共查询到20条相似文献，搜索用时 15 毫秒
1.
The two-dimensional problems concerning the interaction of linear water waves with cylinders of arbitrary shape in two-layer deep water are investigated by use of the Boundary Integral Equation Method (BIEM). Simpler new expressions for the Green functions are derived, and verified by comparison of results obtained by BIEM with those by an analytical method. Examined are the radiation and scattering of linear waves by two typical configurations of cylinders in two-layer deep water. Hydrodynamic behaviors including hydrodynamic coefficients, wave forces, reflection and transmission coefficients and energies are analyzed in detail, and some interesting physical phenomena are observed. 相似文献
2.
A finite-volume method (FVM) using a multi-block grid technique has been applied to investigate the hydrodynamic coefficients and to categorize the two-dimensional flow pattern around a pair of adjacent cylinders (known here after as double cylinders). Matching grids were used at the interface between blocks (cylinders), and the boundary conditions are imposed around the periphery to exchange physical values across the interface. To validate the developed numerical method, a case with laminar viscous flow around a single cylinder was carried out, the results showed good agreement compared to previously published data. Hydrodynamic coefficients, Strouhal number, and stagnation point change were thoroughly investigated as a function of the separation between the two cylinders. It is found that the changes of hydrodynamic coefficients due to variations in separation are well characterized by the five different vortex flow patterns, which can also be used to explain the flow and vortex pattern around the double cylinders. 相似文献
3.
Shen Wang 《Ocean Engineering》1981,8(6):599-621
The radiation problem for two parallel-spaced cylinders is studied. The solution is expressed explicitly in terms of well-behaved convergent series with elementary functions, which are convenient for numerical computation and readily applicable for two-dimensional two-body potential problems. The added mass and damping coefficients together with the phase angles of radiated wave potentials for the forced heave and sway motions of two identical submerged cylinders are presented. The results are useful for determination of the hydrodynamic properties of multi-hull semi-submersibles. In view of the close relationship between a radiation and a scattering problem, the application of the results to the problem of energy extraction from water waves is also noted. 相似文献
4.
The interaction of water waves with multiple circular cylinders is analysed briefly in this paper.The formula obtained by Linton and Evans is improved to introduce a relation of phase between cylinders.The condition for the existence of the solution has been proved.The numerical results are compared with ana-lytic solutions(Linton and Evans),numerical solutions and experimental data(Isaacson),and good agree-ment has been found. 相似文献
5.
S.J. Benno Brenninkmeyer 《Marine Geology》1976,20(2):117-128
A new instrument — an almometer — has been developed which measures, instantaneously and continuously, changes in the vertical density distribution of sediment. The almometer consists of two acrylic cylinders, one contains a fluorescent lamp, the other 64 photo-electric cells placed at 1 - or 2-cm intervals. These two tubes are anchored perpendicular to the bottom 30 cm apart.The amount of sediment that can be measured ranges from 10 to 500 g of sediment per liter of water. Calibration shows that differences in sediment size or mineralogy have little effect on the concentration resistance relationship if the size mean is within the sand range and the sediment is not monomineralic. 相似文献
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摆式波能装置具有结构简单和转化效率高等特点,本文应用AQWA 软件基于势流理论对相交圆柱摆式波能装置进行了数值模拟研究,分析了轴间距比、结构阻尼、净浮力比、水深、波浪特性及吃水深度等主要参数对相交圆柱摆式波能装置俘获效率的影响,并与直板摆式波能装置的俘获效率进行了对比。结果表明：同样条件下,相交圆柱摆式波能装置往往比直板摆式波能装置的俘获效率更高;在研究范围内,轴间距比越大俘获效率越高;潮汐导致的水深变化对底铰摆式波能装置的俘获效率具有明显的影响,在工程应用中应采取适当的措施进行处理。 相似文献
8.
A series of experimental studies about the force of internal solitary wave and internal periodic wave on vertical cylinders have been carried out in a two-dimensional layered internal wave flume. The internal solitary waves are produced by means of gravitational collapse at the layer thickness ratio of 0.2, and the internal periodic waves are produced with rocker-flap wave maker at the layer thickness ratio of 0.93. The wave parameters are obtained through dyeing photography. The vertical cylinders of the same size are arranged in different depths. The horizontal force on each cylinder is measured and the vertical distribution rules are researched. The internal wave heights are changed to study the impact of wave heights on the force. The results show that the horizontal force of concave type internal solitary wave on vertical cylinder in the upper-layer fluid has the same direction as the wave propagating, while it has an opposite direction in the lower-layer. The horizontal force is not evenly distributed in the lower fluid. And the force at different depths increases along with wave height. Internal solitary wave can produce an impact load on the entire pile. The horizontal force of internal periodic waves on the vertical cylinders is periodically changed at the frequency of waves. The direction of the force is opposite in the upper and lower layers, and the value is close. In the upper layer except the depth close to the interface, the force is evenly distributed; but it tends to decrease with the deeper depth in the lower layer. A periodic shear load can be produced on the entire pile by internal periodic waves, and it may cause fatigue damage to structures. 相似文献
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平面波与圆柱群的相互作用分析 总被引：1，自引：1，他引：0
简要分析了水波与圆柱群的相互作用问题。导入柱间的相位关系,改进了文献[2]中的公式,并且证明在柱间互不连接条件下,解是存在的。数值结果与文献[2]的分析解以及文献[6]的数值解和实验数据有很好的一致性。 相似文献
10.
