scholarly journals Full-Scale Maneuvering Trials Correction and Motion Modelling Based on Actual Sea and Weather Conditions

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 3963
Author(s):  
Bin Mei ◽  
Licheng Sun ◽  
Guoyou Shi
Keyword(s):  
Wind Waves ◽  
Measurement Data ◽  
Correction Method ◽  
Pattern Search ◽  
Full Scale ◽  
Sea Surface ◽  
Surface Currents ◽  
Hydrodynamic Coefficients ◽  
Ship Maneuvering ◽  
Ship Maneuverability

Aiming at the poor accuracy and difficult verification of maneuver modeling induced by the wind, waves and sea surface currents in the actual sea, a novel sea trials correction method for ship maneuvering is proposed. The wind and wave drift forces are calculated according to the measurement data. Based on the steady turning hypothesis and pattern search algorithm, the adjustment parameters of wind, wave and sea surface currents were solved, the drift distances and drift velocities of wind, waves and sea surface currents were calculated and the track and velocity data of the experiment were corrected. The hydrodynamic coefficients were identified by the test data and the ship maneuvering motion model was established. The results show that the corrected data were more accurate than log data, the hydrodynamic coefficients can be completely identified, the prediction accuracy of the advance and tactical diameters were 93% and 97% and the prediction of the maneuvering model was accurate. Numerical cases verify the correction method and full-scale maneuvering model. The turning circle advance and tactical diameter satisfy the standards of the ship maneuverability of International Maritime Organization (IMO).

Effect of Ship-Induced Langmuir-Type Circulations on Distribution of Surface-Active Substances and Damping of Short Wind Waves

2019 ◽  
Author(s):  
Ryan Somero ◽  
Andre Basovich ◽  
Eric Paterson
Keyword(s):  
Surface Waves ◽  
Wind Waves ◽  
Sea Surface ◽  
Damping Factor ◽  
Surface Currents ◽  
Ship Wake ◽  
Damping Effect ◽  
Surface Active ◽  
Convergence And Divergence ◽  
Active Substances

It has recently been shown that the interaction of ship-generated nonuniform currents with ambient surface waves can lead to the generation of Langmuir-type circulations (LTCs) (Basovich 2011) and a persistent wake (Somero et al. 2018). Based on this work, it is shown here that the LTC and surface currents of the persistent wake are responsible for the redistribution of surface-active substances (SAS) and a corresponding change in the damping of short surface waves. The persistent wake is a region of the ship wake, where initial ship-generated perturbations have mostly decayed. The LTCs are similar in nature to Langmuir circulations which arise as a result of instability of wind-driven current. LTCs produce a secondary flow with velocity transverse to the direction of the ship, and width significantly larger than the ship beam. Because LTCs are generated in large scale, they persist for a long time after the passage of the ship. Transverse surface currents produced by LTCs in the ship wake redistribute the SAS films at the sea surface. These currents create strong convergence and divergence zones which in turn produce streaks with different concentrations of SAS. The change in concentration of SAS affects the film pressure and the damping effect of SAS on the short surface waves. This effect is represented by a damping factor and is a crucial parameter in determination of the spectral density of short wind waves. Therefore, the damping effect of the film, as represented by the damping factor, is responsible for sea surface roughness modification and is important for prediction of synthetic-aperture RADAR (SAR) imagery of ship wakes on the ocean surface. In this article, we present the mathematical and computational methods, along with simulation results for a naval surface combatant operating in calm, head, and following seas. The simulation results clearly show that the convergence and divergence zones strongly influence the relative SAS concentration and the spatial distribution of the damping factor, the latter of which defines the structure of SAR images of the persistent wake. Comparisons of the magnitude of the damping factor with available SAR data are shown to be in good agreement.

Scale Effects on Ship Maneuverability Using RANS

2018 ◽  
Author(s):  
Motoki Araki
Keyword(s):  
Cfd Simulation ◽  
Scale Effects ◽  
Full Scale ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Ship Maneuvering ◽  
Ship Maneuverability ◽  
Computational Fluid Dynamics Cfd ◽  
Rudder Angle ◽  
Maneuvering Simulations

Predicting ship maneuverability is one of the important topics in ship engineering. However because of the huge difference between model and full scale Reynolds number (Re), it is almost impossible to predict full scale ship maneuverability using conventional methods such as model test. On the other hands, with the developments of computational technologies and computational fluid dynamics (CFD) techniques, CFD simulations are widely applied on ship maneuvering problems (e.g. Stern et al., 2011). Moreover some of the researchers start the CFD simulation with full scale Re especially on propulsion problems (e.g. Tezdogan et al., 2015) which showing reasonable results. Therefore, in this paper, captive maneuvering simulations (rudder angle test) in model/full scale Re on KVLCC2 are carried out using Reynolds-averaged Navier–Stokes (RANS) solver NAGISA (Ohashi et al., 2014) with the overset gird method UP_GRID (Kodama et al., 2012). And the results between model and full scale simulations are compared in maneuvering coefficients and flow field to reveal the scale effect on ship maneuverability.

