共查询到20条相似文献,搜索用时 500 毫秒
1.
2.
The theory for weakly-turbulent surface gravity waves normally identifies some auxiliary function (weakly-turbulent spectrum) with the actual (observed) wave spectrum. In this paper, a general formula for the relationship between weakly-turbulent spectra and observed spectra is derived, and a numerical calculation is provided to show the difference between them. In particular, violation of the exponential nature and angular distribution of weakly-turbulent spectra is noted, along with the occurrence of secondary peaks. Quantitatively, the weakly-turbulent spectra differ insignificantly from the observed spectra.Translated by Vladimir A. Puchkin. 相似文献
3.
Using surface wave parameters and a high-resolution surface wind field derived from Synthetic Aperture Radar (SAR) image mode
data, we have investigated the spatial modification of SAR spectra. We found a surface wind front, formed by sheltering effect
of the Kii Mountains, separating high and low wind-speed regions in a sea area of an European Remote-Sensing Satellite (ERS)
SAR image off the Kii Peninsula. A swell system propagating westward dominates in the whole sea area covered by the SAR image.
The wavelength retrieved from the SAR spectra in the sheltered (non-sheltered) region is longer (shorter). Since the distributions
of surface wave parameters and surface wind speed are so well correlated, it can be considered that the SAR spectra are modified
differently by the sheltered/non-sheltered surface winds. In order to examine the phenomena observed on the SAR image we have
estimated the wind-wave SAR spectrum using the SAR surface winds, a wind-wave spectrum model and a SAR wave imaging model.
We assume that the SAR spectrum related to the swell is homogeneous in the area imaged by SAR, and that the SAR spectrum of
the wind-wave components causes the observed SAR spectra modification. Differences between the observed SAR spectra and the
estimated SAR spectra in the sheltered and non-sheltered regions agree well with each other. In the present case, it can be
concluded that the observed SAR spectra can be regarded as a linear combination of the wind-wave SAR spectra and the swell
SAR spectra. 相似文献
4.
Improved form of wind wave frequency spectrum 总被引:5,自引:0,他引:5
Wen Shengchang 《海洋学报(英文版)》1989,8(4):467-483
The lower frequency part of the theoretical wind wave spectrum proposed by the authors (Wen et al. , 1988a, b,c) has been improved and the form of spectrum is appreciably simplified. In addition to the field data collected in the Bohai Sea region and used in the previous papers, those obtained in the Huanghai Sea, the East China Sea and the South China Sea have been employed so that the improved spectra can be verified on a more extensive observational basis. Computed results agree with the observations well. Further comparisons have been made between the proposed spectra and the JONSWAP spectrum. Though the two types of spectrum are close to each other in form, the former shows, as a whole, better agreement with the observation than the latter. By introducing an improved relation between the peak-ness factor and significant wave steepness, the spectrum contains only significant wave height and period as parameters. For spectra given in this form, the computed peak frequencies coincide approximately wit 相似文献
5.
基于Galieo变换,导出了运动坐标系与静止坐标系中海浪谱间的关系。由于海浪是频散的,两者间的关系是频率相关的。运动坐标系中的海浪频谱是与静止坐标系中的海浪方向谱相联系的。以文氏谱作为静止坐标系中的海浪频谱,给出了不同速度下运动坐标系中的海浪频谱。 相似文献
6.
7.
8.
9.
On the basis of numerical solution of a kinetic equation governing non-linear wave energy redistribution over the spectrum
from sourceG to sinkD, it has been found that spectra of constant flux occur in the case of anisotropic distribution of the source (or sink) with
respect to angle. It has been shown that with sourceG(ω) localized in the upper part of the frequency band, as compared with the sink localization area,D(ω), a flux spectrum that is anisotropic with respect to angle is realized. WithG(ω) andD(ω) being inversely located, the stabilized flux spectrum is essentially anisotropic with respect to angle. Unidimensional
stabilized spectraS(ω), averaged by angle, then have power functions similar to those of the isotropic case of source/sink distribution studied
by Zakharov in 1996. Spectral characteristics have been obtained and the calculated results interpreted.
Translated by Vladimir A. Puchkin. 相似文献
10.