基于Fluent流体计算平台,运用大涡模拟方法对亚临界雷诺数Re=3900下“X”形排列五圆柱体结构群三维绕流特性进行研究,主要分析来流攻角α与间距比L/D两个关键参数对五圆柱体结构群的尾流区三维涡结构演化与流体力系数的影响,并揭示其内在流动互扰机理。研究表明:来流攻角和间距比的变化对五圆柱体结构群流动控制及互扰效应的影响显著。在小间距比工况下,观察到柱体群间隙区域内流体高速流动的现象,导致五圆柱体之间的互扰作用十分强烈。间隙流对中间圆柱体和下游圆柱体有较强的冲击作用,对其表面的流体力分布特性有显著的影响。另外,大间距比工况下,当α=0°与L/D≥5.0工况时,柱体群尾流效应强于其间隙流效应。当α=22.5°与L/D=7.0时,位于下游与中间处的圆柱体流体绕流特性存在较大差异。而当α=45°与L/D≥6.0时,位于上游与中间处的圆柱体尾流区均会产生正负交替的漩涡结构。 相似文献
11.
A review of vortex shedding research and its application 总被引：1，自引：0，他引：1
Roger King 《Ocean Engineering》1977,4(3):141-171
This paper is a review of research work with cylinders in steady currents. The emphasis is mainly on cylinders in water, particularly the research undertaken at BHRA and its general application. Comparisons are made with the work of other authors for both water and air flow and over 60 references are reviewed. The mechanisms of flow-excited oscillations are discussed for isolated vertical and inclined cylinders. The effects of length/diameter ratio, cylinder surface roughness and channel blockage are presented. Wake interactions caused by cylinder-cylinder and cylinder-splitter arrangements are detailed. The results of tests with pane and three-dimensional frames are described and quantified in terms of isolated cylinder data.The paper closes with a section describing methods of avoiding oscillations by calculation at the design stage or by the use of clamp-on devices for completed structures in water flow. 相似文献
12.
A numerical model is presented to predict the interaction of multidirectional random surface waves with one or more rectangular submarine pits. The water depth is assumed uniform and the method involves the superposition of diffraction solutions based on linearized shallow water wave theory obtained by a two-dimensional boundary integral approach. The incident wave conditions are specified using a discrete form of the Mitsuyasu directional spectrum. The present numerical model has been validated through comparisons with previous theoretical results for regular waves. Good agreement was obtained in all cases. Based on these comparisons it is concluded that the present numerical model is an accurate and efficient tool to predict the wave field around multiple submarine pits and navigation channels in many practical situations. 相似文献
13.
C.Z. Wang 《Ocean Engineering》2010,37(4):400-417
Fully nonlinear interactions between water waves and vertical cylinder arrays in a numerical tank are studied based on a finite element method (FEM). The three-dimensional (3D) mesh is constructed through an extension of a 2D Delaunay surface grid along the vertical line. The velocity potential is obtained by solving a linear matrix system of FEM, and a difference scheme is then used to calculate the velocity on the free surface to track its movement. Waves and hydrodynamic forces are obtained for both bottom mounted and truncated cylinders. The simulations have provided many results to show the nature of mutual interference between cylinders in arrays and its effects on waves and forces at the nearly trapped mode frequency. The effect of the tank wall on waves and forces has been investigated, and the nonlinear features of waves and forces have also been discussed. 相似文献
14.
