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J. Mar. Sci. Eng., Volume 8, Issue 2 (February 2020) – 73 articles

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Open AccessArticle
Thermal Infrared Spectral Characteristics of Bunker Fuel Oil to Determine Oil-Film Thickness and API
J. Mar. Sci. Eng. 2020, 8(2), 135; https://doi.org/10.3390/jmse8020135 (registering DOI) - 19 Feb 2020
Abstract
Remote sensing is an important method for monitoring marine oil-spill accidents. However, methods for measuring oil-film thickness remain insufficient. Due to the stable differences in the surface emissivity and temperature of oil and water, the oil film can be detected using thermal infrared. [...] Read more.
Remote sensing is an important method for monitoring marine oil-spill accidents. However, methods for measuring oil-film thickness remain insufficient. Due to the stable differences in the surface emissivity and temperature of oil and water, the oil film can be detected using thermal infrared. This study measured emissivity of seven different oil-film thicknesses and seven different American Petroleum Institute (API) densities, and analyzed the spectral characteristics. Results show an optimal wavelength position for oil-film thickness and fuel API density monitoring is 12.55 μm. Principal component analysis and continuum removal methods were used for data processing. Stepwise multiple linear regression was used to establish relationships between emissivity and oil slick thicknesses and API densities. Oil-film thickness and fuel API density data were analyzed by principal component analysis and continuum removal before regression analysis. The spectral emissivity data was convolved into Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Advanced Very High Resolution Radiometer (AVHRR) thermal bands to determine potential of the sensor in oil-film detection. The result shows that neither could be used to estimate thickness. The AVHRR-4 band and band 12 and 13 of the ASTER could be used to separate oils from water and have potential to distinguish different oil types. Full article
(This article belongs to the Special Issue Marine Oil Spills 2020)
Open AccessArticle
Identifying the Frequency Dependent Interactions between Ocean Waves and the Continental Margin on Seismic Noise Recordings
J. Mar. Sci. Eng. 2020, 8(2), 134; https://doi.org/10.3390/jmse8020134 (registering DOI) - 19 Feb 2020
Abstract
This study presents an exploration into identifying the interactions between ocean waves and the continental margin in the origination of doublefrequency (DF, 0.1–0.5 Hz) microseisms recorded at 33 stations across East Coast of USA (ECUSA) during a 10day period of ordinary ocean wave [...] Read more.
This study presents an exploration into identifying the interactions between ocean waves and the continental margin in the origination of doublefrequency (DF, 0.1–0.5 Hz) microseisms recorded at 33 stations across East Coast of USA (ECUSA) during a 10day period of ordinary ocean wave climate. Daily primary vibration directions are calculated in three frequency bands and projected as great circles passing through each station. In each band, the great circles from all stations exhibit largest spatial density primarily near the continental slope in the western North Atlantic Ocean. Generation mechanisms of three DF microseism events are explored by comparing temporal and spatial variations of the DF microseisms with the migration patterns of ocean wave fronts in Wavewatch III hindcasts. Correlation analyses are conducted by comparing the frequency compositions of and calculating the Pearson correlation coefficients between the DF microseisms and the ocean waves recorded at selected buoys. The observations and analyses lead to a hypothesis that the continental slope causes wave reflection, generating low frequency DF energy and that the continental shelf is where high frequency DF energy is mainly generated in ECUSA. The hypothesis is supported by the primary vibration directions being mainly perpendicular to the strike of the continental slope. Full article
(This article belongs to the Special Issue New Advances in Marine Engineering Geology)
Open AccessFeature PaperArticle
Reflection Analysis of Impermeable Slopes under Bimodal Sea Conditions
J. Mar. Sci. Eng. 2020, 8(2), 133; https://doi.org/10.3390/jmse8020133 - 18 Feb 2020
Viewed by 68
Abstract
Understanding of the reflection characteristics of coastal seawalls is crucial for design. Wave reflection can cause difficulties in small vessel manoeuvring at harbour entrances; this can cause damage to the toe of coastal structures by scouring. Previous studies have examined the reflection characteristics [...] Read more.
Understanding of the reflection characteristics of coastal seawalls is crucial for design. Wave reflection can cause difficulties in small vessel manoeuvring at harbour entrances; this can cause damage to the toe of coastal structures by scouring. Previous studies have examined the reflection characteristics of coastal seawalls under random wind-generated waves without considering the effects of wave bimodality created by the presence of swell waves. This present study focuses on the influence of random wave bimodality on the reflective characteristics of coastal seawalls. 823 experimental tests were conducted to examine the reflection performance of impermeable sloping seawalls under bimodal waves. Reflection coefficients were computed from each test. The analysis of the results suggests that both unimodal and bimodal waves give similar reflection characteristics. However, the reflection coefficient in bimodal sea states seems to be more prolonged than in the unimodal sea states. It was found that the reflection coefficients of coastal seawalls are strongly influenced by the seawall slope, the wave steepness, the relative water depth, and the surf similarity parameters. A new empirical reflection equation to describe the influence of wave bimodality on the reflection characteristics of coastal seawalls has been formulated based on this study. Full article
(This article belongs to the Section Coastal Engineering)
Open AccessFeature PaperArticle
Optimized Dislocation of Mobile Sensor Networks on Large Marine Environments Using Voronoi Partitions
J. Mar. Sci. Eng. 2020, 8(2), 132; https://doi.org/10.3390/jmse8020132 - 18 Feb 2020
Viewed by 78
Abstract
The real-time environmental surveillance of large areas requires the ability to dislocate sensor networks. Generally, the probability of the occurrence of a pollution event depends on the burden of possible sources operating in the areas to be monitored. This implies a challenge for [...] Read more.