ИССЛЕДОВАНИЯ АКУСТИЧЕСКИХ ХАРАКТЕРИСТИК ВЕРХНЕГО СЛОЯ МОРЯ МЕТОДОМ МНОГОЧАСТОТНОГО АКУСТИЧЕСКОГО ЗОНДИРОВАНИЯ

2020 ◽  
Author(s):  
V.A. Bulanov ◽  
I.V. Korskov ◽  
A.V. Storozhenko ◽  
S.N. Sosedko
Keyword(s):  
High Frequency ◽  
Wave Motion ◽  
High Spatial Resolution ◽  
Wind Waves ◽  
Acoustic Parameter ◽  
Sea Surface ◽  
Near Surface ◽  
Acoustical Properties ◽  
Acoustic Spectroscopy ◽  
Sea Bottom

Описано применение акустического зондирования для исследования акустических характеристик верхнего слоя моря с использованием широкополосных остронаправленных инвертированных излучателей,устанавливаемых на дно. В основу метода положен принцип регистрации обратного рассеяния и отраженияот поверхности моря акустических импульсов с различной частотой, позволяющий одновременно измерятьрассеяние и поглощение звука и нелинейный акустический параметр морской воды. Многочастотное зондирование позволяет реализовать акустическую спектроскопию пузырьков в приповерхностных слоях моря,проводить оценку газосодержания и получать данные о спектре поверхностного волнения при различных состояниях моря вплоть до штормовых. Применение остронаправленных высокочастотных пучков ультразвукапозволяет разделить информацию о планктоне и пузырьках и определить с высоким пространственным разрешением структуру пузырьковых облаков, образующихся при обрушении ветровых волн, и структуру планктонных сообществ. Участие планктона в волновом движении в толще морской воды позволяет определитьпараметры внутренних волн спектр и распределение по амплитудам в различное время.This paper represents the application of acoustic probingfor the investigation of acoustical properties of the upperlayer of the sea using broadband narrow-beam invertedtransducers that are mounted on the sea bottom. Thismethod is based on the principle of the recording of thebackscattering and reflections of acoustic pulses of differentfrequencies from the sea surface. That simultaneouslyallows measuring scattering and absorption of the soundand non-linear acoustic parameter of seawater. Multifrequencyprobing allows performing acoustic spectroscopy ofbubbles in the near-surface layer of the sea, estimating gascontent, and obtaining data on the spectrum of the surfacewaves in various states of the sea up to a storm. Utilizationof the high-frequency narrow ultrasound beams allows us toseparate the information about plankton and bubbles and todetermine the structure of bubble clouds, created during thebreaking of wind waves, along with the structure of planktoncommunities with high spatial resolution. The participationof plankton in the wave motion in the seawater columnallows determining parameters of internal waves, such asspectrum and distribution of amplitudes at different times.

scholarly journals Honing in on bioluminescent milky seas from space

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Steven D. Miller ◽  
Steven H. D. Haddock ◽  
William C. Straka ◽  
Curtis J. Seaman ◽  
Cynthia L. Combs ◽  
...  
Keyword(s):  
Scientific Inquiry ◽  
Water Mass ◽  
Marine Ecosystem ◽  
Sea Surface ◽  
Surface Currents ◽  
Maritime Continent ◽  
Low Light ◽  
Composition Formation ◽  
Mass Isolation ◽  
New Generation

AbstractMilky seas are a rare form of marine bioluminescence where the nocturnal ocean surface produces a widespread, uniform and steady whitish glow. Mariners have compared their appearance to a daylit snowfield that extends to all horizons. Encountered most often in remote waters of the northwest Indian Ocean and the Maritime Continent, milky seas have eluded rigorous scientific inquiry, and thus little is known about their composition, formation mechanism, and role within the marine ecosystem. The Day/Night Band (DNB), a new-generation spaceborne low-light imager, holds potential to detect milky seas, but the capability has yet to be demonstrated. Here, we show initial examples of DNB-detected milky seas based on a multi-year (2012–2021) search. The massive bodies of glowing ocean, sometimes exceeding 100,000 km2 in size, persist for days to weeks, drift within doldrums amidst the prevailing sea surface currents, and align with narrow ranges of sea surface temperature and biomass in a way that suggests water mass isolation. These findings show how spaceborne assets can now help guide research vessels toward active milky seas to learn more about them.

