Study of wave field estimate by using wave energy on reef with steep slope

Between the Wave Energy Converters (WECs) of a farm, hydrodynamic interactions occur and have an impact on the surrounding wave field, both close to the WECs (“near field” effects) and at large distances from their location (“far field” effects). To simulate this “far field” impact in a fast and accurate way, a generic coupling methodology between hydrodynamic models has been developed by the Coastal Engineering Research Group of Ghent University in Belgium. This coupling methodology has been widely used for regular waves. However, it has not been developed yet for realistic irregular sea states. The objective of this paper is to present a validation of the novel coupling methodology for the test case of irregular waves, which is demonstrated here for coupling between the mild slope wave propagation model, MILDwave, and the ‘Boundary Element Method’-based wave–structure interaction solver, NEMOH. MILDwave is used to model WEC farm “far field” effects, while NEMOH is used to model “near field” effects. The results of the MILDwave-NEMOH coupled model are validated against numerical results from NEMOH, and against the WECwakes experimental data for a single WEC, and for WEC arrays of five and nine WECs. Root Mean Square Error (RMSE) between disturbance coefficient (Kd) values in the entire numerical domain ( R M S E K d , D ) are used for evaluating the performed validation. The R M S E K d , D between results from the MILDwave-NEMOH coupled model and NEMOH is lower than 2.0% for the performed test cases, and between the MILDwave-NEMOH coupled model and the WECwakes experimental data R M S E K d , D remains below 10%. Consequently, the efficiency is demonstrated of the coupling methodology validated here which is used to simulate WEC farm impact on the wave field under the action of irregular waves.

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Analysis On Characters And Dynamic Mechanism Of The Storm-induced Fluid Mud In the North Passage of the Yangtze Estuary

10.5194/egusphere-egu2020-12649 ◽

2020 ◽

Author(s):

Jiufa Li ◽

Weihua Li ◽

Xiaohe Zhang

Keyword(s):

Storm Surge ◽

Density Profile ◽

Wave Energy ◽

Tidal Current ◽

Steep Slope ◽

Yangtze River Estuary ◽

Main Role ◽

Fluid Mud ◽

The North ◽

Navigation Channel

<p>The development of storm-induced fluid mud is an important factor to disturb the waterway transportation. Based on the observation data of fluid mud from 2010 to 2016, the basic characteristics and dynamic factors of the storm-induced fluid mud in the North Passage of the Yangtze River Estuary are analyzed. The main conclusions are as follows: (1) The sediment composition of the storm-induced fluid mud in the North Passage has little difference with the suspended sediment, which shows high correlation with the bed sediments in the middle/lower channel and the north beach of the North Passage, but the space difference of which is weak. (2) Large-thickness fluid mud in the North Passage mainly locates in the manual dredged navigation channel, and cannot stay in the steep slope beaches. It manly distributes between IIN-C and Y channel unit where is under the protection of the south and north embankments. (3) The storm-induced fluid mud in the North Passage characterizes as three stages. The primary-stage fluid mud develops during the storm surge, characterizes as low density, blurred upper and lower interfaces. It migrates quickly following the tidal current, and can be easily weaken by the peak tidal velocity. The development-stage fluid mud mainly occurs after the storm surge, characterizes as clear upper interface, "h" type density profile, with good stability and slowly migration. The dissipation-stage fluid mud characterizes as decreasing sediment amount, increasing sediment density, fuzzy lower boundary, "L" type or multi-steps type density profile, high stability and very weak flowability. (4) The cumulative wave energy during storm surge processes is the most important factor to determine the scale of the storm-induced fluid mud in the North Passage. The stronger the cumulative wave energy, the longer duration and the larger scale of the storm-induced fluid mud will develops. In addition, the weaker tidal power during the storm surge processes is favorable to the formation of the storm-induced fluid mud in the North Passage. Stronger tidal force would cause the shorter dissipation period of the storm-induced fluid mud. (5) The mechanism that up layer tidal current disturbs the fluid mud layer that make its sediment tends to dissipation and transport to the downstream and reciprocating following the tidal current, which plays the main role during the local extinction process of the storm-induced fluid mud in the North Passage. (6) The process of the high-sediment concentration gravity flow generates in the steep slope of the beach and near-bed invades to the manual dredged navigation channel during the storm surge process, is the key process mechanism for the rapid accumulation of storm-induced fluid mud in the North Passage.</p>

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Spectrally Resolved Energy Dissipation Rate and Momentum Flux of Breaking Waves

Journal of Physical Oceanography ◽

10.1175/2007jpo3762.1 ◽

2008 ◽

Vol 38 (6) ◽

pp. 1296-1312 ◽

Cited By ~ 77

Author(s):

Johannes R. Gemmrich ◽

Michael L. Banner ◽

Chris Garrett

Keyword(s):