The real-time environmental surveillance of large areas requires the ability to dislocate sensor networks. Generally, the probability of the occurrence of a pollution event depends on the burden of possible sources operating in the areas to be monitored. This implies a challenge for devising optimal real-time dislocation of wireless sensor networks. This challenge involves both hardware solutions and algorithms optimizing the displacements of mobile sensor networks in large areas with a vast number of sources of pollutant factors based mainly on diffusion mechanisms. In this paper, we present theoretical and simulated results inherent to a Voronoi partition approach for the optimized dislocation of a set of mobile wireless sensors with circular (radial) sensing power on large areas. The optimal deployment was found to be a variation of the generalized centroidal Voronoi configuration, where the Voronoi configuration is event-driven, and the centroid set of the corresponding generalized Voronoi cells changes as a function of the pollution event. The initial localization of the pollution events is simulated with a Poisson distribution. Our results could improve the possibility of reducing the costs for real-time surveillance of large areas, and other environmental monitoring when wireless sensor networks are involved. Full article
(This article belongs to the Special Issue Signals and Images in Sea Technologies)
Open AccessFeature PaperArticle
Implementation and Validation of a Potential Model for a Moored Floating Cylinder under Waves
J. Mar. Sci. Eng. 2020, 8(2), 131; https://doi.org/10.3390/jmse8020131 - 18 Feb 2020
Viewed by 67
Abstract
A three degrees-of-freedom model based on the potential flow theory was implemented to represent the motion of a slender cylindrical buoy under waves. The model calibration was performed by means of the comparison between the model results and the experiments performed at the [...] Read more.
A three degrees-of-freedom model based on the potential flow theory was implemented to represent the motion of a slender cylindrical buoy under waves. The model calibration was performed by means of the comparison between the model results and the experiments performed at the Laboratory of Hydraulic Engineering of the University of Bologna (Italy). The dynamics of the floating cylinder, placed at the mid-section of the wave flume and anchored at the bottom through a mooring system of four catenaries, were obtained through videography analysis, providing surge, heave and pitch motions. The implementation of the mathematical model consisted of two main parts: The first has been developed in the frequency domain by applying NEMOH to assess the hydrodynamic coefficients of the object, i.e., the excitation, radiation and added mass coefficients; then, the used mooring system was included in the time-domain model, solving the motion of the floating cylinder, by calibrating the mooring coefficients by comparing the results with the data. The simplicity of the implemented model is a very important feature, and it should be used as a preliminary study to understand the response of moored floating cylinders and others floating bodies under waves. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessArticle
Design of a Measuring Device and Winch Structure for Detecting the Distance and Direction of Two Seabed Pipelines
J. Mar. Sci. Eng. 2020, 8(2), 130; https://doi.org/10.3390/jmse8020130 - 18 Feb 2020
Viewed by 93
Abstract
To measure the distance and direction between the flanges of two seabed pipelines, a measuring device for pulling a rope in seawater was designed. Addressing the sealing problem of the key equipment the rotating shaft of the rope winch, we used the magnetic [...] Read more.
To measure the distance and direction between the flanges of two seabed pipelines, a measuring device for pulling a rope in seawater was designed. Addressing the sealing problem of the key equipment the rotating shaft of the rope winch, we used the magnetic coupling principle to transfer the driving moment, and converted the dynamic seal into a static seal structure to reliably seal the motor. Through an experiment measuring two pipelines with the underwater rope pulling device, we verified that the measuring accuracy of the device meets the design requirements, and confirmed the feasibility of applying magnetic coupling technology in winches. Full article
(This article belongs to the Special Issue Advances in Oceanic and Mechatronic Systems Engineering)
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Open AccessFeature PaperArticle
STORMTOOLS, Coastal Environmental Risk Index (CERI) Risk and Damage Assessment App
J. Mar. Sci. Eng. 2020, 8(2), 129; https://doi.org/10.3390/jmse8020129 - 17 Feb 2020
Viewed by 136
Abstract
STORMTOOLS Coastal Environmental Risk Index (CERI) predicts the coastal flooding damage to individual structures using coastal flooding levels, including the effects of sea level rise (SLR), provided in terms of the base flood elevation (BFE), specifications of the structure of interest (type and [...] Read more.
STORMTOOLS Coastal Environmental Risk Index (CERI) predicts the coastal flooding damage to individual structures using coastal flooding levels, including the effects of sea level rise (SLR), provided in terms of the base flood elevation (BFE), specifications of the structure of interest (type and first floor elevation) and the associated damage functions from the U.S. Army Corp of Engineers (USACE), North Atlantic Coast Comprehensive Study (NACCS). CERI has been applied to selected coastal communities in Rhode Island, including those in Narragansett Bay and along the southern Rhode Island shoreline. Users can access the results of CERI via ArcGIS online at the CERI website. The objective of this effort was to develop, test, distribute, and evaluate a mobile phone application (App) that allows the user to assess the risk from coastal flooding and the associated damage at the individual structure level using the CERI methodology. The App is publicly available and has been developed for both iOS and Android operating systems. Environmental data to support the App, in terms of 100 y flood BFE maps, including the effects of SLR and the selected site grade elevation, are provided in the application by the URI Environmental Data Center (EDC). The user enters the location and type of the structure of interest (residential number of stories, with or without basement, pile supported or commercial building and the first-floor elevation (FFE)) and the desired SLR. The App then calculates the percent structural damage based on the specified environmental conditions and structure specifications. The App can be applied to any structure at any coastal location within the state. The CERI App development project has been guided by an Advisory Board made up of key constituents involved in coastal management and development in the state. The effort included extensive testing of the App by various user groups. The App structure makes it simple and straightforward to transfer to coastal and inland flooded areas in other locations, requiring only the specification of BFEs and grade elevations. Full article
(This article belongs to the Section Coastal Engineering)
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Open AccessFeature PaperArticle
Photogrammetry: Linking the World Across the Water Surface
J. Mar. Sci. Eng. 2020, 8(2), 128; https://doi.org/10.3390/jmse8020128 - 17 Feb 2020
Viewed by 135
Abstract
Three-dimensional (3D) surveying and modelling of the underwater environment is challenging; however, it becomes even more arduous when the scene or asset to measure extends from above to underwater through the water surface. While this is topic of high interest for a number [...] Read more.
