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1.
Ａｐｒｏｐｏｓｅｄｄｉｒｅｃｔｉｏｎａｌｆｕｎｃｔｉｏｎａｎｄｗｉｎｄ－ｗａｖｅｄｉｒｅｃｔｉｏｎａｌｓｐｅｃｔｒｕｍ￥ＷｅｎＳｈｅｎｇｃｈａｎｇ；ＷｕＫｅｊｉａｎ；ＧｕａｎＣｈａｎｇｌｏｎｇ；ＳｕｎＳｈｉｃａｉａｎｄＺｈａｎｇＤａｃｕｏ（Ｒｅｃｅｉ... 相似文献
2.
In contrast with the usual method to obtain the wind-wave directional spectrum by multiplying the frequency spectrum with an empirical directional function, the authors attempt to derive analytically the directional spectrum by adopting proper spectral form and using effective parameters, namely, the zero order momentm
0 of the wind-wave frequency spectrumS(), its peak frequency 0 and the so-called peakness factorP=0
S(0)/m
0, where is angular frequency. The directional spectrum is given in a form of frequency spectrum for each direction. The spectral directionality depends on, in addition to frequency, the wind-wave growth status, for the peakness factorP as introduced by the authors previously is a measure of the wave development stage. The salient features of the directional spectrum, comparison with existing formulas and the verification of the spectrum by observational data are to be given in the Part 2 of the paper.Project supported by the National Natural Science Foundation of China. 相似文献
3.
Hiroshi Ichikawa 《Journal of Oceanography》1978,34(4):129-139
The spectral energy balance in the wind-wave spectrum is studied with taking into account the energy input from turbulent wind to waves, the energy rearrangement due to conservative nonlinear wave-wave interaction and the energy dissipation due to water turbulence. Using the Ichikawa's (1978) model on the turbulent wind field over wind-waves and assuming that the energy dissipation is times greater than that due to molecular viscosity of water, the energy input and dissipation are determined so as to satisfy the condition that the nonlinear-transfers of momentum and energy conserve the total momentum and energy of waves. The nonlinear energy-transfer is estimated from the energy balance at each frequency. It is found that the energy input and dissipation satisfying the condition on the conservative nonlinear-transfer are determined by the characteristic height of wind-wave field and the friction velocity of air, and that the spectral distribution of the nonlinear energy-transfer estimated in this paper is qualitatively similar to that estimated by the non-linear wave-wave interaction theory ofHasselmann (1962). 相似文献
4.
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
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5.
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
6.
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
7.
The microwave backscattering from wind-wave surfaces is observed in a windwave tunnel under various conditions of the wind and wind waves, and its statistical features are investigated. The dependence of the backscattered power on the wind speed and the incident angle shows similar features to those predicted by models proposed previously. However, the dependence of the backscattered power on the incident angles also corresponds to the asymmetrical feature of the wind-wave surfaces with respect to the wind direction. The spectral analyses of time series of the backscattered intensity show that the propagating speed of fine structures of the wind-wave surface contributing to the backscattering at large incident angles does not coincide with the phase speed of the freely propagating Braggwaves. Atupwind incidence, the surface structures of wind waves contributing to the backscattering propagates with the dominant waves at their phase speed. This result is inconsistent with the two-scale model in which the Bragg waves are simply superimposed on longer waves, but is consistent with the results of optical observation by Ebuchiet al. (1987). At downwind incidence, the propagating speed is slower than the phase speed of the dominant waves. 相似文献
8.
A new set of empirical formulas for the production rate and the number concentration of sea-water droplets on the sea surface are proposed, synthesizing past observation data of sea-salt particles in the sea and water droplets in wind-wave tanks. A new levelz
c
is introduced as the effective wind-sea surface where seawater droplets are produced. The new formulas are expressed in linear functions in logarithmic scales ofu*2/v
p
, a parameter to describe overall conditions of airsea boundary processes, whereu
* is the friction velocity of air,v the kinematic viscosity of air and
p
the peak angular frequency of wind-wave part of wave spectra. A model of coexistence of spray droplets and suspended particles near the sea surface is proposed. As for the independent parameter, a comparison between the uses ofu*2/v
p
and ofu
*
3 which was the traditional way of parameterization excluding wave measure, shows that the advantage of usingu*2/v
p
is statistically significant with a confidence limit 89% in F-test. 相似文献
9.
The high frequency part (10 Hz50 Hz) of the one-dimensional wave spectrum was measured in a wind-wave channel under accurately controlled conditions. The results are compared with the spectral forms for the capillary range that have been proposed recently byPierson andStacy (1973) andToba (1973). In a general sense, fairly good agreement is found between the present results and those ofPierson andStacy (1973) and ofToba (1973). The spectrum in the capillary range is clearly wind speed dependent, and the spectral density in that range increases with increasing wind speed.However, closer examination shows systematic deviations of the present results from those previously proposed, particularly for high speed winds. 相似文献
10.
