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1.
《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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This work presents a new approach for simulating the random waves in viscous fluids and the associated bottom shear stresses. By generating the incident random waves in a numerical wave flume and solving the unsteady two-dimensional Navier-Stokes equations and the fully nonlinear free surface boundaiy conditions for the fluid flows in the flume, the viscous flows and laminar bottom shear stresses induced by random waves axe determined. The deterministic spectral amplitude method implemented by use of the fast Fourier transform algorithm was adopted to generate the incident random waves. The accuracy of the numerical scheme is confirmed by comparing the predicted wave spectrum with the target spectrum and by comparing the nanlerical transfer function between the shear stress and the surface elevation with the theoretical transfer function. The maximum bottom shear stress caused by random waves, computed by this wave model, is compared with that obtained by Myrhaug＇ s model （1995）. The transfer function method is also employed to determine the maximum shear stress, and is proved accurate. 相似文献
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In this paper, new expressions of radiation stress and volume flux for long waves have been analytically derived by inclusion of higher-order surface elevations up to the sixth-order. To quantify these expressions, surface elevations along a beach are first simulated using the fully nonlinear Boussinesq-type model COULWAVE. Then, based on the large amount of numerical data, new equations for radiation stress and volume flux are statistically formulated. The research unveils the essential roles of the Ursell parameter, Irribarren number and wave steepness described by the local wave height, wave length and bottom slope. The study shows the importance of nonlinear wave properties in wave-induced currents and mean water levels (set-up/down). The higher-order formulations produce lower values for radiation stress and volume flux than calculated from the lower-order and linear waves. Case studies suggest that the new formulations produce an accurate estimation for mean water level. However, improvement on the computed current profiles is marginal for some cases. This implies that the accurate prediction of the current profile would require more than just the proposed improvement of the radiation stress and volume flux. 相似文献
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The applicability of three different wave-propagation models in nonlinear dispersive wave fields has been investigated. The numerical models tested here are based on three different wave theories: a fully nonlinear potential theory, a Stokes second-order theory, and a Boussinesq-type theory with an improved dispersion relation. Physical experiments and computations were conducted for wave evolutions during passage over a submerged shelf under various wave conditions. As expected, the fully nonlinear solutions agree better with the measurements than do the other solutions. Although the second-order solution has sufficient accuracy for smaller-amplitude wave cases, the truncation after the third harmonics causes significant discrepancies in wave form for larger waves. In addition, the second-order model markedly overestimates the first- and second-harmonic amplitudes in transmitted waves. The Boussinesq model provides excellent predictions of wave profile over the shelf even in larger wave cases. However, this model also overestimates the magnitudes of several higher harmonics in transmitted waves. These facts may indicate that energy transfer from bound components into free waves in these higher harmonics cannot be accurately evaluated by the Boussinesq-type equations. 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
8.
《Applied Ocean Research》2004,26(3-4):137-146
A theoretical approach is applied to predict the propagation and transformation of nonlinear water waves. A semi-analytical solution was derived by applying an eigenfunction expansion method. The solution is applied to analyze the effect of wave frequencies and wave steepness on the propagation of nonlinear waves. The main attention is paid to the wave profile, the wave energy spectrum, and the changes of wave profile and energy spectrum due to the interaction of wave components in a wave train. The results show that for waves of low steepness the nonlinear wave effects and effects associated with the interaction of water waves in a wave train are of secondary importance. For waves of moderate steepness and steep waves the effects associated with the interactions between waves in a wave train are becoming significant and a train of initially sinusoidal waves may drastically change its form within a short distance from its original position. The evolution of wave components has substantial effects on the wave spectrum. A train of initially very narrow-banded waves changes its one-peak spectrum to a multi-peak one in a fairly short period of time. Laboratory experiments were conducted in a wave flume to verify theoretical approaches. The free-surface elevation recorded by a system of wave gauges was compared with the results provided by the semi-analytical solution. Theoretical results are in a fairly good agreement with experimental data. A reasonable agreement between theoretical results and experimental data is observed often even for relatively steep waves. 相似文献
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This paper describes the formulation and validation of a nearshore wave model for tropical coastal environment. The governing Boussinesq-type equations include the conservative form of the nonlinear shallow-water equations for shock capturing. A Riemann solver supplies the inter-cell flux and bathymetry source term, while a Godunov-type scheme integrates the evolution variables in time. The model handles wave breaking through momentum conservation with energy dissipation based on an eddy viscosity concept. The computed results show very good agreement with laboratory data for wave propagation over a submerged bar, wave breaking and runup on plane beaches as well as wave transformation over fringing reefs. The model accurately describes transition between supercritical and subcritical flows as well as development of dispersive waves in the processes. 相似文献
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本文基于具备间断捕捉能力的二阶全非线性Boussinesq数值模型,对规则波和随机波在礁坪地形上的传播变形进行了数值模拟。该模型采用高阶有限体积法和有限差分方法求解守恒格式的控制方程,将波浪破碎视为间断,同时采用静态重构技术处理了海岸动边界问题。重点针对礁坪上波浪传播过程中的波高空间分布和沿程衰减,礁坪上的平均水位变化,以及波浪能量频谱的移动和空间差异等典型水动力现象开展数值计算。将数值结果与实验结果对比,两者吻合情况良好,验证了模型具有良好的稳定性,具备模拟破碎波浪和海-岸动边界的能力,能较为准确地模拟波浪在礁坪地形上的传播过程中发生的各种水动力现象。 相似文献
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《Coastal Engineering》1999,36(1):1-16
A weakly-nonlinear and dispersive wave equation recently developed by the authors is used for formulating a spectral-type unidirectional wave propagation model describing spectral transformations of narrow-band waves travelling over arbitrary depths. The essential characteristics of the model equation are recapitulated first and then the spectral domain representation in terms of spatially varying harmonic amplitudes is presented. The resulting evolution equations are used to simulate the experiments concerning harmonic generation in shallow water and nonlinear random wave transformations over a submerged bar. Furthermore, the spectral model predictions are compared with the field measurements in nearshore with satisfactory results. 相似文献