Three-dimensional (3D) surveying and modelling of the underwater environment is challenging; however, it becomes even more arduous when the scene or asset to measure extends from above to underwater through the water surface. While this is topic of high interest for a number of different application fields (engineering, geology, archeology), few solutions are available, usually expensive and with no guarantee of obtaining homogenous accuracy and resolution in the two media. This paper focuses on a procedure to survey and link the above and the underwater worlds based on photogrammetry. The two parts of the asset, above and underwater, are separately surveyed and then linked through two possible analytical procedures: (1) independent model adjustment or (2) relative orientation constraints. In the first case, rigid pre-calibrated rods are installed across the waterline on the object to be surveyed; in the second approach, a synchronized stereo-camera rig, with a camera in water and the other above the water, is employed. The theoretical foundation for the two approaches is provided and their effectiveness is proved through two challenging case studies: (1) the 3D survey of the leak of the Costa Concordia shipwreck and (2) 3D modelling of Grotta Giusti, a complex semi-submerged cave environment in Italy. Full article
(This article belongs to the Special Issue Underwater Imaging)
Open AccessArticle
Improved VIV Response Prediction Using Adaptive Parameters and Data Clustering
J. Mar. Sci. Eng. 2020, 8(2), 127; https://doi.org/10.3390/jmse8020127 - 17 Feb 2020
Viewed by 124
Abstract
Slender marine structures such as deep-water riser systems are continuously exposed to currents, leading to vortex-induced vibrations (VIV) of the structure. This may result in amplified drag loads and fast accumulation of fatigue damage. Consequently, accurate prediction of VIV responses is of great [...] Read more.
Slender marine structures such as deep-water riser systems are continuously exposed to currents, leading to vortex-induced vibrations (VIV) of the structure. This may result in amplified drag loads and fast accumulation of fatigue damage. Consequently, accurate prediction of VIV responses is of great importance for the safe design and operation of marine risers. Model tests with elastic pipes have shown that VIV responses are influenced by many structural and hydrodynamic parameters, which have not been fully modelled in present frequency domain VIV prediction tools. Traditionally, predictions have been computed using a single set of hydrodynamic parameters, often leading to inconsistent prediction accuracy when compared with observed field measurements and experimental data. Hence, it is necessary to implement a high safety factor of 10–20 in the riser design, which increases development costs and adds extra constraints in the field operation. One way to compensate for the simplifications in the mathematical prediction model is to apply adaptive parameters to describe different riser responses. The objective of this work is to demonstrate a new method to improve the prediction consistency and accuracy by applying adaptive hydrodynamic parameters. In the present work, a four-step approach has been proposed: First, the measured VIV response will be analysed to identify key parameters to represent the response characteristics. These parameters will be grouped by using data clustering algorithms. Secondly, optimal hydrodynamic parameters will be identified for each data group by optimisation against measured data. Thirdly, the VIV response using the obtained parameters will be calculated and the prediction accuracy evaluated. Last but not least, classification algorithms will be applied to determine the correct hydrodynamic parameters to be used for new cases. An iteration of the previous steps may be needed if the prediction accuracy of the new case is not satisfactory. This concept has been demonstrated with examples from experimental data. Full article
(This article belongs to the Special Issue Dynamics of Offshore Structures)
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Open AccessArticle
The Contribution of Multispectral Satellite Image to Shallow Water Bathymetry Mapping on the Coast of Misano Adriatico, Italy
J. Mar. Sci. Eng. 2020, 8(2), 126; https://doi.org/10.3390/jmse8020126 - 16 Feb 2020
Viewed by 201
Abstract
The results of absolute satellite-derived bathymetry (SDB) are presented in the current study. A comparative analysis was conducted on empirical methods in order to explore the potential of SDB in shallow water on the coast of Misano, Italy. Operations were carried out by [...] Read more.
The results of absolute satellite-derived bathymetry (SDB) are presented in the current study. A comparative analysis was conducted on empirical methods in order to explore the potential of SDB in shallow water on the coast of Misano, Italy. Operations were carried out by relying on limited in situ water depth data to extract and calibrate bathymetry from a QuickBird satellite image acquired on a highly dynamic coastal environment. The image was processed using the log-band ratio and optimal band ratio analysis (OBRA) methods. Preprocessing steps included the conversion of the raw satellite image into top of atmosphere reflectance, spatial filtering, land and water classification, the determination of the optimal OBRA spectral band pairs, and the estimation of relative SDB. Furthermore, calibration and vertical referencing were performed via in situ bathymetry acquired in November 2007. The relative bathymetry obtained from different band ratios were vertically referenced to the local datum using in situ water depth in order to obtain absolute SDB. The coefficient of determination (R2) and vertical root mean square error (RMSE) were computed for each method. A strong correlation with in situ field bathymetry was observed for both methods, with R2 = 0.8682 and RMSE = 0.518 m for the log-band ratio method and R2 = 0.8927–0.9108 and RMSE = 0.35 m for the OBRA method. This indicated a high degree of confidence of the SDB results obtained for the study area, with a high performance of the OBRA method for SDB mapping in turbid water. Full article
(This article belongs to the Special Issue Remote Sensing for Maritime and Water Monitoring)
Open AccessArticle
Effects of Design Factors on Drag Forces and Deformations on Marine Aquaculture Cages: A Parametric Study Based on Numerical Simulations
J. Mar. Sci. Eng. 2020, 8(2), 125; https://doi.org/10.3390/jmse8020125 - 16 Feb 2020
Viewed by 173
Abstract
In Japan, the marine aquaculture net cage has an important role in farming pacific bluefin tuna farming in oceans, and the design of the net cage needs to ensure robustness against hostile oceanic conditions. Accordingly, this study focuses on the drag forces and [...] Read more.
