ON THE TRANSFORMATION OF WAVE STATISTICS DUE TO SHOALING

The results of a 1:40 scale physical model investigation into the shoaling process are described. The model simulated a nearly constant slope of 1:40 with wave measurements made at a depth of approximately 25 and 9 m. Two hundred individual tests were undertaken, with four offshore significant wave heights as the only test variant. The results indicate that the most severe nearshore wave conditions do not occur with the worst offshore conditions. There is evidence of a significant increase in low frequency wave energy in the nearshore zone.

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WAVE STATISTICS ALONG THE NORTHERN COAST OF EGYPT

Coastal Engineering Proceedings ◽

10.9753/icce.v14.5 ◽

1974 ◽

Vol 1 (14) ◽

pp. 5

Author(s):

M. Manohar ◽

I.E. Mobarek ◽

A. Morcos ◽

H. Rahal

Keyword(s):

Nile Delta ◽

Spectral Band ◽

Northern Coast ◽

Wave Statistics ◽

Wave Measurements ◽

Narrow Spectral Band ◽

Wave Heights ◽

Significant Wave Heights ◽

Nile Delta Coast ◽

Comprehensive Study

As a forerunner of a comprehensive study of wave and energy climate of the Nile Delta coast covering a period of more than 50 years, wave measurements taken in 3 locations along the coast in the year 1972 were statistically analysed. Shortcut methods based on statistical approach were used to analyse the wave records enabling quicker analysis. Spectral analysis of the wave records indicates narrow spectral band similar to Raleigh distribution. The histograms and frequency distribution curves of significant wave heights, and the relationships between various statistical prarameters such as H , H,,,„, H,,„ and H also max 1/10' 1/3 rms agree closely with Raleigh distribution curves and parameters enabling the use of Raleigh distribution function in subsequent studies. Finally since the wave characteristics and wave energy climates are most important in the analysis of coastline changes, they are drawn from the data obtained from the analysis.

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Experimental Investigation of Irregular Wave Cancellation Using a Cycloidal Wave Energy Converter

Volume 7: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2012-83388 ◽

2012 ◽

Cited By ~ 1

Author(s):

Stefan G. Siegel ◽

Casey Fagley ◽

Marcus Römer ◽

Thomas McLaughlin

Keyword(s):

Wave Energy ◽

Deep Ocean ◽

Ocean Waves ◽

Wave Energy Converter ◽

Irregular Waves ◽

Energy Converter ◽

Irregular Wave ◽

Wave Measurements ◽

Wave Heights ◽

Significant Wave Heights

The ability of a Cycloidal Wave Energy Converter (CycWEC) to cancel irregular deep ocean waves is investigated in a 1:300 scale wave tunnel experiment. A CycWEC consists of one or more hydrofoils attached equidistant to a shaft that is aligned parallel to the incoming waves. The entire device is fully submerged in operation. Wave cancellation requires synchronization of the rotation of the CycWEC with the incoming waves, as well as adjustment of the pitch angle of the blades in proportion to the wave height. The performance of a state estimator and controller that achieve this objective were investigated, using the signal from a resistive wave gage located up-wave of the CycWEC as input. The CycWEC model used for the present investigations features two blades that are adjustable in pitch in real time. The performance of the CycWEC for both a superposition of two harmonic waves, as well as irregular waves following a Bretschneider spectrum is shown. Wave cancellation efficiencies as determined by wave measurements of about 80% for the majority of the cases are achieved, with wave periods varying from 0.4s to 0.75s and significant wave heights of Hs ≈ 20mm. This demonstrates that the CycWEC can efficiently interact with irregular waves, which is in good agreement with earlier results obtained from numerical simulations.

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An Idealization of Wave Scatter Diagram for Spectral Fatigue Analysis

Volume 2: Structures, Safety and Reliability ◽

10.1115/omae2009-79721 ◽

2009 ◽

Author(s):

Min Han Oh ◽

Ki Myung Lee ◽

Young Sik Jang

Keyword(s):

Fatigue Analysis ◽

Scatter Diagram ◽

Analysis Method ◽

Sea State ◽

Environmental Loads ◽

Wave Data ◽

Wave Measurements ◽

Spectral Models ◽

Wave Heights ◽

Significant Wave Heights

A spectral fatigue analysis method is most popularly applied for the detailed design of FPSOs. As the environmental loads at the installation site are directly calculated in the spectral analysis, this method gives the most reliable results although it needs much time-consuming works to fully reflect the environmental loads. As the technology of wave measurements advances, the measured wave data increase. Also their spectral models are very complicated because these include many wave components such as swells and wind seas. Since much time and effort are needed to treat these enormous and complicated wave data for the spectral fatigue analysis, a rational idealization of wave data is definitely required. In this paper, wave scatter diagram at Offshore Nigeria was reviewed and their idealization method was proposed. The influence level of each sea state of the wave scatter diagram was identified considering the fatigue damage levels estimated from the significant wave heights and dominant fatigue load RAOs. The sea states giving small fatigue damages were lumped symmetrically by merging or disregarding while those giving large fatigue damages were kept as original. For the validation of this method, the comparisons of dominant fatigue loads and representative fatigue damages were presented for the idealized wave scatter diagram and the original one. From these comparison works, it was confirmed that the idealized wave scatter diagram gives reliable results with reduced amount of calculation work.

