共查询到20条相似文献，搜索用时 31 毫秒
1.
Based on the full water-wave equation, a second-order analytic solution for nonlinear interaction of short edge waves on a constant plane sloping bottom is presented in this paper. For special case of slope angle b=p/2, this solution can be reduced to the same order solution of deep water gravity surface waves traveling along parallel coastline. Interactions between two edge waves including progressive, standing and partially reflected standing waves were also discussed. The unified analytic expressions with transfer functions for kinematic-dynamic elements of edge waves were also discussed. The random model of the unified wave motion processes for linear and nonlinear irregular edge waves is formulated, and the corresponding theoretical autocorrelation and spectral density functions of the first and second orders are derived. The boundary conditions for the determining determination of the parameters of short edge wave are suggested, that may be seen as one special simple edge wave excitation mechanism and an extension to the sea wave refraction theory. Finally some computation results are demonstrated. 相似文献
2.
Based on the full water-wave equation,a second-order analytic solution for nonlinear interaction of short edge waves on a plane sloping bottom is presented in this paper.For special case of slope angle β=π/2,this solution can reduced to the same order solution of deep water gravity surface waves traveling along parallel coastline.Interactions between two edge waves including progressive,standing and partially reflected standing waves are also discussed.The unified analytic expressions with transfer functions for kinematic-dynamic elements of edge waves are also given.The random model of the unified wave motion processes for linear and nonlinear irregular edge waves is formulated,and the corresponding theoretical autocorrelation and spectral density functions of the first and the second orders are derived.The boundary conditions for the determination of the parameters of short edge wave are suggested,that may be seen as one special simple edge wave excitation mechanism and an extension to the sea wave refraction theory.Finally some computation results are demonstrated. 相似文献
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4.
Numerical Wave Channel with Absorbing Wave-Maker 总被引：2，自引：0，他引：2
Wang Yongxue
Professor State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian 《中国海洋工程》1995,(2)
The numerical wave channel has been developed based on the volume of fluid method (VOF) in conjunction with the Navier-Stokes equations. The absorbing wave-maker boundary on the left side of the channel is presented by prescribing velocity reference to linear wave-maker theory. The principle of which is that the numerical wave-maker is designed to move in a way that generates the required incident wave and cancels out any reflected wave that reach it at the same time. On the right side of the channel, the open boundary is set to permit incident waves to be transmitted freely. The parametric studies have been carried out at a range of ratios of water depth to wave length d/ L from 0.124 to 0.219, with wave height in the front of paddle/water depth ratio (H0 / d) from 0.1 to 0.3. Wave height, wave pressure distribution along the channel and velocity field are obtained for both open boundary condition and reflective boundary condition at the other end of the channel. For a reflective case, it is shown that 相似文献
5.
Freak waves are generated based on the mechanism of wave focusing in a 2D numerical wave tank. To set up the nonlinear numerical wave tank, the Boundary Element Method is used to solve potential flow equations incorporated with fully nonlinear free surface boundary conditions. The nonlinear properties of freak waves, such as high frequency components and wave profile asymmetry, are discussed. The kinematic data, which can be useful for the evaluation of the wave forces exerted on structures to avoid underestimation of linear predictions, are obtained, and discussed, from the simulated results of freak waves. 相似文献
6.
SUN Dapeng LI Yucheng TENG Bin
Associate Professor the State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian
Professor the State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian 《中国海洋工程》1999,(2)
For higher accuracy in simulating the transformation of three dimensional waves,in consid-eration of the advantages of constant panels and linear elements,a combined boundary elements is appliedin this research.The method can be used to remove the transverse vibration due to the accumulation ofcomputational errors.A combined boundary condition of sponge layer and Sommerfeld radiation condi-tion is used to remove the reflected waves from the computing domain.By following the water particle onthe water surface,the third order Stokes wave transform is simulated by the numerical wave flume tech-nique.The computed results are in good agreement with theoretical ones. 相似文献
7.
Li Chunzhu Cai Yi Wei Shoulin Associate Professor Ocean University of Qingdao. Qingdao Graduate Student Ocean University of Qingdao Qingdao 《中国海洋工程》1991,(4)
The hollow-pipe perforated breakwater is of low reflection. In this paper the functions of reflection coefficients of both regular and random waves are theoretically derived, based on the concept of linear superimposition of reflected and incident waves and with the total flow rate continuity of integral form instead of the non-continuity of the boundary condition, and based on the concept of linear wave spectrum theory. Comparisons between theoretical results presented here and measurements of model tests show reasonable agreement. 相似文献
8.
