共查询到20条相似文献，搜索用时 31 毫秒
1.
In this paper, the interaction of flexural-gravity waves with a submerged disc is studied. The problem is solved by transforming it into a two-dimensional hypersingular integral equation. Initially, wave scattering problem is studied followed by radiation and radiation-diffraction problems. The effects of the rigidity of the ice cover and submergence depth of the rigid disc are investigated for all the three cases. It is observed that the submergence of a rigid disc causes significant changes in the scattered as well as radiated wave profiles. However, the presence of the rigid disc creates high-frequency resonance. The present study appears to be useful for understanding the nature of the flow physics in presence of a rigid disc beneath the ice-covered surface. 相似文献
2.
The Sonobuoy Dynamic Simulation (SDS) computer program is designed to analyze the three-dimensional, nonlinear dynamic behavior of free-drifting cable-suspended hydrophone systems. It will also simulate other marine systems composed of series-connected cables and rigid bodies, including cable-towed bodies and autonomous vehicles. Models of directed wave fields and three-dimensional currents allow simulation of semi-immersed objects. The present study validates the rigid body models by simulating a helicopter-like free-falling oceanographic vehicle. We describe detailed SDS models of the vehicle body and wings and compare our calculations of vehicle rotation and descent rates with laboratory measurements for various wing attachment angles. SDS reproduced the essential behavior of the laboratory vehicle and matched the published rates to within 10%. 相似文献
3.
This paper presents the use of a modular raft Wave Energy Converter (WEC)-type attachment at the fore edge of a rectangular Very Large Floating Structure (VLFS) for extracting wave energy while reducing hydroelastic responses of the VLFS under wave action. The proposed modular attachment comprises multiple independent auxiliary pontoons (i.e. modules) that are connected to the fore edge of the VLFS with hinges and linear Power Take-Off (PTO) systems. For the hydroelastic analysis, the auxiliary pontoons and the VLFS are modelled by using the Mindlin plate theory while the linear wave theory is used for modelling the fluid motion. The analysis is performed in the frequency domain using the hybrid Finite Element-Boundary Element (FE-BE) method. Parametric studies are carried out to investigate the effects of pontoon length, PTO damping coefficient, gap between auxiliary pontoons, and incident wave angle on the power capture factor as well as reductions in the hydroelastic responses of the VLFS with the modular attachment. It is found that in oblique waves, the modular attachment comprising multiple narrow pontoons outperforms the corresponding rigid attachment that consists of a single wide pontoon with respect to the power capture factor and the reduction in the deflection of the VLFS. In addition, it is possible to have a considerable gap between pontoons without significantly compromising the effectiveness of the modular attachment. 相似文献
4.
AbstractThis paper presents rocking vibrations of a rigid foundation resting on a multi-layered poroelastic half-space. The foundation is assumed to be rigid and massless, and subjected to a time–harmonic moment. In addition, each layer of the multi-layered half-space is governed by Biot’s theory of poroelastodynamics. The contact surface between the foundation and the layered half-space is smooth, and either fully permeable or impermeable. This dynamic interaction problem is studied by employing a discretization technique and an exact stiffness matrix scheme. Comparisons with existing solutions on rocking vibrations of rigid foundations on elastic and poroelastic media are shown to verify the accuracy of the present scheme. Selected numerical results on rocking compliances of rigid foundations of various shapes and mudmat foundations are presented. In addition, a dynamic interaction problem involving closely spaced foundations under rocking vibrations is also presented to demonstrate the applicability of the present solution scheme. 相似文献
5.
对称式布置锚链系统的线性化处理 总被引：6，自引：2，他引：6
用悬链线方程求解了不同锚链状态的锚链力 ,并用多项式回归了锚链力与锚固点位移的关系 ,由此求得锚链恢复力刚度系数。分析了对称式布置锚链系统的非线性程度 ,阐述对称式布置锚链系统所提供的恢复力作线性化处理的可行性及方法 ,并给出了对称布置锚链系统的线性刚度矩阵。为各类受对称式布置锚链系统约束的浮动结构物的动力分析提供了理论依据 相似文献
6.
In this paper a numerical approach to the grounding problem takes place. It aims to show the contribution of the energy dissipated in the structure due to elasto-plastic deformation. The analytical methods developed until now, neglect this amount of energy, since they are simulating the vessel as a rigid beam. A tanker vessel is modelled with the Finite Element Package ABAQUS and energy conservation during a grounding scenario on rigid slope takes place. The results are presented both analytically and numerically and comparison in the energy quantities is shown and discussed. 相似文献
7.
Interaction of solitary waves with emergent, rigid vegetation 总被引：3，自引：0，他引：3
In this study, solitary wave interaction with emergent, rigid vegetation was studied numerically and experimentally. Laboratory experiments were carried out in a wave flume with vegetation models of different lengths and porosities; the Boussinesq equations with the effects of the vegetation being modeled by a quadratic drag law are used to simulate the wave scattering by and the wave propagation through vegetation. Effects of incident wave height, vegetation density, and vegetation length are discussed. An empirical expression for the mean drag coefficient of emergent, rigid vegetation is presented and compared with other available data. The results are useful for studying tsunami hazard mitigation by coastal forests. 相似文献
8.
