共查询到20条相似文献，搜索用时 31 毫秒
1.
The unsteady, two-dimensional Navier–Stokes equations and the exact free surface boundary conditions were solved to study the interaction of a solitary wave and a submerged dike. A piston-type wavemaker was set up in the computational domain to produce the incident solitary waves. The incident wave and the associated boundary layer flow in a wave tank with a flat bed were compared with the analytical solutions to verify the accuracy of this numerical scheme. Effects of the incident wave height and the size of the dike on the wave transformation, the flow fields, and the drag forces on the dike were discussed. Our numerical results showed that even though the induced local shear stress on the top surface of the dike is large at some particular locations, the resultant pressure drag is much larger than the friction drag. The primary vortex generated at the lee side of the dike and the secondary vortex at the right toe of the dike may scour the bottom and cause a severe problem for the dike. 相似文献
2.
M. V. Kalashnik O. G. Chkhetiani G. D. Chagelishvili 《Izvestiya Atmospheric and Oceanic Physics》2018,54(4):305-312
Edge baroclinic waves are generated in a geostrophic flow with a vertical shear near a solid surface. The study investigates a new class of baroclinic waves in flows with horizontal and vertical shears and a linear distribution of potential vorticity. It is shown that taking account of the horizontal shear leads to the appearance of new features of wave dynamics. These include the nonmodal growth of energy in the initial stage of development, the time dependence of the vertical wave scale, and the possibility of generation of stationary or blocked waves. The horizontal shear makes the mechanism of generation of baroclinic waves by initial vortex perturbations more efficient. One important feature is associated with vortex paths, which are formed by the superposition of a baroclinic wave on the flow with horizontal shear. 相似文献
3.
内孤立波具有振幅尺度大、能量集中的特点,其引起流场和密度场的迅速变化可能对海洋工程结构物以及水下潜体造成严重威胁。因此研究不同造波条件下生成的内孤立波运动的流场特征具有重要的学术意义和实际应用价值。采用直接数值模拟方法和给定的初始密度场密度跃迁函数,对重力塌陷激发内孤立波的运动过程进行研究,探讨了不同造波条件下,激发产生的内孤立波波型、涡度、振幅和水平速度等流场特征。结果表明:(1)直接模拟数值方法能够模拟内孤立波传播过程中的密度界面波型反转现象;(2)从定性和定量的角度,证实了不稳定内孤立波传播过程中存在能量的向后传递;(3)对于相同的台阶深度(水闸两侧初始密度界面的高度差),初始涡流保持相同,但是随着上下层水深比的减小,其强度下降显著;(4)台阶深度对初始涡流的垂直结构的影响要大于上下层水深比,且台阶深度对内孤立波的振幅、水平速度的影响显著。 相似文献
4.
《Coastal Engineering》2004,51(7):557-579
In this paper, a Reynolds Averaged Navier–Stokes (RANS) model was developed to simulate the vortex generation and dissipation caused by progressive waves passing over impermeable submerged double breakwaters. The dynamics of the turbulence are described by introducing a k–ɛ model with Boussinesq closure. The Height Function (HF) is implemented to define the free-surface configuration. The governing equations are discretized by means of a finite volume method based on a staggered grid system with variable width and height. The feasibility of the numerical model was verified through a series of comparisons of numerical results with the existing analytical solutions and the experimental data. The good agreements demonstrate the satisfactory performance of the developed numerical model. The flow separation mechanism both near the upstream and the downstream edges of the obstacles demonstrates the physical and expected nature of development of the flow. The present model provides an accurate and efficient tool for the simulation of flow field and wave transformation near coastal structures without breaking. 相似文献
5.
《Coastal Engineering》2005,52(3):257-283
Vortex generation and evolution due to flow separation around a submerged rectangular obstacle under incoming cnoidal waves is investigated both experimentally and numerically. The Particle Image Velocimetry (PIV) technique is used in the measurement. Based on the PIV data, a characteristic velocity, phrased in terms of incoming wave height, phase speed, dimension of the obstacle, and a local Reynolds number are proposed to describe the intensity of vortex. The numerical model, which solves the two dimensional Reynolds Averaged Navier Stokes (RANS) equations, is used to further study the effects of wave period on the vortex intensity. Measurements for the mean and turbulent velocity fields further indicate that the time history of the intensity of fluid turbulence is closely related to that of the vortex intensity. 相似文献
6.