With growing computational power, the first-order wave-maker theory has become well established and is widely used for numerical wave flumes. However, existing numerical models based on the first-order wave-maker theory lose accuracy as nonlinear effects become prominent. Because spurious harmonic waves and primary waves have different propagation velocities, waves simulated by using the first-order wave-maker theory have an unstable wave profile. In this paper, a numerical wave flume with a piston-type wave-maker based on the second-order wave-maker theory has been established. Dynamic mesh technique was developed. The boundary treatment for irregular wave simulation was specially dealt with. Comparisons of the free-surface elevations using the first-order and second-order wave-maker theory prove that second-order wave-maker theory can generate stable wave profiles in both the spatial and time domains. Harmonic analysis and spectral analysis were used to prove the superiority of the second-order wave-maker theory from other two aspects. To simulate irregular waves, the numerical flume was improved to solve the problem of the water depth variation due to low-frequency motion of the wave board. In summary, the new numerical flume using the second-order wave-maker theory can guarantee the accuracy of waves by adding an extra motion of the wave board. The boundary treatment method can provide a reference for the improvement of nonlinear numerical flume. 相似文献
9.
LI Yucheng 《中国海洋工程》2000,14(1):59-67
—An experimental study of regular wave and irregular wave breaking is performed on a gentleslope of 1:200.In the experiment,asymmetry of wave profile is analyzed to determine its effect on wavebreaker indices and to explain the difference between Goda and Nelson about the breaker indices of regu-lar waves on very mild slopes.The study shows that the breaker index of irregular waves is under less influ-ence of bottom slope i,relative water depth d/L_0 and the asymmetry of wave profile than that of regularwaves.The breaker index of regular waves from Goda may be used in the case of irregular waves, whilethe coefficient A should be 0.15.The ratio of irregular wavelength to the length calculated by linear wavetheory is 0.74.Analysis is also made on the waveheight damping coefficient of regular waves after break-ing and on the breaking probability of large irregular waves. 相似文献
10.
A numerical irregular wave flume with active absorption of re-reflected waves is simulated by use of volume of fluid （VOF） method. An active ＇absorbing wave-maker based on linear wave theory is set on the left boundary of the wave flume. The progressive waves and the absorbing waves are generated simultaneously at the active wave generating-absorbing boundary. The absorbing waves are generated to eliminate the waves coming back to the generating boundary due to reflection from the outflow boundary and the structures. SIRW method proposed by Frigaard and Brorsen （1995） is used to separate the incident waves and reflected waves. The digital filters are designed based on the surface elevation signals of the two wave gauges. The corrected velocity of the wave-maker paddle is the output from the digital filter in real time. The numerical results of regular and irregular waves by the active absorbing-generating boundary are compared with the numerical results by the ordinary generating boundary to verify the performance of the active absorbing-generator boundary. The differences between the initial incident waves and the estimated incident waves are analyzed. 相似文献
11.
WANG Yongxue ZANG Jun QIU Dahong Professor the State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian P. R. China
Lecturer the State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian P. R. China
Professor Academician of Chinese Academy of Sciences the State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian P. R. China 《中国海洋工程》1999,(4)
The volume of fluid(VOF)method is used to set up a wave flume with an absorbing wavemaker of cnoidal waves.Based on the transfer function between wave surface and paddle velocity obtained bythe shallow water wave theory,the velocity boundary condition of an absorbing wave maker is introduced toabsorb reflected waves that reach the numerical wave maker.For H/d ranging from 0.1 to 0.59 and T(g/d)~(1/2)from 7.9 to 18.3,the parametric studies have been carried out and compared with experiments. 相似文献
12.
Mathematical Models for Combined Refraction-Diffraction of Waves on Non-Uniform Current and Depth 总被引：12，自引：2，他引：12
Hong Guangwen
Professor Research Institute of Coastal Ocean Engineering Hohai University Xikang Road Nanjing 《中国海洋工程》1996,(4)
Two mathematical models for combined refraction-diffraction of regular and irregular waves on non-uniform current in water of slowly varying topography are presented in this paper. Model I is derived by wave theory and variational principle separately. It has two kinds of expressions including the dissipation term. Model n is based on the energy conservation equation with energy flux through the wave crest lines in orthogonal curvilinear coordinates and the wave kinematic conservation equation. The analysis and comparison and special cases of these two models are also given. 相似文献
13.
Fu Yuhua
Senior Engineer China Offshore Oil Production Research Center P. O. Box Beijing 《中国海洋工程》1997,(4)
As the solution of the two equations for determining the existing fifth order Stokes wave de-rived by Skjelbreia is complex and tedious,the two equations are simplified into one equation for deter-mining d/L,i.e.,f(H,T,d/L)=0.According to this simplified method,three cases of the solution forthe Skjelbreia equations have been found:one accurate solution;more than one accurate solution and noaccurate solution(but there exists the optimum approximate solution in the area of satisfying Skjelbreiaequations).As to the case of more than one accurate solution,the reasonable solution can be judged fromthe method of variational principle,by means of which an optimum solution improved from the solutionof Skjelbreia equations in the area of satisfying the original mathematical equations of non-vortex andnonlinear wave theory,i.e.,the optimum fifth order Stokes wave,is given. 相似文献
14.
