scholarly journals A New Inverse Phase Speed Spectrum of Nonlinear Gravity Wind Waves

2019 ◽  
Vol 124 (8) ◽  
pp. 6097-6119
Author(s):  
Jan‐Victor Björkqvist ◽  
Heidi Pettersson ◽  
William M. Drennan ◽  
Kimmo K. Kahma
Keyword(s):  
Wind Waves ◽  
Phase Speed ◽  
Nonlinear Gravity

Wave Breaking Dissipation in a Young Wind Sea

2014 ◽  
Vol 44 (1) ◽  
pp. 104-127 ◽  
Author(s):  
Michael Schwendeman ◽  
Jim Thomson ◽  
Johannes R. Gemmrich
Keyword(s):  
Wind Waves ◽  
Phase Speed ◽  
Field Studies ◽  
Turbulent Energy ◽  
Strength Parameter ◽  
Video Recordings ◽  
Sonar System ◽  
Wind Sea ◽  
Equilibrium Range

Abstract Coupled in situ and remote sensing measurements of young, strongly forced wind waves are applied to assess the role of breaking in an evolving wave field. In situ measurements of turbulent energy dissipation from wave-following Surface Wave Instrument Float with Tracking (SWIFT) drifters and a tethered acoustic Doppler sonar system are consistent with wave evolution and wind input (as estimated using the radiative transfer equation). The Phillips breaking crest distribution Λ(c) is calculated using stabilized shipboard video recordings and the Fourier-based method of Thomson and Jessup, with minor modifications. The resulting Λ(c) are unimodal distributions centered around half of the phase speed of the dominant waves, consistent with several recent studies. Breaking rates from Λ(c) increase with slope, similar to in situ dissipation. However, comparison of the breaking rate estimates from the shipboard video recordings with the SWIFT video recordings show that the breaking rate is likely underestimated in the shipboard video when wave conditions are calmer and breaking crests are small. The breaking strength parameter b is calculated by comparison of the fifth moment of Λ(c) with the measured dissipation rates. Neglecting recordings with inconsistent breaking rates, the resulting b data do not display any clear trends and are in the range of other reported values. The Λ(c) distributions are compared with the Phillips equilibrium range prediction and previous laboratory and field studies, leading to the identification of several inconsistencies.

On the interaction of surface and internal waves

1972 ◽  
Vol 52 (1) ◽  
pp. 179-191 ◽  
Author(s):  
A. E. Gargettt ◽  
B. A. Hughes
Keyword(s):  
Surface Wave ◽  
Internal Wave ◽  
Surface Waves ◽  
Internal Waves ◽  
Wind Waves ◽  
Phase Speed ◽  
Surface Current ◽  
Propagation Direction ◽  
Wave Crest ◽  
Critical Position

The steady-state interaction between surface waves and long internal waves is investigated theoretically using the radiation stress concepts derived by Longuet-Higgins & Stewart (1964) (or Phillips 1966). It is shown that, over internal wave crests, those surface waves for which cg0cosϕ0 > ci experience a change in direction of propagation towards the line of propagation of the internal waves and their amplitudes are increased. Here cg0 is the surface-wave group speed at U = 0, ϕ0 is the angle between the propagation direction of the surface waves at U = 0 and the propagation direction of the internal waves, and ci is the phase speed of the internal waves. If cg0cos ϕ0 < ci the direction of the surface waves is turned away and their amplitudes are decreased. Over troughs the opposite effects occur.At positions where the local velocity of surface-wave energy transmission measured relative to the internal wave phase velocity is zero, i.e. cg + U − ci = 0, there is a singularity in the energy of the surface waves with resulting infinite amplitudes. It is shown that at these critical positions two wavenumbers which were real and distinct on one side coalesce and become complex on the other. The critical positions are thus shown to be barriers to the propagation of those wave-numbers. It is also shown that there is a critical position representing the coalescence of three wavenumbers. Surface-wave crest configurations are shown for three numerical examples. The frequency and direction of propagation of surface waves that exhibit critical positions somewhere in an internal wave field are shown as a function of the maximum horizontal surface current. This is compared with measurements of wind waves that have been reported elsewhere.

scholarly journals BASIC SYSTEMS OF WIND WAVE FIELD

1974 ◽  
Vol 1 (14) ◽  
pp. 12
Author(s):  
Yu. M. Krylov ◽  
S.S. Strekalov ◽  
V. Ph. Tsyloukhin
Keyword(s):  
Wind Speed ◽  
Continuous Wave ◽  
System Development ◽  
Wind Waves ◽  
Wave Spectrum ◽  
Phase Speed ◽  
Typical Feature ◽  
Sea Waves ◽  
First Results ◽  
Energy Maximum