In Japan, the marine aquaculture net cage has an important role in farming pacific bluefin tuna farming in oceans, and the design of the net cage needs to ensure robustness against hostile oceanic conditions. Accordingly, this study focuses on the drag forces and the cage volume of the net cage, and on their variations induced by different design parameters (netting solidity ratio, netting height, and bottom weight). A series of parametric studies on drag force and deformation of the net cage was conducted using a numerical simulation model. Accordingly, the contribution of each parameter to the drag and volume was analyzed using a generalized additive model. The results indicate that the bottom weight had the highest contribution to the holding ratio of the cage volume, whereas the netting height had the highest contribution to the drag coefficient of the net cage. Finally, a fast prediction model was created by a backpropagation (BP) neural network model and was examined for the accurate prediction of the objective variables. Full article
(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)
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Open AccessArticle
Effect of Tidal Cycles on Bacterial Biofilm Formation and Biocorrosion of Stainless Steel AISI 316L
J. Mar. Sci. Eng. 2020, 8(2), 124; https://doi.org/10.3390/jmse8020124 - 15 Feb 2020
Viewed by 159
Abstract
The effects of tidal cycles associated with the water level on the biocorrosion of stainless steel AISI 316L were studied. Steel coupons were exposed to different conditions of immersion in mesocosms fed by fresh seawater either continuously or in accordance with the periodicity [...] Read more.
The effects of tidal cycles associated with the water level on the biocorrosion of stainless steel AISI 316L were studied. Steel coupons were exposed to different conditions of immersion in mesocosms fed by fresh seawater either continuously or in accordance with the periodicity of natural tides. After 5 and 15 weeks, all coupons were found to have undergone ennoblement associated with the formation of a biofilm. Analysis of the composition of the bacterial community using denaturing gradient gel electrophoresis (DGGE) revealed differences in the biological succession. After 15 weeks, exposure to the simulated tidal conditions resulted in biofilms with lesser bacterial richness; the corresponding rate of corrosion, as determined by weight loss, was about 40 times lower compared to the case for the continuous exposure to seawater. Phylogenetic analysis of selected DGGE bands and the inspection of biofilm morphologies revealed that the faster rate of corrosion was associated with the presence of iron-oxidizing Zetaproteobacteria and eukaryotic photosynthetic microorganisms. On the other hand, intermittent exposure to seawater resulted in the succession of microorganisms resistant to the stress associated with sudden environmental changes, which was associated with a low rate of corrosion. Full article
(This article belongs to the Section Marine Biology)
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Open AccessArticle
Experimental Study on 2D Motion Characteristics of Submerged Floating Tunnel in Waves
J. Mar. Sci. Eng. 2020, 8(2), 123; https://doi.org/10.3390/jmse8020123 - 15 Feb 2020
Viewed by 172
Abstract
Submerged floating tunnel (SFT) is a new type of transportation infrastructure for crossing sea straits in relatively deeper water. Compared with the fixed tunnel, the main challenge in designing a SFT is the stability maintaining in a complex hydrodynamic environment, especially for the [...] Read more.
Submerged floating tunnel (SFT) is a new type of transportation infrastructure for crossing sea straits in relatively deeper water. Compared with the fixed tunnel, the main challenge in designing a SFT is the stability maintaining in a complex hydrodynamic environment, especially for the wave-induced dynamic load. In this study, a series of systematic experiments were conducted to investigate the 2D motion characteristics (i.e., heave, sway and roll) of the SFT exposed to regular waves. The movement of the SFT model is measured by the image processing method which is a noncontact measurement. The experimental observation of SFT motion during the process of wave and SFT interaction is described in detail, and the influence of several governing parameters is thoroughly analyzed, including the wave height and period, submergence depth, buoyancy to weight ratio (BWR), and the mooring line angle. The results show that the motion amplitudes of SFT increase with the wave height increasing. The effect of wave period is related to the natural period of the structure. The sway, heave and roll of the SFT submerged beneath the water surface are much smaller than that of the SFT on the water surface. With the increase of BWR, the motion of SFT decreases. The motion amplitude increases with mooring line angle increasing. Finally, empirical equations are proposed to estimate the motion characteristics of the SFT. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessArticle
The Impact of the Underwater Hull Anti-Fouling Silicone Coating on a Ferry’s Fuel Consumption
J. Mar. Sci. Eng. 2020, 8(2), 122; https://doi.org/10.3390/jmse8020122 - 15 Feb 2020
Viewed by 100
Abstract
There are well-known specifics of ro-pax ferry shipping, such as the time factor as a consequence of keeping a regular timetable and the priority given to minimizing heeling, pitching, and rolling caused by maximum focus on passenger comfort and ro-ro cargo safety. It [...] Read more.
There are well-known specifics of ro-pax ferry shipping, such as the time factor as a consequence of keeping a regular timetable and the priority given to minimizing heeling, pitching, and rolling caused by maximum focus on passenger comfort and ro-ro cargo safety. It is also extremely important to control the ferry’s fuel consumption, being one of the most important cost components. The aim of the article is to draw the attention of shipping company managers to the great potential that lies in the use of routine operational data, collected exclusively on board the ferries. It is worth noting that the research in this paper is based on standard office software packages rather than advanced statistical methods of data analysis, which are usually not accessible for shipping managers. Contrary to typical ocean-going vessels, there are a number of factors that need to be taken into consideration when analyzing ro-pax ferry fuel consumption. Moreover, these factors occur, in many cases, accidentally and, thus, they are difficult to observe on board the ferry without utilizing expensive and time-consuming methods. The possibility of fuel control is important not only for economic reasons but also due to air pollution caused by engine exhausts. The article presents an estimation of increased fuel consumption caused by the degradation of the hull silicone anti-fouling coating. The presented estimations of fuel consumption may be treated as the base for calculations of the economic effectiveness of ferries. The attempt to resolve the above-mentioned problem was made on the basis of research on a real ferry, which took place on the Świnoujście-Trelleborg line between 2007 and 2019. Full article
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Open AccessArticle
Effect of Top Tension on Vortex-Induced Vibration of Deep-Sea Risers
J. Mar. Sci. Eng. 2020, 8(2), 121; https://doi.org/10.3390/jmse8020121 - 15 Feb 2020
Viewed by 125
Abstract
With the increase of water depth, the design and use of the top-tensioned risers (TTR) are facing more and more challenges. This research presents the effect of top tension on dynamic behavior of deep-sea risers by means of numerical simulations and experiments. First, [...] Read more.
