle

Mechanics and Historical Evolution of Sea Level Blowouts in New York Harbor

by Praneeth Gurumurthy, Philip M. Orton, Stefan A. Talke, Nickitas Georgas and James F. Booth

J. Mar. Sci. Eng. 2019, 7(5), 160; https://doi.org/10.3390/jmse7050160 - 23 May 2019

Cited by 8 | Viewed by 3139

Abstract

Wind-induced sea level blowouts, measured as negative storm surge or extreme low water (ELW), produce public safety hazards and impose economic costs (e.g., to shipping). In this paper, we use a regional hydrodynamic numerical model to test the effect of historical environmental change [...] Read more.

Wind-induced sea level blowouts, measured as negative storm surge or extreme low water (ELW), produce public safety hazards and impose economic costs (e.g., to shipping). In this paper, we use a regional hydrodynamic numerical model to test the effect of historical environmental change and the time scale, direction, and magnitude of wind forcing on negative and positive surge events in the New York Harbor (NYH). Environmental sensitivity experiments show that dredging of shipping channels is an important factor affecting blowouts while changing ice cover and removal of other roughness elements are unimportant in NYH. Continuously measured water level records since 1860 show a trend towards smaller negative surge magnitudes (measured minus predicted water level) but do not show a significant change to ELW magnitudes after removing the sea-level trend. Model results suggest that the smaller negative surges occur in the deeper, dredged modern system due to a reduced tide-surge interaction, primarily through a reduced phase shift in the predicted tide. The sensitivity of surge to wind direction changes spatially with remote wind effects dominating local wind effects near NYH. Convergent coastlines that amplify positive surges also amplify negative surges, a process we term inverse coastal funneling. Full article

(This article belongs to the Special Issue Coastal Hazards Related to Water)

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23 pages, 4469 KiB

Open AccessArticle

Interdisciplinary Methodology to Extend Technology Readiness Levels in SONAR Simulation from Laboratory Validation to Hydrography Demonstrator

by James Riordan, Francis Flannery, Daniel Toal, Matija Rossi and Gerard Dooly

J. Mar. Sci. Eng. 2019, 7(5), 159; https://doi.org/10.3390/jmse7050159 - 23 May 2019

Cited by 7 | Viewed by 4032

Abstract

This paper extends underwater SONAR simulation from laboratory prototype to real-world demonstrator. It presents the interdisciplinary methodology to advance the state of the art from level four to level seven on the technology readiness level (TRL) standard scale for measuring the maturity of [...] Read more.

This paper extends underwater SONAR simulation from laboratory prototype to real-world demonstrator. It presents the interdisciplinary methodology to advance the state of the art from level four to level seven on the technology readiness level (TRL) standard scale for measuring the maturity of innovations. While SONAR simulation offers the potential to unlock cost-effective personnel capacity building in hydrography, demonstration of virtualised survey-scale operations is a prerequisite for validation by practitioners. Our research approach uses the TRL framework to identify and map current barriers to the use of simulation to interdisciplinary solutions adapted from multiple domains. To meet the distinct challenges of acceptance tests at each level in the TRL scale, critical knowledge is incorporated from different branches of science, engineering, project management, and pedagogy. The paper reports the simulator development at each escalation of TRL. The contributions to simulator performance and usability at each level of advancement are presented, culminating in the first case study demonstration of SONAR simulation as a real-world hydrographic training platform. Full article

(This article belongs to the Special Issue Underwater Imaging)

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Graphical abstract

28 pages, 14407 KiB

Open AccessFeature PaperArticle

Stochastic Modeling of Forces on Jacket-Type Offshore Structures Colonized by Marine Growth

by Hamed Ameryoun, Franck Schoefs, Laurent Barillé and Yoann Thomas

J. Mar. Sci. Eng. 2019, 7(5), 158; https://doi.org/10.3390/jmse7050158 - 22 May 2019

Cited by 21 | Viewed by 3836

Abstract

The present paper deals with the stochastic modeling of bio-colonization for the computation of stochastic hydrodynamic loading on jacket-type offshore structures. It relies on a multidisciplinary study gathering biological and physical research fields that accounts for uncertainties at all the levels. Indeed, bio-colonization [...] Read more.

The present paper deals with the stochastic modeling of bio-colonization for the computation of stochastic hydrodynamic loading on jacket-type offshore structures. It relies on a multidisciplinary study gathering biological and physical research fields that accounts for uncertainties at all the levels. Indeed, bio-colonization of offshore structures is a complex phenomenon with two major but distinct domains: (i) marine biology, whose processes are modeled with biomathematics methods, and (ii) hydrodynamic processes. This paper aims to connect these two domains. It proposes a stochastic model for the marine organism’s growth and then continues with transfers for the assessment of drag coefficient and forces probability density functions that account for marine growth evolution. A case study relies on the characteristics (growth and shape) of the blue mussel (Mytilus edulis) in the northeastern Atlantic. Full article

(This article belongs to the Special Issue Marine Structures)

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17 pages, 4268 KiB

Open AccessArticle

Estimation of Coastal Currents Using a Soft Computing Method: A Case Study in Galway Bay, Ireland

by Lei Ren, Jianming Miao, Yulong Li, Xiangxin Luo, Junxue Li and Michael Hartnett

J. Mar. Sci. Eng. 2019, 7(5), 157; https://doi.org/10.3390/jmse7050157 - 20 May 2019

Cited by 5 | Viewed by 2934

Abstract

In order to obtain forward states of coastal currents, numerical models are a commonly used approach. However, the accurate definition of initial conditions, boundary conditions and other model parameters are challenging. In this paper, a novel application of a soft computing approach, random [...] Read more.