Energy Dissipation ◽

Wave Field ◽

Wave Energy ◽

Dissipation Rate ◽

Momentum Flux ◽

Phase Speed ◽

Breaking Waves ◽

Energy Dissipation Rate ◽

Small Scale ◽

Breaking Wave

Abstract Video observations of the ocean surface taken from aboard the Research Platform FLIP reveal the distribution of the along-crest length and propagation velocity of breaking wave crests that generate visible whitecaps. The key quantity assessed is Λ(c)dc, the average length of breaking crests per unit area propagating with speeds in the range (c, c + dc). Independent of the wave field development, Λ(c) is found to peak at intermediate wave scales and to drop off sharply at larger and smaller scales. In developing seas breakers occur at a wide range of scales corresponding to phase speeds from about 0.1 cp to cp, where cp is the phase speed of the waves at the spectral peak. However, in developed seas, breaking is hardly observed at scales corresponding to phase speeds greater than 0.5 cp. The phase speed of the most frequent breakers shifts from 0.4 cp to 0.2 cp as the wave field develops. The occurrence of breakers at a particular scale as well as the rate of surface turnover are well correlated with the wave saturation. The fourth and fifth moments of Λ(c) are used to estimate breaking-wave-supported momentum fluxes, energy dissipation rate, and the fraction of momentum flux supported by air-entraining breaking waves. No indication of a Kolmogorov-type wave energy cascade was found; that is, there is no evidence that the wave energy dissipation is dominated by small-scale waves. The proportionality factor b linking breaking crest distributions to the energy dissipation rate is found to be (7 ± 3) × 10−5, much smaller than previous estimates.

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Theory of scattered P- and S-wave energy in a random isotropic scattering medium

Bulletin of the Seismological Society of America ◽

10.1785/bssa0830041264 ◽

1993 ◽

Vol 83 (4) ◽

pp. 1264-1276 ◽

Cited By ~ 5

Author(s):

Yuehua Zeng

Keyword(s):

Elastic Wave ◽

Wave Field ◽

Wave Energy ◽

Wave Scattering ◽

Energy Equation ◽

P Wave ◽

Isotropic Scattering ◽

Scattering Medium ◽

S Wave ◽

Elastic Wave Energy

Abstract A new theory is presented to study the scattered elastic wave energy propagation in a random isotropic scattering medium. It is based on a scattered elastic wave energy equation that extends the work of Zeng et al. (1991) on multiple scattering by considering S to P and P to S wave scattering conversions. We obtain a complete solution of the scattered elastic wave energy equation by solving the equation in the frequency/wave-number domain. Using a discrete wave-number sum technique combined with a modified repeated averaging and the FFT method, we compute numerically the complete solution. By considering that the scattering conversion from P- to S-wave energy is about (α/β)4 times greater than that from S to P waves (Aki, 1992), we found that the P-wave scattering field was converted quickly to the S-wave scattering field, leading to the conclusion that coda waves generated from both P- and S-wave sources are actually dominated by scattered S waves. We also compared our result with that obtained under the acoustic wave assumption. The acoustic wave assumption for seismic coda works quite well for the scattered S-wave field but fails for the scattered P-wave field. Our scattered elastic wave energy equation provides a theoretical foundation for studying the scattered wave field generated by a P-wave source such as an explosion. The scattered elastic wave energy equation can be easily generalized to an inhomogeneous random scattering medium by considering variable scattering and absorption coefficients and elastic wave velocities in the earth.

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A Global Model for the Diapycnal Diffusivity Induced by Internal Gravity Waves

Journal of Physical Oceanography ◽

10.1175/jpo-d-12-0207.1 ◽

2013 ◽

Vol 43 (8) ◽

pp. 1759-1779 ◽

Cited By ~ 44

Author(s):

Dirk Olbers ◽

Carsten Eden

Keyword(s):

Energy Density ◽

Internal Wave ◽

Wave Field ◽

Ocean Circulation ◽

Gravity Waves ◽

Wave Energy ◽

Internal Gravity Waves ◽

Radiation Balance ◽

Dissipation Rates ◽

Diapycnal Diffusivity

Abstract An energetically consistent model for the diapycnal diffusivity induced by breaking of internal gravity waves is proposed and tested in local and global settings. The model [Internal Wave Dissipation, Energy and Mixing (IDEMIX)] is based on the spectral radiation balance of the wave field, reduced by integration over the wavenumber space, which yields a set of balances for energy density variables in physical space. A further simplification results in a single partial differential equation for the total energy density of the wave field. The flux of energy to high vertical wavenumbers is parameterized by a functional derived from the wave–wave scattering integral of resonant wave triad interactions, which also forms the basis for estimates of dissipation rates and related diffusivities of ADCP and hydrography fine-structure data. In the current version of IDEMIX, the wave energy is forced by wind-driven near-inertial motions and baroclinic tides, radiating waves from the respective boundary layers at the surface and the bottom into the ocean interior. The model predicts plausible magnitudes and three-dimensional structures of internal wave energy, dissipation rates, and diapycnal diffusivities in rough agreement to observational estimates. IDEMIX is ready for use as a mixing module in ocean circulation models and can be extended with more spectral components.