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Round Robin Testing: Exploring Experimental Uncertainties through a Multifacility Comparison of a Hinged Raft Wave Energy Converter

Journal of Marine Science and Engineering ◽

10.3390/jmse9090946 ◽

2021 ◽

Vol 9 (9) ◽

pp. 946

Author(s):

Thomas Davey ◽

Javier Sarmiento ◽

Jérémy Ohana ◽

Florent Thiebaut ◽

Sylvain Haquin ◽

...

Keyword(s):

Wave Energy ◽

Physical Modelling ◽

Round Robin ◽

Wave Energy Converter ◽

Energy Converter ◽

Mean Power ◽

Wave Heights ◽

Significant Wave Heights ◽

Similar Good ◽

Six Degree Of Freedom

The EU H2020 MaRINET2 project has a goal to improve the quality, robustness and accuracy of physical modelling and associated testing practices for the offshore renewable energy sector. To support this aim, a round robin scale physical modelling test programme was conducted to deploy a common wave energy converter at four wave basins operated by MaRINET2 partners. Test campaigns were conducted at each facility to a common specification and test matrix, providing the unique opportunity for intercomparison between facilities and working practices. A nonproprietary hinged raft, with a nominal scale of 1:25, was tested under a set of 12 irregular sea states. This allowed for an assessment of power output, hinge angles, mooring loads, and six-degree-of-freedom motions. The key outcome to be concluded from the results is that the facilities performed consistently, with the majority of variation linked to differences in sea state calibration. A variation of 5–10 % in mean power was typical and was consistent with the variability observed in the measured significant wave heights. The tank depth (which varied from 2–5 m) showed remarkably little influence on the results, although it is noted that these tests used an aerial mooring system with the geometry unaffected by the tank depth. Similar good agreement was seen in the heave, surge, pitch and hinge angle responses. In order to maintain and improve the consistency across laboratories, we make recommendations on characterising and calibrating the tank environment and stress the importance of the device–facility physical interface (the aerial mooring in this case).

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Evaluation of an Extended Operational Boussinesq-Type Wave Model for Calculating Low-Frequency Waves in Intermediate Depths

Volume 1: Offshore Technology; Polar and Arctic Sciences and Technology ◽

10.1115/omae2011-49480 ◽

2011 ◽

Author(s):

Martijn P. C. de Jong ◽

Mart Borsboom ◽

Jan A. M. de Bont ◽

Bas van Vossen

Keyword(s):

Low Frequency ◽

Wave Model ◽

Coastal Engineering ◽

Extended Model ◽

Depth Range ◽

Frequency Range ◽

Frequency Wave ◽

Type Wave ◽

Wave Heights ◽

Low Frequency Waves

The motions of (LNG) vessels moored offshore at depths ranging from about 20 to 100 m may depend significantly on the presence of (bound) low-frequency waves with periods in the order of 100 s. This is because these moored vessels show a large motion response in this frequency range and because the energy contents of low-frequency waves at these ‘intermediate’ depths is relatively large. As part of the Joint Industry Project HawaI, the operational Boussinesq-type wave model of Deltares, TRITON, was used to investigate whether this type of wave models could predict bound low-frequency waves (setdown waves) at intermediate depths. Comparison to measured and theoretical data, however, showed an underestimation of the computed levels of bound low-frequency wave heights for this depth range by a factor 2 to 4. Recently, additional tests were made with TRITON in situations for which the model has been designed: coastal engineering applications in shallow water (depths up to at most 20 m). These also showed an underestimation of the bound low-frequency wave heights, albeit smaller, up to a factor 2. In view of the importance of the energy contained in the low-frequency range for certain nearshore and shoreline processes, such as morphological processes, this underestimation is also of concern in coastal engineering. This triggered the development of a higher-order extension of the TRITON model equations (Borsboom, 2008, Wellens, 2010), with the aim to improve the accuracy of the model for long waves while still keeping computational times within acceptable (operational) limits. This paper reports on the usefulness of the extended model for the field of application considered in JIP HawaI/II: providing wave data for calculating the motions of vessels moored in intermediate depths. The results show a significant improvement of the modeling of nonlinear wave dynamics, including the prediction of bound low-frequency waves. This means that the model extension is an important step towards an operational Boussinesq-type wave model with sufficient accuracy in both the wave-frequency (sea, swell) and the low-frequency range for applications in intermediate depths.