In order to obtain forward states of coastal currents, numerical models are a commonly used approach. However, the accurate definition of initial conditions, boundary conditions and other model parameters are challenging. In this paper, a novel application of a soft computing approach, random forests (RF), was adopted to estimate surface currents for three analysis points in Galway Bay, Ireland. Outputs from a numerical model and observations from a high frequency radar system were used as inputs to develop soft computing models. The input variable structure of soft computing models was examined in detail through sensitivity experiments. High correlation of surface currents between predictions from RF models and radar data indicated that the RF algorithm is a most promising means of generating satisfactory surface currents over a long prediction period. Furthermore, training dataset lengths were examined to investigate influences on prediction accuracy. The largest improvement for zonal and meridional surface velocity components over a 59-h forecasting period was 14% and 37% of root mean square error (RMSE) values separately. Results indicate that the combination of RF models with a numerical model can significantly improve forecasting accuracy for surface currents, especially for the meridional surface velocity component. Full article

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

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17 pages, 5161 KiB

Open AccessArticle

Improved Double-Layer Soil Consolidation Theory and Its Application in Marine Soft Soil Engineering

by Deqiang Chen, Junhui Luo, Xianlin Liu, Decai Mi and Longwang Xu

J. Mar. Sci. Eng. 2019, 7(5), 156; https://doi.org/10.3390/jmse7050156 - 18 May 2019

Cited by 9 | Viewed by 3687

Abstract

Marine soft soil foundation is a double-layer foundation structure with a crust layer and soft substratum. Moreover, it is common that there are various forms of drainage. Accordingly, based on Terzaghi’s consolidation theory and the continuous drainage boundary conditions theory of controllable drainage [...] Read more.

Marine soft soil foundation is a double-layer foundation structure with a crust layer and soft substratum. Moreover, it is common that there are various forms of drainage. Accordingly, based on Terzaghi’s consolidation theory and the continuous drainage boundary conditions theory of controllable drainage conditions, an improved double-layer soil consolidation theory considering continuous drainage boundary conditions was proposed. To improve the computational efficiency and accuracy, the Laplace transform and the Stehfest algorithm was used to deduce the numerical solution of the improved double-layer soil consolidation theory considering continuous drainage boundary conditions and to compile a computer program. Subsequently, the theory was validated and analyzed by the degenerated model of the perfectly permeable boundary conditions and the semi-permeable boundary conditions, respectively, which showed that this theory has higher accuracy. Simultaneously, the analysis of double-layer consolidation settlement under continuous drainage boundary conditions for marine soft soil foundation of Guangxi Binhai Highway was carried on. The result showed that the consolidation settlement calculated by the improved double-layer consolidation theory presented is basically consistent with the field measurement results, and that the correlation coefficient between them is higher. Accordingly, the research results can provide useful basic information for marine soft foundation engineering. Full article

(This article belongs to the Special Issue New Advances in Marine Engineering Geology)

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22 pages, 7336 KiB

Open AccessArticle

Influence Mechanism of Different Flow Patterns on the Softening of Red-Bed Soft Rock

by Zhen Liu, Xinfu He and Cuiying Zhou

J. Mar. Sci. Eng. 2019, 7(5), 155; https://doi.org/10.3390/jmse7050155 - 18 May 2019

Cited by 16 | Viewed by 2647

Abstract

As a typical representative of red beds, the softening and disintegration of red sandstone when it encounters water is an important cause of initiated engineering disasters. However, research on the softening of this kind of rock has mainly focused on the still water–rock [...] Read more.

As a typical representative of red beds, the softening and disintegration of red sandstone when it encounters water is an important cause of initiated engineering disasters. However, research on the softening of this kind of rock has mainly focused on the still water–rock interaction. There is still a lack of quantitative analysis and a mechanistic explanation for the basic experimental study of dynamic water–rock interactions. Therefore, based on the independently developed multifunctional open channel hydraulic test equipment, the still water was used as the reference by designing the saturation test of red sandstone under two typical flow patterns—laminar flow and turbulent flow—and combined with a three-dimensional numerical simulation; specifically, the chemical, physical and mechanical effects of different flow patterns on the softening of red sandstone are discussed, and the mechanism of the influence of different flow patterns on the softening of red sandstone was further revealed. The results show that under different flow patterns, as the flow of water increased, the alkalinity of the circulating solution became stronger, the speed of stabilization of the ion concentration became faster, the development of the microscopic structure of the corresponding rock became higher and the decrease in mechanical strength became greater. The flow state affects the processes of rock softening and breaking by acting on the rock from the three aspects of chemistry, physics and mechanics. The study makes up for the deficiency of the quantitative analysis index of rock softening under dynamic water conditions and further improves the influence mechanism of different flow patterns on soft rock softening in red beds under dynamic water conditions. This research also provides a specific method for the protection of estuarine and coastal bank slopes with rich red-bed soft rock dissection under different flow patterns. Full article

(This article belongs to the Section Coastal Engineering)

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20 pages, 2441 KiB

Open AccessArticle

Parametric Study of Tsunamis Generated by Earthquakes and Landslides

by Natalia Perez del Postigo Prieto, Alison Raby, Colin Whittaker and Sarah J. Boulton

J. Mar. Sci. Eng. 2019, 7(5), 154; https://doi.org/10.3390/jmse7050154 - 17 May 2019

Cited by 2 | Viewed by 3954

Abstract

Tsunami generation and propagation mechanisms need to be clearly understood in order to inform predictive models and improve coastal community preparedness. Physical experiments, supported by mathematical models, can potentially provide valuable input data for standard predictive models of tsunami generation and propagation. A [...] Read more.

Tsunami generation and propagation mechanisms need to be clearly understood in order to inform predictive models and improve coastal community preparedness. Physical experiments, supported by mathematical models, can potentially provide valuable input data for standard predictive models of tsunami generation and propagation. A unique experimental set-up has been developed to reproduce a coupled-source tsunami generation mechanism: a two-dimensional underwater fault rupture followed by a submarine landslide. The test rig was located in a 20 m flume in the COAST laboratory at the University of Plymouth. The aim of the experiments is to provide quality data for developing a parametrisation of the initial conditions for tsunami generation processes which are triggered by a dual-source. During the test programme, the water depth and the landslide density were varied. The position of the landslide model was tracked and the free surface elevation of the water body was measured. Hence the generated wave characteristics were determined. For a coupled-source scenario, the generated wave is crest led, followed by a trough of smaller amplitude decreasing steadily as it propagates along the flume. The crest amplitude was shown to be influenced by the fault rupture displacement scale, whereas the trough was influenced by the landslide’s relative density. Full article

(This article belongs to the Special Issue Tsunami Science and Engineering II)

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18 pages, 8994 KiB

Open AccessArticle

Design and Experiment of Clamper Used in Antarctic Subglacial Bedrock Drilling

by Pavel Talalay, Xingchen Li, Da Gong, Xiaopeng Fan, Nan Zhang, Yang Yang, Yongwen Liu, Yunchen Liu, Ting Wang and Xiao Li

J. Mar. Sci. Eng. 2019, 7(5), 153; https://doi.org/10.3390/jmse7050153 - 17 May 2019

Cited by 3 | Viewed by 3470

Abstract

As a result of the severe natural environment with oxygen deficit in the Antarctic, using conventional manual work to screw and unscrew the drill pipe increases the labor intensity tremendously and causes an efficiency reduction. Therefore, it would be useful to design a [...] Read more.

