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1.
在势能流及微小振幅波理论假设下,采用复合边界元素法(CBEM)数值解析规则波通过单根外壁透水cosine-type型同心圆柱结构物绕射。将cosine-type外壁不透水条件改为透水外,并在内部设有一半径为b的不透水内圆柱共同组成同心圆柱,为了验证CBEM数值模式正确性与可行性,将其退化成圆柱,均得到合理结果。数值计算条件包含波浪正向入射凸端、透水参数及绕射参数,探讨波浪通过单根cosine-type同心圆柱体四周水面波动变化情况,并与双重圆筒同心圆柱作比较。计算结果显示结构物外壁采用透水型式,可以大幅降低cosine-type同心圆柱体四周整个波浪绕射场的水面波动。 相似文献
2.
Wave interaction with a concentric porous cylinder system 总被引：1，自引：0，他引：1
This is a theoretical investigation of wave interaction with a concentric surface-piercing two-cylinder system. The exterior cylinder is porous and considered to be thin in thickness and the interior cylinder is impermeable. Both cylinders are rigidly fixed at the sea bed. The fluid motion is idealized as a linearized potential flow. The free-surface elevation and the total net hydrodynamic forces acting on both cylinders are determined analytically. The wave-induced overturning moments are also evaluated. It is found that, with the existence of the exterior porous cylinder, the hydrodynamic force acting on the interior cylinder is reduced if compared to the force exerted on the interior cylinder by a direct wave impact. The reduction of the wave amplitude around the leeward side of the outer porous cylinder is shown from the free-surface computations. In this paper, results are also presented to illustrate the effects of wave parameter and structural porosity on this wave and cylinder interaction problem. The role played by the ratio of radii of the inner and outer cylinders is duscussed. 相似文献
3.
In this paper, theoretical study is carried out to investigate the general 3D short-crested wave interaction with a concentric two-cylinder system. The interior cylinder is impermeable and the exterior cylinder is thin in thickness and porous to protect the interior cylinder. Both cylinders are surface-piercing and bottom mounted. Analytical solution is derived based on the linear potential theory. The effects of the wide range wave parameters and structure configuration including porosity of the exterior cylinder and the annular spacing on the wave forces, surface elevations and the diffracted wave contours are examined. 相似文献
4.
Theoretical investigations on solitary waves interacting with a surface-piercing concentric porous cylinder system are presented in this paper. The outer cylinder is porous and considered thin in thickness, while the inner cylinder is solid. Both cylinders are rigidly fixed on the bottom. Following Isaacson's [Isaacson, Micheal de St. Q., 1983. Solitary wave diffraction around large cylinder. Journal of the Waterway, Port, Coastal and Ocean Engineering 109(1), 121–127.] approach, we obtained the solutions for free-surface elevation and the corresponding velocity potential in terms of Fourier integrals. Numerical results are presented to show the effects of incident wave condition, porosity of the outer cylinder and radius ratio on wave forces and wave elevations around the inner and outer cylinders. 相似文献
5.
An array of large concentric porous cylinder arrays is mounted in shallow water exposed to cnoidal waves. The interactions between waves and cylinders are studied theoretically using an eigenfunction expansion approach. Semi-analytical solutions of hydrodynamic loads and wave run-up on each cylinder are obtained using first approximation to cnoidal waves. The square array configuration of four-legged identical concentric porous cylinder is investigated in present study. Numerical results reveal the variation of dimensionless wave force and wave run-up on individual cylinder with angle of incidence, porosity parameter, spacing between outer and inner cylinders, spacing between concentric porous cylinders and wave parameter. Different mechanism of wave force is found under different range of scattering parameter. 相似文献
6.
比例边界有限元法(SBFEM)是一种半解析数值分析的新方法,既融合了有限元法和边界元法的优点,又有其特有的优点。用该方法可求解有限水深下狭缝对双箱水动力作用的影响,为波浪与多浮体超大型结构的相互作用探索一些规律。整个计算域划分成2个无限子域和4个有限子域,并利用加权余量法在各个子域上推导了SBFEM的积分方程;计算了4个数值算例并与边界元等其它数值方法进行了比较,验证了该方法是一种用很少单元便能得到精确结果的高效方法。应用SBFEM对不同箱体宽度、不同狭缝宽度、不同吃水深度条件的双箱作了计算,得出了狭缝对双箱水动力干涉影响的一些规律,对超大型浮体水动力分析和结构设计具有一定的参考价值。 相似文献
7.