Dike resilience against wave overtopping has gained more and more attention in recent years due to the effect of expected future climate changes. The overtopping flow velocities and flow depths on dikes have recently been studied in 2D small-scale experiments. This has led to semi-empirical formulae for the estimation of flow depths and flow velocities across a dike. The results have been coupled to the actual erosion of the landward dike slope determined by full-scale 2D tests using the so-called “Overtopping Simulator”. This paper describes the results from 96 small-scale tests carried out in a shallow water basin at Aalborg University to cover the so far unknown 3D effects from oblique long-crested and short-crested waves. Based on results from the laboratory tests, expansions are proposed to the existing 2D formulae so as to cover oblique and short-crested waves. The wave obliquity is seen to significantly reduce the overtopping flow velocities and flow depths on especially the landward slope of a sea dike. Moreover, the tests showed that the average flow directions on the dike crest from oblique long-crested and short-crested waves correspond approximately to the incident wave direction. Flow depths and the squared flow velocities on the dike are concluded to be Rayleigh-distributed in case of both long-crested and short-crested waves for all considered incident wave obliquities. Findings in the present paper are needed to obtain more realistic estimates of dike erosion caused by wave overtopping. 相似文献
7.
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
8.
《Coastal Engineering》2006,53(4):311-318
The extended mild-slope equations of Suh et al. [Suh, K.D., Lee, C., Park, W.S., 1997. Time-dependent equations for wave propagation on rapidly varying topography. Coastal Eng., 32, 91–117] and Lee et al. [Lee, C., Kim, G., Suh, K.D., 2003. Extended mild-slope equation for random waves. Coastal Eng., 48, 277–287] are compared analytically and numerically to determine their applicability to random wave transformation. The geometric optics approach is used to compare the two models analytically. In the model of Suh et al., the wave number of the component wave with a local angular frequency ω is approximated with an accuracy of O(ω − ω¯) at a constant water depth, where ω¯ is the carrier frequency of random waves. In the model of Suh et al., however, the diffraction effects and higher-order bottom effects are considered only for monochromatic waves, and the shoaling coefficient of random waves is not accurately approximated. This inaccuracy arises because the model of Suh et al. was derived for regular waves. In the model of Lee et al., all the parameters of random waves such as wave number, shoaling coefficient, diffraction effects, and higher-order bottom effects are approximated with an accuracy of O(ω − ω¯). This approximation is because the model of Lee et al. was developed using the Taylor series expansion technique for random waves. The result of dispersion relation analysis suggests the use of the peak and weighted-average frequencies as a carrier frequency for Suh et al. and Lee et al. models, respectively. All the analytical results are verified by numerical experiments of shoaling of random waves over a slightly inclined bed and diffraction of random waves through a breakwater gap on a flat bottom. 相似文献
9.
《Coastal Engineering》2001,42(2):155-162
It is studied whether the mass transport or energy transport is the proper viewpoint for internally generating waves in the extended Boussinesq equations of Nwogu [J. Waterw., Port, Coastal Ocean Eng. 119 (1993) 618–638]. Numerical solutions of the Boussinesq equations with the internal generation of sinusoidal waves show that the energy transport approach yields the required wave amplitude properly while the mass transport approach yields wave amplitude different from the required one by the ratio of phase velocity to energy velocity. The waves which pass through the wave generation point do not cause any numerical distortion while the incident waves are generated. The technique of internal generation of waves shows its capability of generating nonlinear cnoidal waves as well as linear sinusoidal waves. 相似文献
10.
Qiao Fangli 《海洋学报(英文版)》1996,15(2):145-158
Ｔｈｅｍｉｘｉｎｇｍｅｃｈａｎｉｓｍｉｎｔｈｅｆｏｒｍａｔｉｏｎｏｆｏｃｅａｎｓｈｅａｒｗａｖｅｓ￥ＱｉａｏＦａｎｇｌｉ（ＦｉｒｓｔＩｎｓｔｉｔｕｔｅｏｆＯｃｅａｎｏｇｒａｐｈｙ，ＳｔａｔｅｏｃｅａｎｉｃＡｄｍｉｎｉｓｔｒａｔｉｏｎ，Ｑｉｎｇｄａｏ２... 相似文献
11.
