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以不规则波在缓变地形和缓变流场水域的折射-绕射理论以及风浪的成长、衰减理论为基础,得到近岸区不规则波成长模型。结合近岸波浪特性和海洋工程应用的实际情况,建立综合考虑海岸、折射、白浪、底摩擦、流、风和非线性作用诸因素的近岸不规则波数值计算模型。该模型具有二维波谱特性及实用性。文章力图使模式更合理地反映近岸波浪的传播、成长和衰减规律,而整个计算工作量则较小,可在微型电子计算机上得以实现。 相似文献
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M. V. Kosnik V. A. Dulov V. N. Kudryavtsev 《Izvestiya Atmospheric and Oceanic Physics》2010,46(3):369-378
We investigate the role of different physical mechanisms in the generation of the capillary-gravity wind wave spectrum. This
spectrum is calculated by integrating a nonstationary kinetic equation until the solution becomes stready. The mechanisms
of spectrum generation under consideration include three-wave interactions, viscous dissipation, energy influx from wind,
nonlinear dissipation, and the generation of a parasitic capillary ripple. The three-wave interactions are taken into account
as an integral of collisions without additional simplifications. It is shown that the three-wave interactions lead to solution
instability if the kinetic equation takes into account only linear sources. To stabilize the solution, the kinetic equation
should incorporate a nonlinear dissipation term, which in the range of short gravity waves corresponds to energy losses during
wave breaking and microscale wave breaking. In the range of capillary waves, the account of nonlinear dissipation is also
needed to ensure a realistic level of the spectrum for large wind velocities. For the steady-state spectrum, the role of three-wave
interactions remains essential merely in the range of the minimum of phase velocity, where a trough on the curvature spectrum
is formed. At the remaining intervals of the spectrum, the main contribution into the spectral energy balance is provided
by the mechanisms of wave injection, nonlinear dissipation, and the generation of parasitic capillaries. 相似文献
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中咀湾是一个天然的避风良港,一般情况下外海波浪影响很小,主要受局部风场产生的局部风浪影响。本文采用曹宏生在Massel的扩展缓坡方程基础上推导出来的考虑陡变地形和能量耗散效应的缓坡方程为控制方程,结合固边界的反射边界条件,构成波浪传播变形的联合折射、绕射和反射的数学模型。文中将此方法运用在中国台州市大陈岛中咀湾避风港中,用波浪数学模型计算极端高水位和设计高水位时3种波况分别在3组重现期时工程海域的波浪要素,提供防波堤的堤前波高,并分析比较此处实心式和透空式防波堤的防浪性能。 相似文献
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A. K. Laing 《新西兰海洋与淡水研究杂志》2013,47(4):541-553
A model is described for hindcasting or forecasting waves in finite‐depth waters. The model is particularly applicable to coastal sites where the water is depth‐limited. The wave energy density spectrum is modelled in the frequency‐directional domain. For each spectral component a ray is defined along which wave energy propagates to reach the site. For sites exposed to the open ocean a background spectral wave model is required to provide input to the ray endpoints. Further growth and dissipation is then effected along the rays according to the local wind and water depth. The model was used to hindcast wave spectra over a period of 9 months for a site in the Canterbury Bight, New Zealand. The results were compared with measurements from a Waveridcr buoy at the site. The model succeeds in explaining about 40% of the variance in measured significant wave heights. However, the present application is handicapped by errors inherent in the background spectral model and in specifying the local wind. 相似文献
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《中国海洋工程》2021,(4)
The main objective of this paper is to examine the influences of both the principal wave direction and the directional spreading parameter of the wave energy on the wave height evolution of multidirectional irregular waves over an impermeable sloping bottom and to propose an improved wave height distribution model based on an existing classical formula. The numerical model FUNWAVE 2.0, based on a fully nonlinear Boussinesq equation, is employed to simulate the propagation of multidirectional irregular waves over the sloping bottom. Comparisons of wave heights derived from wave trains with various principal wave directions and different directional spreading parameters are conducted. Results show that both the principal wave direction and the wave directional spread have significant influences on the wave height evolution on a varying coastal topography. The shoaling effect for the wave height is obviously weakened with the increase of the principal wave direction and with the decrease of the directional spreading parameter. With the simulated data, the classical Klopman wave height distribution model is improved by considering the influences of both factors. It is found that the improved model performs better in describing the wave height distribution for the multidirectional irregular waves in shallow water. 相似文献