The scaled boundary finite element method （SBFEM） is a novel semi-analytical technique combining the advantage of the finite element method （FEM） and the boundary element method （BEM） with its unique properties. In this paper, the SBFEM is used for computing wave passing submerged breakwaters, and the reflection coeffcient and transmission coefficient are given for the case of wave passing by a rectangular submerged breakwater, a rigid submerged barrier breakwater and a trapezium submerged breakwater in a constant water depth. The results are compared with the analytical solution and experimental results. Good agreement is obtained. Through comparison with the results using the dual boundary element method （DBEM）, it is found that the SBFEM can obtain higher accuracy with fewer elements. Many submerged breakwaters with different dimensions are computed by the SBFEM, and the changing character of the reflection coeffcient and the transmission coefficient are given in the current study. 相似文献
8.
比例边界有限元法(SBFEM)是一种半解析的数值方法,比完全数值方法具有更高的精度,该方法结合了有限元和边界元的优点,采用相对少的剖分单元就可以得到较高精度的模拟结果。通过改变有限子域内部比例中心的位置,使这种方法可以应用到多种形式浮体在波浪作用下的水动力特性的计算中。同时还给出了各种形式浮体的波浪力及反射、透射系数的数值结果,并与边界元方法(BEM)计算结果和特征函数展开方法得到解析解进行了比较,均吻合良好。研究表明比例边界有限元不仅可以计算矩形的浮体结构,而且对于多种结构形式的浮体都可以计算,这为多种结构形式浮体的水动力分析提供了一个可行的方法。 相似文献
9.
《Applied Ocean Research》2005,27(4-5):224-234
The modified scaled boundary finite-element method (SBFEM), keeping the advantages of the original SBFEM, eliminates the restriction of the scaling center location so that this approach can solve two-dimensional problems with parallel side-faces. In this paper, the modified SBFEM is applied to solutions of two types of problems—wave diffraction by a single and twin surface rectangular obstacles and wave radiation induced by an oscillating mono-hull and twin-hull structures in a finite depth of water. For wave diffraction problems, numerical results agree extremely well with the analytic solution for the single obstacle case and other numerical results of a different approach for the twin obstacle case. For wave radiation problems, the particular solutions to the scaled boundary finite-element equation are presented for cases of heave, sway and roll motions. The added mass and damping coefficients for heave, sway and roll motions of a two-dimensional rectangular container are computed and the numerical results are compared with those from independent analytical solution and numerical solution using the boundary element method (BEM). It is found that the SBFEM method achieves equivalent accuracy to the conventional BEM with only a few degrees of freedom. In the last example, wave radiation by a two-dimensional twin-hull structure is analyzed. Comparisons of the results with those obtained using conventional Green's function method (GFM) demonstrate that the method presented in this paper is free from the irregular frequency problems. 相似文献
10.
A composite numerical model is presented for computing the wave field in a harbor. The mild slope equation is discretized by a finite element method in the domain concerned. Out of the computational domain, the water depth is assumed to be constant. The boundary element method is applied to the outer boundary for dealing with the infinite boundary condition. Because the model satisfies strictly the infinite boundary condition, more accurate results can be obtained. The model is firstly applied to compute the wave diffraction in a narrow rectangular bay and the wave diffraction from a porous cylinder. The numerical results are compared with the analytical solution, experimental data and other numerical results. Good agreements are obtained. Then the model is applied to computing the wave diffraction in a square harbor with varying water depth. The effects of the water depth in the harbor and the incoming wave direction on the wave height distribution are discussed. 相似文献
11.
A composite numerical model is presented for computing the wave field in a harbor. The mild slope equation is discretized by a finite element method in the domain concerned. Out of the computational domain, the water depth is assumed to be constant. The boundary element method is applied to the outer boundary for dealing with the infinite boundary condition. Because the model satisfies strictly the infinite boundary condition, more accurate results can be obtained. The model is firstly applied to compute the wave diffraction in a narrow rectangular bay and the wave diffraction from a porous cylinder. The numerical results are compared with the analytical solution, experimental data and other numerical results. Good agreements are obtained. Then the model is applied to computing the wave diffraction in a square harbor with varying water depth. The effects of the water depth in the harbor and the incoming wave direction on the wave height distribution are discussed. 相似文献
12.