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The applicability of existing nonlinear (triad) spectral models for steep slopes (0.1–0.2) characteristic of reef environments was investigated, using both deterministic (phase-resolving) and stochastic (phased-averaged) formulations. Model performance was tested using laboratory observations of unidirectional wave transformation over steep and smooth bathymetry profiles. The models, developed for mild slopes, were implemented with minimal modifications (the inclusion of breaking parametrizations and linear steep-slope corrections) required by laboratory data. The deterministic model produced typically more accurate predictions than the stochastic one, but the phase averaged formulation proved fast enough to allow for an inverse modeling search for the optimal breaking parametrization. The effects of the additional assumptions of the stochastic approach resulted in a slower than observed evolution of the infragravity band. Despite the challenge posed by the fast wave evolution and energetic breaking characteristic to the steep reef slopes, both formulations performed overall well, and should be considered as good provisional candidates for use in numerical investigation of wave–current interaction processes on steep reefs. 相似文献
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A fully nonlinear domain decomposed solver is proposed for efficient computations of wave loads on surface piercing structures in the time domain. A fully nonlinear potential flow solver was combined with a fully nonlinear Navier–Stokes/VOF solver via generalized coupling zones of arbitrary shape. Sensitivity tests of the extent of the inner Navier–Stokes/VOF domain were carried out. Numerical computations of wave loads on surface piercing circular cylinders at intermediate water depths are presented. Four different test cases of increasing complexity were considered; 1) weakly nonlinear regular waves on a sloping bed, 2) phase-focused irregular waves on a flat bed, 3) irregular waves on a sloping bed and 4) multidirectional irregular waves on a sloping bed. For all cases, the free surface elevation and the inline force were successfully compared against experimental measurements. 相似文献
15.
An integral description of the propagation of steady-state perturbations of the heavy liquid surface
The system of equations of motion describing the gravity wave propagation in a perfect heavy liquid layer is transformed into
a new integral equation for the free surface elevations. In the limit cases, this integral equation describes the linear and
nonlinear periodic waves as well as the known types of solitary waves. In this case a dispersion equation arises because perturbations
of the second and higher orders of smallness are neglected. The integral equation allows for the propagation of invariable
surface perturbations of arbitrary forms if their spatial spectrum is concentrated near small wave numbers (compared to the
inverse wave amplitude). Several examples of solutions are presented. 相似文献
16.
Surf zone dynamics simulated by a Boussinesq type model. Part I. Model description and cross-shore motion of regular waves 总被引：2，自引：0，他引：2
This is the first of three papers on the modelling of various types of surf zone phenomena. In this first paper, part I, the model is presented and its basic features are studied for the case of regular waves. The model is based on two-dimensional equations of the Boussinesq type and it features improved linear dispersion characteristics, possibility of wave breaking, and a moving boundary at the shoreline. The moving shoreline is treated numerically by replacing the solid beach by a permeable beach characterized by an extremely small porosity. Run-up of nonbreaking waves is verified against the analytical solution for nonlinear shallow water waves. The inclusion of wave breaking is based on the surface roller concept for spilling breakers using a geometrical determination of the instantaneous roller thickness at each point and modelling the effect of wave breaking by an additional convective momentum term. This is a function of the local wave celerity, which is determined interactively. The model is applied to cross-shore motions of regular waves including various types of breaking on plane sloping beaches and over submerged bars. Model results comprise time series of surface elevations and the spatial variation of phase-averaged quantities such as the wave height, the crest and trough elevations, the mean water level, and the depth-averaged undertow. Comparisons with physical experiments are presented. The phaseaveraged balance of the individual terms in the momentum and energy equation is determined by time-integration and quantities such as the cross-sectional roller area, the radiation stress, the energy flux and the energy dissipation are studied and discussed with reference to conventional phase-averaged wave models. The companion papers present cross-shore motions of breaking irregular waves, swash oscillations and surf beats (part II) and nearshore circulations induced by breaking of unidirectional and multidirectional waves (part III). 相似文献
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Based on the filtered Navier-Stokes equations and Smagorinsky turbulence model,a numerical wave flume is developed to investigate the overtopping process of irregular waves over smooth sea dikes.Simulations of fully nonlinear standing wave and regular wave’s run-up on a sea dike are carried out to validate the implementation of the numerical wave flume with wave generation and absorbing modules.To model stationary ergodic stochastic processes,several cases with different random seeds are computed for each specified irregular wave spectrum.It turns out that the statistical mean overtopping discharge shows good agreement with empirical formulas,other numerical results and experimental data. 相似文献
18.
Euler's equations of motion in conjunction with the dynamic boundary condition are manipulated to obtain exact (and approximate) alternative momentum equations for nonlinear irrotational surface waves. The Airy and Boussinesq equations are re-derived as demonstrative examples. A fully nonlinear version of the improved Boussinesq equations is presented as a new application of the proposed equations. Further use of the equations in developing depth-integrated wave models, which are not necessarily restricted to finite depths, is also pointed out. 相似文献
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In this paper,a numerical model for nonlinear wave propagation in currents is formulated by a set of enhanced fully nonlinear Boussinesq equations with ambient currents.This model is verified by comparison with the published results.Then the influence of currents on nonlinear focusing waves is studied by use of the numerical model.It is found that the effect of currents on the surface elevations at the focal location is negligible.Following currents can augment the maximum crest of focusing wave while decre... 相似文献