As a result of the severe natural environment with oxygen deficit in the Antarctic, using conventional manual work to screw and unscrew the drill pipe increases the labor intensity tremendously and causes an efficiency reduction. Therefore, it would be useful to design a clamper inside the drilling shelter, which could help to assemble and disassemble the ice core barrel with screw connection. This paper describes the design of and experiments with the clamper inside the movable drilling shelter. A related testing stand was also designed and built to experiment on relationships between the clamper motor current versus clamping torque and force. Through experimental data collation and calculation analysis, the following conclusions could be drawn: (1) according to the rotary ability of the Ice and Bedrock Electromechanical Drill (IBED) to calculate and determine the torque of clamper, the clamping torque required to provide by the clamper is 100 N·m; (2) finite element simulation and analysis of the non-standard transmission chain showed that the mechanical reliability of the subparts; (3) the experimental results showed the range of the clamping force and clamping torque of the clamper. The clamping force and clamping torque increased with the increase of clamper DC motor current, presenting proportional linear relationships. The clamper can meet the clamping requirements of IBED for screwing, unscrewing, and clamping, which will be greatly helpful when it is tested in the field. Full article

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10 pages, 2654 KiB

Open AccessArticle

Giant Submarine Landslide in the South China Sea: Evidence, Causes, and Implications

by Chaoqi Zhu, Sheng Cheng, Qingping Li, Hongxian Shan, Jing’an Lu, Zhicong Shen, Xiaolei Liu and Yonggang Jia

J. Mar. Sci. Eng. 2019, 7(5), 152; https://doi.org/10.3390/jmse7050152 - 17 May 2019

Cited by 29 | Viewed by 7062

Abstract

Submarine landslides can be tremendous in scale. They are one of the most important processes for global sediment fluxes and tsunami generation. However, studies of prodigious submarine landslides remain insufficient. In this review paper, we compile, summarize, and reanalyze the results of previous [...] Read more.

Submarine landslides can be tremendous in scale. They are one of the most important processes for global sediment fluxes and tsunami generation. However, studies of prodigious submarine landslides remain insufficient. In this review paper, we compile, summarize, and reanalyze the results of previous studies. Based on this reanalysis, we discover the giant Baiyun–Liwan submarine slide in the Pearl River Mouth Basin, South China Sea. We describe three concurrent pieces of evidence from ~23 Ma to 24 Ma, the Oligocene–Miocene boundary, for this landslide: the shoreward shift of the shelf break in the Baiyun Sag, the slump deposition to the southeast, and the abrupt decrease in the accumulation rate on the lower continental slope. This landslide extends for over 250 km, and the total affected area of the slide is up to ~35,000–40,000 km². The scale of the landslide is similar to that of the Storegga slide, which has long been considered to be the largest landslide on earth. We suggest that strike–slip movement along the Red River Fault and ridge jump of the South China Sea caused the coeval Baiyun–Liwan submarine slide. The identification of the giant landslide will promote the understanding of not only its associated geohazards but also the steep rise of the Himalayan orogeny and marine engineering. More attention needs to be paid to areas with repeated submarine landslides and offshore installations. Full article

(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)

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26 pages, 7481 KiB

Open AccessArticle

Mapping the Sandy Beach Evolution Around Seaports at the Scale of the African Continent

by Wiebe de Boer, Yongjing Mao, Gerben Hagenaars, Sierd de Vries, Jill Slinger and Tiedo Vellinga

J. Mar. Sci. Eng. 2019, 7(5), 151; https://doi.org/10.3390/jmse7050151 - 16 May 2019

Cited by 21 | Viewed by 4971

Abstract

In Africa, several new seaport developments are being considered. In sedimentary environments, such port developments can have adverse impacts on the evolution of adjacent coastlines. To learn from past port engineering practice, we created a unique database containing the coastline evolution and characteristics [...] Read more.

In Africa, several new seaport developments are being considered. In sedimentary environments, such port developments can have adverse impacts on the evolution of adjacent coastlines. To learn from past port engineering practice, we created a unique database containing the coastline evolution and characteristics of 130 existing African seaports. Whereas the systematic mapping of coastal impacts was previously hampered by data availability, innovative automated satellite image processing techniques have enabled us to intercompare ports at an unprecedented continental scale. We found large geographical differences with respect to the beach evolution. The total detected changes in the beach area between 1984 and 2018 totaled 44 km², of which ca. 23 km² is accretion and ca. 21 km² is erosion. The top 10% “hotspot” ports account for more than 65% of these changes. These hotspots exhibit common characteristics, namely: they are located on open coastlines, have large alongshore sediment transport potential, and have large cross-shore breakwaters. Although these driving characteristics are well established in coastal engineering theory, our results indicate that the beaches adjacent to the existing seaports have been and remain seriously affected by these drivers. Our results can be used to inform beach maintenance strategies for existing seaports and to support planners and engineers to minimize long-term coastal impacts of port expansions and new port developments in Africa in the future. Full article

(This article belongs to the Section Coastal Engineering)

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16 pages, 7916 KiB

Open AccessArticle

Variations in Winter Ocean Wave Climate in the Japan Sea under the Global Warming Condition

by Kenji Taniguchi

J. Mar. Sci. Eng. 2019, 7(5), 150; https://doi.org/10.3390/jmse7050150 - 15 May 2019

Cited by 2 | Viewed by 2847

Abstract

Future variations in the ocean wave climate caused by global warming could affect various coastal issues. Using a third-generation wave model, this study produced projections of the ocean wave climate for winter around Japan, focusing on the Japan Sea side. Wave simulation forcing [...] Read more.