This paper presents a new submarine landslide model based on the non-hydrostatic wave model NHWAVE of Ma et al. (2012). The landslide is modeled as a water–sediment mixture. The dense plume is driven by baroclinic pressure forcing introduced by spatial density variations. The model is validated using laboratory measurements of turbidity currents and of water wave generation by a granular landslide. The model is then utilized to study the dependence of landslide motion and associated tsunami wave generation on parameters including sediment settling velocity, initial depth of the landslide and slide density. Model results show that the slide motion and water waves which it generates are both sensitive to these parameters. The relative tsunamigenic response to rigid and deformable landslides of equal initial geometry and density is also examined. It is found that the wave energy is mostly concentrated on a narrow band of the dominant slide direction for the waves generated by rigid landslides, while directional spreading is more significant for waves generated by deformable landslides. The deformable landslide has larger speed and acceleration at the early stage of landslide, resulting in larger surface waves. The numerical results indicate that the model is capable of reasonably simulating tsunami wave generation by submarine landslides. 相似文献
12.
《Coastal Engineering》2001,44(1):13-36
Interactions between a solitary wave and a submerged rectangular obstacle are investigated both experimentally and numerically. The Particle Image Velocimetry (PIV) technique is used to measure the velocity field in the vicinity of the obstacle. The generation and evolution of vortices due to flow separation at the corners of the obstacle are recorded and analyzed. It is found that although the size of the vortex at the weatherside of the obstacle is smaller than that at the leeside, the turbulence intensity is, however, stronger. A numerical model, based on the Reynolds Averaged Navier–Stokes (RANS) equations with a k–ϵ turbulence model, is first verified with the measurements. Overall, the agreement between the numerical results and laboratory velocity measurements is good. Using the RANS model, a series of additional numerical experiments with different wave heights and different heights of the rectangular obstacle are then performed to test the importance of the energy dissipation due to the generation of vortices. The corresponding wave transmission coefficient, the wave reflection coefficient and the energy dissipation coefficient are calculated and compared with solutions based on the potential flow theory. As the height of the obstacle increases to D/h=0.7, the energy dissipation inside the vortices can reach nearly 15% of the incoming wave energy. 相似文献
13.
《Ocean Modelling》2009,26(3-4):154-171
Ocean surface mixing and drift are influenced by the mixed layer depth, buoyancy fluxes and currents below the mixed layer. Drift and mixing are also functions of the surface Stokes drift Uss, volume Stokes transport TS, a wave breaking height scale Hswg, and the flux of energy from waves to ocean turbulence Φoc. Here we describe a global database of these parameters, estimated from a well-validated numerical wave model, that uses traditional forms of the wave generation and dissipation parameterizations, and covers the years 2003–2007. Compared to previous studies, the present work has the advantage of being consistent with the known physical processes that regulate the wave field and the air–sea fluxes, and also consistent with a very large number of in situ and satellite observations of wave parameters. Consequently, some of our estimates differ significantly from previous estimates. In particular, we find that the mean global integral of Φoc is 68 TW, and the yearly mean value of TS is typically 10–30% of the Ekman transport, except in well-defined regions where it can reach 60%. We also have refined our previous estimates of Uss by using a better treatment of the high frequency part of the wave spectrum. In the open ocean, Uss ≃ 0.013U10, where U10 is the wind speed at 10 m height. 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.
16.
A series of hydraulic model tests are carried out to investigate random wave run-up and overtopping on smooth, impermeable single slope and composite slope. Based on analysis of the influences of wave steepness, structure slope, incident wave angle, width of the berm and water depth on the berm and the wave run-up, empirical formulas for wave run-up on dike are proposed. Moreover, empirical formula on estimating the wave run-up on composite slope with multiple berms is presented for practical application of complex dike cross-section. The present study shows that the influence factors for wave overtopping are almost the same as those for wave run-up and the trend of the wave overtopping variation with main influence parameters is also similar to that for wave run-up. The trend of the wave overtopping discharge variations can be well described by two main factors, i.e. the wave run-up and the crest freeboard of the structure. A new prediction method for wave overtopping discharge is proposed for random waves. The proposed prediction formulas are applied to case study of over forty cases and the results show that the prediction methods are good enough for practical design purposes. 相似文献
17.
