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A new analytical method is proposed to analyze the force acting on a rectangular oscillating buoy due to linear waves. In the method a new analytical expression for the diffraction velocity potential is obtained first by use of the eigenfunction expansion method and then the wave excitation force is calculated by use of the known incident wave potential and the diffraction potential. Compared with the classical analytical method, it can be seen that the present method is simpler for a two-dimensional problem due to the comparable effort needed for the computation of diffraction potential and for that of radiated potential. To verify the correctness of the method, a classical example in the reference is recomputed and the obtained results are in good accordance with those by use of other methods, which shows that the present method is correct. 相似文献
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月池内流体存在活塞和晃荡两类振荡现象。基于线性势流理论,推导了波浪斜向入射下,直墙前矩形月池辐射和绕射问题的解析解。通过分离变量法和特征函数展开法求解了速度势函数,根据边界条件来确定速度势函数中的未知系数,由速度势函数计算斜向波与矩形月池相互作用的水动力系数和波浪激励力,对它们的变化规律进行了分析讨论,研究了底部开口大小、波浪入射角度对矩形月池水动力特性的影响以及直墙远近对波浪力的影响。结果表明,月池底部开口大小对流体水平作用的影响较小,而对流体垂直作用的影响较大;波浪入射角度的变化对矩形月池横荡和横摇运动时的水动力特性有一定的影响;在一定条件下,直墙的存在会使得月池在水平方向所受到的波浪力比开敞水域中的要大。 相似文献
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摇板式波浪能转换装置具有频率响应范围广、可靠性好、常规海况下转换效率高、建造成本低等优点。基于势流理论建立具有沉箱基础的摇板式波浪能装置水动力性能的解析解。将解析结果与文献中已有结果和边界元数值结果进行了对比,验证了解析解求解过程的正确性。通过算例分析,研究了波浪入射频率、沉箱基础高度、沉箱基础宽度、摇板位置、摇板厚度和摇板密度对装置能量俘获效率的影响。研究结果表明：采用合适高度的沉箱基础能显著提升装置性能;长波海况下,摇板铰接在沉箱基础背浪侧上表面时装置性能更佳,而短波海况下,摇板铰接在沉箱基础迎浪侧上表面更为合理;沉箱基础宽度的推荐值为0.5到1.0倍水深;适当减小摇板厚度能够提升装置性能;应优先选用密度较大的摇板。 相似文献
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The linear wave radiation by a long floating rectangular structure in oblique seas of finite depth is investigated by use of the method of separation of variables and the eigenfunction expansion matching method. Analytical expressions for the radiated potentials, wave forces and hydrodynamic coefficients are given. The correctness of these expressions is verified through two specific examples investigated previously by other numerical methods. Using the present analytical solution, the hydrodynamic effects of the angle of incidence, the draft and the width of the structure on the wave forces and hydrodynamic coefficients are discussed in detail which may provide some useful information for the design of rectangular structures in oblique seas. 相似文献
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A radiation and diffraction boundary value problem is investigated. It arises from the interaction of linear water waves with a freely floating rectangular structure in a semi-infinite fluid domain of finite water depth with the leeward boundary being a vertical wall. Analytical expressions for the radiated potentials and the diffracted potential are obtained by use of the method of separation of variables and the eigenfunction expansion method. The added masses and damping coefficients for the structure heaving, swaying and rolling in calm water are obtained by use of the corresponding radiated potentials and the wave excitation forces are calculated by use of the diffracted potential. To verify the correctness of the method, a boundary element method is used. A comparison of the analytical results with those obtained by the boundary element method is made and good agreement is achieved, which shows that the analytical expressions for the radiated and diffracted potentials are correct. By use of the present analytical solution, the added mass, damping coefficients, wave excitation force, together with the hydrodynamic effects of the draft, width of the structure and the clearance between the structure and the sidewall are also investigated. 相似文献
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The interaction of diagonal waves with perforated-wall breakwater partially filled with rock fill is studied using the linear potential theory. By means of the matched eigenfunction expansion method, an analytical method is presented to calculate the reflection coefficient and the wave force coefficient of the breakwater. The calculated results of the reflection coefficient for limiting cases are the same to the existing results. The main effect factors of the reflection coefficient and the wave force coefficient are analyzed by numerical examples. With the increasing of thickness of rock fill, the wave force coefficient on the perforated wall generally decreases, while the reflection coefficient increases. With the increasing of the incident angle of the wave, the reflection coefficient of the breakwater first decreases, reaches its minimum, and then increases monotonously. 相似文献
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Transmissions of oblique incident wave from a row of rectangular piles are analyzed theoretically. The incident angle of plane wave is taken as , there then is the transmission coefficient (This is a paradox). In this paper, by means of the approximate relation between the transmitted and incident wave angle found from the shape of a slit, the paradoxical phenomenon is removed. On the basis of the continuality of the pressure and flux and the analysis of flow resistance at the row of rectangular piles, formulas of reflection and transmission coefficients are obtained. The transmission and reflection coefficients predicted by the present model quite agree with those of laboratory experiments in previous references 相似文献