沿海城市工业迅速发展所造成的酸雾问题已引起了国内外环保部门的高度重视,如美国加州南部沿岸多次出现酸雾的pH值在3.0以下,最低为1.63。青岛地区1983年观测到酸雾pH值为4.22-4.52,而我们在1991年6-7月份的观测表明,pH平均为3.84,最低(娄山化工厂)为1.7,酸度有显著增强的趋势。近几年来青岛市酸雨的pH值平均为4.42,最小为3.48,可以看出,酸雾的酸性远较酸雨为强。因此城市酸雾的研究更为重要和迫切。
海雾是山东半岛沿海城市的主要气候特点,青岛是海雾发生的中心,大雾年平均为61.2天,轻雾106.9天,每年4-7月为海雾盛行期。海雾总是发生在逆温层结的大气中,在稳定的逆温层下,低空所产生的污染物不容易扩散到高空,使得排放的大量污染物质聚集在低层,与雾水混合酸化形成酸雾。
夏季的海雾多为平流雾,青岛海雾季节平流雾占总雾出现率的70.9%-80.4%(王彬华,1983;赵永平等,1994),因此研究平流冷却雾的生成与发展,以及雾发生条件下的大气污染与雾水酸化是研究酸雾的主要内容。本文在考虑了湍流交换、平流传输、长波辐射冷却、重力沉降和化学转换等过程的基础上,建立了二维平流辐射雾物理化学模式,模拟了海雾的形成发展、登陆和酸化等物理化学过程,计算了夏季二氧化硫的扩散,研究了海雾发生后青岛市区酸雾的二维分布,其结果与实测数据基本一致。这对于研究酸雾的形成机理,了解酸雾的发生背景,预测酸雾的未来发展和科学地制定酸雾的防治对策具有理论研究意义和实用价值。 相似文献
15.
The hydrodynamic interference phenomena arising from multiple two-dimensional horizontal cylinders interacting with obliquely incident linear monochromatic waves are treated. A finite element method incorporating radiation boundary dampers is employed to solve the corresponding diffraction/radiation boundary value problems, where flexural mode responses are assumed. Both extreme cases of a rigidly connected catamaran and freely floating cylinders are studied in detail. Numerical results of both cases compare closely with those obtained by the method of multipoles. Important interference phenomena are identified which would assist in the design of facilities and operations involving multiple structures. 相似文献
16.
Following the successful experiences of solving water wave scattering problems for multiple impermeable cylinders by the authors' group, we extend the null-field integral formulation in conjunction with the addition theorem and the Fourier series to deal with the problems of surface-piercing porous cylinders in this paper. In the implementation, the null-field point can be exactly located on the real boundary free of calculating the Cauchy and Hadamard principal values, thanks to the introduction of degenerate kernels (or separable kernels) for fundamental solutions. This method is a semi-analytical approach, since errors attribute from the truncation of the Fourier series. Not only a systematic approach is proposed but also the effect on the near-trapped modes due to porous cylinders and disorder of layout is examined. Several advantages such as mesh-free generation, well-posed model, principal value free, elimination of boundary-layer effect and exponential convergence, over the conventional boundary element method (BEM) are achieved. It is found that the disorder has more influence to suppress the occurrence of near-trapped modes than the porosity. The free-surface elevation is consistent with the results of William and Li and those using the conventional BEM. Besides, the numerical results of the force on the surface of cylinders agree well with those of William and Li. Besides, the present method is a semi-analytical approach for problems containing circular and elliptical shapes at the same time. 相似文献
17.
The linear water wave scattering and radiation by an array of infinitely long horizontal circular cylinders in a two-layer fluid of infinite depth is investigated by use of the multipole expansion method. The diffracted and radiated potentials are expressed as a linear combination of infinite multipoles placed at the centre of each cylinder with unknown coefficients to be determined by the cylinder boundary conditions. Analytical expressions for wave forces, hydrodynamic coefficients, reflection and transmission coefficients and energies are derived. Comparisons are made between the present analytical results and those obtained by the boundary element method, and some examples are presented to illustrate the hydrodynamic behavior of multiple horizontal circular cylinders in a two-layer fluid. It is found that for two submerged circular cylinders the influence of the fluid density ratio on internal-mode wave forces is more appreciable than surface-mode wave forces, and the periodic oscillations of hydrodynamic results occur with the increase of the distance between two cylinders; for four submerged circular cylinders the influence of adding two cylinders on the wave forces of the former cylinders is small in low and high wave frequencies, but the influence is appreciable in intermediate wave frequencies. 相似文献
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Experimental results are reported on the wave reflection from and transmission through one row or two rows of closely spaced rectangular cylinders. An empirical expression is proposed for the friction factor which models the head loss due to closely spaced rectangular cylinders. Algebraic expressions are presented to calculate the reflection and transmission coefficients of regular waves for a single slotted wall or double slotted walls. The model is validated by the published and present experimental results. The proposed method can be used for the preliminary design of slotted-wall breakwaters. 相似文献
20.
波浪的方向分布对波浪的传播及其与工程结构物的作用都具有明显影响，目前现有的研究大多是基于单向波浪进行的。为了研究方向分布对群墩结构上的爬高影响，基于规则波浪与群墩作用的理论解，结合多向不规则波浪的造波方法，建立了多向不规则波浪与群墩作用的计算模型，同时进行了物理模型试验对模型的有效性进行了验证。系统地对群墩周围及表面上的波浪爬高进行了计算分析，结果表明，方向分布对波浪爬高具有较大的影响，且不同位置处的影响并不相同，在实际的工程设计中如果按照单向波浪计算，可能低估或者高估群墩周围的爬高。 相似文献