scholarly journals Observations of Steep Wave Statistics in Open Ocean Waters

2005 ◽  
Vol 22 (3) ◽  
pp. 258-271 ◽  
Author(s):  
Nicholas Scott ◽  
Tetsu Hara ◽  
Edward J. Walsh ◽  
Paul A. Hwang
Keyword(s):  
Wind Speed ◽  
Ocean Waves ◽  
Open Ocean ◽  
Breaking Wave ◽  
Wave Statistics ◽  
Analysis Methodology ◽  
Wide Range ◽  
Wave Slope ◽  
Steep Waves ◽  
Steep Wave

Abstract A new wavelet analysis methodology is proposed to estimate the statistics of steep waves. The method is applied to open ocean wave height data from the Southern Ocean Waves Experiment (1992) and from a field experiment conducted at Duck, North Carolina (1997). Results show that high wave slope crests appear over a wide range of wavenumbers, with a large amount being much shorter than the dominant wave. At low wave slope thresholds, all wave fields have roughly the same amount of wave crests regardless of wind forcing. The steep wave statistic decays exponentially with the square of the wave slope threshold, with a decay rate that is larger for the low wind cases than the high wind cases. Comparison of the steep wave statistic with independent measurements of the breaking wave statistic suggests a breaking wave slope threshold of about 0.12. The steep wave statistic does not scale with the cube of the wind speed, suggesting that other factors besides the wind speed also affect its level. Comparison of the steep wave statistic to the saturation spectrum reveals a reasonable correlation at moderate wave slope thresholds.

scholarly journals Directionality and Crest Length Statistics of Steep Waves in Open Ocean Waters

2005 ◽  
Vol 22 (3) ◽  
pp. 272-281 ◽  
Author(s):  
Nicholas Scott ◽  
Tetsu Hara ◽  
Paul A. Hwang ◽  
Edward J. Walsh
Keyword(s):  
Ocean Waves ◽  
Open Ocean ◽  
One Dimensional ◽  
Analysis Methodology ◽  
Wave Slope ◽  
The Mean ◽  
Steep Waves ◽  
The One ◽  
Crest Length ◽  
Steep Wave

Abstract A new wavelet analysis methodology is applied to open ocean wave height data from the Southern Ocean Waves Experiment (1992) and from a field experiment conducted at Duck, North Carolina, in 1997 with the aim of estimating the directionality and crest lengths of steep waves. The crest directionality statistic shows that most of the steep wave crests are normal to the direction of the mean wind. This is inconsistent with the Fourier wavenumber spectrum that shows a broad bimodal directional spreading at high wavenumbers. The crest length statistics demonstrate that the wave field is dominated by short-crested waves with small crest length/wavelength ratios. The one-dimensional steep wave statistic obtained from the integration of the directional (two dimensional) steep wave statistic is consistent with the one-dimensional steep wave statistic obtained from the one-dimensional analysis at high wave slope thresholds.

scholarly journals Law of spreading of the crest of a breaking wave

2008 ◽  
Vol 464 (2095) ◽  
pp. 1851-1866 ◽  
Author(s):  
Y Pomeau ◽  
T Jamin ◽  
M Le Bars ◽  
P Le Gal ◽  
B Audoly
Keyword(s):  
Theoretical Analysis ◽  
Fluid Motion ◽  
Ocean Waves ◽  
Wave Crest ◽  
Spanwise Direction ◽  
Breaking Wave ◽  
Square Root ◽  
Fluid Surface ◽  
Wide Range ◽  
Experimental Findings

In a wide range of conditions, ocean waves break. This can be seen as the manifestation of a singularity in the dynamics of the fluid surface, moving under the effect of the fluid motion underneath. We show that, at the onset of breaking, the wave crest expands in the spanwise direction as the square root of time. This is first derived from a theoretical analysis and then compared with experimental findings. The agreement is excellent.

scholarly journals Semiempirical Dissipation Source Functions for Ocean Waves. Part I: Definition, Calibration, and Validation

2010 ◽  
Vol 40 (9) ◽  
pp. 1917-1941 ◽  
Author(s):  
Fabrice Ardhuin ◽  
Erick Rogers ◽  
Alexander V. Babanin ◽  
Jean-François Filipot ◽  
Rudy Magne ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
Wave Breaking ◽  
Wave Spectrum ◽  
Remote Sensing Data ◽  
Ocean Waves ◽  
Breaking Waves ◽  
Global Ocean ◽  
Short Waves ◽  
Wide Range