Prediction of an actual RPM and engine power of an LNGC based on full-scale measurement data

2018 ◽  
Vol 147 ◽  
pp. 496-516 ◽  
Author(s):  
Youngjun You ◽  
Jaehan Kim ◽  
Min-Guk Seo
Keyword(s):  
Measurement Data ◽  
Full Scale ◽  
Engine Power

scholarly journals Controls of Caribbean surface hydrology during the mid- to late Holocene: insights from monthly resolved coral records

2013 ◽  
Vol 9 (2) ◽  
pp. 841-858 ◽  
Author(s):  
C. Giry ◽  
T. Felis ◽  
M. Kölling ◽  
W. Wei ◽  
G. Lohmann ◽  
...  
Keyword(s):  
Late Holocene ◽  
Hydrological Cycle ◽  
Summer Precipitation ◽  
Caribbean Sea ◽  
Sea Surface ◽  
Surface Currents ◽  
Surface Hydrology ◽  
Multidecadal Variability ◽  
Southern Caribbean ◽  
The Caribbean

Abstract. Several proxy-based and modeling studies have investigated long-term changes in Caribbean climate during the Holocene, however, very little is known on its variability on short timescales. Here we reconstruct seasonality and interannual to multidecadal variability of sea surface hydrology of the southern Caribbean Sea by applying paired coral Sr/Ca and δ18O measurements on fossil annually banded Diploria strigosa corals from Bonaire. This allows for better understanding of seasonal to multidecadal variability of the Caribbean hydrological cycle during the mid- to late Holocene. The monthly resolved coral Δδ18O records are used as a proxy for the oxygen isotopic composition of seawater (δ18Osw) of the southern Caribbean Sea. Consistent with modern day conditions, annual δ18Osw cycles reconstructed from three modern corals reveal that freshwater budget at the study site is influenced by both net precipitation and advection of tropical freshwater brought by wind-driven surface currents. In contrast, the annual δ18Osw cycle reconstructed from a mid-Holocene coral indicates a sharp peak towards more negative values in summer, suggesting intense summer precipitation at 6 ka BP (before present). In line with this, our model simulations indicate that increased seasonality of the hydrological cycle at 6 ka BP results from enhanced precipitation in summertime. On interannual to multidecadal timescales, the systematic positive correlation observed between reconstructed sea surface temperature and salinity suggests that freshwater discharged from the Orinoco and Amazon rivers and transported into the Caribbean by wind-driven surface currents is a critical component influencing sea surface hydrology on these timescales.

Clustering Applied to Large Sets of Environmental Conditions for Selecting Typical Scenarios for Ship Maneuvering Real-Time Simulations

2021 ◽  
Author(s):  
Felipe M. Moreno ◽  
Eduardo A. Tannuri
Keyword(s):  
Time Series ◽  
Cluster Analysis ◽  
Environmental Conditions ◽  
Wind Waves ◽  
Fast Time ◽  
Large Set ◽  
Ship Maneuvering ◽  
Partitioning Around Medoids ◽  
Waves And Currents ◽  
Maneuvering Simulations

Abstract The methodology described in this paper is used to reduce a large set of combined wind, waves, and currents to a smaller set that still represents well enough the desired site for ship maneuvering simulations. This is achieved by running fast-time simulations for the entire set of environmental conditions and recording the vessel’s drifting time-series while it is controlled by an automatic-pilot based on a line-of-sight algorithm. The cases are then grouped considering how similar the vessel’s drifting time-series are, and one environmental condition is selected to represent each group found by the cluster analysis. The measurement of dissimilarity between the time-series is made by application of Dynamic Time Warping and the Cluster Analysis is made by the combination of Partitioning Around Medoids algorithm and the Silhouette Method. Validation is made by maneuvering simulations made with a Second Deck Officer.

Scanning laser wave recorder with registration of “instantaneous” sea surface profiles

2021 ◽  
Author(s):  
V.V. Sterlyadkin ◽  
K.V. Kulikovsky ◽  
A.V. Kuzmin ◽  
E.A. Sharkov ◽  
M.V. Likhacheva
Keyword(s):  
Spatial Scales ◽  
Wind Waves ◽  
Single Point ◽  
Video Recording ◽  
Surface Profile ◽  
Weather Conditions ◽  
Sea Surface ◽  
Sea Waves ◽  
Wide Range ◽  
Wave Recorder

