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1.
The estimates of wave-induced dynamic pressures around surface piercing twin-tandem rigid vertical circular cylinders fixed at the bottom of a wave flume, obtained using the source distribution method, are compared with the measured values. The influence of flume confinement on dynamic pressures is estimated by the method of images. The experiments are carried out on cylinders of 40 cm diameter mostly in deep water conditions in a wave flume 4 m wide, for different values of scattering parameters and spacings between the cylinders. 相似文献
2.
Vertical variations of wave-induced radiation stress tensor 总被引：3，自引：0，他引：3
INTRODUcrIONThe concept of radiation stress was deve1oPed by tonguet--Higgins and Stewart (1964 ),who intreduced the definition of radiation stress as the excess mornentum due to the presence ofwaves, on the basis of time-averaged laws of Newtonian fluid mechanics and the assmption ofa unifOrm velocity distribution over depth. Subequently, the theory has been applied success-fully in the investigation of phenomena such as wave set-up and set--down (Bowen et al.,l968), longshore currents … 相似文献
3.
The third order triple-frequency wave load on fixed axisymmetric bodies by monochromatic waves is considered within the frame of potential theory. Waves are assumed to be weak non-linearity and a perturbation method is used to expand velocity potentials and wave loadings into series according to a wave steepness of kA. Integral equation method is used to compute velocity potentials up to second order in wave steepness. The third order triple-frequency wave loads are computed by an indirect method and an efficient method is applied to form the third order forcing term on the free surface quickly. The method can be used to compute third order triple-frequency surge force, heave force and pitch moment on any revolution bodies with vertical axes. The comparison with Malenica and Molin's results is made on surge force on a uniform cylinder, and comparison with experimental results is made on third order surge force, heave force and pitch moment on a truncated cylinder. More numerical computations are carried out for third order forces and moments on a uniform cylinder, truncated cylinders and a hemisphere. 相似文献
4.
基于映像理论将部分反射直墙前物体的散射问题,等效于开敞水域中原物体的散射和关于直墙映像体散射的线性叠加进行求解。采用高阶边界元方法建立了部分反射直墙前二维任意形状物体波浪绕射和辐射问题的数值分析模型,通过与已发表的海底方箱和淹没圆柱结果的对比验证了数值模型的准确性。应用该模型研究了直墙反射系数幅值及相位、方箱与墙间距离等参数对水面方箱上波浪激振力、附加质量和辐射阻尼的影响。结果表明：直墙反射系数幅值越大,波浪激振力、附加质量和辐射阻尼的波动越大,附加质量在一些频率下出现负值;相位角的变化会改变波浪激振力、附加质量和辐射阻尼曲线的偏移,在低频区对升沉附加质量有显著影响;方箱距离直墙越远,方箱上的波浪激振力、附加质量和辐射阻尼随波数振荡的频率越快,峰值频率向低频侧移动。 相似文献
5.
S.A. Mavrakos 《Ocean Engineering》1997,24(4):381-399
The paper deals with the linearized exciting wave forces and hydrodynamic coefficients of a toroidal body floating in water of finite depth. For the solution of the diffraction and the radiation problems the flow field around the body is subdivided into ring-shaped fluid regions, in each of which axisymmetric eigenfunction expansions for the velocity potential is made. By implementing Galerkin's method the various potential solutions are matched and numerical results concerning the exciting wave forces and the hydrodynamic coefficients in all modes of motion are obtained. 相似文献
6.
Experimental and Theoretical Investigation of Wave Forces on A Partially-Perforated Caisson Breakwater with A Rock-Filled Core 总被引：2，自引：0，他引：2
1.IntroductionVertical breakwaters are widely used for harbor and coastline protection in coastal engineering.Recently,perforated breakwaters have been often used in practice as they can effectively reduce thewaveforces actingon,the wave reflectionfromand… 相似文献
7.
An approximate method is presented for calculating drift forces on arrays of vertically axisymmetric bodies in a wave tank. It is assumed that the wave scattering properties of an isolated element and of the array in the open sea are known. The procedure described allows the open-sea results to be post-processed to give good estimates of drift forces when a structural array is placed in a wave tank. For the particular case of an array of vertical circular cylinders extending throughout the depth, the method is compared with accurate results from the full linear problem for scattering by the array both when the array is in the tank and when it is in the open sea. The results show how the mean forces on the array when in the tank may differ considerably from those experienced in the open sea. 相似文献
8.
