Nonlinear Laser-Like Ocean Waves Radiation Orthogonal to the Wind

2020 ◽  
Author(s):  
Andrei Pushkarev ◽  
Vladimir Zakharov
Keyword(s):  
Wave Energy ◽  
Wind Waves ◽  
Wave Interaction ◽  
Ocean Waves ◽  
Wave Turbulence ◽  
Wave System ◽  
Self Similar ◽  
Similar Solutions ◽  
Ocean Wind ◽  
The Waves

Abstract We study deep water ocean wind-driven waves in strait, with wind directed orthogonally to the shore, through exact Hassel-mann equation. The strait has “dissipative” shores, there is no any reflection from the coast lines. We show that the wave turbulence evolution can be split in time into two different regimes. During the first regime, the waves propagate along the wind, and the wind-driven sea can be described by the self-similar solutions of Hasselmann equation. The second regime starts later in time, after significant enough wave energy accumulation at the down-wind boundary. Since this moment the ensemble of waves propagating against the wind starts its formation. Also, orthogonal to the wind waves, propagating along the strait, start to appear. The wave system eventually reaches asymptotic stationary state in time, consisting of two co-existing states: the first, self-similar wave ensemble, propagating with the wind, and the second – quasi-monochromatic waves, propagating almost orthogonally to the wind direction, and tending to slant against the wind at the angle of 15° closer to the wave turbulence origination shore line. Those “secondary waves” appear only due to intensive nonlinear wave-wave interaction. The total wave energy exceeds its “expected value” approximately by the factor of two, with respect to estimated in the absence of the shores. It is expected that in the reflective shores presence this amplification will grow essentially. We propose to call this “secondary” laser-like Nonlinear Ocean Waves Amplification mechanism by the acronym NOWA.

Using Remote Sensed Data for Wave Energy Resource Assessment

2008 ◽  
Author(s):  
M. T. Pontes ◽  
M. Bruck
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Wind Waves ◽  
Energy Resource ◽  
Ocean Waves ◽  
Resource Assessment ◽  
Altimeter Data ◽  
Zero Crossing ◽  
Frequency Wave ◽  
Buoy Data

The conversion of the energy contained in ocean waves into an useful form of energy namely electrical energy requires the knowledge at least of wave height and period parameters. Since 1992 at least one altimeter has been accurately measuring significant wave height Hs. To derive wave period parameters namely zero-crossing period Tz from the altimeter backscatter coefficient various models have been proposed. Another space-borne sensor that measures ocean waves is SAR (or the advanced ASAR) from which directional spectra are obtained. In this paper various models proposed to compute Tz from altimeter data are presented and verified against a collocated set of Jason altimeter and NDBC buoy data. A good fitting of altimeter estimates to buoy data was found. Directional spectra obtained from ENVISAT ASAR measurements were compared against NDBC buoy data. It was concluded that for the buoys that are more sensitive to long low-frequency wave components the fitting of wave parameters and spectral form is good for short spatial distances. However, since the cut-off ASAR frequency is low (reliable information is provided only for long waves) their use for wave energy resource assessment in areas where wind-waves are important is limited.

On self-similarity of waves in tropical cyclones

2021 ◽  
Author(s):  
Maria Yurovskaya ◽  
Vladimir Kudryavtrsev ◽  
Bertrand Chapron
Keyword(s):  
Wave Field ◽  
Tropical Cyclones ◽  
Numerical Solutions ◽  
Parametric Model ◽  
Linear Wave ◽  
Wave System ◽  
Large Computer ◽  
State Assignment ◽  
Self Similar ◽  
Similar Solutions

<p>Wave fields generated by tropical cyclones (TC) are of strong interest for marine engineering, navigation safety, determination of coastal sea levels and coastal erosion. Considerable efforts have been made to improve knowledge about the surface waves in TC, both from measurements and numerical experiments. Full sophisticated spectral wave models certainly have the capability to provide detailed wave information, but they require large computer power, precise well-resolved surface winds and/or needs to consider large ensembles of solutions. In this context, more simplified but robust solutions are demanded.</p><p>This work is based on 2D-parametric model of waves evolution forced by wind field varying in space and time, non-linear wave interactions and wave breaking dissipation [submitted to J. Geoph. Res., see also preprint DOI: https://doi.org/10.1002/essoar.10504620.1]. Numerical solutions of model provide efficient visualization on how waves develop under TC and leave it as swell. Superposition of wave-rays exhibits coherent spatial patterns of wave parameters depending on TC characteristics, - maximal wind speed (um), radius (Rm), and translation velocity (V).</p><p>In this presentation we demonstrate how solutions of 2D-parametric model can be described analytically through self-similar functionsusing proper scaling involving the main TC parameters: um, Rm, and V. These self-similar solutions can be treated as TC-wave Geophysical Model Function (TC-wave GMF), to help analytically derive azimuthal-radial distributions of the primary wave system parameters (SWH, wavelength, direction) under TC characterized by arbitrary sets of um, Rm and V conditions. Self-similar solutions describe the main properties of wave field under TC, in particular: right-to-left half asymmetry of wave field under TC; strong dependence of wave energy and wavelength on V, um and Rm caused by group velocity resonance; division of TCs on “slow” and “fast” when TC-induced waves outrun TC and form wake of swell trailing TC.</p><p>Comparisons between self-similar solutions and measurements of TC-generated waves reported in the literature, demonstrate excellent agreement to warrant their use for research and practical applications.</p><p>The core support for this work was provided by the Russian Science Foundation through the Project №21-47-00038 at RSHU. The support of the Ministry of Science and Education of the Russian Federation under State Assignment No. 0555-2021-0004 at MHI RAS, and State Assignment No. 0736-2020-0005 at RSHU are gratefully acknowledged.</p>