Abstract New parameterizations for the spectral dissipation of wind-generated waves are proposed. The rates of dissipation have no predetermined spectral shapes and are functions of the wave spectrum and wind speed and direction, in a way consistent with observations of wave breaking and swell dissipation properties. Namely, the swell dissipation is nonlinear and proportional to the swell steepness, and dissipation due to wave breaking is nonzero only when a nondimensional spectrum exceeds the threshold at which waves are observed to start breaking. An additional source of short-wave dissipation is introduced to represent the dissipation of short waves due to longer breaking waves. A reduction of the wind-wave generation of short waves is meant to account for the momentum flux absorbed by longer waves. These parameterizations are combined and calibrated with the discrete interaction approximation for the nonlinear interactions. Parameters are adjusted to reproduce observed shapes of directional wave spectra, and the variability of spectral moments with wind speed and wave height. The wave energy balance is verified in a wide range of conditions and scales, from the global ocean to coastal settings. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Some systematic defects are still present, but, overall, the parameterizations probably yield the most accurate estimates of wave parameters to date. Perspectives for further improvement are also given.

Designing Against Capsize in Beam Seas: Recent Advances and New Insights

1997 ◽  
Vol 50 (5) ◽  
pp. 307-325 ◽  
Author(s):  
J. M. T. Thompson
Keyword(s):  
Symmetry Breaking ◽  
Invariant Manifolds ◽  
Damping Ratio ◽  
Historical Review ◽  
Ocean Waves ◽  
Worst Case ◽  
Wide Range ◽  
Wave Slope ◽  
Stiffness And Damping ◽  
Damping Functions

The mechanics of ship capsize under steady and transient conditions is reviewed, focusing on recent applications of global geometrical techniques of nonlinear dynamics. These yield significant new ideas about capsize in waves and its generalization, the escape of a driven oscillator from a potential well. These ideas are robust against gross changes in the forms of the stiffness and damping functions. Fractal basin boundaries in phase and control space yield useful design criteria against transient capsize, which have been applied to real ships. Invariant manifolds are used to explain and predict the sudden loss of safe basin in the space of the starting conditions, and indeterminate resonant jumps to capsize. Further work is concerned with capsize suppression by heave-roll coupling; effects of parametric excitation; and capsize under a propagating wave front. After this historical review, the practical relevance of the results is assessed, and suggestions are made for a standardized transient testing procedure for hulls. A systematic formulation for rolling in beam waves, employing the effective gravitational field perpendicular to the wave surface and the Froude-Krilov assumption, allows the use of the calm-water GZ curve. With general stiffness and damping functions, dimensional analysis offers insights that are often overlooked: for example, the sustainable wave slope is always proportional to the angle of vanishing stability. A degree of quantification is provided by a design formula derived from the displacement magnification of linear resonance. This is validated by Melnikov theory and simulation. It predicts that under worst-case excitation we have: sustainable wave slope = 2 ζθv, where θv is the angle of vanishing stability and ζ is a damping ratio appropriate for heavy roll. So in ocean waves of slope 0.5 (≈30°), a vessel with a θv of one radian needs a damping ratio of about 1/4. Implications for the design of hulls reveal counter-intuitive results: it is the distance of the potential barrier, not its height, that prevents escape or capsize. The formula helps to define a universal capsize diagram. New results on symmetry breaking are finally presented. These show that capsize studies of a symmetric unbiased vessel can give seriously unsafe results. The sustainable wave slope is so sensitive to a symmetry-breaking bias (due to wind or cargo imbalance) that a static heel of 2.5° can halve the sustainable slope over a wide range of sea states. This review article has 112 references.

scholarly journals Ocean Wave Slope Observations Using Radar Backscatter and Laser Altimeters

2004 ◽  
Vol 34 (12) ◽  
pp. 2825-2842 ◽  
Author(s):  
D. Vandemark ◽  
B. Chapron ◽  
J. Sun ◽  
G. H. Crescenti ◽  
H. C. Graber
Keyword(s):  
Wind Speed ◽  
Gravity Wave ◽  
Radar Data ◽  
Open Ocean ◽  
Ocean Wave ◽  
Satellite Altimeter ◽  
Radar Backscatter ◽  
Ka Band ◽  
Long Wave ◽  
Wave Slope