V. G. Polnikov 《Izvestiya Atmospheric and Oceanic Physics》2010,46(4):511-523
Based on different modifications of the source function in the WAM(C4) wind-wave model, a large series of verification calculations
aimed at increasing the quality of the numerical model (with respect to the parameters of accuracy and performance) is performed.
We propose a methodology allowing us to solve the following fundamental and practical problems of numerical modeling: (1)
determining the minimum interval of verification of numerical wind-wave models, (2) finding a criterion for choosing the best
model out of all models subjected to verification, and (3) formulating the accuracy requirement for specifying the input field
necessary for the given accuracy of wind-wave field calculations. Particularly, we have found that (a) the minimum term of
verification calculations for numerical wind-wave models is three months; (b) according to our criterion, the proposed modification
of the WAM model impartially is “essentially preferable” to the original model; and (c) the relative errors (yielded by the
proposed version of the WAM model) in the calculated wave heights ρH
s
and average periods ρT
m
for different levels of the relative error of the input wind-wave field ρW make it possible to solve the third problem mentioned
above. 相似文献
11.
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
12.
measurements by a circular array consisting of 18 wave gauges in a large wave tank, directional spectra of wind-generated waves in deep water are systematically determined by using maximum likelihood method The investigations reveal that the angular spreading of the wave energy is consistent with cos2s(θ/2) proposed by Longuet-Higgins et al.(1963, Ocean Wave Spectra, 111-136), if the bimodal distributions of wave energy are not taken into account. Bimodality occurring on higher frequency than peak frequency is too rare to affect our whole resalts. Surprisingly, a much broader directional spreading than that of the field, which is interpreted by the strongly nonlinear energy transfer because of the very young waves in laboratory, is found. The parameter s depends on frequency in the same way as observed by Mitsuyasu et al.(1975, Journal of Physical Oceanography, 5, 750-760) and Hasselmann et al.(1980, Journal of Physical Oceanography, 10, 1264-1280) in the field, and the relationship between the four nondimensional parameters sm, fo, b1 and b2, determining the directional width, and ū10 (corresponding to the inverse of wave age) are given respectively. The observed distributions are found to agree well with the suggestion of Donelan et al.(1985, Philosophical Transaction of Royal Society of London, A315, 509-562) when applied to field waves. 相似文献
13.
Parameters in wind-wave frequency spectra and their bearings on spectrum forms and growth 总被引：2，自引：0，他引：2
Wen Shengchang 《海洋学报(英文版)》1989,8(1):15-39
The spectrum variance m0, peak frequency ω0 and peakness factor p are expressed in terms of nondimensional fetch and duration by making use of relations which are derived through comparing and analyzing existing empirical formulas for the growth of significant wave height and period. The main features of spectrum growth as specified by these parameters agree with those of the JONS-WAP experiments. For given wind speed and fetch, the high frequency parts beyond the peaks of shallow water spectra almost coincide with that of the corresponding deep water spectrum, whereas the low frequency parts differ appreciably. The method developed in this paper predicts smaller significant wave height as well as smaller wave period for shallow water spectra in contrast to the theoretical result of Kitaigorodskii ef al, in which the peak frequency, and consequently the significant wave period, remains basically unchanged for different water depths. Spectra are further reduced to a form in which only significant wave h 相似文献
14.
《Coastal Engineering》2006,53(4):311-318
The extended mild-slope equations of Suh et al. [Suh, K.D., Lee, C., Park, W.S., 1997. Time-dependent equations for wave propagation on rapidly varying topography. Coastal Eng., 32, 91–117] and Lee et al. [Lee, C., Kim, G., Suh, K.D., 2003. Extended mild-slope equation for random waves. Coastal Eng., 48, 277–287] are compared analytically and numerically to determine their applicability to random wave transformation. The geometric optics approach is used to compare the two models analytically. In the model of Suh et al., the wave number of the component wave with a local angular frequency ω is approximated with an accuracy of O(ω − ω¯) at a constant water depth, where ω¯ is the carrier frequency of random waves. In the model of Suh et al., however, the diffraction effects and higher-order bottom effects are considered only for monochromatic waves, and the shoaling coefficient of random waves is not accurately approximated. This inaccuracy arises because the model of Suh et al. was derived for regular waves. In the model of Lee et al., all the parameters of random waves such as wave number, shoaling coefficient, diffraction effects, and higher-order bottom effects are approximated with an accuracy of O(ω − ω¯). This approximation is because the model of Lee et al. was developed using the Taylor series expansion technique for random waves. The result of dispersion relation analysis suggests the use of the peak and weighted-average frequencies as a carrier frequency for Suh et al. and Lee et al. models, respectively. All the analytical results are verified by numerical experiments of shoaling of random waves over a slightly inclined bed and diffraction of random waves through a breakwater gap on a flat bottom. 相似文献
15.