The interaction of linear water waves with a semi-porous cylindrical breakwater surrounding a rigid vertical circular cylinder mounted on a storage tank is investigated theoretically. The cylindrical breakwater structure is porous in the vicinity of the free-surface, while at some distance below the water surface it becomes impermeable. Under the assumptions of linearized potential flow, the coupled problem of flow in the interior and exterior fluid regions is solved by an eigenfunction expansion approach. Analytical expressions are obtained for the wave motion in both the interior and exterior flow regions. Numerical results are presented which illustrate the effects of the various wave and structural parameters on the hydrodynamic loads and interior and exterior wave fields. It is found that for certain parameter combinations the semi-porous, cylindrical breakwater may result in a significant reduction in the wave field and hydrodynamic forces experienced by the interior structure. 相似文献
13.
波浪对上部开孔带内柱的圆筒结构的绕射 总被引：1，自引：0，他引：1
应用透空壁内流体速度与两壁间压力差成正比的线性模型和特征函数展开方法,建立了外壁上部开孔并带有内柱的圆筒结构对波浪绕射的解析解.通过数值计算研究了外壁开孔率的大小、圆筒与内柱半径之比、筒内水深等因素对圆筒上总的波浪作用力和圆筒周围波浪高度的影响.经数值研究发现随着外壁开孔率的增大圆筒迎浪端的波浪高度和圆筒结构上总的波浪力明显减小,外壁孔隙特性G虚部的增加对波高和波浪力的衰减也有一定的影响;增加圆筒内部的水深可减小圆筒周围的波浪高度,降低圆筒结构上的总波浪力. 相似文献
14.
波浪与外壁透空双方形沉箱相互作用 总被引：1，自引：1，他引：0
在线性波浪理论下,利用复合边界元素法(composite BEM)数值解析在等水深、规则波浪入射二种外壁透空双方形沉箱的无因次波力及Kd绕射分布图,并分别与其他研究者所作双圆筒内、外圆柱无因次波力及绕射分布图的计算结果进行比较,都说明本模式的合理性和可行性。在考虑不同透水参数下,分别计算波浪作用在内、外结构物的波力及沉箱四周绕射系数大小分布图。计算结果显示:波浪作用于外壁透空全透水双方形沉箱,外方柱无因次最大波力值会随着透水参数增加而降低;内方柱无因次最大波力值则随着透水参数增加而增加。本研究结果可供设计外海透水方形沉箱结构交互作用参考。 相似文献
15.
Diffraction of linear waves around a group of dual porous cylinders consisting of a thin and porous outer cylinder with an impermeable inner cylinder is investigated analytically based on the eigenfunction expansion method proposed by Spring and Monkmeyer [Spring BH, Monkmeyer PL. Interaction of plane waves with vertical cylinders. In: Proceedings 14th international coastal engineering conference. 1974. p. 1828–47] and further modified by Linton and Evans [Linton CM, Evans DV. The interaction of waves with arrays of vertical circular cylinders. Journal of Fluid Mechanics 1990;215:549–69]. The present formulation is an extension of the work of Wang and Ren [Wang KH, Ren X. Wave interaction with a concentric porous cylinder system. Ocean Engineering 1994;21(4):343–60], wherein; the interaction of linear waves with a single concentric porous cylinder system was studied. This paper aims at investigating the influence of multiple interactions between the cylinders in the group on the hydrodynamic wave forces, wave run-up and free-surface elevation in their vicinity. Further, the study focuses on the variation of the forces and run-up on the individual cylinders within the group compared to that on isolated cylinders. 相似文献
16.
