共查询到20条相似文献，搜索用时 695 毫秒
1.
Vessels operating in shallow waters require careful observation of the finite-depth effect. In present study, a Rankine source method that includes the shallow water effect and double body steady flow effect is developed in frequency domain. In order to verify present numerical methods, two experiments were carried out respectively to measure the wave loads and free motions for ship advancing with forward speed in head regular waves. Numerical results are systematically compared with experiments and other solutions using the double body basis flow approach, the Neumann-Kelvin approach with simplified m-terms, and linearized free surface boundary conditions with double-body m-terms. Furthermore, the influence of water depths on added mass and damping coefficients, wave excitation forces, motions and unsteady wave patterns are deeply investigated. It is found that finite-depth effect is important and unsteady wave pattern in shallow water is dependent on both of the Brard number τ and depth Froude number Fh. 相似文献
2.
3.
By using the theories on Stokes multicolored water waves and taking the two- layer ocean as a basic model of stratified ocean, the paper analyzes the problems related to the effects of the nonlinear water wave on offshore structures. A mathematical expression is presented to describe second order wave radiation conditions. Using integral principle, the analytical integral solutions are given to evaluate second order scattered wave loads on general vertical circular cylinders in the two-layer ocean, and the special recurrence formulas for infinite integrals over free and stratified surfaces are derived. 相似文献
4.
The formation of a stationary (equilibrium) range in a wind-wave spectrum is investigated by numerical simulation. The equation of evolution of the wind-wave spectrum is solved using the exact calculation of the Hasselmann kinetic integral and involving various modifications of known parameterizations of the mechanisms of wave pumping by wind (In) and of wave dissipation (Dis). It is shown that it is these two mechanisms that are responsible for the shape of the stationary range of the wind-wave spectrum, whereas the nonlinear mechanism plays a stabilizing but subsidiary role. With an appropriate choice of mathematical representations for In and Dis, any known empirical shape of the stationary range of the spectrum can be obtained. During the calculations it is found that, for real wind waves, the known representations of In and Dis do not ensure the existence of the inertial interval required for Kolmogorov-type spectra formation due to the nonlinear interactions between waves. 相似文献
5.
It is difficult to compute far-field waves in a relative large area by using one wave generation model when a large calculation domain is needed because of large dimensions of the waterway and long distance of the required computing points. Variation of waterway bathymetry and nonlinearity in the far field cannot be included in a ship fixed process either. A coupled method combining a wave generation model and wave propagation model is then used in this paper to simulate the wash waves generated by the passing ship. A NURBS-based higher order panel method is adopted as the stationary wave generation model; a wave spectrum method and Boussinesq-type equation wave model are used as the wave propagation model for the constant water depth condition and variable water depth condition, respectively. The waves calculated by the NURBS-based higher order panel method in the near field are used as the input for the wave spectrum method and the Boussinesq-type equation wave model to obtain the far-field waves. With this approach it is possible to simulate the ship wash waves including the effects of water depth and waterway bathymetry. Parts of the calculated results are validated experimentally, and the agreement is demonstrated. The effects of ship wash waves on the moored ship are discussed by using a diffraction theory method. The results indicate that the prediction of the ship induced waves by coupling models is feasible. 相似文献
6.
The experimental investigation of unidirectional random wave slamming on the three-dimensional structure in the splash zone is presented. The experiment is conducted in the marine environment channel in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. The test wave is unidirectional irregular wave. The experiments are carried out with perpendicular random waves (β=0°) and oblique random waves (β=15°, 30°, 45°), the significant wave heights H1/3 ranging from 7.5 to 20 cm with 2.5 cm increment, the peak wave periods Tp ranging from 0.75 to 2.0 s with 0.25 s increment, and the clearance of the model with respect to the significant wave height s/H1/3 ranging from 0.0 to 0.5 with 0.1 increment. The statistical analysis results of different test cases are presented. The statistical distribution characteristics of the perpendicular irregular wave impact pressures are compared with that of the oblique irregular wave on the underside of the structure. The effect of the wave direction β on the wave impact forces on the underside of the structure is determined. The relation between the impact forces and the parameters such as the significant wave height, the relative structure width and the relative clearance of the structure is also discussed. 相似文献
7.