With the increase of water depth, the design and use of the top-tensioned risers (TTR) are facing more and more challenges. This research presents the effect of top tension on dynamic behavior of deep-sea risers by means of numerical simulations and experiments. First, the governing equation of vortex-induced vibration (VIV) of TTR based on Euler-Bernoulli theory and Van der Pol wake-oscillator model was established, and the effect of top tension on natural vibration of TTR was discussed. Then, the dynamic response of TTR in shear current was calculated numerically by finite difference method. The displacement, bending stress and vibration frequency of TTR with the variation of top tension were investigated. Finally, a VIV experiment of a 5 m long flexible top-tensioned model was carried out at the towing tank of Tianjin University. The results show that the vibration displacement of TTR increases and the bending stress decreases as the top tension increases. The dominant frequency of VIV of TTR is controlled by the current velocity and is barely influenced by the top tension. With the increase of top tension, the natural frequency of TTR increases, the lower order modes are excited in the same current. Full article
(This article belongs to the Special Issue Waves and Ocean Structures)
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Open AccessEditorial
Offshore Wind Farms
J. Mar. Sci. Eng. 2020, 8(2), 120; https://doi.org/10.3390/jmse8020120 - 14 Feb 2020
Viewed by 131
Abstract
In 2018, we were approached by the editorial team of the Journal of Marine Science and Engineering (MDPI editorial) to act as guest editors of a Special Issue related to offshore wind energy [...] Full article
(This article belongs to the Special Issue Offshore Wind Farms)
Open AccessArticle
Numerical Investigation into Freak Wave Effects on Deepwater Pipeline Installation
J. Mar. Sci. Eng. 2020, 8(2), 119; https://doi.org/10.3390/jmse8020119 - 14 Feb 2020
Viewed by 175
Abstract
Freak waves are an extreme marine environment factor in offshore structure design and become a potential risk, particularly for laying oil-gas pipelines in deep waters. The objective of this study was to reveal the freak wave effects on dynamic behaviors of offshore pipelines [...] Read more.
Freak waves are an extreme marine environment factor in offshore structure design and become a potential risk, particularly for laying oil-gas pipelines in deep waters. The objective of this study was to reveal the freak wave effects on dynamic behaviors of offshore pipelines for deepwater installation. Thus, a dedicated finite element model (FEM) for deepwater pipeline installation by the S-lay method was developed with special consideration of freak waves. The FEM also took pipelay vessel motions, pipe–stinger roller interactions, and the cyclic contacts between the pipeline and seabed soil into account. Real vessel and stinger data from an actual engineering project in the South China Sea were collected to obtain an accurate simulation. Moreover, an effective superposition approach of combined transient wave trains and random wave trains was introduced, and various types of freak wave trains were simulated. Extensive numerical analyses of a 12 inch gas pipeline being installed into a water depth of 1500 m were implemented under various freak wave conditions. The noticeable influences of freak waves on the pipeline and seabed responses were identified, which provides significant awareness of offshore pipelines for deepwater installation design and field operation monitoring. Full article
Open AccessArticle
Mitigation Effect of Perforation Drilling on the Sliding Risk During Spudcan Installation Close to Footprints
J. Mar. Sci. Eng. 2020, 8(2), 118; https://doi.org/10.3390/jmse8020118 - 14 Feb 2020
Viewed by 152
Abstract
Perforation drilling is a promising technique to mitigate the sliding risk of jackup units installed around footprints. Based on the coupled Eulerian–Lagrangian (CEL) method, a 1/2 finite element model, including a rigid Lagrangian spudcan and a Eulerian soil part, was established, and the [...] Read more.
Perforation drilling is a promising technique to mitigate the sliding risk of jackup units installed around footprints. Based on the coupled Eulerian–Lagrangian (CEL) method, a 1/2 finite element model, including a rigid Lagrangian spudcan and a Eulerian soil part, was established, and the contact interface was modelled with the Coulomb friction model. Validated against an indoor perforation test, the model was adopted to investigate the mitigation mechanism and effects of the borehole diameter, number, depth, and the drilling range. The simulations reveal that the mitigation efficiency increases with the borehole diameter, number, and depth. However, it shows little improvement if the borehole depth increases beyond double footprint depth. The semidrilling at the outer side of the footprint is a little more effective than the fulldrilling at both the inner and outer sides of the footprint. The present work emphasizes the effects of perforation drilling parameters on the mitigation efficiency, which are of great significance to guide the engineering practice and guarantee the safe operation of the jack-up reinstallation close to existing footprints. Full article
Open AccessArticle
Ultimate Limit State Function and Its Fitting Method of Damaged Ship under Combined Loads
J. Mar. Sci. Eng. 2020, 8(2), 117; https://doi.org/10.3390/jmse8020117 - 14 Feb 2020
Viewed by 99
Abstract
The ultimate limit state function is one of the premises for the assessment of structure strength and the safety of ships under severe conditions. In order to study the residual strength of damaged ships under the combined load of vertical and horizontal bending [...] Read more.
The ultimate limit state function is one of the premises for the assessment of structure strength and the safety of ships under severe conditions. In order to study the residual strength of damaged ships under the combined load of vertical and horizontal bending moments acting on the hull girder, the ultimate limit state function of a damaged ship under combined load, and its fitting methods are investigated in this paper. An improved Smith Method is adopted to calculate the residual load carrying capacity of damage ships, where the rotation and translation of the neutral axis of the damaged cross-section are obtained using a particle swarm optimisation method. Because the distribution curve of the residual load carrying capacity of a damaged ship under combined load is asymmetric, the application of traditional explicit polynomial fitting methods results in poor accuracy. In this study, a piecewise weighted least square fitting method is adopted so as to guarantee the continuity in the transitions, and a method is proposed for fitting the ultimate limit state function of a damaged ship under combined load. Calculations of the residual strength show that the improved Smith Method is more accurate than the original Smith Method for the accurate position of the neutral axis. The error analysis of the fitting methods shows that the ultimate limit state function that is fitted using a piecewise weight least square method is more accurate. Full article
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Open AccessArticle
Initial Description of Pilotage and Tug Services in the Context of e-Navigation
J. Mar. Sci. Eng. 2020, 8(2), 116; https://doi.org/10.3390/jmse8020116 - 13 Feb 2020
Viewed by 119
Abstract
The International Maritime Organization (IMO)’s Maritime Safety Committee (MSC), at its 101st session (5 to 14 June 2019), adopted Resolution MSC.467(101) on the guidance on the definition and harmonization of the format and structure of maritime services in the context of e-Navigation and [...] Read more.
