共查询到20条相似文献，搜索用时 31 毫秒
1.
A preliminary theoretical and experimental study was conducted on internal wave modes and their weak nonlinear resonant interaction in a nonlinearly stratified fluid . An asymptotical solution of the modes and a dispersion relation of internal waves in a stratified fluid with density profile similar to that in our experiment were obtained theoretically . The resonant-interaction mechanism to 2nd order approximation is also discussed . The resonant interaction of the 3rd and 4th mode internal waves excited by the unstable 1st mode wave is analyzed on the basis of data obtained by conductivity probes. The resonant-interaction condition, , is examined . It is shown that the resonant instability increases with pycnocline thickness and wave maker driving frequency . 相似文献
2.
Capillary and capillary-gravity waves possess a random character, and the slope wavenumber spectra of them can be used to
represent mean distributions of wave energy with respect to spatial scale of variability. But simple and practical models
of the slope wavenumber spectra have not been put forward so far. In this article, we address the accurate definition of the
slope wavenumber spectra of water surface capillary and capillary-gravity waves. By combining the existing slope wavenumber
models and using the dispersion relation of water surface waves, we derive the slope wavenumber spectrum models of capillary
and capillary-gravity waves. Simultaneously, by using the slope wavenumber models, the dependence of the slope wavenumber
spectrum on wind speed is analyzed using data obtained in an experiment which was performed in a laboratory wind wave tank.
Generally speaking, the slope wavenumber spectra are influenced profoundly by the wind speed above water surface. The slope
wavenumber spectrum increases with wind speed obviously and do not cross each other for different wind speeds. But, for the
same wind speed, the slope wavenumber spectra are essentially identical, even though the capillary and capillary-gravity waves
are excited at different times and locations. Furthermore, the slope wavenumber spectra obtained from the models agree quite
well with experimental results as regards both the values and the shape of the curve. 相似文献
3.
A WEAKLY NONLINEAR WATER WAVE MODEL TAKING INTO ACCOUNT DISPERSION OF WAVE PHASE VELOCITY 总被引：1，自引：0，他引：1
This paper presents a weakly nonlinear water wave model using a mild slope equation and a new explicit formulation which takes into account dispersion of wave phase velocity, approximates Hedges‘ (1987) nonlinear dispersion relationship, and accords well with the original empirical formula. Comparison of the calculating results with those obtained from the experimental data and those obtained from linear wave theory showed that the present water wave model considering the dispersion of phase ve-locity is rational and in good agreement with experiment data. 相似文献
4.
With the horizontal Coriolis terms included in motion equations and the influence of compressibility of seawater on Brunt-Visl frequency considered, a numerical method of calculating the dispersion relation for linear internal waves, which is an improvement of Cai and Gan (1995), and hence Fliegel and Hunkins (1975), had been set up. For different models (Pacific model, Atlantic model and Arctic model), simulations using the three different methods were compared and the following conclusions were reached:(1) the influence of horizontal Coriolis terms on dispersion relation cannot be neglected and is connected with the direction of the wave celerity, the latitude, and the modes of the wave;(2) the effect of compressibility of seawater in stratification is not an important factor for the dispersion relation of linear internal wave, at least for those three models. With the improved method, the wavefunction curves for the Pacific model had also been built. 相似文献
5.
Fractional energy losses of waves due to wave breaking when passing over a submerged bar are studied systematically using
a modified numerical code that is based on the high-order Boussinesq-type equations. The model is first tested by the additional
experimental data, and the model’s capability of simulating the wave transformation over both gentle slope and steep slope
is demonstrated. Then, the model’s breaking index is replaced and tested. The new breaking index, which is optimized from
the several breaking indices, is not sensitive to the spatial grid length and includes the bottom slopes. Numerical tests
show that the modified model with the new breaking index is more stable and efficient for the shallow-water wave breaking.
Finally, the modified model is used to study the fractional energy losses for the regular waves propagating and breaking over
a submerged bar. Our results have revealed that how the nonlinearity and the dispersion of the incident waves as well as the
dimensionless bar height (normalized by water depth) dominate the fractional energy losses. It is also found that the bar
slope (limited to gentle slopes that less than 1:10) and the dimensionless bar length (normalized by incident wave length)
have negligible effects on the fractional energy losses. 相似文献
6.
Some approximate formulas, based on the internal- wave directional spectral model established by Schott and Willebrand (1973),
of vertically standing wavemode eigenfunctions and a dispersion relation of internal waves in shallow seas are presented.
An optimization method to estimate internal wave directional spectra is described and the confidence interval expression of
the estimates is established.
