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1.
The experimental investigation of the run-up of periodic internal waves in a two-layer fluid on the coastal slope is performed
in an open hydrochannel at the Physical Department of the Lomonosov Moscow State University. The waves are produced by a wave
generator. We study the transformation of waves, the vertical structure of the field of velocities of mass transfer, and the
behavior of the parameters of internal waves propagating over the sloping bottom. It is shown that the run-up and breaking
of internal waves are accompanied by periodic emissions of portions of the heavier fluid from the bottom layer upward along
the slope. The Stokes drift velocity changes its sign as a function of depth. Moreover, both the wave length (the horizontal
distance between the neighboring crests) and the height of waves over the sloping bottom (the elevation of the crest over
the slope along the vertical) decrease as the wave approaches the coast. 相似文献
2.
《Marine and Petroleum Geology》2012,33(1):95-109
Using an integrated multi-beam bathymetry, high-resolution seismic profile, piston core, and AMS 14C dating data set, the current study identified two sediment wave fields, fields 1 and 2, on the South China Sea Slope off southwestern Taiwan. Field 1 is located in the lower slope, and sediment waves within it are overall oriented perpendicular to the direction of down-slope gravity flows and canyon axis. Geometries, morphology, and internal seismic reflection configurations suggest that the sediment waves in field 1 underwent significant up-slope migration. Field 2, in contrast, is located more basinward, on the continental rise. Instead of having asymmetrical morphology and discontinuous reflections as observed in field 1, the sediment waves in field 2 show more symmetrical morphology and continuous reflections that can be traced from one wave to another, suggesting that vertical aggradation is more active and predominant than up-slope migration.Three sediment wave evolution stages, stage 1 through stage 3, are identified in both field 1 and field 2. During stage 1, the sediment waves are built upon a regional unconformity that separates the underlying mass-transport complexes from the overlying sediment waves. In both of these two fields, there is progressive development of the sediment waves and increase in wave dimensions from the oldest stage 1 to the youngest stage 3, even though up-slope migration is dominant in field 1 whereas vertical aggradation is predominant in field 2 throughout these three stages.The integrated data and the depositional model show that the upper slope of the study area is strongly dissected and eroded by down-slope gravity flows. The net result of strong erosion is that significant amounts of sediment are transported further basinward into the lower slope by gravity flows and/or turbidity currents. The interactions of these currents with bottom (contour) currents induced by the intrusion of the Northern Pacific Deep Water into the South China Sea and preexisting wavy topography in the lower slope result in the up-slope migrating sediment waves in field 1 and the contourites as observed from cores TS01 and TS02. Further basinward on the continental rise, turbidity currents are waned and diluted, whereas along-slope bottom (contour) currents are vigorous and most likely dominate over the diluted turbidity currents, resulting in the vertically aggraded sediment waves in field 2.The results from this study also provide the further evidence for the intrusion of the Northern Pacific Deep Water into the South China Sea and suggest that this intrusion has probably existed and been capable of affecting sedimentation in South China Sea at least since Quaternary. 相似文献
3.
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
4.
A new coupling model of wave interaction with porous medium is established in which the wave field solver is based on the two dimensional Reynolds Averaged Navier-Stokes (RANS) equations with a kε closure. Incident waves, which could be linear waves, cnoidal waves or solitary waves, are produced by a piston-type wave maker in the computational domain and the free surface is traced through the Piecewise Linear Interface Construction-Volume of Fluid (PLIC-VOF) method. Nonlinear Forchheimer equations are adopted to calculate the flow field within the porous media. By introducing a velocity–pressure correction equation, the wave field and the porous flow field are highly and efficiently coupled. The two fields are solved simultaneously and no boundary condition is needed at the interface of the internal porous flow and the external wave. The newly developed numerical model is used to simulate wave interaction with porous seabed and the numerical results agree well with the experimental data. The additional numerical tests are also conducted to study the effects of seabed thickness, porosity and permeability coefficient on wave damping and the pore water pressure responses. 相似文献
5.