The International Maritime Organization (IMO)’s Maritime Safety Committee (MSC), at its 101st session (5 to 14 June 2019), adopted Resolution MSC.467(101) on the guidance on the definition and harmonization of the format and structure of maritime services in the context of e-Navigation and agreed to consolidate the descriptions of maritime services and to consider them together with all involved international organizations and interested member states, in order to harmonize the provision and exchange of maritime information and data. In doing so, the MSC also approved the initial descriptions of maritime services in the context of e-Navigation (IMO MSC.1/Circ.1610), which had been prepared by the Sub-Committee on Navigation, Communications and Search and Rescue, at its sixth session (16 to 25 January 2019). The information contained in this paper constitutes the descriptions of two selected examples of maritime services, an initial contribution for the harmonization of the formats and structures of pilotage and tug services. The initial description of each of maritime services is expected to be next periodically updated, taking into account developments and related work on international harmonization. Full article
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Open AccessArticle
Collision Prevention Algorithm for Fishing Vessels Using mmWAVE Communication
J. Mar. Sci. Eng. 2020, 8(2), 115; https://doi.org/10.3390/jmse8020115 - 13 Feb 2020
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Abstract
This study leveraged the millimeter wireless access in vehicular environments (mmWAVE) communication technology to reflect the maneuvering characteristics of small fishing vessels and constructed a collision prevention algorithm that can be applied relatively easily. The algorithm was verified through simulation and actual ship [...] Read more.
This study leveraged the millimeter wireless access in vehicular environments (mmWAVE) communication technology to reflect the maneuvering characteristics of small fishing vessels and constructed a collision prevention algorithm that can be applied relatively easily. The algorithm was verified through simulation and actual ship experiments. The algorithm had four components: detection of vessels within three miles; identification of dangerous vessels by applying the time to the closest point of approach (TCPA) and distance at the closest point of approach (DCPA) criteria; continuous monitoring of maritime traffic risk; and incremental alarm signaling. The simulations and experiments confirmed that the alarm was generated incrementally in accordance with the distance to a dangerous situation, with no false alarms. Thus, the proposed algorithm offers potential to enhance the safety of small fishing vessels. Full article
(This article belongs to the Special Issue Maritime Safety)
Open AccessFeature PaperArticle
Prediction of Unsteady Developed Tip Vortex Cavitation and Its Effect on the Induced Hull Pressures
J. Mar. Sci. Eng. 2020, 8(2), 114; https://doi.org/10.3390/jmse8020114 - 13 Feb 2020
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Abstract
Reducing the on-board noise and fluctuating pressures on the ship hull has been challenging and represent added value research tasks in the maritime industry. Among the possible sources for the unpalatable vibrations on the hull, propeller-induced pressures have been one of the main [...] Read more.
Reducing the on-board noise and fluctuating pressures on the ship hull has been challenging and represent added value research tasks in the maritime industry. Among the possible sources for the unpalatable vibrations on the hull, propeller-induced pressures have been one of the main causes due to the inherent rotational motion of propeller and its proximity to the hull. In previous work, a boundary element method, which solves for the diffraction potentials on the ship hull due to the propeller, has been used to determine the propeller induced hull pressures. The flow around the propeller was evaluated via a panel method which solves in time for the propeller loading, trailing wake, and the sheet cavities. In this article, the propeller panel method is extended so that it also solves for the shape of developed tip vortex cavities, the effects of which are also included in the evaluation of the hull pressures. The employed unsteady wake alignment scheme is first applied, in the absence of cavitation, to investigate the propeller performance in non-axisymmetric inflow, such as the inclined-shaft flow or the flow behind an upstream body. In the latter case, the propeller panel method is coupled with a Reynolds-Averaged Navier–Stokes (RANS) solver to determine the effective wake at the propeller plane. The results, including the propeller induced hull pressures, are compared with those measured in the experiments as well as with those from RANS, where the propeller is also simulated as a solid boundary. Then the methods are applied in the cases where partial cavities and developed tip vortex cavities coexist. The predicted cavity patterns, the developed tip vortex trajectories, and the propeller-induced hull pressures are compared with those measured in the experiments. Full article
Open AccessFeature PaperArticle
Severe Weather-Induced Exchange Flows through a Narrow Tidal Channel of Calcasieu Lake Estuary
J. Mar. Sci. Eng. 2020, 8(2), 113; https://doi.org/10.3390/jmse8020113 - 13 Feb 2020
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Abstract
Exchange flows between estuaries and the coastal ocean are important for land-ocean interactions and ecosystem health. This study is aimed at resolving severe weather-induced exchange flows between the Calcasieu Lake Estuary and Gulf of Mexico. For that purpose, we use data from a [...] Read more.