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Mixed Rossby–Gravity Wave–Wave Interactions

Journal of Physical Oceanography ◽

10.1175/jpo-d-18-0074.1 ◽

2019 ◽

Vol 49 (1) ◽

pp. 291-308 ◽

Cited By ~ 4

Author(s):

Carsten Eden ◽

Manita Chouksey ◽

Dirk Olbers

Keyword(s):

Kinetic Equation ◽

Wave Field ◽

Gravity Wave ◽

Rossby Wave ◽

Wave Energy ◽

Wave Mode ◽

Linear Wave ◽

Wave Interactions ◽

First Case ◽

Linear Gravity

AbstractMixed triad wave–wave interactions between Rossby and gravity waves are analytically derived using the kinetic equation for models of different complexity. Two examples are considered: initially vanishing linear gravity wave energy in the presence of a fully developed Rossby wave field and the reversed case of initially vanishing linear Rossby wave energy in the presence of a realistic gravity wave field. The kinetic equation in both cases is numerically evaluated, for which energy is conserved within numerical precision. The results are validated by a corresponding ensemble of numerical model simulations supporting the validity of the weak-interaction assumption necessary to derive the kinetic equation. Since they are generated by nonresonant interactions only, the energy transfers toward the respective linear wave mode with vanishing energy are small in both cases. The total generation of energy of the linear gravity wave mode in the first case scales to leading order as the square of the Rossby number in agreement with independent estimates from laboratory experiments, although a part of the linear gravity wave mode is slaved to the Rossby wave mode without wavelike temporal behavior.

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A Novel Method for Estimating Wave Energy Converter Performance in Variable Bathymetry Regions and Applications

Energies ◽

10.3390/en11082092 ◽

2018 ◽

Vol 11 (8) ◽

pp. 2092 ◽

Cited By ~ 13

Author(s):

Kostas Belibassakis ◽

Markos Bonovas ◽

Eugen Rusu

Keyword(s):

Wave Field ◽

Wave Energy ◽

Water Waves ◽

Bottom Topography ◽

Wave Energy Converter ◽

Diffraction Radiation ◽

Floating Bodies ◽

Energy Converter ◽

Coupled Mode ◽

Energy Absorbers

A numerical model is presented for the estimation of Wave Energy Converter (WEC) performance in variable bathymetry regions, taking into account the interaction of the floating units with the bottom topography. The proposed method is based on a coupled-mode model for the propagation of the water waves over the general bottom topography, in combination with a Boundary Element Method for the treatment of the diffraction/radiation problems and the evaluation of the flow details on the local scale of the energy absorbers. An important feature of the present method is that it is free of mild bottom slope assumptions and restrictions and it is able to resolve the 3D wave field all over the water column, in variable bathymetry regions including the interactions of floating bodies of general shape. Numerical results are presented concerning the wave field and the power output of a single device in inhomogeneous environment, focusing on the effect of the shape of the floater. Extensions of the method to treat the WEC arrays in variable bathymetry regions are also presented and discussed.

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Acoustic wave driven mass loss in late-type giant stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900156645 ◽

1987 ◽

Vol 122 ◽

pp. 325-326 ◽

Cited By ~ 1

Author(s):

M. Cuntz ◽

L. Hartmann ◽

P. Ulmschneider

Keyword(s):

Acoustic Wave ◽

Mass Loss ◽

Wave Field ◽

Wave Energy ◽

Acoustic Waves ◽

Late Type ◽

Large Wave ◽

Giant Stars ◽

Wave Energy Flux ◽

Type Giant

Mass loss generated by radiatively damped acoustic waves is investigated. We find that a persistent wave energy flux leads to extended chromospheres. Mass loss is quite likely produced if the wave field retains a transient character and if large wave periods are used.

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Measurement of the Effect of Power Absorption in the Lee of a Wave Energy Converter

Volume 4: Ocean Engineering; Ocean Renewable Energy; Ocean Space Utilization, Parts A and B ◽

10.1115/omae2009-79793 ◽

2009 ◽

Cited By ~ 3

Author(s):

Ian G. C. Ashton ◽

Lars Johanning ◽

Brian Linfoot

Keyword(s):

Wave Field ◽

Wave Energy ◽

Ocean Waves ◽

Wave Climate ◽

Wave Energy Converter ◽

Energy Converter ◽

Wave Measurements ◽

Temporal And Spatial Variability ◽

Power Capture ◽

Local Wave

Monitoring the effect of floating wave energy converter (WEC) devices on the surrounding wave field will be an important tool for monitoring impacts on the local wave climate and coastlines. Measurement will be hampered by the natural variability of ocean waves and the complex response of WEC devices, causing temporal and spatial variability in the effects. Measurements taken during wave tank tests at MARINTEK are used to analyse the effectiveness of point wave measurements at resolving the influence of an array of WEC on the local wave conditions. The variability of waves is measured in front and in the lee of a device, using spectral analysis to identify changes to the incident wave field due to the operating WEC. The power capture and radiation damping are analysed in order to predict the measured changes. Differences in the wave field across the device are clearly observable in the frequency domain. However, they do not unanimously show a reduction in wave energy in the lee of a device and are not well predicted by measured power capture.

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