EFFECTS OF AN OIL SLICK ON WIND WAVES1

1979 ◽  
Vol 1979 (1) ◽  
pp. 665-674 ◽  
Author(s):  
Hsien-Ta Liu ◽  
Jung-Tai Lin
Keyword(s):  
Wave Breaking ◽  
Wind Wave ◽  
Wind Waves ◽  
Ocean Waves ◽  
Diesel Oil ◽  
Wave Tank ◽  
Oil Slick ◽  
Wave Profiles ◽  
The Waves ◽  
Integrated Program

ABSTRACT Laboratory experiments were performed to investigate the effects of an oil slick on ocean waves. This is part of an integrated program aimed at understanding the vertical dispersion of oil in the upper ocean. The experiments were conducted in a wind-wave tank which measured 9.1 m long, 1.2 m wide, and 1.8 m deep. Both wind waves and mechanically-generated waves with wind were considered. No. 2 Diesel oil was fed at a rate of 0.35 liters/sec onto the water surface from the upstream end of the wave tank. To measure the wave profiles, an optical sensor-photodiode wave gauge was developed and is described herein. The effects of an oil slick on wind waves were examined in terms of wave profiles and rms wave amplitudes. For wind waves, the presence of the oil slick damps the waves significantly. The amount of damping increases with the wind speed in the range from U∞ = 4 m/sec to 10 m/sec. At U∞ = 10 m/sec, the oil slick breaks into small lenses. The rms amplitudes of the wind-generated waves increase with the fetch without the oil slick, but they do not change appreciably in the presence of the oil slick. For mechanically-generated waves with wind, wave damping by the oil slick becomes insignificant when the waves are sufficiently steep and wave breaking occurs. Prior to wave breaking, however, steepening of the wave crests due to the presence of the oil slick has been observed occasionally as a result of the reduction in the surface tension by the oil film.

Experimental Study of a Lift-Type Wave Energy Converter Rotor in a Freewheeling Mode

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Yingchen Yang ◽  
Fredrick Jenet ◽  
Ben Xu ◽  
Juan Carlos Garza ◽  
Benjamin Tamayo ◽  
...  
Keyword(s):  
Wave Energy ◽  
Wave Interaction ◽  
Vertical Axis ◽  
Ocean Waves ◽  
Vertical Axis Wind Turbine ◽  
Wells Turbine ◽  
Cross Sectional ◽  
Practical Applications ◽  
Wave Flume ◽  
Research Findings

Abstract In pursuit of energy harvesting from ocean waves, our recent progress on studying wave interaction with a lift-type rotor is discussed in this paper. The particular focus is on the characterization of the rotor's unidirectional responsiveness in waves. The rotor consists of six hydrofoil blades in two sets. One blade set has three blades laid out as a vertical-axis wind turbine of the Darrieus type. The other blade set has three blades configured like a Wells turbine. In combination, the formed rotor can be driven by flows in any direction to perform a unidirectional rotation about its vertically mounted shaft. This unidirectional responsiveness of the rotor also holds in waves, making the rotor an effective device for wave energy conversion. For the parametric study of the rotor, hydrofoil blades using different cross-sectional profiles and chord lengths have been employed to configure the rotor. The rotor was then tested in a wave flume under various wave conditions in a freewheeling mode. Experimental results were analyzed and discussed. The yielded research findings will greatly enhance the fundamental understanding of the rotor performance in waves and effectively guide the prototype rotor development for practical applications.

scholarly journals ATTENUATION OF WIND WAVES BY A HYDRAULIC BREAKWATER

2011 ◽  
Vol 1 (8) ◽  
pp. 29
Author(s):  
John A. Williams ◽  
R.L. Wiegel
Keyword(s):  
Wave Energy ◽  
Water Surface ◽  
Wind Waves ◽  
Energy Spectra ◽  
Horizontal Current ◽  
Water Jets ◽  
Before And After ◽  
Air Blowing ◽  
The Waves