Exchange flows between estuaries and the coastal ocean are important for land-ocean interactions and ecosystem health. This study is aimed at resolving severe weather-induced exchange flows between the Calcasieu Lake Estuary and Gulf of Mexico. For that purpose, we use data from a long-term deployment of side-looking acoustic Doppler current profilers (ADCPs) and conductivity-temperature-depth sensors (CTDs) as well as flow velocity data from a boat operated survey. Regression between the transport measured from a boat mounted ADCP and the velocity data from a fixed side-looking ADCP is done to calculate a long-term transport along the Calcasieu Pass. Analyses have been done for the hydrodynamic response to 16 cold fronts passing the study area. Effects of six strongest cold fronts are discussed in more detail. Results have confirmed that the hydrodynamics is highly correlated with the frequent cold fronts. The highest correlation coefficient is r ~0.75 between the north wind and along channel transport. In general, winds from the southern quadrants push water into the estuary before each frontal passage; after the passage of the front, a rapid change of wind direction to the northern quadrants produces strong outward flows. A quasi-steady state balance between the wind stress and water level difference proposed in recent studies for different systems is further confirmed and discussed in this system. The quasi-steady state balance leads to a relatively high R2 value of greater than 0.8 between the modeled water level gradient and actual observed gradient. We have also applied a regression model, derived from the momentum balance requirement, for the subtidal exchange flow as a function of wind components and their squares which yield an R2 value greater than 0.7. With a confidence in the regression model, we further implement it for twelve years from 26 February 2007 to 10 April 2019. Four extreme events during this 12-year period of time are discussed–they include the Hurricane Ike (2008), Tropical Storm Lee (2011), a warm front, and a cold front. This hindcast of the exchange flows over multiple years can provide a useful tool for coastal management and research for estuarine channels where continuous observations of velocity are not always available. Full article
(This article belongs to the Section Physical Oceanography)
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Open AccessArticle
Detection of Small Ship Objects Using Anchor Boxes Cluster and Feature Pyramid Network Model for SAR Imagery
J. Mar. Sci. Eng. 2020, 8(2), 112; https://doi.org/10.3390/jmse8020112 - 12 Feb 2020
Viewed by 184
Abstract
The synthetic aperture radar (SAR) has a special ability to detect objects in any climate and weather conditions. Consequently, SAR images are widely used in maritime transportation safety and fishery law enforcement for maritime object detection. Currently, deep-learning models are being extensively used [...] Read more.
The synthetic aperture radar (SAR) has a special ability to detect objects in any climate and weather conditions. Consequently, SAR images are widely used in maritime transportation safety and fishery law enforcement for maritime object detection. Currently, deep-learning models are being extensively used for the detection of objects from images. Among them, the feature pyramid network (FPN) uses pyramids for representing semantic information regardless of the scale and has an improved accuracy of object detection. It is also suitable for the detection of multiple small ship objects in SAR images. This study aims to resolve the problems associated with small-object and multi-object ship detection in complex scenarios e.g., when a ship nears the port, by proposing a detection method based on an optimized FPN model. The feature pyramid model is first embedded in a traditional region proposal network (RPN) and mapped into a new feature space for object identification. Subsequently, the k-means clustering algorithm based on the shape similar distance (SSD) measure is used to optimize the FPN. Initial anchor boxes and tests are created using the SAR ship dataset. Experimental results show that the proposed algorithm for object detection shows an accuracy of 98.62%. Compared with Yolo, the RPN based on VGG/ResNet, FPN based on VGG/ResNet, and other models in complex scenarios, the proposed model shows a higher accuracy rate and better overall performance. Full article
(This article belongs to the Special Issue Maritime Safety)
Open AccessArticle
Robust Classification Method for Underwater Targets Using the Chaotic Features of the Flow Field
J. Mar. Sci. Eng. 2020, 8(2), 111; https://doi.org/10.3390/jmse8020111 - 12 Feb 2020
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Abstract
Fish can sense their surrounding environment by their lateral line system (LLS). In order to understand the extent to which information can be derived via LLS and to improve the adaptive ability of autonomous underwater vehicles (AUVs), a novel strategy is presented, which [...] Read more.
Fish can sense their surrounding environment by their lateral line system (LLS). In order to understand the extent to which information can be derived via LLS and to improve the adaptive ability of autonomous underwater vehicles (AUVs), a novel strategy is presented, which directly uses the information of the flow field to distinguish the object obstacle. The flow fields around different targets are obtained by the numerical method, and the pressure signal on the virtual lateral line is studied based on the chaos theory and fast Fourier transform (FFT). The compounded parametric features, including the chaotic features (CF) and the power spectrum density (PSD), which is named CF-PSD, are used to recognize the kinds of obstacles. During the research of CF, the largest Lyapunov exponent (LLE), saturated correlation dimension (SCD), and Kolmogorov entropy (KE) are taken into account, and PSD features include the number, amplitude, and position of wave crests. A two-step support vector machine (SVM) is built and used to classify the shapes and incidence angles based on the CF-PSD. It is demonstrated that the flow fields around triangular and square targets are chaotic systems, and the new findings indicate that the object obstacle can be recognized directly based on the information of the flow field, and the consideration of a parametric feature extraction method (CF-PSD) results in considerably higher classification success. Full article
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Open AccessFeature PaperArticle
Using Video Monitoring to Test a Fetch-Based Aeolian Sand Transport Model
J. Mar. Sci. Eng. 2020, 8(2), 110; https://doi.org/10.3390/jmse8020110 - 12 Feb 2020
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Abstract
Transport of beach sand to the foredune by wind is essential for dunes to grow. The aeolian sand transport rate is related to wind velocity, but wind-based models often overpredict this transport for narrow beaches (<100 m). To better predict aeolian sand transport, [...] Read more.
Transport of beach sand to the foredune by wind is essential for dunes to grow. The aeolian sand transport rate is related to wind velocity, but wind-based models often overpredict this transport for narrow beaches (<100 m). To better predict aeolian sand transport, the fetch-based Aeolus model was developed. Here, we qualitatively test this model by comparing its transport-rate output to visual signs of aeolian transport on video imagery collected at Egmond aan Zee, the Netherlands, during a six-month winter period. The Aeolus model and the Argus images often agree on the timing of aeolian transport days, except when transport is small; that is not always visible on the Argus images. Consistent with the imagery (minimal signs of aeolian activity in strong winds), the Aeolus model sometimes predicts the actual transport to be smaller than the potential transport. This difference is largest when wind velocity is large, and its direction is cross-shore. Although transport limitations are not predicted to be common, the results suggest that their effect on the total transport in the study period was substantial. This indicates that the fetch distance should be taken into account when calculating aeolian transport for narrow beaches on longer timescales (>weeks). Full article
(This article belongs to the Special Issue Observation, Analysis, and Modeling of Nearshore Dynamics)
Open AccessFeature PaperArticle
Numerical Analysis of NOx Reduction Using Ammonia Injection and Comparison with Water Injection
J. Mar. Sci. Eng. 2020, 8(2), 109; https://doi.org/10.3390/jmse8020109 - 11 Feb 2020
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Abstract
This work analyzes NOx reduction in a marine diesel engine using ammonia injection directly into the cylinder and compares this procedure with water injection. A numerical model based on the so-called inert species method was applied. It was verified that ammonia injection [...] Read more.