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多方向不规则波传播变形数值模拟 总被引：1，自引：1，他引：1
在推广的缓坡方程数学模型基础上建立了多方向不规则波数学模型，综合考虑了波浪折射、绕射、反射、底摩擦和风能输入等因素。基于线性波浪理论，将波浪方向谱在频率和方向上按等能量分割法离散后，分别计算各组成波的传播变形，再计算合成波要素。缓坡方程数学模型采用改进的ADI法求解，计算效率高，稳定性好。采用椭圆形浅滩不规则波模型试验结果和单突堤不规则波绕射理论解对数学模型进行了验证，数值模拟结果和试验值及理论解符合良好。利用该模型进行了某港港内波浪折射、绕射和反射的联合数值模拟，给出了合理的港内波高分布。 相似文献
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Conventional spectral wave models, which are used to determine wave conditions in coastal regions, can account for all relevant processes of generation, dissipation and propagation, except diffraction. To accommodate diffraction in such models, a phase-decoupled refraction–diffraction approximation is suggested. It is expressed in terms of the directional turning rate of the individual wave components in the two-dimensional wave spectrum. The approximation is based on the mild-slope equation for refraction–diffraction, omitting phase information. It does therefore not permit coherent wave fields in the computational domain (harbours with standing-wave patterns are excluded). The third-generation wave model SWAN (Simulating WAves Nearshore) was used for the numerical implementation based on a straightforward finite-difference scheme. Computational results in extreme diffraction-prone cases agree reasonably well with observations, analytical solutions and solutions of conventional refraction–diffraction models. It is shown that the agreement would improve further if singularities in the wave field (e.g., at the tips of breakwaters) could be properly accounted for. The implementation of this phase-decoupled refraction–diffraction approximation in SWAN shows that diffraction of random, short-crested waves, based on the mild-slope equation can be combined with the processes of refraction, shoaling, generation, dissipation and wave–wave interactions in spectral wave models. 相似文献
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A semi-analytical nonlinear wavemaker model is derived to predict the generation and propagation of transient nonlinear waves in a wave flume. The solution is very efficient and is achieved by applying eigenfunction expansions and FFT. The model is applied to study the effect of the wavemaker and its motion on the generation and propagation of nonlinear waves. The results indicate that the linear wavemaker theory may be applied to predict only the generation of waves of low steepness for which the nonlinear terms in the kinematic wavemaker boundary condition and free-surface boundary conditions are of secondary importance. For waves of moderate steepness and steep waves these nonlinear terms have substantial effects on wave profile and wave spectrum just after the wavemaker. A wave spectrum corresponding to a sinusoidally moving wavemaker possesses a multi-peak form with substantial nonlinear components, which disturbs or may even exclude physical modeling in wave flumes. The analysis shows that the widely recognized weakly nonlinear wavemaker theory may only be applied to describe the generation and propagation of waves of low steepness. This is subject to further restrictions in shallow and deep waters because the kinematic wavemaker boundary condition as well as the nonlinear interaction of wave components and the evolution of wave energy spectrum is not properly described by weakly nonlinear wavemaker theory. Laboratory experiments were conducted in a wave flume to verify the nonlinear wavemaker model. The comparisons show a reasonable agreement between predicted and measured free-surface elevation and the corresponding amplitudes of Fourier series. A reasonable agreement between theoretical results and experimental data is observed even for fairly steep waves. 相似文献
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Implementation and evaluation of alternative wave breaking formulas in a coastal spectral wave model 总被引：2，自引：0，他引：2
This paper describes methods and results of research for incorporating four different parameterized wave breaking and dissipation formulas in a coastal wave prediction model. Two formulations assume the breaking energy dissipation to be limited by the Rayleigh distribution, whereas the other two represent the breaking wave energy by a bore model. These four formulations have been implemented in WABED, a directional spectral wave model based on the wave action balance equation with diffraction, reflection, and wave–current interaction capabilities. Four parameterized wave breaking formulations are evaluated in the present study using two high-quality laboratory data sets. The first data set is from a wave transformation experiment at an idealized inlet entrance, representing four incident irregular waves in a slack tide and two steady-state ebb current conditions. The second data set is from a laboratory study of wave propagation over a complex bathymetry with strong wave-induced currents. Numerical simulation results show that with a proper breaking formulation the wave model can reproduce laboratory data for waves propagating over idealized or complicated bathymetries with ambient currents. The extended Goda wave breaking formulation with a truncated Rayleigh distribution, and the Battjes and Janssen formulation with a bore model produced the best agreement between model and data. 相似文献