Future variations in the ocean wave climate caused by global warming could affect various coastal issues. Using a third-generation wave model, this study produced projections of the ocean wave climate for winter around Japan, focusing on the Japan Sea side. Wave simulation forcing (sea surface wind) was generated through five different global warming experiments. More than half the future wave projections showed an increasing tendency of the climatological mean significant wave height during winter. However, the maximum significant wave height did not show any clear tendency in future variation. The top 1% of significant wave heights and mean wave periods showed apparent increases in frequencies of higher/longer waves in three out of the five future projections. Frequency distributions of significant wave height, mean wave period, mean wavelength and wave direction showed various future variations (reduction of small ocean waves, increasing frequency of waves from the west). There are large uncertainties in future variations of wave climate in the Japan Sea, but the high probability of variations in daily wave climate is recognized, based on the future wave projections. Variations in daily wave climate are important because they could affect the topography and environment of the coast through long-term repetitive actions. Full article

(This article belongs to the Section Coastal Engineering)

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26 pages, 3967 KiB

Open AccessArticle

Mathematical Modeling Framework of Physical Effects Induced by Sediments Handling Operations in Marine and Coastal Areas

by Iolanda Lisi, Alessandra Feola, Antonello Bruschi, Andrea Pedroncini, Davide Pasquali and Marcello Di Risio

J. Mar. Sci. Eng. 2019, 7(5), 149; https://doi.org/10.3390/jmse7050149 - 15 May 2019

Cited by 7 | Viewed by 3642

Abstract

In recent years increasing attention has been paid to environmental effects that may result from marine dredging and disposal operations. In general, the fine-grained fraction of handled sediments can be dispersed far from the intervention site as a turbidity plume, depending on the [...] Read more.

In recent years increasing attention has been paid to environmental effects that may result from marine dredging and disposal operations. In general, the fine-grained fraction of handled sediments can be dispersed far from the intervention site as a turbidity plume, depending on the specific site and operational parameters. Starting from a literature review, this paper suggests standards for estimating and characterizing the sediment source term, for setting up far-field modeling studies and analyzing numerical results, with the aim of optimizing, also from an economic point of view, the different project, execution and monitoring phases. The paper proposes an integrated modeling approach for simulating sediment dispersion due to sediment handling operations in different marine-coastal areas (off-shore, near-shore and semi-enclosed basins). Attention is paid to the characterization of sediment source terms due to different operational phases (removal, transport and disposal). The paper also deals with the definition of accuracy level of modeling activities, with regard to the main physical processes characterizing the different marine–coastal areas and to the type of environmental critical issues near the intervention site (if any). The main relationships between modeling and monitoring are given for the different design and management phases to support the selection of appropriate technical alternatives and monitoring actions and to ensure the environmental compliance of the proposed interventions. Full article

(This article belongs to the Special Issue Marine Sediments: Processes, Transport and Environmental Aspects)

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21 pages, 6312 KiB

Open AccessArticle

Performance Evaluation of Wave Input Reduction Techniques for Modeling Inter-Annual Sandbar Dynamics

by Bruna de Queiroz, Freek Scheel, Sofia Caires, Dirk-Jan Walstra, Derrick Olij, Jeseon Yoo, Ad Reniers and Wiebe de Boer

J. Mar. Sci. Eng. 2019, 7(5), 148; https://doi.org/10.3390/jmse7050148 - 15 May 2019

Cited by 10 | Viewed by 3493

Abstract

In process-based numerical models, reducing the amount of input parameters, known as input reduction (IR), is often required to reduce the computational effort of these models and to enable long-term, ensemble predictions. Currently, a comprehensive performance assessment of IR-methods is lacking, which hampers [...] Read more.

In process-based numerical models, reducing the amount of input parameters, known as input reduction (IR), is often required to reduce the computational effort of these models and to enable long-term, ensemble predictions. Currently, a comprehensive performance assessment of IR-methods is lacking, which hampers guidance on selecting suitable methods and settings in practice. In this study, we investigated the performance of 10 IR-methods and 36 subvariants for wave climate reduction to model the inter-annual evolution of nearshore bars. The performance of reduced wave climates is evaluated by means of a brute force simulation based on the full climate. Additionally, we tested how the performance is affected by the number of wave conditions, sequencing, and duration of the reduced wave climate. We found that the Sediment Transport Bins method is the most promising method. Furthermore, we found that the resolution in directional space is more important for the performance than the resolution in wave height. The results show that a reduced wave climate with fewer conditions applied on a smaller timescale performs better in terms of morphology than a climate with more conditions applied on a longer timescale. The findings of this study can be applied as initial guidelines for selecting input reduction methods at other locations, in other models, or for other domains. Full article

(This article belongs to the Section Coastal Engineering)

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18 pages, 13196 KiB

Open AccessArticle

Energy Yield Assessment from Ocean Currents in the Insular Shelf of Cozumel Island

by Juan Carlos Alcérreca-Huerta, Job Immanuel Encarnacion, Stephanie Ordoñez-Sánchez, Mariana Callejas-Jiménez, Gabriel Gallegos Diez Barroso, Matthew Allmark, Ismael Mariño-Tapia, Rodolfo Silva Casarín, Tim O’Doherty, Cameron Johnstone and Laura Carrillo

J. Mar. Sci. Eng. 2019, 7(5), 147; https://doi.org/10.3390/jmse7050147 - 15 May 2019

Cited by 28 | Viewed by 5355

Abstract

Marine renewables represent a promising and innovative alternative source for satisfying the energy demands of growing populations while reducing the consumption of fossil fuels. Most technological advancements and energy yield assessments have focused on promoting the use of kinetic energy from tidal streams [...] Read more.

Marine renewables represent a promising and innovative alternative source for satisfying the energy demands of growing populations while reducing the consumption of fossil fuels. Most technological advancements and energy yield assessments have focused on promoting the use of kinetic energy from tidal streams with flow velocities higher than 2.0 m s⁻¹. However, slower-moving flows from ocean currents are recently explored due to their nearly continuous and unidirectional seasonal flows. In this study, the potential of the Yucatan Current was analysed at nearshore sites over the insular shelf of Cozumel Island in the Mexican Caribbean. Field measurements were undertaken using a vessel-mounted Acoustic Doppler Current Profiler (ADCP) to analyse the spatial distribution of flow velocities, along with Conductivity-temperature-depth (CTD) profiles as well as data gathering of bathymetry and water elevations. Northward directed flow velocities were identified, with increasing velocities just before the end of the strait of the Cozumel Channel, where average velocities in the region of 0.88–1.04 m s⁻¹ were recorded. An estimation of power delivery using horizontal axis turbines was undertaken with Blade Element Momentum theory. It was estimated that nearly 3.2 MW could be supplied to Cozumel Island, amounting to about 10% of its electricity consumption. Full article

(This article belongs to the Special Issue The Development of Marine Energy Extraction)

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21 pages, 5889 KiB

Open AccessArticle

Experiment and Analysis of Submarine Landslide Model Caused by Elevated Pore Pressure

by Tao Liu, Yueyue Lu, Lei Zhou, Xiuqing Yang and Lei Guo

J. Mar. Sci. Eng. 2019, 7(5), 146; https://doi.org/10.3390/jmse7050146 - 15 May 2019

Cited by 11 | Viewed by 3160

Abstract

Hydrate decomposition is an important potential cause of marine geological disasters. It is of great significance to understand the dynamic relationship between hydrate reservoir system and the overlying seabed damage caused by its decomposition. The purpose of this study is to understand the [...] Read more.