In this study, a set of generalized analytical solutions are developed for the wave-induced response of a saturated porous seabed under plane strain condition. When considering the water waves originating in deep water and travelling towards the shore, their velocities, lengths and heights vary. Depending on the characteristics of the wave and the properties of the seabed, different formulations (fully dynamic, partly dynamic, quasi-static) for the wave-induced response of the seabed are possible. The solutions for the response with these formulations are established in terms of non-dimensional parameters. The results are presented in terms of pore pressure, shear stress and vertical effective stress distributions within the seabed. For typical values of wave period and seabed permeability, the regions of applicability of the three formulations are identified and plotted in parametric spaces. With given wave and seabed characteristics, these regions provide quick identification of the appropriate formulation for an adequate evaluation of the wave-induced seabed response. 相似文献
9.
The size, complexity and critical operations of many offshore structures, including the mobile offshore bases (MOBs) of current interest, require careful determination of wave forces on the neighboring structures, including their interactions. This paper describes an analytical/numerical approach that determines the wave forces on multiple structures in the vicinity of one another. The method involves the consideration of multiple vessel interaction and scattering in waves. The analysis is an extension of the semi-analytical multiple vertical cylinder analysis published by the author. The analysis is similar to the one proposed by Kagemoto and Yue for axisymmetric bodies.The direct method of linear diffraction, while quite accurate and efficient in solving the hydrodynamic problem, demands a large amount of memory and requires considerable execution time. The present analysis is very efficient in these respects. It is accomplished by marrying the direct method with a semi-closed analytical method of multiple scattering developed for an array composed of vertical cylindrical structures. It is recognized that this analytical method has a limitation owing to the geometry of many offshore structures including MOBs. Therefore, the analysis is extended to an arbitrary geometry. In this method, the direct matrix method of diffraction problem is applied to an isolated module and then extended to structures with the multiple scattering technique to account for the interaction of multiple structures.Comparisons are made of the results from the analytical and conventional numerical diffraction theory with those of the semi-analytical tool using the above-mentioned analysis. 相似文献
10.
A theory is given for a two-dimensional wave power device which consists of a train of floating rafts whose wave-induced rotation about the hinges is used to generate energy. Ideal efficiency, wave forces and raft movements are studied by a linearized shallow water theory which is sufficiently simple to enable an investigation for optimum designs under a variety of criteria of efficiency and cost-effectiveness. For a sample raft train, a numerical theory for arbitrary wavelength is also applied, yielding results which are not essentially different from those by the long wave approximation. 相似文献
11.
The paper provides a detailed analysis for the second-order diffraction of monochromatic waves. For the second-order potential on the free surface, the paper proposed a forward prediction method for computing the integration on the free surface. By this method we only need to run the infinity integration on the free surface directly for a few points; a one-step quadrature can then be applied successively outward from the body for potentials at other points. For wave diffraction from a body of revolution with a vertical axis, the paper derives a new integral equation, which can cancel the leading singularity in the derivative of ring Green's functions automatically. To obtain accurate results, different approaches are also used to deal with singularities in the ring Green's functions in the integration on both the body surface and free surface. The method has been implemented for bodies of revolution with vertical axes, but the theory is also available for arbitrary bodies.A numerical examination is made to validate the numerical code by comparing the second-order forces and moments on uniform and truncated cylinders and second-order diffraction potentials on the free surface with some published results. The comparison shows that the present results are in good agreement with those published. The method is also used to compute the second-order wave elevation around uniform and truncated cylinders. 相似文献
12.
The hydrodynamic problem arising form the interaction of linear water waves with a wave energy device consisting of two coaxial vertical cylinders of different radii is investigated. One cylinder is riding in waves, while another is submerged in fluid. By use of the method of separation of variables and the method of matched eigenfunction expansion, analytical expressions for the potentials are obtained. Using the expressions for the potentials, analytical expressions for the hydrodynamic coefficients and exciting forces/moments on the device are obtained. Numerical results of the hydrodynamic coefficients and exciting forces/moments are presented for some ratios of the radius of the submerged cylinder to that of the riding one. It is found that the radius of the submerged cylinder has a significant influence on the hydrodynamic coefficients and exciting forces/moments for relatively bigger radius of the submerged cylinder at low frequencies. 相似文献
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14.