I. B. Palymskii 《Izvestiya Atmospheric and Oceanic Physics》2009,45(5):646-653
The problem of the incompressible liquid convection between two horizontal planes heated on the underside is considered in
the three-dimensional statement. The horizontal boundaries are assumed to be free of tangential stresses and isothermal. The
calculated temporal spectrum of the temperature pulsations at the convection cell center at a supercriticality of 410 agrees
well with the experimental measurement result. The Bolgiano-Obukhov (BO), k
−11/5, k
−3, and k
−5, were obtain for the velocity pulsations. The Kolmogorov spectra k
−5/3 and k
−2.4 were obtained for the temperature pulsations. The presence of clearly identified spectra in the convective flow under study
allows this process to be characterized as developed turbulence. 相似文献
11.
Aproposeddirectionalfunctionandwind-wavedirectionalspectrum¥WenShengchang;WuKejian;GuanChanglong;SunShicaiandZhangDacuo(Recei... 相似文献
12.
Analysis of freak wave measurements in the Sea of Japan 总被引:3,自引:0,他引:3
This paper presents an analysis of a set of available freak wave measurements gathered from several periods of continuous wave recordings made in the Sea of Japan during 1986–1990 by the Ship Research Institute of Japan. The analysis provides an ideal opportunity to catch a glimpse of the statistics of freak waves in the ocean. The results show that a well-defined freak wave may occur in the developed wind–wave condition: S(f)∝f−4, with single-peak directional spectra. The crest and trough amplitude distributions of the observed sea waves including freak waves are different from the Rayleigh distribution, although the wave height distribution tends to agree with the Rayleigh distribution. Freak waves can be readily identified from the wavelet spectrum where a strong energy density occurs in the spectrum, and is instantly surged and seemingly carried over to the high-frequency components at the instant the freak wave occurs. 相似文献
13.
Analytically derived wind-wave directional spectrum part 2. Characteristics,comparison and verification of spectrum 总被引:1,自引:0,他引:1
Sheng-Chang Wen Pei-Fang Guo Da-Cuo Zhang Chang-Long Guan Hai-Gang Zhan 《Journal of Oceanography》1993,49(2):149-172
The dependence of the angular spreading on frequency and wind-wave growth status is discussed in great detail for the proposed spectrum. The calculated angular spreading agrees with the measurements of Donelanet al. but is slightly broader. Explanation is given to the appearance of the narrowest spreading at a frequency slightly smaller than that of the wind-wave frequency spectrum peak as found by these authors. There is also basic agreement between the calculated spreading and the formulas of Mitsuyasuet al. and Hasselmannet al. for the specific wind-wave status on which these empirical formulas are based, though the former is narrower. The wind-wave frequency spectrum obtained by integrating the proposed directional spectrum with respect to direction agrees with the JONSWAP spectrum and that derived by the authors previously. The proposed spectrum is preliminarily verified with field data obtained by optical method.Project supported by the National Natural Science Foundation of China. 相似文献
14.
Paul C. Liu 《Ocean Engineering》1983,10(6):429-441
This paper proposes the following generalized representation for a wind-wave frequency spectrum:
where E = ∫S(f)df is the variance of the surface displacement; fm is the frequency of the spectral peak; and Ci's, i = 1,2,3, are dimensionless parameters that can be determined from the internal spectral parameters of a given spectrum.When applied to 234 sets of wave spectra recorded in the Great Lakes, this representation has been realistic, accurate, and capable of representing widely varied wave processes. The Ci's are clearly related to wave growth processes; they are large during early growth, decrease as waves grow, and reach approximate equilibrium when waves are fully developed. 相似文献
Full-size image (1K)
15.
Exact distributions for apparent waves in irregular seas 总被引:2,自引:0,他引:2
We discuss the long-run distributions of several characteristics for the apparent waves in a Gaussian sea. Three types of one-dimensional wave records are considered: 1) the seaway in time at a fixed position; 2) the instantaneous profile along a horizontal line; 3) the encountered seaway. Exact integral forms of the joint long run distributions are derived for the apparent periods, lengths, and heights. Results of numerical approximations of these distributions are presented in examples. For the computations we considered, as the input spectra, empirical estimates of the frequency spectra as well as JONSWAP type spectra. Effective algorithms are discussed and utilized in the form of a comprehensive computer package of numerical routines. 相似文献
16.