Hydrate decomposition is an important potential cause of marine geological disasters. It is of great significance to understand the dynamic relationship between hydrate reservoir system and the overlying seabed damage caused by its decomposition. The purpose of this study is to understand the instability and destruction mechanisms of a hydrated seabed using physical simulations and to discuss the effects of different geological conditions on seabed stability. By applying pressurized gas to the low permeability silt layer, the excess pore pressure caused by the decomposition of hydrate is simulated and the physical appearance process of the overlying seabed damage is monitored. According to the test results, two conclusions were drawn in this study: (1) Under the action of excess pore pressure caused by hydrate decomposition, typical phenomena of overlying seabed damage include pockmark deformation and shear–slip failure. In shallower or steeper strata, shear-slip failure occurs in the slope. The existence of initial crack in the stratum is the main trigger cause. In thicker formations or gentler slopes, the surface of the seabed has a collapse deformation feature. The occurrence of cracks in the deep soil layer is the main failure mechanism. (2) It was determined that the thickness and slope of the seabed, among other factors, affect the type and extent of seabed damage. Full article

(This article belongs to the Special Issue Participation of Gas Hydrate to Form Oil-Gas Deposit in the Seas)

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16 pages, 3932 KiB

Open AccessArticle

Variability of Best-Estimate Flood Depth Return Periods in Coastal Louisiana

by Mikaela R. Meyer and David R. Johnson

J. Mar. Sci. Eng. 2019, 7(5), 145; https://doi.org/10.3390/jmse7050145 - 14 May 2019

Viewed by 2562

Abstract

Estimates of surge-based flood depth exceedance curves are useful to inform flood risk management strategies. Estimated return periods associated with flood depth exceedances naturally vary over time, even under assumptions of stationarity, due to the irreducible randomness associated with storm events as new [...] Read more.

Estimates of surge-based flood depth exceedance curves are useful to inform flood risk management strategies. Estimated return periods associated with flood depth exceedances naturally vary over time, even under assumptions of stationarity, due to the irreducible randomness associated with storm events as new observations accrue with each passing year. We empirically examine the degree to which best-estimates of coastal Louisiana floodplains have changed over time and consider implications for risk management policies. We generate variation in estimated 100-year flood depths by truncating a historical data set of observed tropical cyclones to end in years ranging from 1980 to 2016, adopting three procedures for updating various inputs to an existing flood risk model using the truncated data set to identify which factors are most important in driving variation in risk estimates over time. The landscape used for modeling hydrodynamics is kept constant, allowing us to isolate the impacts of randomness in storm occurrence from other factors. Our findings indicate that the 100-year floodplain extent has substantially expanded in populated areas since 1980 due to these effects. Due to the low frequency at which flood maps are updated, it is possible that thousands of coastal residents are misclassified as being outside of the 100-year floodplain relevant to flood insurance rates and other regulations. Full article

(This article belongs to the Special Issue Coastal Hazards Related to Water)

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13 pages, 6171 KiB

Open AccessArticle

Geomorphological Processes and Environmental Interpretation at Espalmador islet (Western Mediterranean)

by Laura del Valle Villalonga, Alida Timar-Gabor and Joan J. Fornós

J. Mar. Sci. Eng. 2019, 7(5), 144; https://doi.org/10.3390/jmse7050144 - 14 May 2019

Cited by 5 | Viewed by 2786

Abstract

This study presents a sedimentological and stratigraphical description of the Pleistocene deposits cropping out in Espalmador islet (Illes Pitiüses). Four major sedimentary facies including the succession of aeolian, marine, colluvial and edaphic environments are described. The sedimentological and stratigraphical analysis of these deposits [...] Read more.

This study presents a sedimentological and stratigraphical description of the Pleistocene deposits cropping out in Espalmador islet (Illes Pitiüses). Four major sedimentary facies including the succession of aeolian, marine, colluvial and edaphic environments are described. The sedimentological and stratigraphical analysis of these deposits allows the reconstruction of the coastal Pleistocene environmental and geomorphological history of the Espalmador islet. The coastal relief and the fluctuations of the sea level mainly control the Pleistocene coastal landscape evolution on Espalmador. Episodes of aeolian activity and dune formation related to a predominant northwestern wind direction can be linked to periods of low sea level where a high amount of marine sediment is exposed on the shelf platform. Full article

(This article belongs to the Special Issue Coastal Morphodynamics II)

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11 pages, 5607 KiB

Open AccessArticle

Field Test on Buoyancy Variation of a Subsea Bottom-Supported Foundation Model

by Tianyi Fang, Guojun Liu, Guanlin Ye, Shang Pan, Haibin Shi and Lulu Zhang

J. Mar. Sci. Eng. 2019, 7(5), 143; https://doi.org/10.3390/jmse7050143 - 13 May 2019

Cited by 6 | Viewed by 2806

Abstract

The bottom-supported foundation is the most important component of offshore platforms, as it provides the major support to the upper structure. The buoyancy of the bottom-supported foundation is a critical issue in platform design because it counteracts parts of the vertical loads. In [...] Read more.