《Ocean Modelling》2011,39(3-4):230-243
A three-dimensional numerical model was established to simulate the wave-induced currents. The depth-varying residual momentum, surface roller, wave horizontal and vertical turbulent mixing effects were incorporated as major driving forces. A surface roller evolution model considering the energy transfer, roller density and bottom slope dissipation was developed. The expression of the wave-induced horizontal turbulent mixing coefficient proposed by Larson and Kraus (1991) was extended to three-dimensional form. Plenty of experimental cases were used to validate the established model covering the wave setup, undertow, longshore currents and rip currents. Validation results showed the model could reasonably describe the main characteristics of different wave-induced current phenomena. The incorporation of surface roller for breaking waves should not be neglected in the modeling of surfzone hydrodynamics. The wave-induced turbulent mixing affects the structures of wave-induced current either in horizontal or in vertical directions. Sensitivity analysis of the major calibration parameters in the established model was made and their ranges were evaluated. 相似文献
15.
The velocity fluctuations of wind over wind-waves in a wind tunnel are measured with a X-type hot-wire anemometer at some heights over the water surface.The observed vertical profiles of the wave-induced velocity fluctuations and the wave-induced Reynolds stress at the wave spectral peak frequency are different from those expected from the inviscid quasi-laminar model;i.e., the observed vertical profiles of the power spectral density of the wave-induced horizontal or vertical velocity fluctuations of wind have the minimum value at the height much heigher than the critical layer, and the value of the wave-induced Reynolds stress is negative at several heights over the water surface. From the comparison between the experimental results and the numerical solutions of a linear model of the turbulent shear flow over the wavy boundary, it is shown that the discrepancy described above can be attributed to the atmospheric turbulence. 相似文献
16.
The modified hybrid element method (MHEM) is utilized to predict and analyze wave forces on arbitrarily shaped multiple bodies. This method can be applied to waves of all water depths, i. e. shallow, intermediate, and deep waters, on slowly varying seabed. The MHEM employs the ICCG method to save CPU and storage, thus the computation of wave forces for large multi-body systems can be carried out on microcomputers. Numerical results of the present method are compared with experimental data and other solutions. It is shown that the MHEM provides more accurate solutions of the wave forces than other numerical methods do. Therefore, the methodology presented herein can be used in the design of coastal and ocean structures. 相似文献
17.
The membrane forces are included in the hydroelastic analysis of a floating plate undergoing large vertical deflections in regular monochromatic multidirectional waves. The first-order vertical displacements induced by the linear wave exciting forces are calculated by the mode expansion method in the frequency domain. The second-order vertical displacements induced by the membrane forces are calculated by the von Karman plate theory. The results show that the membrane contribution both in terms of the axial stresses and the effect on the bending stresses can be important. 相似文献
18.
W. Koterayama 《Ocean Engineering》1980,7(3):399-412
This paper presents a method of estimating wave forces acting on a submerged horizontal circular cylinder fixed in oblique waves.The experiments show that drag and inertia coefficients in beam sea are available for calculating the wave forces in oblique waves.Wave forces exerted on a vertical circular cylinder in deep waves are also investigated.The experimental results show that wave forces acting on the vertical cylinder coincide approximately with hydrodynamic forces acting on a submerged circular cylinder in an oscillating fluid. 相似文献
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20.
Fabrice Ardhuin 《Journal of Oceanography》2006,62(6):917-922
In a recent paper, Kenyon (2004) proposed that the wave-induced energy flux is generally not conserved, and that shoaling
waves cause a mean force and torque on the bottom. That force was equated to the divergence of the wave momentum flux estimated
from the assumption that the wave-induced mass flux is conserved. This assumption and conclusions are contrary to a wide body
of observations and theory. Most importantly, waves propagate in water, so that the momentum balance generally involves the
mean water flow. Although the expression for the non-hydrostatic bottom force given by Kenyon is not supported by observations,
a consistent review of existing theory shows that a smaller mean wave-induced force must be present in cases with bottom friction
or wave reflection. That force exactly balances the change in wave momentum flux due to bottom friction and the exchange of
wave momentum between incident and reflected wave components. The remainder of the wave momentum flux divergence, due to shoaling
or wave breaking, is compensated by the mean flow, with a balance involving hydrostatic pressure forces that arise from a
change in mean surface elevation that is very well verified by observations. 相似文献