Validation of the three-wave quasi-kinetic approximation for the spectral evolution in shallow water
This paper aims at validating the three-wave quasi-kinetic approximation for the spectral evolution of weakly nonlinear gravity waves in shallow water. The problem is investigated using a one-dimensional numerical wave propagation model, formulated in the spectral representation. This model includes both a nonlinear triad interactions term and a wave breaking dissipation term. Some numerical tests were carried out in order to show the importance of using the triad nonlinear term in wave propagation spectral models, particularly to describe both behavior of the spectral integral parameters and of the spectral shape evolution in shallow water depth. Furthermore; a comparison against different set of experimental observations was carried out. Comparing the numerical results with the experimental observations made it possible to show the modeling efficiency of the three-wave quasi-kinetic approximation. 相似文献
8.
In this study the evolution of internal solitary waves shoaling onto a shelf is considered. The results of high resolution two-dimensional numerical simulations of the incompressible Euler equations are compared with the predictions of several weakly-nonlinear shoaling models of the Korteweg–de Vries family including the Gardner equation and the cubic regularized long wave (or Benjamin–Bona–Mahoney) equation. Wave models in both physical x–t space and in s–x space are considered where s is a commonly used characteristic time variable. The effects of rotation, background currents and damping are ignored. The Boussinesq and rigid lid approximations are also used. The shoaling internal solitary waves generally fission into several waves. Reflected waves are negligible in the cases considered here. Several hyperbolic tangent stratifications are considered with and without a critical point. Among the equations in x–t space the cubic regularized long wave equation gives the best predictions. The Gardner equation in s–x space gives the best predictions of the shape of the leading waves on the shelf, but for many stratifications it predicts a propagation speed that is too large. 相似文献
9.
A higher-order non-hydrostatic model in a σ-coordinate system is developed. The model uses an implicit finite difference scheme on a staggered grid to simultaneously solve the unsteady Navier-Stokes equations (NSE) with the free-surface boundary conditions. An integral method is applied to resolve the top-layer non-hydrostatic pressure, allowing for accurately resolving free-surface wave propagation. In contrast to the previous work, a higher-order spatial discretization is utilized to approximate the large horizontal pressure gradient due to steep surface waves or rapidly varying topographies. An efficient direct solver is developed to solve the resulting block hepta-diagonal matrix system. Accuracy of the new model is validated by linear and nonlinear standing waves and progressive waves. The model is then used to examine freak (extreme) waves. Features of downshifting focusing location and wave asymmetry characteristics are predicted on the temporal and spatial domains of a freak wave. 相似文献
10.
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
11.
Numerical simulations of gravity waves with high-order nonlinearities in two-dimensional domain are performed by using the pseudo spectral method. High-order nonlinearities more than third order excite apparently chaotic evolutions of the Fourier energy in deep water random waves. The high-order nonlinearities increase kurtosis, wave height distribution and Hmax/H1/3 in deep water and decrease these wave statistics in shallow water. Moreover, they can generate a single extreme high wave with an outstanding crest height in deep water. High-order nonlinearities (more than third order) can be regarded as one cause of freak waves in deep water. 相似文献
12.
A comparison of the diffraction of multidirectional random waves using several selected wave spectrum models is presented in this paper. Six wave spectrum models, Bretschneider, Pierson–Moskowitz, ISSC, ITTC, Mitsuyasu, and JONSWAP spectrum, are considered. A discrete form for each of the given spectrum models is used to specify the incident wave conditions. Analytical solutions based on both the Fresnel integrals and polynomial approximations of the Fresnel integrals and numerical solutions of a boundary integral approach have been used to obtain the two-dimensional wave diffraction by a semi-infinite breakwater at uniform water depth. The diffraction of random waves is based on the cumulative superposition of linear diffraction solution. The results of predicted random wave diffraction for each of the given spectrum models are compared with those of the published physical model presented by Briggs et al. [1995. Wave diffraction around breakwater. Journal of Waterway, Port, Coastal and Ocean Engineering—ASCE 121(1), 23–35]. Reasonable agreement is obtained in all cases. The effect of the directional spreading function is also examined from the results of the random wave diffraction. Based on these comparisons, the present model for the analysis of various wave spectra is found to be an accurate and efficient tool for predicting the random wave field around a semi-infinite breakwater or inside a harbor of arbitrary geometry in practical applications. 相似文献
13.