Abstract Combination of laser and radar aboard an aircraft is used to directly measure long gravity wave surface tilting simultaneously with nadir-viewing microwave backscatter from the sea surface. The presented dataset is extensive, encompassing varied wind conditions over coastal and open-ocean wave regimes. Laser-derived slope statistics and Ka-band (36 GHz) radar backscatter are detailed separately to document their respective variations versus near-surface wind speed. The slope statistics, measured for λ > 1–2 m, show good agreement with Cox and Munk's oil-slickened sea measurements. A notable exception is elevated distribution peakedness and an observed wind dependence in this likely proxy for nonlinear wave–wave interactions. Aircraft Ka-band radar data nearly mimic Ku-band satellite altimeter observations in their mean wind dependence. The present calibrated radar data, along with relevant observational and theoretical studies, suggest a large (−5 dB) bias in previous Ka-band results. Next, wave-diverse inland, coastal, and open-ocean observations are contrasted to show wind-independent long-wave slope variance changes of a factor of 2–3, always increasing as one heads to sea. Combined long-wave and radar data demonstrate that this long-wave tilt field variability is largely responsible for radar backscatter variations observed at a given wind speed, particularly at wind speeds below 5–7 m s−1. Results are consistent with, and provide quantititative support for, recent satellite altimeter studies eliciting signatures of long-wave impacts resident in the radar backscatter. Under a quasi-optical scattering assumption, the results illustrate long-wave control on the variance of the total mean square slope parameter due to changes in the directional long-wave spectrum, with high-wavenumbers being relatively unaffected in a mean sense. However, further analysis suggests that for winds above 7 m s−1 the high-wavenumber subrange also varies with change in the longer wave field slope and/or energy, the short gravity wave roughness being measurably greater for smoother seas.

scholarly journals On the Variation of the Effective Breaking Strength in Oceanic Sea States

2016 ◽  
Vol 46 (7) ◽  
pp. 2049-2061 ◽  
Author(s):  
Christopher J. Zappa ◽  
Michael L. Banner ◽  
Russel P. Morison ◽  
Sophia E. Brumer
Keyword(s):  
Breaking Strength ◽  
Wave Model ◽  
Ocean Waves ◽  
Breaking Wave ◽  
Strength Coefficient ◽  
Wide Range ◽  
Momentum Fluxes ◽  
Energy And Momentum ◽  
The Waves ◽  
Robust Evidence

AbstractA spectral framework for quantifying the geometric/kinematic and dynamic/energetic properties of breaking ocean waves was proposed by Phillips in 1985. Phillips assumed a constant breaking strength coefficient to link the kinematic/geometric breaking crest properties to the associated excess energy and momentum fluxes from the waves to the upper ocean. However, a scale-dependent (spectral) breaking strength coefficient is needed, but is unavailable from measurements. In this paper, the feasibility of a parametric mean effective breaking strength coefficient valid for a wide range of sea states is investigated. All available ocean breaking wave datasets were analyzed and complemented with wave model behavior. Robust evidence is found supporting a single linear parameter relationship between the effective breaking strength and wave age or significant wave steepness. Envisaged applications for the effective breaking strength are described.

scholarly journals Statistical Characteristics of Wave Breakings and their Relation with the Wind Waves’ Energy Dissipation Based on the Field Measurements

2020 ◽  
Vol 36 (5) ◽  
Author(s):  
A. E. Korinenko ◽  
V. V. Malinovsky ◽  
V. N. Kudryavtsev ◽  
V. A. Dulov ◽  
◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Wind Speed ◽  
Wave Breaking ◽  
Wind Waves ◽  
Field Measurements ◽  
Sea Surface ◽  
Breaking Wave ◽  
Movement Velocity ◽  
Wide Range ◽  
The Waves

Purpose. The work is aimed at studying geometric similarity of wind wave breakings in natural conditions, estimating the Duncan constant which connects the wave energy dissipation conditioned by wave breakings, with distribution of the lengths of a breaking wave crests Λ(с). Methods and Results. The field measurements of the wave breaking characteristics were carried out at the stationary oceanographic platform located in the Golubaya Bay near the village Katsiveli. Geometric dimensions of the wave breakings’ active phase, velocities and directions of their movement were determined from the video records of the sea surface; simultaneously, the meteorological information was recorded and the surface waves’ characteristics were measured. Altogether 55 video records of the sea surface were obtained; duration of each of them was 40–60 minutes. The measurements were performed in a wide range of meteorological conditions and wave parameters (wind speed varied from 9.2 to 21.4 m/s). Conclusions. It is found that the probability densities of the ratio between the maximum length of a breaking and the length of a breaking wave, obtained in various wind and wave conditions are similar. The average value of this ratio is 0.1. Distributions of the wave breakings’ total length are constructed in the movement velocity intervals on a surface unit. It is shown that the experimental estimates of dependence of these distributions upon the wind speed and the wave breaking movement velocity are consistent with the theoretical predictions of O.M. Phillips (1985); at that no dependence on the waves’ age was found. Quantitative characteristics of the relation between the wave lengths’ distribution and the energy dissipation are obtained. The Duncan constant was estimated; it turned out to be equal to 1.8⋅10-3 and independent upon the waves’ and atmosphere parameters.

scholarly journals Statistical Characteristics of Wave Breakings and their Relation with the Wind Waves’ Energy Dissipation Based on the Field Measurements