Waves generated in a tank by air blowing over the water surface were subjected to a horizontal current of water created by horizontal water jets issuing from a manifold at the water surface (hydraulic breakwater). The energy spectra of the waves were computed for conditions before and after the hydraulic breakwater was turned on. It was found that the shorter, steeper wave components were attenuated to a much greater extent than were the longer wave components. Thus, although a large portion of the wave energy could get past such a breakwater, the waves in the lee of the breakwater looked considerably lower to the observer.

scholarly journals Interplay of Resonant and Quasi-Resonant Interaction of the Directional Ocean Waves

2009 ◽  
Vol 39 (9) ◽  
pp. 2351-2362 ◽  
Author(s):  
Takuji Waseda ◽  
Takeshi Kinoshita ◽  
Hitoshi Tamura
Keyword(s):  
Wave Interaction ◽  
Ocean Waves ◽  
Resonant Interaction ◽  
Wave System ◽  
Spectral Evolution ◽  
Relative Significance ◽  
Freak Wave ◽  
Recent Experimental Study ◽  
Resonant Wave ◽  
Insight Into

Abstract Recent experimental study of the evolution of random directional gravity waves in deep water provides new insight into the nature of the spectral evolution of the ocean waves and the relative significance of resonant and quasi-resonant wave interaction. When the directional angle containing half the total energy is broader than ∼20°, the spectrum evolves following the energy transfer that can be described by the four-wave resonant interaction alone. In contrast, in the case of a directionally confined spectrum, the effect of quasi-resonant wave–wave interaction becomes important, and the wave system becomes unstable. When the temporal change of the spectral shape due to quasi resonance becomes irreversible owing to energetic breaking dissipation, the spectrum rapidly downshifts. Under such extreme conditions, the likelihood of a freak wave is high.

scholarly journals SELF-SIMILAR AND LASER-LIKE REGIMES IN NUMERICAL MODELING OF HASSELMANN KINETIC EQUATION FOR OCEAN WAVES

2019 ◽  
Vol 47 (1) ◽  
pp. 103-106
Author(s):  
A.N. Pushkarev ◽  
V.E. Zakharov
Keyword(s):  
Numerical Modeling ◽  
Kinetic Equation ◽  
Wave Breaking ◽  
Wind Waves ◽  
Ocean Waves ◽  
Black Box ◽  
Wind Forcing ◽  
Power Type ◽  
Self Similar ◽  
Interaction Approximation

The absence of mathematically justified criteria in the models of prediction of wind waves of the ocean, used by the world’s largest centers NOAA (USA) and ECMWF (UK), based on numerical modeling of the Hasselmann kinetic equation, led to erroneous hierarchy and erroneous nonlinear interaction approximation, wind forcing and waves dissipation terms due to wave-breaking. Existing models of wind waves operate in the paradigm of the adjustable «black box», each time requiring reconfiguration. On the basis of numerical simulation, we were able to construct a model, taking into account the wind forcing of the power type in combination with the «implicit» dissipation.

scholarly journals WIND WAVES AND SWELL

2011 ◽  
Vol 1 (7) ◽  
pp. 1 ◽  
Author(s):  
R. L. Wiegel
Keyword(s):  
Water Surface ◽  
Large Scale ◽  
Wind Waves ◽  
Main Body ◽  
Wave System ◽  
Air Resistance ◽  
Component Wave ◽  
Forced Waves ◽  
The Waves ◽  
Surface Generate

Winds blowing over the water surface generate waves. In general the higher the wind velocity, the larger the fetch over which it blows, and the longer it blows the higher and longer will be the average waves . Waves still under the action of the winds that created them are called wind waves, or a sea. They are forced waves rather than free waves. They are variable in their direction of advance (Arthur, 1949). They are irregular in the direction of propagation. The flow is rotational due to the shear stress of the wind on the water surface and it is quite turbulent as observations of dye in the water indicates. After the waves leave the generating area their characteristics become somewhat different, principally they are smoother, losing the rough appearance due to the disappearance of the multitude of smaller waves on top of the bigger ones and the whitecaps and spray. When running free of the storm the waves are known as swell. In Fig. 1 are shown some photographs taken in the laboratory of waves still rising under the action of wind and this same wave system after it has left the windy section of the wind-wave tunnel. It can be seen thati-the freely running swell has a smoother appearance than the waves in the windy section. The motion of the swell is nearly irrotational and nonturbulent, unless the swell runs into other regions where the water is in turbulent motion. Turbulence is a property of the fluid rather than of the wave motion. After the waves have travelled a distance from the generating area they have lost some energy due to air resistance, internal friction, and by large scale turbulent scattering if they run into other storm areas, and the rest of the energy has become spread over a larger area due to the dispersive and angular spreading characteristics of water gravity waves. All of these mechanisms lead to a decrease in energy density. Thus, the waves become lower in height. In addition, due to their dispersive characteristic the component wave periods tend to segregate in such a way that the longest waves lead the main body of waves and the shortest waves form the tail of the main body of waves. Finally, the swell may travel through areas where winds are present, adding new wind waves to old swell, and perhaps directly increasing or decreasing the size of the old swell.

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