Diapycnal mixing plays an important role in the ocean circulation.Internal waves are a kind of bridge relating the diapycnal mixing to external sources of mechanical energy.Difficulty in obtaining eigen solutions of internal waves over curved topography is a limitation for further theoretical study on the generation problem and scattering process.In this study,a kind of transform method is put forward to derive the eigen solutions of internal waves over subcritical topography in twodimensional and linear framework.The transform converts the curved topography in physical space to flat bottom in transform space while the governing equation of internal waves is still hyperbolic if proper transform function is selected.Thus,one can obtain eigen solutions of internal waves in the transform space.Several examples of transform functions,which convert the linear slope,the convex slope,and the concave slope to flat bottom,and the corresponding eigen solutions are illustrated.A method,using a polynomial to approximate the transform function and least squares method to estimate the undetermined coefficients in the polynomial,is introduced to calculate the approximate expression of the transform function for the given subcritical topography. 相似文献
6.
A study of SAR remote sensing of internal solitary waves in the north of the South China Sea:I.Simulation of internal tide transformation 总被引：2，自引：1，他引：1
For settlement of the well-known problem of contemporary radar imaging models,i.e.,the pmblem of a general underestimation of radar signatures of hydrodynamic features over oceanic internal waves and underwater bottom topography in tidal watels at at high radar frequency bands(X-band and C-band),the impact of the ocean surface mixed layer turbulence and the significance of strat-ified oceanic model on SAR remote sensing of internal solitary waves are proposed.In the north of the South China Sea by utilizing seme observed data of background field the nonlinearity coefficient,the dispersion coefficient,the horizontal variability coefficient and the phase speed in the generalized K-dV equation are determined approximately.Through simulations of internal tide transfor-mation the temporal evolution and spatial distribution of the vertical displacement and horizontal velocity of intereal wave field are obtained.The simulation results indicate that the maximum amplitudes of internal solitary waves occur at depth 35 m,but the maximum current speeds take place at depth 20 m in this area of the sea(about 20°30'N,114°E)in August.It was noticed that considering the effects of flood current and ebb current respectively is appropriate to investigate influence of the background shear flow on coefficients of the K-dV equation.The obtained results provide the possibility for the simulation of SAR signatures of inter-nal solitary waves under considering the impact of ocean surface mixed layer turbulence in the companion paper. 相似文献
7.
It is well known that wave induced bottom oscillations become more and more negligible when the water depth exceeds half the wavelength of the surface gravity wave. However, it was experimentally demonstrated for regular waves that the bottom pressure oscillations at both first and second wave harmonic frequencies could be significant even for incoming waves propagating in deep water condition in the presence of a submerged plate [16]. For a water depth h of about the wavelength of the wave, measurements under the plate (depth immersion of top of plate h/6, length h/2) have shown bottom pressure variations at the wave frequency, up to thirty times larger than the pressure expected in the absence of the plate. In this paper, not only regular but also irregular wave are studied together with wave following current conditions. This behavior is numerically verified by use of a classical linear theory of waves. The wave bottom effect is explained through the role of evanescent modes and horizontally oscillating water column under the plate which still exist whatever the water depth. Such a model, which allows the calculation of the velocity fields, has shown that not only the bottom pressure but also the near bed fluid velocity are enhanced. Two maxima are observed on both sides of the location of the plate, at a distance of the plate increasing with the water depth. The possible impact of such near bed dynamics is then discussed for field conditions thanks to a scaling based on a Froude similarity. It is demonstrated that these structures may have a significant impact at the sea bed even in very deep water conditions, possibly enhanced in the presence of current. 相似文献
8.
A study of SAR remote sensing of internal solitary waves in the north of the South China Sea: Ⅰ. Simulation of internal tide transformation 总被引：1，自引：0，他引：1
For settlement of the well-known problem of contemporary radar imaging models, i. e. , the problem of a general underestimation of radar signatures of hydrodynamic features over oceanic internal waves and underwater bottom topography in tidal waters at high radar frequency bands （ X-band and C-band）, the impact of the ocean surface mixed layer turbulence and the significance of strat- ified oceanic model on SAR remote sensing of internal solitary waves are proposed. In the north of the South China Sea by utilizing some observed data of background field the nonlinearity coefficient, the dispersion coefficient, the horizontal variability coefficient and the phase speed in the generalized K-dV equation are determined approximately. Through simulations of internal tide transfor- mation the temporal evolution and spatial distribution of the vertical displacement and horizontal velocity of internal wave field are obtained. The simulation results indicate that the maximum amplitudes of internal solitary waves occur at depth 35 m, but the maximum current speeds take place at depth 20 m in this area of the sea （about 20°30＇N, 114°E） in August. It was noticed that considering the effects of flood current and ebb current respectively is appropriate to investigate influence of the background shear flow on coefficients of the K-dV equation. The obtained results provide the possibility for the simulation of SAR signatures of internal solitary waves under considering the impact of ocean surface mixed layer turbulence in the companion paper. 相似文献
9.