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A study of a speed amplified linear generator for low-frequency wave energy conversion

Mechanical Systems and Signal Processing ◽

10.1016/j.ymssp.2020.107226 ◽

2021 ◽

Vol 149 ◽

pp. 107226

Author(s):

Zhenwei Liu ◽

Xu Wang ◽

Elie Al Shami ◽

Nick J. Baker ◽

Xueyu Ji

Keyword(s):

Energy Conversion ◽

Wave Energy ◽

Low Frequency ◽

Wave Energy Conversion ◽

Frequency Wave ◽

Linear Generator

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Wave energy potency in East Java coast

MATEC Web of Conferences ◽

10.1051/matecconf/201817701018 ◽

2018 ◽

Vol 177 ◽

pp. 01018

Author(s):

Heri Saptono Warpindyasmoro

Keyword(s):

Wave Energy ◽

Energy Supply ◽

Data Access ◽

Energy Resources ◽

Environmental Research ◽

Ocean Wave Energy ◽

Energy Needs ◽

Wave Heights ◽

Significant Wave Heights ◽

Access Program

It is predicted that in 2025, Indonesia energy needs is going to reach 280% of current needs. Presently, the renewable energy has only contributed 5.7% of total energy supply. The aim of this research is to investigate wave energy potency in several coasts of East Java which were Pacitan, Jember, Besuki and Tuban. Wave data (significant wave heights and wave periods) were obtained from the ERDDAP server (Environmental Research Division's Data Access Program). Southern East Java Coast showed potency for ocean wave energy resources. The coast of Pacitan had energy of 232 MWh/m/year and the coast of Jember had energy of 190 MWh/m/year.

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Global Wave Data Assimilation Model using Optimal Interpolation Method

10.5194/egusphere-egu2020-12145 ◽

2020 ◽

Author(s):

Kyeong Ok Kim ◽

Hanna Kim ◽

Kyung Tae Jung ◽

Young Ho Kim

Keyword(s):

Data Assimilation ◽

Wave Energy ◽

Interpolation Method ◽

Energy Spectra ◽

Global Ocean ◽

Optimal Interpolation ◽

Significant Wave ◽

Wave Data ◽

Wave Heights ◽

Significant Wave Heights

To construct a reanalyzed global ocean wave data set with improved accuracy, which is important for the better understanding and simulation of various near-surface ocean dynamics, a data assimilation method has been embedded to the global spectral wave model based on WW3. The major factors controlling the wave simulation accuracy are the wind condition and the parameterization on the wave energy development, dissipation and nonlinear processes between wave components. However, the atmospheric prediction accuracy is still not sufficient, and the parameterization cannot be generalized due to the local geographic conditions.In detail, the data assimilation using the optimal interpolation method has been applied, verification through the comparison with satellite altimeters and buoy observations has been made with examination of the data assimilation effects. The significant wave heights computed by the integration of wave energy spectra are showed to be quite similar with observed results. However, the wave periods and directions related to the shape of wave energy spectra are not sufficiently comparable. Generally there have been difficulties in predicting the propagation of long period waves such as swells.The wave energy spectra on wave number and direction domains was multiplied by optimal interpolation method with the ratio of observed significant wave heights on first guessed simulated results. The energy spectra was thereafter shifted by the difference between simulated and observed peak wave periods and directions. From then examination of the reanalysis simulation during 1 year, it could be seen that the accuracy of the model with the data assimilation shows better results than that without data assimilation.

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Extreme Inundation Statistics on a Composite Beach

Water ◽

10.3390/w12061573 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1573

Author(s):

Ahmed Abdalazeez ◽

Ira Didenkulova ◽

Denys Dutykh ◽

Céline Labart

Keyword(s):

Time Series ◽

Wave Breaking ◽

Statistical Characteristics ◽

Wave Runup ◽

Incoming Wave ◽

Wave Statistics ◽

Nonlinear Shallow Water Equations ◽

Wave Heights ◽

Wave Nonlinearity ◽

Constant Slope

The runup of initial Gaussian narrow-banded and wide-banded wave fields and its statistical characteristics are investigated using direct numerical simulations, based on the nonlinear shallow water equations. The bathymetry consists of the section of a constant depth, which is matched with the beach of constant slope. To address different levels of nonlinearity, time series with five different significant wave heights are considered. The selected wave parameters allow for also seeing the effects of wave breaking on wave statistics. The total physical time of each simulated time-series is 1000 h (~360,000 wave periods). The statistics of calculated wave runup heights are discussed with respect to the wave nonlinearity, wave breaking and the bandwidth of the incoming wave field. The conditional Weibull distribution is suggested as a model for the description of extreme runup heights and the assessment of extreme inundations.

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