再论台风波浪的波型及其与海岸工程设计波浪要素的关系 总被引：3，自引：0，他引：3
本文以实测台风波浪资料对台风影响过程中固定点波浪能量集中度的变化和有效波陡的变化进行分析，得出华南近岸浅水区台风波浪的波型与台风中心位置的统计关系，并进一步阐明了台风过程中固定点出现较大台风波浪的波型是风浪以及用于海岸工程设计的台风波浪亦为风浪的结论。文中还讨论了台风波浪波型对海岸工程建设中的设计波高、周期等要素取值的影响。 相似文献
14.
An analysis of spectra of wave disturbances with zonal wave numbers 1 ≤ k ≤ 10 is carried out using winter (November to March) ERA-Interim reanalysis geopotential data in the troposphere and stratosphere for 1979–2016. Contributions of eastward-traveling (E), westward-traveling (W), and stationary (S) waves are estimated. The intensification of wave activity is observed in the tropical troposphere and stratosphere and in the upper stratosphere of the entire Northern Hemisphere. The intensification of wave activity in the tropics and subtropics is noted for waves of all types (E, W, and S), while in the middle and higher latitudes it is related mainly to stationary and eastward waves. Near the subtropical tropopause, the energy of stationary waves has increased in recent decades. In addition, in the tropical and subtropical troposphere and in the subtropical lower stratosphere, the energy of the eastward-traveling waves in El Niño years may be one and a half times or twice the energy in La Niña years. The spectrally weighted zonal wave numbers for waves of all types (E, W, and S) are the largest in the upper subtropical troposphere. The spectrally weighted zonal wave number for W and S waves is correlated with the Atlantic Multidecadal Oscillation index and varies by 15% in 1979–2016 (on an interdecadal time scale). The spectrally weighted wave period is larger in the stratosphere than in the troposphere. It is maximal in the middle extratropical stratosphere. The spectrally weighted wave periods correlate with the activity of sudden stratospheric warmings. The sign of this correlation depends on the latitude, atmospheric layer, and zonal wave number. 相似文献
15.
Philip L.-F.LIU 《中国海洋工程》1998,(2)
The nonlinear capillary-gravity wave produced by a vertically oscillating plate,in which thecontact-angle model is considered,is studied by use of the Boundary Integral Equation Method(BIEM).The present numerical experiment shows that the code is robust and efficient for modeling the generationand propagation of capillary-gravity waves.It is found that the wave heights of stationary periodicnonlinear waves radiated away from the plate are dependent on the parameters involved in the contact-an-gle model.The effect of the contact-angle hysteresis and the nonlinearity of capillary-gravity waves on thewave profile is discussed in the paper. 相似文献
16.
17.
18.
19.
20.
Hirofumi Hinata Satoshi Fujii Keita Furukawa Tomoya Kataoka Masafumi Miyata Takashi Kobayashi Masahiro Mizutani Takahiro Kokai Nobuyoshi Kanatsu 《Estuarine, Coastal and Shelf Science》2011
Signals from the tsunami waves induced by the March 11, 2011 moment magnitude (Mw) 9.0 Tohoku-Oki earthquake and from subsequent resonances were detected as radial velocity variability by a high-frequency ocean surface radar (HF radar) installed on the eastern coast of the Kii Channel, at a range of about 1000 km from the epicenter along the eastern to southern coasts of Honshu Island. A time–distance diagram of band-passed (9–200 min) radial velocity along the beam reveals that the tsunami waves propagated from the continental shelf slope to the inner channel as progressive waves for the first three waves, and then natural oscillations were excited by the waves; and that the direction of the tsunami wave propagation and the axis of the natural oscillations differed from that of the radar beam. In addition, spectral analyses of the radial velocities and sea surface heights obtained in the channel and on the continental shelf slope suggest complex natural oscillation modes excited by the tsunami waves. 相似文献