Oceanology - The problem of far fields of internal gravity waves from a nonstationary source moving in a stratified ocean of finite depth is considered. It is shown that the wave pattern of the... 相似文献
10.
While shoaling from deep water in a stratified ocean, an internal wave may encounter different types of submarine topography. As it travels, the wave may generate vortex motion on a slope, turbulent mixing between the upper and bottom layer, and even waveform inversion on the plateau of a slope-shelf feature. Although many oceanographers have believed that the inversion from depression to elevation may commence at the turning point where the upper and low layer are equal in depth, this phenomenon has not been fully verified in field observations or numerical schemes. In order to clarify this unique phenomenon, a series of laboratory experiments were conducted on the evolution of an interfacial solitary wave of depression across a slope followed by a horizontal plateau on slope-shelf obstacle. Experimental results indicate the length of the plateau may become a proxy to determine whether the inverted waveform could maintain its strength or be weakened swiftly, which could inflict direct impact on the ecology of the local oceanic environment. Comparison on the internal flow field is also presented in this paper to illustrate the process of waveform inversion as an internal wave propagating over a trapezoidal, triangular ridge and uniform long slope, respectively. 相似文献
11.
V. P. Smagin S. V. Semkin V. N. Savchenko 《Izvestiya Atmospheric and Oceanic Physics》2013,49(5):541-547
The electric and magnetic field and electric charges at the medium interface induced by a two-dimensional marine surface and internal waves are considered. The influence of the magnetic permeability and electric conductivity of the bottom rocks on the induced fields is analyzed. 相似文献
12.
A non-linear coupled-mode system of horizontal equations is presented, modelling the evolution of nonlinear water waves in finite depth over a general bottom topography. The vertical structure of the wave field is represented by means of a local-mode series expansion of the wave potential. This series contains the usual propagating and evanescent modes, plus two additional terms, the free-surface mode and the sloping-bottom mode, enabling to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries. The present coupled-mode system fully accounts for the effects of non-linearity and dispersion, and the local-mode series exhibits fast convergence. Thus, a small number of modes (up to 5–6) are usually enough for precise numerical solution. In the present work, the coupled-mode system is applied to the numerical investigation of families of steady travelling wave solutions in constant depth, corresponding to a wide range of water depths, ranging from intermediate depth to shallow-water wave conditions, and its results are compared vs. Stokes and cnoidal wave theories, as well as with fully nonlinear Fourier methods. Furthermore, numerical results are presented for waves propagating over variable bathymetry regions and compared with nonlinear methods based on boundary integral formulation and experimental data, showing good agreement. 相似文献
13.
The problem of constructing uniform asymptotics of surface perturbations of far fields from a localized harmonic source in the flow of a heavy homogeneous fluid of infinite depth is considered. It is shown that the wave pattern of generated far fields at specific parameters is a system of hybrid wave disturbances that simultaneously possesses the properties of waves of two types: annular (transverse) and wedgeshaped (longitudinal) waves. The properties of the phase structure and wave fronts of the generated fields are studied. Uniform asymptotics of the solutions describing hybrid surface wave disturbances far from a harmonic source are constructed. 相似文献
14.
A three-dimensional, multi-level model was used to study the energy dissipation of semidiurnal internal Kelvin waves due to their interaction with bottom topography. A simplified topography consisting of a channel with an additional shallow bay was used to clarify the wave’s scattering process. When the first mode semidiurnal internal wave given at an open boundary arrives at the bay mouth, higher-mode internal waves are generated at a step bottom of the bay mouth. As a result, the energy of the first mode internal Kelvin wave is effectively decayed. The decay rate of the internal Kelvin wave depends on both the width and length of the additional bay. The maximum decay rate was found when a resonance condition occurs the bay, that is, the bay length is equal to a quarter of wave length of the first mode internal wave on the shallow region. The decay rate in the wide bay cases is higher than that in a narrow case, due to a contribution from the scattering due to the Poincare wave that emanates from the corners of the bay head. The decay rate with the additional bay is 1.1–1.8 times that of the case without the additional bay. The decay rate due to the scattering process is found to be of the same order as that of the internal and bottom friction. 相似文献
15.