The study of wind waves is usually carried out in the following manner. At the first moment a homogenous wind field with the constant speed directed from the shore to the basin is occurred over the water surface restricted by a straight shore line. It is required to calculate statistic wave characteristics as functions of time and distance from the shore. When solving the problem in such a way the explorers [.1-6 ~] usually came to a conclusion of the system development of gravitational waves with a main energy maximum the amplitude and period of which rise in process developing from small magnitudes to limiting values. Some explorers noted that the two -or three-wave systems under the conditions of constant wind are available. The first results of this theory were obtained by L.Ph. Tytov. In studies of stereophotographs of sea waves he noted and described quantitatively two types of waves: "prevailing" and "large", f7l I* is possible to show that the first type of waves has a phase speed that is less than wind speed, and the second one is equal to wind speed. At a later time G.Neumann [6J generalizing results of ocean observations has come to the conclusion that under the action of constant wind three "specific" wave systems which have phase speeds less, equal and 1.2 more than the speed of wind are developed. However, Tytov's and Neumann's results didn't receive a progress, and later on they were substituted by the conception of continuous wave spectrum with one energy maximum £3-6J • Nevertheless, the opinions of availability of two-or three-wave systems as a typical feature of wind rough sea [8,9] were published in the press.

scholarly journals WIND-GENERATED CURRENT AND PHASE SPEED OF WIND WAVES

1972 ◽  
Vol 1 (13) ◽  
pp. 26
Author(s):  
Omar H. Shemdin
Keyword(s):  
Wind Waves ◽  
Wave Length ◽  
Phase Speed ◽  
Shear Velocity ◽  
Wave Number ◽  
Coherent Signals ◽  
Number Range ◽  
Wave Number Range ◽  
The Waves ◽  
Measured Phase

Measurements of drift were made in a wind and wave facility at different elevations below the mean water level. The drift profiles were obtained for reference wind speeds, Ur = 3.1, 5.7 and 9.6 m/sec. The measurement technique involved tracing the movement of small paper discs which were soaked in water to become neutrally buoyant at the elevation of release. A logarithmic drift profile is proposed. The water shear velocity, U*w, predicts a surface stress, TS = pw U*S, in agreement with that obtained from the wind shear velocity, Ts = Pa U*li where pa and pw refer to air and water densities, respectively. The influence of wind on phase speeds of waves was investigated by solving the first order perturbation problem of the coupled shear flows in air and water. The air velocity profile was described by a logarithmic distribution and the drift profile was described by the proposed drift profile. Adequate agreement is found between the calculated and measured phase speed using Doppler radar in the wave number range 1.9 - 10 cm-1. In the wave number range 0.05 - 0.5 cm-1, measurements of phase speeds were obtained by using two wave gages. The waves were mechanically generated without wind and the wave gages were spaced to obtain coherent signals. The wind was then allowed to blow over the waves and the distance between wave gages was increased to maintain coherence. The wave length and frequency were obtained from the distance between the gages and from the generator frequency, respectively. The measured phase speeds were found to increase with wind speed consistent with theoretical computations.

scholarly journals Asymmetry of wind waves studied in a laboratory tank

1995 ◽  
Vol 2 (3/4) ◽  
pp. 280-289 ◽  
Author(s):  
I. A. Leykin ◽  
M. A. Donelan ◽  
R. H. Mellen ◽  
D. J. McLaughlin
Keyword(s):  
Wind Wave ◽  
Wind Waves ◽  
Phase Speed ◽  
Rate Of Change ◽  
Surface Elevation ◽  
Order Moment ◽  
Wave System ◽  
Third Order ◽  
Time Asymmetry ◽  
Laboratory Tank

Abstract. Asymmetry of wind waves was studied in laboratory tank tinder varied wind and fetch conditions using both bispectral analysis of wave records and third-order statistics of the surface elevation. It is found skewness S (the normalized third-order moment of surface elevation describing the horizontal asymmetry waves) varies only slightly with the inverse wave u*/Cm (where u* is the air friction velocity and Cm is phase speed of the dominant waves). At the same time asymmetry A, which is determined from the Hilbert transform of the wave record and characterizes the skewness of the rate of change of surface elevation, increase consistently in magnitude with the ratio u*/Cm. This suggests that nonlinear distortion of the wave profile determined by the degree of wind forcing and is a sensitive indicator of wind-wave interaction processes. It is shown that the asymmetric profile of waves can described within the frameworks of the nonlinear nonspectral concept (Plate, 1972; Lake and Yuen, 197 according to which the wind-wave field can be represented as a coherent bound-wave system consisting mainly of dominant component w. and its harmonics propagating with the same speed C. , as observed by Ramamonjiaris and Coantic (1976). The phase shift between o). harmonics is found and shown to increase with the asymmetry of the waves.

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.

Generation of Wind Waves in Large Streams

2020 ◽  
Vol 24 (1) ◽  
pp. 518-525
Author(s):  
Eshev S.S.– DSc ◽  
I.X. Gayimnazarov ◽  
А.R. Rakhimov ◽  
Latipov Sh. A
Keyword(s):  
Wind Waves ◽  
Generation Of Wind Waves

Source Term Balance for Finite Depth Wind Waves

2000 ◽  
Author(s):  
Ian R. Young ◽  
Michael L. Banner ◽  
Mark M. Donelan
Keyword(s):  
Source Term ◽  
Wind Waves ◽  
Finite Depth
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