The bottom-supported foundation is the most important component of offshore platforms, as it provides the major support to the upper structure. The buoyancy of the bottom-supported foundation is a critical issue in platform design because it counteracts parts of the vertical loads. In this paper, a model box was designed and installed with earth pressure transducers and pore pressure transducers to simulate the sitting process of the bottom-supported foundation. The buoyancy acting on the model box was calculated on the basis of two different methods, i.e., the water pressure difference between top and bottom surface and the effective stress at the bottom of the model. Field tests with different sitting times were carried out on the saturated soft clay seabed. Numerical coupled analysis was performed to verify the dissipation of the excess pore pressure at the bottom of the model. The results showed that the buoyancy of the model could reach twice the calculated value of Archimedes’ law in the initial stage, however, it eventually stabilized near the theoretical value as the excess pore pressure dissipated. There was a slight fluctuation in buoyancy due to the phase lag of the pore pressure response caused by the low permeability of the seabed. Full article

(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)

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17 pages, 7580 KiB

Open AccessArticle

A Study on the Wind Energy Potential in the Romanian Coastal Environment

by Florin Onea and Liliana Rusu

J. Mar. Sci. Eng. 2019, 7(5), 142; https://doi.org/10.3390/jmse7050142 - 13 May 2019

Cited by 24 | Viewed by 3597

Abstract

At the European level, offshore wind projects are already considered a competitive market. Nevertheless, this is not yet the case of the enclosed sea basins, such as the Black Sea, where no offshore wind farm is operating at this moment. From this perspective, [...] Read more.

At the European level, offshore wind projects are already considered a competitive market. Nevertheless, this is not yet the case of the enclosed sea basins, such as the Black Sea, where no offshore wind farm is operating at this moment. From this perspective, the objective of the present work is to identify the most suitable sites where a wind project can be developed in the Romanian coastal areas. Various parameters, such as wind speed, water depth, distance to shore, and turbine performance, are considered. A picture of the local wind characteristics is first provided considering 20 years of reanalysis data, which cover the time interval from January 1998 to December 2017. The results indicated that the best sites to implement a wind project are located in the northern sector of the Black Sea, close to the Danube Delta. It was also noticed an important variation of the wind speed between onshore and 20 km offshore, for which an increase of about 55% was estimated. Full article

(This article belongs to the Special Issue Renewable Energy Extraction in the Marine Environment and Its Coastal Impact)

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27 pages, 13242 KiB

Open AccessArticle

Numerical Analyses of Wave Generation and Vortex Formation under the Action of Viscous Fluid Flows over a Depression

by Chih-Hua Chang

J. Mar. Sci. Eng. 2019, 7(5), 141; https://doi.org/10.3390/jmse7050141 - 12 May 2019

Cited by 3 | Viewed by 3291

Abstract

Transient free-surface deformations and evolving vortices due to the passage of flows over a submerged cavity are simulated. A two-dimensional stream function–vorticity formulation with a free-surface model is employed. Model results are validated against the limiting case of pure lid-driven cavity flow with [...] Read more.

Transient free-surface deformations and evolving vortices due to the passage of flows over a submerged cavity are simulated. A two-dimensional stream function–vorticity formulation with a free-surface model is employed. Model results are validated against the limiting case of pure lid-driven cavity flow with comparisons of the vortical flow pattern and velocity profiles. The verification of the free-surface computations are also carried out by comparing results with published potential flow solutions for cases of flows over a depressed bottom topography. The agreements are generally good. Investigations are extended to other viscous flow conditions, where the cavity is set to have the normalized dimension of one by one when scaled by the still water depth. The free-surface elevations and streamline patterns for cases with Froude numbers ranging from 0.5 to 1.1 and different Reynolds numbers (Re = 5000 and 500) are calculated. At the condition of near-critical flow (Fr ≈ 1.0), the phenomenon of upstream advancing solitons is produced. Viscous effects on the free-surface profile reveal that at a lower value of Re (e.g., Re = 500) larger advancing solitary waves are generated. Vortical flow patterns in the cavity are examined for the cases with Fr = 1.0 and various values of Re. When Re = 5000, the vortex pattern includes a primary and a weak, but dominated secondary vortices at the time reaching a nearly quasi-steady motion. For the case of lower Re (e.g., Re = 500), a steady-state vortex pattern can be established with a clockwise primary vortex mostly occupied inside the cavity. Full article

(This article belongs to the Special Issue Marine Structures)

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16 pages, 4429 KiB

Open AccessArticle

Effect of Girder Spacing and Depth on the Solitary Wave Impact on Coastal Bridge Deck for Different Airgaps

by Rameeza Moideen, Manasa Ranjan Behera, Arun Kamath and Hans Bihs

J. Mar. Sci. Eng. 2019, 7(5), 140; https://doi.org/10.3390/jmse7050140 - 11 May 2019

Cited by 20 | Viewed by 3540

Abstract

Coastal bridge damage has become a severe issue of concern in the recent past with the destruction of a considerable number of bridges under the impact of waves during tsunami and storm surges. These events have become more frequent, with waves reaching the [...] Read more.

Coastal bridge damage has become a severe issue of concern in the recent past with the destruction of a considerable number of bridges under the impact of waves during tsunami and storm surges. These events have become more frequent, with waves reaching the bridge deck and causing upliftment and destruction. Past studies have demonstrated the establishment of various theoretical equations which works well for the submerged deck and regular wave types but show much scatter and uncertainty in case of a deck that is above still water level (SWL). The present study aims to generate a solitary wave to represent an extreme wave condition like a tsunami in the numerical wave tank modeled using the open source computational fluid dynamics (CFD) model REEF3D and to study the vertical impact force on the coastal bridge deck. A parametric study is carried out for increasing wave heights, girders spacing and depth for varying airgaps to analyze the effect of these parameters on the peak vertical impact force. It is observed that increasing the girder spacing and girder depth is effective in reducing the peak vertical impact force for the cases considered. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics for Ocean Surface Waves)

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21 pages, 4036 KiB

Open AccessArticle

Storm Waves at the Shoreline: When and Where Are Infragravity Waves Important?

by Oliver Billson, Paul Russell and Mark Davidson

J. Mar. Sci. Eng. 2019, 7(5), 139; https://doi.org/10.3390/jmse7050139 - 11 May 2019

Cited by 16 | Viewed by 3770

Abstract

Infragravity waves (frequency, f = 0.005–0.05 Hz) are known to dominate hydrodynamic and sediment transport processes close to the shoreline on low-sloping sandy beaches, especially when incident waves are large. However, in storm wave conditions, how their importance varies on different beach types, [...] Read more.