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Design of an offshore wind turbine requires estimation of loads on its rotor, tower and supporting structure. These loads are obtained by time-domain simulations of the coupled aero-servo-hydro-elastic model of the wind turbine. Accuracy of predicted loads depends on assumptions made in the simulation models employed, both for the turbine and for the input wind and wave conditions. Currently, waves are simulated using a linear irregular wave theory that is not appropriate for nonlinear waves, which are even more pronounced in shallow water depths where wind farms are typically sited. The present study investigates the use of irregular nonlinear (second-order) waves for estimating loads on the support structure (monopile) of an offshore wind turbine. We present the theory for the irregular nonlinear model and incorporate it in the commonly used wind turbine simulation software, FAST, which had been developed by National Renewable Energy Laboratory (NREL), but which had the modeling capability only for irregular linear waves. We use an efficient algorithm for computation of nonlinear wave elevation and kinematics, so that a large number of time-domain simulations, which are required for prediction of long-term loads using statistical extrapolation, can easily be performed. To illustrate the influence of the alternative wave models, we compute loads at the base of the monopile of the NREL 5MW baseline wind turbine model using linear and nonlinear irregular wave models. We show that for a given environmental condition (i.e., the mean wind speed and the significant wave height), extreme loads are larger when computed using the nonlinear wave model. We finally compute long-term loads, which are required for a design load case according to the International Electrotechnical Commission guidelines, using the inverse first-order reliability method. We discuss a convergence criteria that may be used to predict accurate 20-year loads and discuss wind versus wave dominance in the load prediction. We show that 20-year long-term loads can be significantly higher when the nonlinear wave model is used. 相似文献
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Wave dissipation characteristics in SWAN (Simulating Waves Nearshore) model are investigated through numerical experiments. It is found that neither the fully developed integral parameters of wind waves (significant wave height and peak frequency) nor the high frequency spectral tail can be well reproduced by the default wave dissipation source terms. A new spectral dissipation source term is proposed, which comprises saturation based dissipation above two times of peak frequency and improved whitecapping dissipation at lower frequency spectrum. The reciprocal wave age (u /c p ) is involved into the whitecapping model to adjust dissipation rate at different wind speed. The Phillips higher frequency saturation parameter in the saturation-based dissipation is no longer taken as a constant, but varies with wave age. Numerical validations demonstrate that both the wind wave generation process and higher frequency spectrum of wind waves can be well simulated by the new wave dissipation term. 相似文献
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V. N. Kudryavtsev 《Physical Oceanography》1997,8(2):69-80
A model for the spectrum of capillary waves has been constructed. These waves are generated at the crests of short gravity
waves and decay due to viscosity. Capillary wave generation leads to short gravity wave dissipation. Using empirical data
on the short gravity wave dissipation spectrum, a relation for the capillary wave spectrum is derived from the equation of
energy balance of capillary waves. The capillary wave spectrum is matched with the known Donelan-Pierson spectrum for short
gravity waves. The obtained relation for the spectrum of wind-generated ripple is compared with the data of laboratory experiments.