This work analyzes NOx reduction in a marine diesel engine using ammonia injection directly into the cylinder and compares this procedure with water injection. A numerical model based on the so-called inert species method was applied. It was verified that ammonia injection can provide almost 80% NOx reduction for the conditions analyzed. Furthermore, it was found that the effectiveness of the chemical effect using ammonia is extremely dependent on the injection timing. The optimum NOx reduction was obtained when ammonia is injected during the expansion stroke, while the optimum injection timing using water is near top dead center. Chemical, thermal, and dilution effects of both ammonia and water injection were compared. The chemical effect was dominant in the case of ammonia injection. On the other hand, water injection reduces NOx through dilution and, more significantly, through a thermal effect. Full article
(This article belongs to the Special Issue Marine Engines Performance and Emissions)
Open AccessArticle
Model of Bio-Colonisation on Mooring Lines:Updating Strategy Based on a Static Qualifying Sea State for Floating Wind Turbines
J. Mar. Sci. Eng. 2020, 8(2), 108; https://doi.org/10.3390/jmse8020108 - 11 Feb 2020
Viewed by 153
Abstract
Bio-colonisation affects the ageing of materials and the behaviour of offshore structures. Mooring systems and umbilicals belong to the family of slender bodies which are components sensitive to bio-colonisation because of a change of dynamic behaviour due to shape, roughness and mass modifications. [...] Read more.
Bio-colonisation affects the ageing of materials and the behaviour of offshore structures. Mooring systems and umbilicals belong to the family of slender bodies which are components sensitive to bio-colonisation because of a change of dynamic behaviour due to shape, roughness and mass modifications. However, this stochastic process in time and space is hard to predict. The purpose is then twofold: first, to provide a stochastic spatial model of the bio-colonisation on a mooring line; second, to show that in some defined environmental conditions, such as low wave height, low wind and current velocities, the monitoring of mooring lines tension can help to assess and reduce uncertainty on this model. Therefore, a comprehensive stochastic modelling based on mussels colonisation was carried out using on-site videotapes, experimental campaigns and expert knowledge. We studied the efficiency of a virtual sensing network using this model and a conditional entropy metric. It is first shown that the spatial model fits well with experimental data, and second that a denser medium accuracy sensor network is to be preferred to a single high accuracy fairlead sensor to reduce the uncertainty on the model parameters. It is then worth updating bio-colonisation on mooring lines during the life-time of a floating wind turbine. Full article
(This article belongs to the Special Issue Monitoring of Coastal and Offshore Structures)
Open AccessFeature PaperArticle
Filling the Gap of Data-Limited Fish Species in the Eastern Mediterranean Sea: A Contribution by Citizen Science
J. Mar. Sci. Eng. 2020, 8(2), 107; https://doi.org/10.3390/jmse8020107 - 10 Feb 2020
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Abstract
The biodiversity of the Mediterranean Sea is rapidly changing due to anthropogenic activity and the recent increase of seawater temperature. Citizen science is escalating as an important contributor in the inventory of rare and data-limited species. In this study, we present several records [...] Read more.
The biodiversity of the Mediterranean Sea is rapidly changing due to anthropogenic activity and the recent increase of seawater temperature. Citizen science is escalating as an important contributor in the inventory of rare and data-limited species. In this study, we present several records of five data-limited native fish species from the eastern Mediterranean Sea: Alectis alexandrina (Geoffroy Saint-Hilaire, 1817), Ranzania laevis (Pennant, 1776), Dalatias licha (Bonnaterre, 1788), Lophotus lacepede (Giorna, 1809), and Sudis hyalina (Rafinesque, 1810). All of the records were collected by a participatory process involving fishers and validated by associated taxonomic experts of the citizen science programme “Is it Alien to you? Share it!!!”. This study fills an important gap for the distribution of the reported species and signifies the important role of citizen participation as a tool for extending marine biodiversity knowledge and fisheries management in an area with several gaps of knowledge on targeted and non-targeted species. Full article
(This article belongs to the Special Issue Coastal Fish Research)
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Open AccessArticle
Numerical Study on Hydrodynamics of Ships with Forward Speed Based on Nonlinear Steady Wave
J. Mar. Sci. Eng. 2020, 8(2), 106; https://doi.org/10.3390/jmse8020106 - 10 Feb 2020
Viewed by 175
Abstract
In this paper, an improved potential flow model is proposed for the hydrodynamic analysis of ships advancing in waves. A desingularized Rankine panel method, which has been improved with the added effect of nonlinear steady wave-making (NSWM) flow in frequency domain, is employed [...] Read more.
In this paper, an improved potential flow model is proposed for the hydrodynamic analysis of ships advancing in waves. A desingularized Rankine panel method, which has been improved with the added effect of nonlinear steady wave-making (NSWM) flow in frequency domain, is employed for 3D diffraction and radiation problems. Non-uniform rational B-splines (NURBS) are used to describe the body and free surfaces. The NSWM potential is computed by linear superposition of the first-order and second-order steady wave-making potentials which are determined by solving the corresponding boundary value problems (BVPs). The so-called mj terms in the body boundary condition of the radiation problem are evaluated with nonlinear steady flow. The free surface boundary conditions in the diffraction and radiation problems are also derived by considering nonlinear steady flow. To verify the improved model and the numerical method adopted in the present study, the nonlinear wave-making problem of a submerged moving sphere is first studied, and the computed results are compared with the analytical results of linear steady flow. Subsequently, the diffraction and radiation problems of a submerged moving sphere and a modified Wigley hull are solved. The numerical results of the wave exciting forces, added masses, and damping coefficients are compared with those obtained by using Neumann–Kelvin (NK) flow and double-body (DB) flow. A comparison of the results indicates that the improved model using the NSWM flow can generally give results in better agreement with the test data and other published results than those by using NK and DB flows, especially for the hydrodynamic coefficients in relatively low frequency ranges. Full article
(This article belongs to the Special Issue Stability and Seakeeping of Marine Vessels)
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