The GM spectral model of oceanic internal waves cannot be used in shallow seas (01 bers, 1983). Internal waves in shallow
seas have two origins: oceanic (those generated in and propagating from the deep sea and ocean) and local (Phillips, 1977).
As both reveal obvious propagation orientations, it is important to investigate the directional properties of the internal
wave field. Though cross correlation function or cross-spectrum analyses can reveal the directional properties in some degree
(Fang et al., 1984, and Fang, 1987), internal- wave directional spectrum analysis can further estimate the main propagation
directions of wave components with different modenumbers and frequencies. So the latter is a more effective analysis tool.
Because internal- wave directional spectrum analysis requires high quality data and long computer time, there are very few
study reports so far on this subject. Among them. Schott and Willebrands' (1973) work is noteworthy. On the supposition, of
linearization, they derived an internal- wave directional spectrum model. Internal-wave directional-spectra in shallow seas
are investigated in the present study with their work as reference.
Project supported by the National Natural Science Foundation of China. 相似文献
7.
Depth inversion in coastal water based on SAR image of waves 总被引：1，自引：0，他引：1
Wave-number spectrum technique is proposed to retrieve coastal water depths by means of Synthetic Aperture Radar （SAR） image of waves. Based on the general dispersion relation of ocean waves the wavelength changes of a surface wave over varying water depths can be derived from SAR. Approaching the analysis of SAR images of waves and using the general dispersion relation of ocean waves, this indirect technique of remote sensing bathymetry has been applied to a coastal region of Xiapu in Fujian Province, China. Results show that this technique is suitable for the coastal waters especially for the near-shore regions with variable water depths. 相似文献
8.
从正压涡度方程出发,在弱非线性和弱基流切变条件下,导得了描述非线性大气长波活动的推广的Ｋｄｖ方程,并得到了方程的孤立波解及其色散关系。取近似于实际大气运动的物理参数作数值计算,得到了振荡型Ｒｏｓｂｙ孤立波的水平结构和移动特征,其结果较之寻常的Ｋｄｖ孤立波更接近于实际大气中的阻塞流型。 相似文献
9.
罗德海 《成都信息工程学院学报》1993,(4)
本文在基本气流具有水平切变的情况下,利用摄动法导出了非线性Rossby波所满足的三阶Zakharov方程,然后,考虑了基流具有弱切变的情况,通过使用三阶Zakharov方程研究了Rossby波列的第一类不稳定性问题。结果表明:通过非线性作用,大气中的Rossby波列可产生调制不稳定。同时,本文对这种不稳定的区域,增长率和周期进行了详细的计算,并讨论了波振幅、波数、纬度和基流切变对它们的影响,指出Rossby波列的调制不稳定可以激发30～60天的低频振荡。 相似文献
10.
In order to solve the problems of multi-parameter,multi-extreme and multi-solution in the nonlinear iterative optimization process of Rayleigh wave inversion,the artificial bee colony(ABC)algorithm is selected for global nonlinear inversion.The global nonlinear inversion method does not rely on a strict initial model and does not need to calculate the derivative of the objective function.The ABC algorithm uses the local optimization behavior of each individual artificial bee to finally highlight the global optimal value in the colony,and the convergence speed is faster.While searching for the global optimal solution,an effective local search can also be performed to ensure the reliability of the inversion results.This paper uses the ABC algorithm to perform Rayleigh wave dispersion inversion on the actual seismic data to obtain a clear undergrounding of shear wave velocity profile and accurately identify the location of the high-velocity interlayer.It is verified that the ABC algorithm used in the inversion of the Rayleigh wave dispersion curve is stable and converges quickly. 相似文献
11.
Surface waves comprise an important aspect of the interaction between the atmosphere and the ocean, so a dynamically consistent framework for modelling atmosphere-ocean interaction must take account of surface waves, either implicitly or explicitly. In order to calculate the effect of wind forcing on waves and currents, and vice versa, it is necessary to employ a consistent formula- tion of the energy and momentum balance within the airflow, wave field, and water column. It is very advantageous to apply sur- face-following coordinate systems, whereby the steep gradients in mean flow properties near the air-water interface in the cross-interface direction may be resolved over distances which are much smaller than the height of the waves themselves. We may account for the waves explicitly by employing a numerical spectral wave model, and applying a suitable theory of wave–mean flow interaction. If the mean flow is small compared with the wave phase speed, perturbation expansions of the hydrodynamic equations in a Lagrangian or generalized Lagrangian mean framework are useful: for stronger flows, such as for wind blowing over waves, the presence of critical levels where the mean flow velocity is equal to the wave phase speed necessitates the application of more general types of surface-following coordinate system. The interaction of the flow of air and water and associated differences in temperature and the concentration of various substances (such as gas species) gives rise to a complex boundary-layer structure at a wide range of vertical scales, from the sub-millimetre scales of gaseous diffusion, to several tens of metres for the turbulent Ekman layer. The bal- ance of momentum, heat, and mass is also affected significantly by breaking waves, which act to increase the effective area of the surface for mass transfer, and increase turbulent diffusive fluxes via the conversion of wave energy to turbulent kinetic energy. 相似文献
12.