Translated by Vladimir A. Puchkin. 相似文献
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利用实测资料分析重构了大亚湾和大鹏湾潮汐水位“双峰”现象,确定了浅水分潮的异常增长是潮位“双峰”现象的主要成因,其中四分之一日分潮和六分之一日分潮起着至关重要的作用。通过SCHISM模型构建大亚湾和大鹏湾附近海域高分辨率水动力模型,模拟结果表明近岸海域,在大亚湾以东,潮汐类型为不规则全日潮,以西为不规则半日潮,在两个海湾内均为不规则半日潮;研究海域的潮流均表现为不规则半日潮流。四分之一日分潮和六分之一日分潮在大亚湾和大鹏湾的不同变形过程是造成两个相邻海湾水文差异的直接原因。通过构建不同底摩擦强度、消除水底地形以及改变海湾水深的数值实验研究表明,分潮传播方向与水深变浅方向是否一致,是导致两个海湾潮波浅水变形不同的根本原因。 相似文献
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The pycnocline in a closed domain is tilted by external wind forcing and tends to restore to a level posi- tion when the wind falls. An internal seiche oscillation exhibits if the forcing is weak, otherwise internal surge and internal solitary waves emerge, which serve as a link to cascade energy to small-scale processes. A two-dimensional non-hydrostatic code with a turbulence closure model is constructed to extend previous laboratory studies. The model could reproduce all the key phenomena observed in the corresponding labo- ratory experiments. The model results further serve as a comprehensive and reliable data set for an in-depth understanding of the related dynamical process. The comparative analyses indicate that nonlinear term favors the generation of internal surge and subsequent internal solitary waves, and the linear model predicts the general trend reasonably well. The vertical boundary can approximately reflect all the incoming waves, while the slope boundary serves as an area for small-scale internal wave breaking and energy dissipation. The temporal evolutions of domain integrated kinetic and potential energy are also analyzed, and the results indicate that about 20% of the initial available potential energy is lost during the first internal wave breaking process. Some numerical tactics such as grid topology and model initialization are also briefly discussed. 相似文献
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Oscillating Water Column (OWC) is one of the pioneer devices in harnessing wave energy; however, it is not fully commercialized perhaps due to the complicated hydrodynamic behavior. Previous studies are significantly devoted to OWC devices located in nearshore and coastal regions where incident wave energy would experience dissipation more than offshore. In this paper, a 1:15 scaled fixed offshore OWC model is tested in a large towing tank of National Iranian Marine Laboratory. Wave spectrum shape effect on the efficiency of the OWC model is addressed. Moreover, the paper investigates the effects of the geometric and hydrodynamic factors on OWC device efficiency and uncovers new points in nonlinear interaction occurring inside the chamber; i.e. sloshing. The results indicate that shape of the spectrum inside the chamber is affected by the type of incident wave spectrum, especially for long waves. Pierson–Moskowitz spectrum leaded to higher efficiency rather than JONSWAP spectrum at longer incident wave periods. According to efficiency analysis, increasing wave height may lead to air leakage from the chamber followed by vortex generation, which is a reason for decreasing the efficiency of the OWC device. Furthermore, no shift in the resonant period of the OWC model, due to wave height increase, was observed at the opening ratios equal or smaller than 1.28%. Spectral analysis of water fluctuation inside the OWC chamber illustrates two modes of sloshing. The first mode can be seen at short period waves while the second mode is visible at long period waves. The sloshing modes approximately vanish by increasing draft value. 相似文献
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大亚湾冬季水位的亚潮变化及其与南海的耦合 总被引：1，自引：0，他引：1
本文应用常规时间序列谱分析方法和频域的多输入线性模型研究了冬季广东省大亚湾内水位的亚潮变化及其与大亚湾本地和外海远处各种强迫作用因素间的关系。结果表明：冬季在亚湾亚潮水位的能量主要集中在６．４ｄ和３．６ｄ频带,而在１０．７ｄ频带还有一较弱谱峰,同期广东沿海风的低频能量也主要集中于２－７ｄ频段。造成冬季亚潮水位变化的原因包含了大亚湾本地气象条件的影响,但主要是远地因素作用于大亚湾的结果。外海影响一方 相似文献