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In this study, a two-dimensional floating pier consists of single rectangular impermeable pontoon with side supporting pile-columns is studied. The purpose of this study is to present a theoretical solution for the linearized problem of incident waves exerting on a floating pier with pile-restrained. All boundary conditions are linearized in the problem, which is incorporated into a scattering problem and radiation problem with unit displacement. The method of separation of variables is used to solve for velocity potentials. For the radiation problem with unit heave and pitch amplitude, the boundary value problem with non-homogeneous boundary condition beneath the structure is solved by using a solution scheme. By calculating the wave force from velocity potential and solving the equation of motion of the floating structure simultaneously a close form theoretical solution for the problem is developed. The finite element method was also applied to calculate the dynamic responses on the supporting piles subjected to the pontoon motions and incident waves. 相似文献
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基于线性势流假定,对斜向波作用下带横隔板局部开孔沉箱防波堤的水平波浪力进行了理论研究。给出了开孔沉箱法向水平力和横隔板受力的理论计算方法,在极限情况下波浪力的计算结果与文献中的已有结果一致。利用数值算例分析了开孔沉箱总水平力的主要影响因素。开孔沉箱法向总水平力的减小主要集中于结构上半部分波浪影响范围以内。增加单个开孔沉箱的长度有利于减小结构所受总水平波浪力。当波浪入射角或沉箱前开孔墙孔隙影响系数幅值较大时,开孔沉箱横隔板上总水平力的最大值要超过相应的沉箱法向总水平力,此时要注意横隔板的强度问题。 相似文献
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《Ocean Engineering》2004,31(8-9):1063-1082
An analytical method is presented to analyze the radiation and diffraction of water waves by a rectangular buoy in an infinite fluid domain of finite water depth. Analytical expressions for the radiated potentials and the diffracted potentials are obtained by use of the method of separation of variables. The unknown coefficients in the expressions are determined by use of the eigenfunction expansion matching method. The added masses and damping coefficients for the buoy heaving, swaying and rolling in calm water are obtained by use of the corresponding radiated potentials. Wave excitation forces are calculated by two different approaches, one is by use of the radiated potentials through Haskind’s theorem and the other is by the diffracted potential. It can be seen that the latter approach for wave forces on a rectangular buoy is much simpler than the former. To verify the correctness of the method, two specific examples in the past references are recomputed and the obtained results are in good agreement with those by use of other methods, which shows that the present method is correct. 相似文献
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An obvious motivation of this paper is to examine the effectiveness of the lateral vibration control of a jacket type offshore platform with an AMD control device, in conjunction with H2 control algorithm, which is an optimal frequency domain control method based on minimization of H2 norm of the system transfer function. In this study, the offshore platform is modeled numerically by use of the finite element method, instead of a lumped mass model. This structural model is later simplified to be single-degree-of-freedom (SDOF) system by extracting the first vibration mode of the structure. The corresponding "generalized" wave force is determined based on an analytical approximation of the first mode shape function, the physical wave loading being calculated from the linearized Morison equation. This approach facilitates the filter design for the generalized force. Furthermore, the present paper also intends to make numerical comparison between H2 active control and the corresponding passive control using a T 相似文献
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1 Introduction A vertical wall is one of the typical maritime sheltering structures in the coastal region, which is mainly subjected to wave forces. It has been a com- mon engineering assumption adopted for design pur- poses that normally incident wave fo… 相似文献
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The nonlinear diffraction of 2D single and twin hulls are studied by employing a mixed Eulerian–Lagrangian model based on a higher-order cubic-spline boundary element solver. Two types of simulations are considered. In the first, waves are generated by a piston-type wave-maker in a rectangular tank and in the second case a nonlinear incident wave is assumed to exist in the tank in which the body is introduced. For the application of this model, the full nonlinear diffraction problem is recast in terms of a perturbation wave-field. Computations are performed for rectangular and triangular hull geometries. Computed results show significant nonlinearities, particularly in the heave force. The twin hull results show the influence of wave interference on the diffraction forces. This interference influences the surge force considerably, but heave force is less affected. 相似文献
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Lao Guosheng Feng Hong Associate Professor Dalian University of Technology Dalian Postgraduate Dalian University of Technology Dalian 《中国海洋工程》1992,(4)
- In this paper, the theoretical calculation of floating breakwater performance in regular waves with arbitrary wave direction is discussed. Under the hypothesis of linearized system and applying the strip theory, we can solve the boundary condition problems of diffraction potential and radiation potential. Introducing the asymptotic expression of the wave velocity potential at infinity and using wave energy conservation, we can separately calculate the transmitted waves generated by the sway, heave and roll motion of the floating breakwater and by the fixed breakwater. Finally, we define the amplitude ratio of the transmitted wave to the incident wave as the transmitted wave coefficient CT which describes the floating breakwater effectiveness. Two examples are given and the theoretical results obtained by the present method agree well with experimental results. 相似文献