A distinct type of nonlinear internal-wave packet, with the largest internal solitary wave in the middle of the packet, was
regularly observed in the South China Sea during the Asian Seas International Acoustics Experiment in 2001. Data analysis
shows that the occurrence of the distinct internal wave packet is closely related with the occurrence of lower-high internal
tides; the internal tides are mixed in the experimental area and, thus, there is diurnal inequality between the heights of
two neighboring internal tides. Modeling of internal tides and internal solitary waves in a shoaling situation suggests that
this type of wave packet can be generated in the South China Sea by the large shoaling of internal solitary waves and internal
tides. Both the internal solitary waves and the internal tides come from the direction of Luzon Strait. The initial large
internal solitary waves contribute to the occurrence of the largest internal solitary wave in the middle of the packet and
the waves behind the largest internal solitary wave, while the shoaling internal tides bring about the nonlinear internal
waves in front of the largest internal solitary wave via interaction with the local shelf topography. 相似文献
13.
In a two-dimensional and linear framework, a transformation was developed to derive eigensolutions of internal waves over a subcritical hyperbolic slope and to approximate the continental slope and shelf. The transformation converts a hyperbolic slope in physical space into a flat bottom in transform space while the governing equations of internal waves remain hyperbolic. The eigensolutions are further used to study the evolution of linear internal waves as it propagates to subcritical continental slope and shelf. The stream function, velocity, and vertical shear of velocity induced by internal wave at the hyperbolic slope are analytically expressed by superposition of the obtained eigensolutions. The velocity and velocity shear increase as the internal wave propagates to a hyperbolic slope. They become very large especially when the slope of internal wave rays approaches the topographic slope, which is consistent with the previous studies. 相似文献
14.
Studying the relationship between wave steepness and wave age is important for describing wind wave growth with energy balance equation of significant waves. After invoking the dispersion rela- tion of surface gravity wave in deep water, a new relationship between wave steepness and wave age is revealed based on the “3/2-power law” (Toba, 1972), in which wave steepness is a function of wave age with a drag coefficient as a parameter. With a given wave age, a larger drag coefficient would lead to larger wave steepness. This could be interpreted as the result of interaction between wind and waves. Comparing with previous relationships, the newly proposed one is more consistent with observational data in field and laboratory. 相似文献
15.
This new method can simulate the nonlinear random wavcs processes by computer if the higherorder moments of the probability distribution of the sea surface elevation reflecting the nonlinearity ofthe sea wave are given. Compared with other methods, this method has greater accuracy andflexibility, wider application and faster simulation. Statistical analysis of the sea surface elevationdistribution of the simulated wave process showed obviously the Gram-Charlier series can be used to depictthe distribution of the sea surface elevation. 相似文献
16.
瑞雷波法已在研究地球内部结构、近地表地球物理工程和超声无损检测等领域中获得了广泛应用,尤其是近年来瑞雷波法作为近地表场地表征新兴领域的前沿技术已成为国际学术研究与应用的热点。对国内外近地表弹性介质瑞雷波勘探的主要研究成果与进展进行了综述,通过对瑞雷波勘探现有的研究成果和进展密切追踪发现当前近地表瑞雷波勘探主要基于水平地表弹性水平层状介质模型,利用单分量瑞雷波相速度频散曲线单目标反演获得一维横波速度剖面和相关岩土力学参数。但是,该方法也存在着现有瑞雷波频散曲线反演极易出现模式误识别、现有单分量单目标瑞雷波反演未充分利用多分量信息、现有瑞雷波相速度反演未充分利用群速度传播特性、现有瑞雷波反演未充分利用质点椭圆极化振动特性等挑战性学术难题和不足。基于上述问题,建议未来近地表弹性介质瑞雷波勘探重点研究方向应集中在进行多模式表面波全速度谱反演研究、多站多分量表面波相速度多目标全速度谱反演研究、单站多分量表面波群速度多目标全速度谱反演研究和单站多分量表面波椭圆极化振动特性多目标反演研究。由此构建新的近地表多分量瑞雷波多目标全速度谱反演理论,引领多分量瑞雷波多目标反演学科前沿,拓展现有单分量瑞雷波单目标反演理论范畴,推动多分量瑞雷波高精度实用勘探技术的发展。 相似文献
17.