Infragravity waves (frequency, f = 0.005–0.05 Hz) are known to dominate hydrodynamic and sediment transport processes close to the shoreline on low-sloping sandy beaches, especially when incident waves are large. However, in storm wave conditions, how their importance varies on different beach types, and with different mixes of swell and wind-waves is largely unknown. Here, a new dataset, comprising shoreline video observations from five contrasting sites (one low-sloping sandy beach, two steep gravel beaches, and two compound/mixed sand and gravel beaches), under storm wave conditions (deep water wave height, H₀ up to 6.6 m, and peak period, T_p up to 18.2 s), was used to assess: how the importance and dominance of infragravity waves varies at the shoreline? In this previously unstudied combination of wave and morphological conditions, significant infragravity swash heights (S_ig) at the shoreline in excess of 0.5 m were consistently observed on all five contrasting beaches. The largest infragravity swash heights were observed on a steep gravel beach, followed by the low-sloping sandy beach, and lowest on the compound/mixed sites. Due to contrasting short wave breaking and dissipation processes, infragravity frequencies were observed to be most dominant over gravity frequencies on the low-sloping sandy beach, occasionally dominant on the gravel beaches, and rarely dominant on the compound/mixed beaches. Existing empirical predictive relationships were shown to parameterize S_ig skillfully on the sand and gravel beaches separately. Deep water wave power was found to accurately predict S_ig on both the sand and gravel beaches, demonstrating that, under storm wave conditions, the wave heights and periods are the main drivers of infragravity oscillations at the shoreline, with the beach morphology playing a secondary role. The exception to this was the compound/mixed beach sites where shoreline infragravity energy remained low. Full article

(This article belongs to the Special Issue Storm Erosion)

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19 pages, 11792 KiB

Open AccessFeature PaperArticle

A Diesel Engine Modelling Approach for Ship Propulsion Real-Time Simulators

by Marco Altosole, Ugo Campora, Massimo Figari, Michele Laviola and Michele Martelli

J. Mar. Sci. Eng. 2019, 7(5), 138; https://doi.org/10.3390/jmse7050138 - 11 May 2019

Cited by 32 | Viewed by 4990

Abstract

A turbocharged diesel engine numerical model, suitable for real-time ship manoeuvre simulation, is presented in this paper. While some engine components (mainly the turbocharger, intercooler and manifolds) are modelled by a filling and emptying approach, the cylinder simulation is based on a set [...] Read more.

A turbocharged diesel engine numerical model, suitable for real-time ship manoeuvre simulation, is presented in this paper. While some engine components (mainly the turbocharger, intercooler and manifolds) are modelled by a filling and emptying approach, the cylinder simulation is based on a set of five-dimensional numerical matrices (each matrix is generated by means of a more traditional thermodynamic model based on in-cylinder actual cycle). The new cylinder calculation approach strongly reduces the engine transient computation time, making it possible to transform the simulation model into a real-time executable application. As a case study, the simulation methodology is applied to a high speed four stroke turbocharged marine diesel engine, whose design and off design running data are available from the technical sheet. In order to verify the suitability of the proposed model in real-time simulation applications, a yacht propulsion plant simulator is developed. Numerical results in ship acceleration and deceleration manoeuvres are shown, reducing the simulation running time of 99% in comparison with the corresponding in-cylinder actual cycle engine model. Full article

(This article belongs to the Special Issue Advances in Marine Dynamic Simulation)

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16 pages, 8274 KiB

Open AccessArticle

Statistical Deviations in Shoreline Detection Obtained with Direct and Remote Observations

by Giovanni Pugliano, Umberto Robustelli, Diana Di Luccio, Luigi Mucerino, Guido Benassai and Raffaele Montella

J. Mar. Sci. Eng. 2019, 7(5), 137; https://doi.org/10.3390/jmse7050137 - 11 May 2019

Cited by 17 | Viewed by 2922

Abstract

Remote video imagery is widely used for shoreline detection, which plays a fundamental role in geomorphological studies and in risk assessment, but, up to now, few measurements of accuracy have been undertaken. In this paper, the comparison of video-based and GPS-derived shoreline measurements [...] Read more.

Remote video imagery is widely used for shoreline detection, which plays a fundamental role in geomorphological studies and in risk assessment, but, up to now, few measurements of accuracy have been undertaken. In this paper, the comparison of video-based and GPS-derived shoreline measurements was performed on a sandy micro-tidal beach located in Italy (central Tyrrhenian Sea). The GPS survey was performed using a single frequency, code, and carrier phase receiver as a rover. Raw measurements have been post-processed by using a carrier-based positioning algorithm. The comparison between video camera and DGPS coastline has been carried out on the whole beach, measuring the error as the deviation from the DGPS line computed along the normal to the DGPS itself. The deviations between the two dataset were examined in order to establish possible spatial dependence on video camera point of view and on beach slope in the intertidal zone. The results revealed that, generally, the error increased with the distance from the acquisition system and with the wash up length (inversely proportional to the beach slope). Full article

(This article belongs to the Special Issue Remote Sensing in Coastline Detection)

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22 pages, 10792 KiB

Open AccessArticle

Reduction of Hydrodynamic Noise of 3D Hydrofoil with Spanwise Microgrooved Surfaces Inspired by Sharkskin

by Zhigao Dang, Zhaoyong Mao and Wenlong Tian

J. Mar. Sci. Eng. 2019, 7(5), 136; https://doi.org/10.3390/jmse7050136 - 10 May 2019

Cited by 23 | Viewed by 4218

Abstract

Loud hydrodynamic noise is not only potentially harmful to the health of organisms in the ocean, but it is also a threat to the survival of underwater vehicles. Different from the general noise reduction technologies at present, a new idea for a flow-induced [...] Read more.

Loud hydrodynamic noise is not only potentially harmful to the health of organisms in the ocean, but it is also a threat to the survival of underwater vehicles. Different from the general noise reduction technologies at present, a new idea for a flow-induced noise reduction design with spanwise microgrooved surfaces inspired by sharkskin is introduced in this paper. Large eddy simulations (LES) combined with the Ffowcs Williams and Hawkings (FW-H) equation are adopted to simulate the hydrodynamic noise of the three-dimensional (3D) hydrofoil. The accuracy of the numerical predictions is checked against existing experimental data, achieving good agreement. With the increase of observing distance, the noise reduction effect at the trailing edge direction is gradually apparent, and a maximum noise reduction of up to 7.28 dB can be observed. It is seen from the noise spectra of the biomimetic hydrofoil that the main peaks are eliminated, and the noise level at high frequency is also decreased. The cause of noise reduction lies in the secondary vortex generated in the microgrooves, which hinder the process of turbulence, consume the energy of the flow, and weaken the intensity of turbulent burst. The results of this study provide a new way to design low-noise underwater structures with hydrofoils. Full article

(This article belongs to the Section Ocean Engineering)

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12 pages, 2187 KiB

Open AccessArticle

Impact of Anthropogenic Climate Change on United States Major Hurricane Landfall Frequency

by Emma L. Levin and Hiroyuki Murakami

J. Mar. Sci. Eng. 2019, 7(5), 135; https://doi.org/10.3390/jmse7050135 - 10 May 2019

Cited by 9 | Viewed by 4573

Abstract

Although anthropogenic climate change has contributed to warmer ocean temperatures that are seemingly more favorable for Atlantic hurricane development, no major hurricanes made landfall in the United States between 2006 and 2016. The U.S., therefore, experienced a major hurricane landfall drought during those [...] Read more.