Directional wave spectra measured by a cloverleaf buoy in the East China Sea during AMTEX '75 have been compared with those calculated with the operational numerical MRI wave model developed at the Meteorological Research Institute of the Japan Meteorological Agency (J.M.A.). It is shown that the numerical wave model MRI can predict rather well, not only the frequency spectrum, but also the angular distribution function of the spectrum. The frequency dependence of the calculated angular distribution function is quite similar to that observed; the angular distribution is narrower for the spectral components near the peak spectral frequency but widens toward high frequencies and approaches the cos2-distribution. 相似文献
16.
Local balance in the air-sea boundary processes 总被引：2，自引：0，他引：2
Yoshiaki Toba 《Journal of Oceanography》1973,29(5):209-220
A combination of the three-second power law, presented in part I for wind waves of simple spectrum, and the similarity of the spectral form of wind waves, leads to a new concept on the energy spectrum of wind waves. It is well substantiated by data from a wind-wave tunnel experiment.In the gravity wave range, the gross form of the high frequency side of the spectrum is proportional tog u
*
–4, whereg represents the acceleration of gravity,u
* the friction velocity, the angular frequency, and the factor of proportionality is 2.0×l0–2. The wind waves grow in such a way that the spectrum slides up, keeping its similar form, along the line of the gross form, on the logarithmic diagram of the spectral density,, versus. Also, the terminal value of, at the peak frequency of the fully developed sea, is along a line of the gradient ofg
2
–5.The fine structure of the spectrum from the wind-wave tunnel experiment shows a characteristic form oscillating around the
–4-line. The excess of the energy density concentrates around the peak frequency and the second- and the third-order harmonics, and the deficit occurs in the middle of these frequencies. This form of the fine structure is always similar in the gravity wave range, in purely controlled conditions such as in a wind-wave tunnel. Moving averages of these spectra tend very close to the form proportional to
–5.As the wave number becomes large, the effect of surface tension is incorporated, and the
–4-line in the gravity wave range gradually continues to a
–8/3-line in the capillary wave range, in accordance with the wind-wave tunnel data. Likewise, the
–5-line gradually continues to a
–7/3-line.Also, through a discussion on these results, is suggested the existence of a kind of general similarity in the structure of wind wave field. 相似文献
17.
基于拟层流风波生成机制的海浪谱模型 总被引：1，自引：0，他引：1
海浪谱的能量可以视为由具有不同相速度的谐波携带的能量所组成。基于对风波形成、发展过程的认识,认为各组成谐波的能量由谐波自平均风摄取而来,由此根据拟层流模型推导出谐波能量密度的计算公式,建立以等效风速和峰值频率等为基本参数的海浪谱模型——随机Fourier函数模型,并给出了确定谐波频率、波长、相速度、振幅以及等效风速等模型参数的原则和计算方法。在59个实测样本谱基础上,采用随机建模方法确定模型参数的取值及其概率分布。结果表明,海浪谱模型可以很好地预测谱能,所计算的物理谱与实测谱均值吻合良好。 相似文献
18.
INTRODUCTIONForavarietyofapplications,includingcoastalandoceanengineering,shiproutingandtheinterpretationofremotelysensedata,informationonthedirectionalwavespectrumisdesirable.Knowledegeoftheintegratedorone-dimensionalspectrumisconsiderable,duelargelytofieldmeasurementssuchasJONSWAP.Asimilarsituation,however,doesnotexistinthecaseofdirectionalsprectra.Thisislargelyduetotheaddedcomplexityandthecostofdirectionalmeasure1.InstituteofPhysicalOceanography,OceanUniversityofQingdao,Qingdao266… 相似文献
19.
Local equilibrium of winds and wind-waves is discussed as a basis for research of the drag coefficient of the water surface as well as for the spectral growth of wind-waves. This hypothesis assumes, in a narrow sense, that statistical properties are determined from four physical quantities, which represent winds and wind-waves: the friction velocityu
*, the gravitational accelerationg, the powerE of the surface displacement, and the peak frequency
p
of a wind-wave spectrum. Then one has only one nondimensionalcontrol parameter, which may be either the wave age or wave nonlinearity (slope) of dominant waves. In a wide-sense, one can take into account viscosity and surface tension in terms of one more additional parameter by virtue of the virtual invariance of those material constants; that parameter describes the scale ratio between dominant waves and the short waves for which viscosity or surface tension is important. A unified expression for the roughness height according to this hypothesis turns out to include Charnock's and Toba's formulas as special cases. On the basis of a preliminary analysis of the experimental data, a new empirical formula is proposed. 相似文献
20.
Noriyuki Iwata 《Journal of Oceanography》1983,39(2):43-52
Backscatter cross-sections of microwaves from the sea surface are calculated by using the facet model and are compared withJonswap '75 experimental results. The principal features obtained are: (1) asymmetry of backscatter cross-sections between upwind and downwind directions is attributable to the modulation of the short gravity-capillary wave spectrum by a larger wave, and the non-Gaussian wave slope distribution has a tendency to cancel this effect, (2) angular spreading of the energy spectrum in the higher frequency range should have a narrower band than a simple cosine distribution, (3) the facet model itself should begin to break down at a larger incident angle than previously supposed. 相似文献