南海北部内孤立波数学模型 总被引：3，自引：0，他引：3
在二层内潮数学模型的基础上,考虑非静力平衡扰动压力的影响,导出潮频内孤立波产生、传播的数学模型。该模型不受小地形假设的限制,并适用于南海。应用该模型能解释说明产生以下现象的物理机制：潮流流过巴坦-萨布坦海脊时,在一定海洋环境条件下,通过潮流与起伏的底地形相互作用可激发产生潮频内孤立波,并西传至东沙群岛附近的海域。 相似文献
16.
Theoretically, propagating internal tides in the ocean may reflect at turning depths, where buoyancy frequencies equal tidal frequencies, before colliding with the air-sea interface or rugged bottom topography. Globally, the internal tide lower turning depths（ITLTDs） in the open ocean have been mapped; however, knowledge of the presence of ITLTDs in the South China Sea（SCS） is lacking. In this study, 2 125 high-quality temperature-salinity profiles（including 58 deep-sea hydrographic measurements... 相似文献
17.
I. I. Didenkulova E. N. Pelinovsky O. I. Didenkulov 《Izvestiya Atmospheric and Oceanic Physics》2014,50(5):532-538
We study the run-up of long solitary waves of different polarities on a beach in the case of composite bottom topography: a plane sloping beach transforms into a region of constant depth. We confirm that nonlinear wave deformation of positive polarity (wave crest) resulting in an increase in the wave steepness leads to a significant increase in the run-up height. It is shown that nonlinear effects are most strongly pronounced for the run-up of a wave with negative polarity (wave trough). In the latter case, the run-up height of such waves increases with their steepness and can exceed the amplitude of the incident wave. 相似文献
18.
This paper addresses the problem of the generation of internal waves by a barotropic tide propagating in a uniformly stratified sea across the frontal zone overlying a submerged ridge or a continental slope. Using Riemann's technique, we have performed computations and analysed the wave fields' spatial characteristics and have defined the dependences of the generated wave amplitudes, bottom topography parameters, and density field. It is shown that the presence of a horizontally-inhomogeneous density region over a subwater feature may lead to substantial alteration of the maximum amplitudinal values of internal waves, both inside and around the frontal zone.Translated by Vladimir A. Puchkin. 相似文献
19.
Using the recently developed expansion formulae for wave structure interaction problems, the scattering of surface water waves by a semi-infinite floating membrane due to abrupt change in bottom topography is analyzed. Both the cases of finite and infinite steps are analyzed. In the present paper, the analysis is based on the linearized theory of water waves and small amplitude membrane response. Combining the linearized kinematic and dynamic surface conditions on the water surface with the dynamic pressure condition on the membrane, a third order differential equation is derived to describe the membrane covered free surface condition. General wave energy relation for wave scattering by floating horizontal membrane is derived by the application of law of conservation of energy flux and alternately by the direct application of Green's second identity. In the floating membrane covered region, the wave energy density is a combination of the kinetic and potential energy density due to the surface gravity waves, and the surface energy density which is due to the existence of the floating membrane on the free surface. Gravity wave transformations due to an abrupt change in bottom topography in the presence of a floating membrane in finite water depth are analyzed based on shallow water approximation. Numerical results are computed and analyzed to understand the wave transformation due to the floating membrane when there is an abrupt change in topography in different cases. 相似文献
20.
The conditions under which the interaction between internal waves and the rough bottom topography may be the reason for synchronous fluctuations of pressure at the bottom have been studied. Disturbances of the depth are assumed to be small compared with the mean depth of the ocean, and the Väisälä-Brunt frequency is constant. It is shown that synchronous fluctuations of pressure exist with a frequency equal to that of internal waves. The amplitude of pulsations can be approximately an order lower than the amplitude of fluctuations generated by standing surface waves. However, local maxima can exist in the low-frequency minimum of the spectrum of microseisms (in the range of 20–1000 s).Translated by Mikhail M. Trufanov. 相似文献