The deployment of suitable configurations of mutually interacting floating bodies for efficiently controlling their hydrodynamic interactions towards the reduction of the wave drift forces and, thus, of the mooring lines’ loads, has, nowadays, gained a great scientific interest. In this paper, the hydrodynamic behaviour of a floating cylinder and a concentric annular flexible plate is analysed in the frequency domain aiming at the minimization of the drift forces acting on the cylinder by optimizing the flexural rigidity of the plate. The diffraction/radiation problem is solved using a higher-order boundary element method. The analysis is implemented assuming that both floating bodies oscillate freely in heave, while for the plate, flexible modes are, additionally, considered for describing its structural deformations. The required modes shapes are determined in vacuum (“dry” mode superposition approach) through analytical expressions. The flexural rigidity of the plate, D, is optimized at a specific wave number using a real-coded genetic algorithm. Initially, results are compared with numerical results of other investigators for the case of two rigid concentric floating cylinders. Next, extended results are presented, focusing on the effect of D, including its optimum value, on various physical quantities describing the behaviour of both the cylinder and the plate. Contrary to the isolated cylinder, the presence of the plate introduces sharp peaks in the variation pattern of the drift force of the cylinder, bounded at specific wave numbers, where resonance of the seiche mode of water motion in the annular cavity or of specific flexible modes of the plate occurs. However, by reducing D to its optimum value, the cylinder’s drift force obtains practically zero values at the target wave number, due to an efficient improvement of the wave field in the annular cavity around the cylinder. Moreover, a great reduction of the drift force compared to the isolated cylinder is achieved in the subsequent high frequency range. 相似文献
17.
The regular wave interaction with a twin concentric porous circular cylinder system consisting of an inner impermeable cylinder and an outer perforated cylinder was studied through physical model and numerical model studies. The experiments were carried out on the twin concentric cylinder model in a wave flume to study the wave runup and rundown at the leading and trailing edges of the perforated cylinder. It was found that the maximum wave runup on the perforated cylinder is almost same as the incident wave height. The experimental results were used to develop the predictive formulae for the wave runup and rundown on the perforated cylinder, which can be easily used for design applications. The wave runup profiles around the perforated cylinder for different values of ka and porosities were studied numerically using Green's Identity Method. The results of the numerical study are presented and compared with the experimental measurements. 相似文献
18.
Water wave interaction with a floating porous cylinder 总被引：1，自引：0，他引：1
The interaction of water waves with a freely floating circular cylinder possessing a side-wall that is porous over a portion of its draft is investigated theoretically. The porous side-wall region is bounded top and bottom by impermeable end caps thereby resulting in an enclosed fluid region within the structure. The problem is formulated based on potential flow and linear wave theory and assuming small-amplitude structural oscillations. An eigenfunction expansion approach is then used to obtain semi-analytical expressions for the hydrodynamic excitation and reaction loads on the structure. Numerical results are presented which illustrate the effects of the various wave and structural parameters on these quantities. It is found that the permeability, size and location of the porous region may have a significant influence on the horizontal components of the hydrodynamic excitation and reaction loads, while its influence on the vertical components in most cases is relatively minor. 相似文献
19.
The hydrodynamic performance of a dual cylindrical caisson breakwater (DCBW) formed by a row of caissons each of which consisting of a porous outer cylinder circumscribing an impermeable inner cylinder has been theoretically investigated. The theoretical formulation is based on the eigenfunction expansion method proposed by Spring and Monkmeyer (1974) which was further modified by Linton and Evans [Linton, C.M., Evans, D.V., 1990. The interaction of waves with arrays of vertical circular cylinders. Journal of Fluid Mechanics 215, 549–569] for an array of impermeable cylinders. The present formulation is an extension of the work of Wang and Ren [Wang, K.H., Ren, X., 1994. Wave interaction with a concentric porous cylinder system. Ocean Engineering 21(4), 343–360], wherein; the interaction of linear waves with a single concentric porous cylinder system was studied. In the present study, the formulation has been extended to the case of a group of porous dual cylinder system. Parametric studies are carried out to study the influence of porosity (G0) on the outer caisson, width of the doughnut chamber (a/b) and the angle of wave incidence on the variation in the hydrodynamic loading, wave run-up, free-surface elevation in its vicinity as well as the transmission on its lee-side. The importance of the presence of the inner cylinder in achieving the required hydrodynamic performance in terms of either protection or providing tranquility on its lee side keeping higher stability for the breakwater system is highlighted. 相似文献
20.
This paper deals with hydrodynamic forces of a single semisubmerged circular cylinder containing a concentric cylindrical hole constrained to move in a water domain of finite depth. The fluid domain is divided into inner and outer regions. The Laplace equations governing velocity potentials for the three regions are solved by separation of variables and expressed in terms of eigenfunctions of the resulting equations which satisfy appropriate boundary conditions. Continuity of pressure and velocity at the interface of the regions provides the necessary equations from which the velocity potentials, pressures and forces are obtained. Numerical results are plotted for added mass and damping coefficients for different draft-to-depth and radius-to-depth values and for various wave amplitudes. 相似文献