A lift based wave energy converter, namely, a cycloidal turbine, is investigated. This type of wave energy converter consists of a shaft with one or more hydrofoils attached eccentrically at a radius. The main shaft is aligned parallel to the wave crests and submerged at a fixed depth. In the two-dimensional limit, i.e. for large spans of the hydrofoil (or an array of these), the geometry of the converter is suitable for wave termination of straight crested Airy waves. Results from two-dimensional potential flow simulations, with thin hydrofoils modeled as either a point vortex or discrete vortex panel, are presented. The operation of the cycloidal turbine both as a wave generator as well as a wave-to-shaft energy converter interacting with a linear Airy wave is demonstrated. The impact on the performance of the converter for design parameters such as device size, submergence depth, and number of hydrofoils is shown. For optimal parameter choices, simulation results demonstrate inviscid energy conversion efficiencies of more than 99% of the incoming wave energy to shaft energy. This is achieved using feedback control to synchronize the rotational rate, blade pitch angle, and phase of the cycloidal wave energy converter to the incoming wave. While complete termination of the incoming wave is shown, the remainder of the energy is lost to harmonic waves traveling in the up-wave and down-wave directions. 相似文献
18.
为完善内孤立波与海底斜坡沉积物相互作用研究,本文着眼于内孤立波破碎后在斜坡上继续运动的阶段,开展物理模拟实验,分析斜坡响应的土压力和超孔隙水压力的变化状况,揭示内波作用过程。研究发现:斜坡沉积物颗粒在内孤立波破碎引起的涡旋和渗流的共同作用下,会发生再悬浮,斜坡坡度变化不改变沉积物产生动力响应的主导动力作用;内孤立波振幅大小影响涡旋与渗流两者的比例,即在小振幅条件下由涡旋作用主导,在大振幅条件下由渗流作用主导;破碎流体在沿斜坡冲出坡顶位置后形成新的涡流,沉积物在新生涡流作用下的动力响应受斜坡坡度的影响。本文结果对于研究内孤立波再悬浮运移海底沉积物、改造海底地形地貌具有参考价值。 相似文献
19.
We describe experiments with multi-directional focused waves interacted with a vertical circular cylinder in a 3D wave basin. The focus of this study is on the run-up of multi-directional focused waves, wave forces, and wave pressures on the cylinder. Part I, the study on wave run-up, has already been presented by Li et al. (2012). In this paper, the analysis of the wave force on the vertical cylinder is presented.In this experiment, a cylinder with 0.25 m in diameter was adopted and different wave parameters, such as focused wave amplitude, peak frequency, frequency bandwidth and directional spreading index, are considered. The model scale kpa (kp is the wave number corresponding to peak frequency, a is the radium of the cylinder) varies from 0.32 to 0.65. The maximum forces of multi-directional focused wave on cylinder were measured and investigated. The results showed that the wave parameters have a significant influence on the wave force, and that the spatial profile of the surface of multi-directional focused wave can also affect its force on the cylinder, which is different from two-dimensional wave. In addition, the ‘secondary loading cycle’ phenomenon was also observed and discussed. In our experiments, the ‘secondary loading cycles’ occur when kA > 0.36 for all cases. While in some referred small scale experiments, the secondary load cycles are observed even for kA = 0.2, when the waves are longer enough. To larger model scale, the pronounced secondary load cycle occurs with larger wave steepness waves. 相似文献
20.
《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(8):1005-1021
The main sill of the Strait of Gibraltar (Camarinal Sill) is an area of very energetic internal wave activity. The highest amplitude internal wave is the well-known internal bore, generated at critical conditions over Camarinal Sill. A very energetic lee wave has recently been found and reported. This occurs in neap tides when favorable combination of the stratification, vertical profile of horizontal background velocity, and bottom topography determines its generation. When the lee wave is developed the manifestation of high-amplitude internal waves is observed at the sea surface as high-frequency chaotic oscillations, named boiling waters. We analyze the generation of the lee wave over the main sill of Gibraltar Strait on the basis of the data from a ship mounted ADCP, multi-probe CTD data taken during a survey carried out in November 1998, and the numerical solution of the Taylor–Goldstein equation for the prevailing hydraulic conditions previous to its generation. Stratification is computed from CTD data, and the tidal current prediction is made from the 2 years of ADCP hourly data at Camarinal Sill gathered during the Gibraltar Experiment 94-96. The main characteristic is that they happen during neap tides, and their magnitude is comparable to the internal bore generated during spring tides. The classical internal bore and the lee waves are different phenomena, and the presence of the latter is an indicator of minimum flow over Camarinal Sill. A prediction model for lee waves based on the tidal hydrodynamic conditions is also developed. 相似文献