Numerical simulation of non-linear regular and focused waves in an infinite water-depth 总被引：3，自引：0，他引：3
Inviscid three-dimensional free surface wave motions are simulated using a novel quadratic higher order boundary element model (HOBEM) based on potential theory for irrotational, incompressible fluid flow in an infinite water-depth. The free surface boundary conditions are fully non-linear. Based on the use of images, a channel Green function is developed and applied to the present model so that two lateral surfaces of an infinite-depth wave tank can be excluded from the calculation domain. In order to generate incident waves and dissipate outgoing waves, a non-reflective wave generator, composed of a series of vertically aligned point sources in the computational domain, is used in conjunction with upstream and downstream damping layers. Numerical experiments are carried out, with linear and fully non-linear, regular and focused waves. It can be seen from the results that the present approach is effective in generating a specified wave profile in an infinite water-depth without reflection at the open boundaries, and fully non-linear numerical simulations compare well with theoretical solutions. The present numerical technique is aimed at efficient modelling of the non-linear wave interactions with ocean structures in deep water. 相似文献
15.
Underwater ultrasonic acoustic transducers are frequently used in ocean wave measurements as they measure surface level using acoustic waves. However, their effectiveness can be severely affected in rough sea conditions, when bubbles generated by breaking waves interfere with their acoustic signals. When the seas are rough, one therefore often has to rely on a pressure transducer, which is generally used as a back-up for the acoustic wave gauge. A pressure transfer function is then used to obtain the surface wave information. Alternatively, the present study employed an artificial neural network to convert the pressure signal into significant wave height, significant wave period, maximum wave height, and spectral peakedness parameter using data obtained from various water depths. The results showed that, for water depths greater than 20 m, the wave parameters obtained from the artificial neural network were significantly closer to those obtained by the acoustic measurements than those obtained by using a linear pressure transfer function. Moreover, for a given water depth, the wave heights estimated by the network model from pressure data were not as good as those estimated by linear wave theory for large wave heights (above a 4 m significant wave height in this study). This can be improved if the training data set has more records with large wave heights. 相似文献
16.
In this paper.the characteristics of laboratory wind waves under various wind speeds and wat-er depths are studied.It is found that either the real or the imaginary part of the bispectrum can be relatedto the asymmetry of the wave profile,and the bicoherence is related to the ratio of nonlinear to linear wavecomponent.Occasionally,these two categories of nonlinear index lead to opposite inferences,because eachof them has its own significance and functions.The applicability of linear wave spectral model in oceanwaves becomes questionable only when strong nonlinearity is indicated by both of these two indexes.Thelinear spectral representation of wave fields does not necessarily become inadequate as water depth de-creases,and its appropriateness can be examined through the characteristics of the bispectrum. 相似文献
17.
利用大型水槽设计了在由深水到近岸不同坡度处海浪在变浅作用下诱导产生的长周期重力波的实验。正态随机海浪在深水生成并沿斜坡向浅水传播,记录了不同水深处波面高度随时间的变化过程并进行统计分析和谱分析。实验数据分析结果表明,长周期重力波的能量随着水深的变浅而增高,其谱锋频率位于0.2~0.3fp附近,这里fp是深水正态海浪过程的谱峰频率。长周期重力波的能量与入射波的能量比与波面高度分布的偏度密切相关。进一步分析了两种波动的能量谱峰值比和波面高度分布偏度的相关关系,获得了经验关系,为预测近岸浅水长周期重力波提供了科学依据。 相似文献
18.
根据线性系统理论,首先由给定的靶谱模拟海浪信号,再把此信号转换为造波控制输入信号,最后在水槽中指定的截面处产生具有给定靶谱的随机波。这种模拟方法已在青岛海洋大学物理海洋实验室的大型水槽中实现,并取得良好的效果。 相似文献
19.
基于非静压单相流模型NHWAVE,设计不同的计算工况,系统研究了规则波与非规则波作用下,非淹没刚性植物的消波特性。将计算结果和实验数据进行对比分析,验证了非静压模型NHWAVE计算植物消波特性的准确性。进一步研究了波高、周期和水深等因素对植物消波特性的影响,探讨了植物消波特性与这些水动力因素的内在联系。结果表明:非淹没刚性植物的消波效率受波高和周期的影响较大,水深对消波效率的影响很小。由于波浪非线性的影响,基于线性波理论的消波理论模型对植物消波能力的估计偏小。 相似文献
20.
In this paper, a wave generating approach for long-crest irregular waves in a numerical tank by our in-house solver naoe-FOAM-SJTU is presented. The naoe-FOAM-SJTU solver is developed using an open source tool kit, OpenFOAM. Reynolds-averaged Navier?Stokes (RANS) equations are chosen as governing equations and the volume of fluid (VOF) is employed to capture the two phases interface. Incoming wave group is generated by imposing the boundary conditions of the tank inlet. A spectrum based correction procedure is developed to make the measured spectrum approaching to the target spectrum. This procedure can automatically adjust the wave generation signal based on the measured wave elevation by wave height probe in numerical wave tank. After 3 to 4 iterations, the measured spectrum agrees well with the target one. In order to validate this method, several wave spectra are chosen and validated in the numerical wave tank, with comparison between the final measured and target spectra. In order to investigate a practical situation, a modified Wigley hull is placed in the wave tank with incoming irregular waves. The wave-induced heave and pitch motions are treated by Fourier analysis to obtain motion responses, showing good agreements with the measurements. 相似文献