By using a new concept of the discrete amplitude, we examine the statistical properties of narrow-banded random waves. The main results are as follows: (1) the wave height distribution follows the Rayleigh distribution in the case of an infinitely narrow-banded spectrum in the strict sense; (2) the discrete amplitudes, different from the crest heights, are distributed according to the Rayleigh distribution for arbitrary bandwidth spectra; (3) the statistical distribution of the gap length between the discrete amplitude and the crest is examined and derived theoretically. The derived distribution agrees well with the result of numerical simulations; (4) taking into account the gap length distribution, the probability density function of crest heights is derived, which deviates from the Rayleigh distribution. 相似文献
17.
On the Spectrum Width of Wind Waves 总被引:1,自引:1,他引:1
Based on the universal expression of wind wave spectra, four commonly used definitions of the spectrum width are re-examined. The results show that the non-dimensional spectrum width can measure the width of non-dimensional spectra hut it does not reflect the developing state of the spectra. The dimensional spectrum width expresses the degree of concentration of wave energy of the spectrum in (he process of wind wave growth. Tests show that the spectrum width presented by Wen et al. can objectively measure the degree of concentration of wave energy of the spectrum, reflect the state of wind wave growth, and provides a better result for practical application. The rules for definition of the spectrum width are discussed. 相似文献
18.
Based on the ray theory and Longuet-Higgins’s linear model of sea waves, the joint distribution of wave envelope and apparent wave number vector is established. From the joint distribution, we define a new concept, namely the outer wave number spectrum, to describe the outer characteristics of ocean waves. The analytical form of the outer wave number spectrum, the probability distributions of the apparent wave number vector and its components are then derived. The outer wave number spectrum is compared with the inner wave number spectrum for the average status of wind-wave development corresponding to a peakness factor P = 3. Discussions on the similarity and difference between the outer wave number spectrum and inner one are also presented in the paper. 相似文献
19.
Yoshihiko Sekine Fukuji Yamada Yoshiaki Toba Eugene C. Lafond 《Journal of Oceanography》1994,50(4):391-401
Two-dimensional temperature data observed by use of a 275 meter towed thermistor chain deployed from an oceanographic research vessel USS MARYSVILLE, which cruised with a speed of 6.2 knots in July 1966 across the Kuroshio Extension in the North Pacific, are investigated. Two-dimensional variations of the distribution of the isotherms along the ship's track are analyzed with special reference to their slope, wavelength and wave height. The results show that the slope and wave height of isotherms have a tendency to increase as the temperature decreases. Even if the contribution of wave heights smaller than 1.5 m is neglected, i.e., contribution of large scale slope with a horizontal scale of 5–30 km is subtracted, this tendency is still detected. In contrast to this, the wavelength evaluated by the crest to crest method has no dependency on the temperature. Power spectrum of the isotherm depth is proportional tok
–1.87 for 13°C andk
–2.13 for 27°C, wherek is the wave number. It is shown that the spectra of warmer isotherms are relatively well approximated by –2 power law (Garrett and Munk spectrum) for internal waves rather than the –5/3 power law (Kolmogorov spectrum) for three dimensional isotropic turbulence. 相似文献
20.
Wen Shengchang 《海洋学报(英文版)》1988,7(1):1-16
In this part ot the paper theoretical wind-wave spectra nave been derived oy (I) expressing the spectrum in series composed of exponential terms; (2) assuming that the spectrum satisfies a high order linear ordinary differential equation; (3) introducing proper parameters in the spectrum; and (4) making use of some known charateristics of wind-wave spectrum, for instance, the law governing the equilibrium range. The spectrum obtained contains the zero order moment of the spectrum m0, the peak frequency ω0 and the ratio R =ω/ω0 (ω being the mean zero-crossing frequency) as parameters. The shape of the nondimensional spectrum S(ω) = ω0S(ω)/m0(ω=ω/ω0) changes with R and theoretically reduces to a Dirac delta function δ(ω-1) when R = 1. A spectrum of simplified form is given for practical uses, in which R is replaced by a peakness factor P=S(1). 相似文献