AbstractA direct optical method for measuring the “instantaneous” profile of the sea surface with an accuracy of 1 mm and a spatial resolution of 3 mm is described. Surface profile measurements can be carried out on spatial scales from units of millimeters to units of meters with an averaging time of 10−4 s. The method is based on the synchronization of the beginning of scanning a laser beam over the sea surface and the beginning of recording the radiation scattered on the surface onto the video camera matrix. The heights of all points of the profile are brought to a single point in time, which makes it possible to obtain “instantaneous” profiles of the sea surface with the frequency of video recording. The measurement technique and data processing algorithm are described. The errors of the method are substantiated. The results of field measurements of the parameters of sea waves are presented: amplitude spectra, distribution of slopes at various spatial averaging scales. The applied version of the wave recorder did not allow recording capillary oscillations, but with some modernization it will be possible. The method is completely remote, does not distort the properties of the surface, is not affected by wind, waves and sea currents, it allows you to measure the proportion of foam on the surface. The possibility of applying the proposed method at any time of the day and in a wide range of weather conditions has been experimentally proved.

scholarly journals Improving the GNSS-R Specular Reflection Point Positioning Accuracy Using the Gravity Field Normal Projection Reflection Reference Surface Combination Correction Method

2018 ◽  
Vol 11 (1) ◽  
pp. 33 ◽  
Author(s):  
Fan Wu ◽  
Wei Zheng ◽  
Zhaowei Li ◽  
Zongqiang Liu
Keyword(s):  
Gravity Field ◽  
Specular Reflection ◽  
Correction Method ◽  
Sea Surface ◽  
Reference Surface ◽  
Reflection Point ◽  
Positioning Accuracy ◽  
Normal Projection ◽  
Point Positioning ◽  
Surface Correction

Global Navigation Satellite System Reflectometry (GNSS-R) is of great significance for the extraction and research of precise information of sea surface topography. Improving measurement accuracy is necessary for realizing spaceborne GNSS-R sea surface altimetry application. The main error source of GNSS-R distance measurement is the error of the specular reflection point positioning, which directly affects the sea surface altimetry accuracy on the reference datum. There is an elevation error of several tens of meters between the reflection reference surface used by the existing specular reflection point geometric positioning methods and the sea surface elevation, which is importantly influenced by the earth’s gravity field. Therefore, the gravity field reflection reference surface correction is the key to improving the specular reflection point positioning accuracy. In this study, based on the correction of the GNSS-R reflection reference surface, research on improving the positioning accuracy of the specular reflection point is carried out. Firstly, in order to reduce the positioning error caused by the elevation difference between the reflection reference surface and the sea surface, the gravity field reflection reference surface correction method (GFRRSCM) which corrects the reflection reference surface from the WGS-84 ellipsoid to geoid is proposed, and the positioning accuracy is improved by 25.15 m. Secondly, the normal projection reflection reference surface correction method (NPRRSCM) is proposed to correct the specular reflection point determined by the GFRRSCM from the reflection reference plane of the radial to that of the normal. Additionally, in the process of solving the spatial geometric relationship of the reflection path, the approximate substitution error is reduced by directly solving the normal projection on the plane, and the positioning accuracy is further improved by 13.05 m towards the normal. Thirdly, based on the gravity field normal projection reflection reference surface combination correction method (GF-NPRRSCCM), the specular reflection point positioning accuracy is synthetically improved by 28.66 m.

scholarly journals On Capabilities of Tracking Marine Surface Currents Using Artificial Film Slicks

2019 ◽  
Vol 11 (7) ◽  
pp. 840 ◽  
Author(s):  
Ivan Kapustin ◽  
Olga Shomina ◽  
Alexey Ermoshkin ◽  
Nikolay Bogatov ◽  
Alexander Kupaev ◽  
...  
Keyword(s):  
Water Film ◽  
Remote Sensing Data ◽  
Sea Surface ◽  
Application Of Surfactants ◽  
Surface Currents ◽  
Band Formation ◽  
Suggested Approach ◽  
Marine Currents ◽  
Sar Imagery ◽  
Film Spreading

It is known that films on the sea surface can appear due to ship pollution, river and collector drains, as well as natural biological processes. Marine film slicks can indicate various geophysical processes in the upper layer of the ocean and in the atmosphere. In particular, slick signatures in SAR-imagery of the sea surface at low and moderate wind speeds are often associated with marine currents. Apart from the current itself, other factors such as wind and the physical characteristics of films can significantly influence the dynamics of slick structures. In this paper, a prospective approach aimed at measuring surface currents is developed. The approach is based on the investigation of the geometry of artificial banded slicks formed under the action of marine currents and on the retrieval of the current characteristics from this geometry. The developed approach is applied to quasi stationary slick bands under conditions when the influence of the film spreading effects can be neglected. For the stationary part of the slick band where transition processes of the band formation, e.g., methods of application of surfactants on water, film spreading processes, possible wind transformation etc., become negligible, some empirical relations between the band geometrical characteristics and the characteristics of the surface currents are obtained. The advantage of the approach is a possibility of getting information concerning the spatial structure of marine currents along the entire slick band. The suggested approach can be efficient for remote sensing data verification.

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