Large amplitude internal solitary waves (ISWs) often exhibit highly nonlinear effects and may contribute significantly to
mixing and energy transporting in the ocean. We observed highly nonlinear ISWs over the continental shelf of the northwestern
South China Sea (19°35′N, 112°E) in May 2005 during the Wenchang Internal Wave Experiment using in-situ time series data from
an array of temperature and salinity sensors, and an acoustic Doppler current profiler (ADCP). We summarized the characteristics
of the ISWs and compared them with those of existing internal wave theories. Particular attention has been paid to characterizing
solitons in terms of the relationship between shape and amplitude-width. Comparison between theoretical prediction and observation
results shows that the high nonlinearity of these waves is better represented by the second-order extended Korteweg-de Vries
(KdV) theory than the first-order KdV model. These results indicate that the northwestern South China Sea (SCS) is rich in
highly nonlinear ISWs that are an indispensable part of the energy budget of the internal waves in the northern South China
Sea. 相似文献
18.
IU Zhongbo ZHANG Rixiang CHEN Bing 《中国海洋大学学报(英文版)》2007,6(4):421-423
Based on the hyperbolic mild-slope equations derived by Copeland (1985), a numerical model is established in unstag- gered grids. A composite 4 th-order Adam-Bashforth-Moulton (ABM) scheme is used to solve the model in the time domain. Terms involving the first order spatial derivatives are differenced to O ( Δx )4accuracy utilizing a five-point formula. The nonlinear dispersion relationship proposed by Kirby and Dalrymple (1986) is used to consider the nonlinear effect. A numerical test is performed upon wave propagating over a typical shoal. The agreement between the numerical and the experimental results validates the present model. Biodistribution and applications are also summarized. 相似文献
19.
LIU Yuguang ) * YAN Xiao-Hai ) SU Ming-Yang ) ) Physical Oceanography Laboratory College of Marine Environment Ocean University of China Qingdao P..R.China) Center for Remote Sensing Graduate College of Marine Studies University of Delaware Newark DE USA ) Oceanography Division Naval Research Laboratory Stennis Space Center MS USA 《中国海洋大学学报(英文版)》2003,2(1)
1 Introduction1.1 Proposed ModelonDirectionalFrequencySpec trum ThisisthePartⅡofthetwo papersetondirection alspectraofwindwaves.Anewmodelonthedirec tionalspectrumofwindwavesfordeepwaterispro posedbasedonthestatisticsofwindwavesinthePartⅠ .Substituting (4 5 )ofPartⅠinto (4 0 )andaddingapeak enhancementitemγΓ,weobtainS(ω ,) =0 .0 0 93αaαwD( ,k) ωpω2 ξ- 4g2ω5×exp - 2 ξ+14[bωp +(1-b)ωp]4ω4 γΓ. (1)Here ,αaisthewaveagefactorofspectralcoefficientdefinedbyαa = ω0 .55… 相似文献
20.
The destructiveness of impulse waves generated by landslides(IWL) originates from the wave's movement and load, wherein the impulse wave's load is the major cause of sub-aerial building damage and casualties. In this study, an experiment involving 16 groups of physical tests for the wave pressure generated by a landslide was designed, consisting of 4 sets of IWL and 4 opposite bank slope angles. A high-frequency strain system was used to measure the total pressure of the impulse wave in a water tank. The tests showed that the dynamic pressure caused by the IWL can be divided into two types: impact pressure generated by the jetflow and the pulsating pressure caused by the wave. Under the same impulse wave conditions, the maximum run-up becomes smaller as the opposite bank's slope angle increases, and the jetflow maximum impact pressure experienced by the opposite bank increases, while the maximum pulsating pressure caused by the impulse wave is slightly decreased. Different from previous studies, the spatial maximum pressure distributions of the wave generated by landslide were concluded that the position of the maximum pulsating pressure appears adjacent to the still water surface, and the overall spatial distribution pattern of maximum wave pressure is presented as an inclined "M" shape.Meanwhile, this study is the first to quantitatively analyzed that impact pressure has a very short action time, is even 7 times of the pulse pressure value, and there is a simple mathematical linear relationship between the two. Currently, some wave-load formulas for wind waves and tides are not applicable to calculating the loads of IWL. Research on the load of IWL will explain the hazard of impulse wave very clearly, and will greatly contribute to hazard prevention, mitigation and risk assessment work associated with IWL. 相似文献