2020 ◽  
Vol 27 (5) ◽  
Author(s):  
A. E. Korinenko ◽  
V. V. Malinovsky ◽  
V. N. Kudryavtsev ◽  
V. A. Dulov ◽  
◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Wind Speed ◽  
Wave Breaking ◽  
Wind Waves ◽  
Field Measurements ◽  
Sea Surface ◽  
Breaking Wave ◽  
Movement Velocity ◽  
Wide Range ◽  
The Waves

Purpose. The work is aimed at studying geometric similarity of wind wave breakings in natural conditions, estimating the Duncan constant which connects the wave energy dissipation conditioned by wave breakings, with distribution of the lengths of a breaking wave fronts Λ(с). Methods and Results. The field measurements of the wave breaking characteristics were carried out at the stationary oceanographic platform located in the Golubaya Bay near the Katsiveli village. Geometric dimensions of the wave breakings’ active phase, velocities and directions of their movement were determined from the video records of the sea surface; simultaneously, the meteorological information was recorded and the surface waves’ characteristics were measured. Altogether 55 video recordings (duration 40–50 mins) of the sea surface were obtained. The measurements were carried out in a wide range of meteorological conditions and wave parameters (wind speed varied from 9.2 to 21.4 m/s). Conclusions. It is found that the probability densities of the ratio between the maximum length of a breaking and the length of a breaking wave, obtained in various wind and wave conditions are similar. The average value of this ratio is 0.1. Distributions of the wave breakings’ total length are constructed in the movement velocity intervals on a surface unit. It is shown that the experimental estimates of dependence of these distributions upon the wind speed and the wave breaking movement velocity are consistent with the theoretical predictions of O.M. Phillips (1985); at that no dependence on the waves’ age was found. Quantitative characteristics of the relation between the wave lengths’ distribution and the energy dissipation are obtained. The Duncan constant was estimated; it turned out to be equal to 1.8·10-3 and independent upon the waves’ and atmosphere parameters.

scholarly journals Dust Production around Carbon-Rich Stars: The Role of Metallicity

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 233
Author(s):  
Ambra Nanni ◽  
Sergio Cristallo ◽  
Jacco Th. van Loon ◽  
Martin A. T. Groenewegen
Keyword(s):  
Wind Speed ◽  
Galactic Halo ◽  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Chemical Enrichment ◽  
Wide Range ◽  
The Universe

Background: Most of the stars in the Universe will end their evolution by losing their envelope during the thermally pulsing asymptotic giant branch (TP-AGB) phase, enriching the interstellar medium of galaxies with heavy elements, partially condensed into dust grains formed in their extended circumstellar envelopes. Among these stars, carbon-rich TP-AGB stars (C-stars) are particularly relevant for the chemical enrichment of galaxies. We here investigated the role of the metallicity in the dust formation process from a theoretical viewpoint. Methods: We coupled an up-to-date description of dust growth and dust-driven wind, which included the time-averaged effect of shocks, with FRUITY stellar evolutionary tracks. We compared our predictions with observations of C-stars in our Galaxy, in the Magellanic Clouds (LMC and SMC) and in the Galactic Halo, characterised by metallicity between solar and 1/10 of solar. Results: Our models explained the variation of the gas and dust content around C-stars derived from the IRS Spitzer spectra. The wind speed of the C-stars at varying metallicity was well reproduced by our description. We predicted the wind speed at metallicity down to 1/10 of solar in a wide range of mass-loss rates.

scholarly journals Multiscaling and joint multiscaling description of the atmospheric wind speed and the aggregate power output from a wind farm

2014 ◽  
Vol 21 (2) ◽  
pp. 379-392 ◽  
Author(s):  
R. Calif ◽  
F. G. Schmitt
Keyword(s):  
Wind Speed ◽  
Power Output ◽  
Wind Farm ◽  
Power Spectra ◽  
Physical Space ◽  
Scaling Properties ◽  
Developed Turbulence ◽  
Output Fluctuations ◽  
Wide Range ◽  
Generalized Correlation

Abstract. We consider here wind speed time series and the aggregate output wind power from a wind farm. We study their scaling statistics in the framework of fully developed turbulence and Kolmogorov's theory. We estimate their Fourier power spectra and consider their scaling properties in the physical space. We show that the atmospheric wind speed and the aggregate power output from a wind farm are intermittent and multifractal over a wide range of scales. The coupling between simultaneous data of the wind speed and aggregate power output is investigated through a joint multifractal description using the generalized correlation functions (GCFs). This multiscaling test is compatible with a linear relation between the wind speed and the aggregate power output fluctuations for timescales T ⩾ 103 s ≃ 15 min.

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