Although anthropogenic climate change has contributed to warmer ocean temperatures that are seemingly more favorable for Atlantic hurricane development, no major hurricanes made landfall in the United States between 2006 and 2016. The U.S., therefore, experienced a major hurricane landfall drought during those years. Using the high-resolution Geophysical Fluid Dynamics Laboratory 25 km grid High-Resolution Forecast-Oriented Low Ocean Resolution (HiFLOR) global climate model, the present study shows that increases in anthropogenic forcing, due to increases in greenhouse gasses, are associated with fewer long-duration major hurricane landfall droughts in the U.S., which implies an increase in major hurricane landfall frequency. We create six different fixed-distance ‘buffers’ that artificially circle the United States coastline in 100 km radial increments and can compensate for the bias in hurricane landfall calculations with six-hourly datasets. Major hurricane landfall frequencies are computed by applying the buffer zones to the six-hourly observed and simulated storm track datasets, which are then compared with the observed recorded major hurricane frequencies. We found that the major hurricane landfall frequencies generated with the 200 km buffer using the six-hourly observed best-track dataset are most correlated with the observed recorded major hurricane landfall frequencies. Using HiFLOR with an implemented buffer system, we found less frequent projections of long-duration major hurricane landfall drought events in controlled scenarios with greater anthropogenic global warming, which is independent on the radius of the coastal buffer. These results indicate an increase in U.S. major hurricane landfall frequencies with an increase in anthropogenic warming, which could pose a substantial threat to coastal communities in the U.S. Full article

(This article belongs to the Special Issue Extreme Weather and Climate Events: Physical Drivers, Modeling and Impact Assessment)

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17 pages, 3907 KiB

Open AccessArticle

Dynamic Impedances of Offshore Rock-Socketed Monopiles

by Rui He, Ji Ji, Jisheng Zhang, Wei Peng, Zufeng Sun and Zhen Guo

J. Mar. Sci. Eng. 2019, 7(5), 134; https://doi.org/10.3390/jmse7050134 - 09 May 2019

Cited by 18 | Viewed by 3407

Abstract

With the development of offshore wind energy in China, more and more offshore wind turbines are being constructed in rock-based sea areas. However, the large diameter and thin-walled steel rock-socketed monopiles are very scarce at present, and both the construction and design are [...] Read more.

With the development of offshore wind energy in China, more and more offshore wind turbines are being constructed in rock-based sea areas. However, the large diameter and thin-walled steel rock-socketed monopiles are very scarce at present, and both the construction and design are very difficult. For the design, the dynamic safety during the whole lifetime of the wind turbine is difficult to guarantee. Dynamic safety of a turbine is mostly controlled by the dynamic impedances of the rock-socketed monopile, which are still not well understood. How to choose the appropriate impedances of the socketed monopiles so that the wind turbines will neither resonant nor be too conservative is the main problem. Based on a numerical model in this study, the accurate impedances are obtained for different frequencies of excitation, different soil and rock parameters, and different rock-socketed lengths. The dynamic stiffness of monopile increases, while the radiative damping decreases as rock-socketed depth increases. When the weathering degree of rock increases, the dynamic stiffness of the monopile decreases, while the radiative damping increases. Full article

(This article belongs to the Special Issue Coastal Geohazard and Offshore Geotechnics)

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16 pages, 3138 KiB

Open AccessArticle

Ultrasound Assisted Adsorptive Removal of Cr, Cu, Al, Ba, Zn, Ni, Mn, Co and Ti from Seawater Using Fe₂O₃-SiO₂-PAN Nanocomposite: Equilibrium Kinetics

by Denga Ramutshatsha-Makhwedzha, Jane Catherine Ngila, Patrick G. Ndungu and Philiswa Nosizo Nomngongo

J. Mar. Sci. Eng. 2019, 7(5), 133; https://doi.org/10.3390/jmse7050133 - 09 May 2019

Cited by 17 | Viewed by 2943

Abstract

This work reports the preparation and application of Fe₂O₃-SiO₂-PAN nanocomposite for the removal of Cr³⁺, Cu²⁺, Al³⁺, Ba²⁺, Zn²⁺, Ni²⁺, Mn²⁺, Co²⁺ [...] Read more.

This work reports the preparation and application of Fe₂O₃-SiO₂-PAN nanocomposite for the removal of Cr³⁺, Cu²⁺, Al³⁺, Ba²⁺, Zn²⁺, Ni²⁺, Mn²⁺, Co²⁺, and Ti³⁺ from seawater. X-ray diffraction (XRD), scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscope (TEM), and Brunauer-Emmett-Teller (BET) characterized the synthesized composite. The following experimental parameters (Extraction time, adsorbent mass and pH) affecting the removal of major and trace metals were optimized using response surface methodology (RSM). The applicability of the RSM model was verified by performing the confirmation experiment using the optimal condition and the removal efficiency ranged from 90% to 97%, implying that the model was valid. The adsorption kinetic data was described by the pseudo-second order model. The applicability of the materials was tested on real seawater samples (initial concentration ranging from 0.270–203 µg L⁻¹) and the results showed satisfactory percentage efficiency removal that range from 98% to 99.9%. The maximum adsorption capacities were found to be 4.36, 7.20, 2.23, 6.60, 5.06, 2.60, 6.79, 6.65 and 3.00 mg g⁻¹, for Cr³⁺, Cu²⁺, Al³⁺, Ba²⁺, Zn²⁺, Ni²⁺, Mn²⁺, Co²⁺, and Ti⁴⁺, respectively. Full article

(This article belongs to the Special Issue Nanomaterials Applied in Water Treatments)

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J. Mar. Sci. Eng., Volume 7, Issue 5 (May 2019) – 42 articles

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