Michael Stiassnie 《Applied Ocean Research》1980,2(3):107-111
A simple mathematical model, based on the solution of the two-dimensional problem of a vertical floating plate and on rigid body dynamics, is used to investigate the influence of different characteristics (such as mass, draft and anchoring) on the breakwater performance. The results include information about the transmission coefficient as well as about the plate displacement and anchoring forces, as functions of the plate and incident wave parameters. 相似文献
9.
In this work, the problem of optimizing the shape of a thin floating plate (sometimes called a dock) to maximize radiation damping is investigated. The plate is modeled with zero draft and floats on the surface of an irrotational, incompressible ocean of infinite extent. For simplicity, only rigid heave motions are considered. The flow problem is analyzed using the Chen and Mei variational principle wherein the potential field inside a hemisphere surrounding the plate is represented using a spherical harmonic expansion and matched on the hemisphere to an outer field described by distributing sources on the hemisphere. The plate shape is parameterized using a Fourier series which is suitable for use with the variational principle. Gradients of the damping coefficient with respect to the shape parameters are developed by solving an adjoint flow problem whose potential is shown to be a scalar multiple of the original flow potential. Optimal plate shapes are determined using the well-known optimization code NPSOL which makes use of the damping coefficient calculation and gradients. 相似文献
10.
Effect of ice cover on oscillations of fluid in a closed basin 总被引：1，自引：0，他引：1
I. V. Sturova 《Izvestiya Atmospheric and Oceanic Physics》2007,43(1):112-118
Within the framework of the linear theory of long waves, the problem of the effect of ice cover on seiche oscillations of fluid in a two-dimensional constant-depth basin is solved. The eigenfrequencies and eigenfunctions of seiche oscillations are obtained for different boundary conditions at ice edges: rigid coupling and free edges. The forced oscillations of fluid and ice under the action of a moving disturbance of atmospheric pressure are investigated. The change in the stress of ice bending is considered and it is shown that the coast ice can be broken. 相似文献
11.
On the heave radiation of a rectangular structure 总被引：2，自引：0，他引：2
Jaw-Fang Lee 《Ocean Engineering》1995,22(1)
In this paper, an analytic solution to the heave radiation problem of a rectangular structure is presented. To solve the problem analytically, the nonhomogeneous boundary value problem is linearly decomposed into homogeneous ones, which can be readily solved. To provide further comparisons to the present analytic solution, a boundary element method is also presented to solve the problem. The present analytic solution is compared with the result by Black et al. [(1971)] Radiation and scattering of water waves by rigid bodies. J. Fluid Mech. 46, 151–164], and the boundary element solution, and the comparisons show very good agreements. Upon examination of the present analytic solution, it is shown that the solution satisfies the nonhomogeneous boundary condition in a sense of series convergence. Using the present analytic solution, the generated waves, the added mass and the radiation damping coefficients, as well as the hydrodynamic effects of the submergence and the width of the structure, are investigated. 相似文献
12.
A barotropic model on the -plane is used to consider the problem of mushroom-like flow formation. The method of contour dynamics is applied to investigate the evolution of a bounded jet flow whose linear axi is identified with a rigid wall. The quasi-stationary form of the flow's head part and the velocity of its propagation have been found. The stability of the stationary solution has been studied.Translated by V. Puchkin. 相似文献
13.
The linear time-dependent motion of a floating elastic or rigid body, subject to some initial displacement, which subsequently evolves freely is considered. The solution is derived by a Fourier transform and by the generalized eigenfunction method. Compared to other solutions, such as the Cummins method, the present solution requires neither time-stepping nor high-frequency calculations. A series of new identities for the frequency-domain problem are also presented. The Fourier transform solution allows an approximate solution to be calculated by an expansion over the complex resonances known as the singularity expansion method. Simple expressions for the singularity expansion method approximation are given. The method is illustrated with a series of numerical calculations. 相似文献
14.
An exact two dimensional hydrodynamic analysis based on the linear potential theory is introduced to study the free liquid sloshing characteristics of transverse oscillation modes in a non-deformable horizontal circular cylindrical baffled container which is filled to an arbitrary depth with an inviscid incompressible liquid. Three common baffle configurations are considered: a pair of internal rigid horizontal side baffles of arbitrary extension installed at the free liquid surface, and a surface-piercing or a bottom-mounted vertical rigid baffle of arbitrary extension positioned along the tank vertical axis of symmetry. The problem solution is obtained by the method of successive conformal coordinate transformations, leading to standard truncated matrix eigenvalue problems on simple (rectangular) regions which are then solved numerically for the resonance eigen-frequencies. The effects of liquid fill level, baffle arrangement and length upon the three lowest antisymmetric and symmetric sloshing frequencies and the associated hydrodynamic pressure mode shapes are examined. Also, convergence of the adopted approach with respect to the fill condition, and baffle type/extension is discussed. Limiting cases are considered and the validity of results is established in comparison with the data in the existing literature. 相似文献
15.
Effects of a cover layer on wave-induced pore pressure around a buried pipe in an anisotropic seabed 总被引：1，自引：0，他引：1
In engineering practice, a cover layer of coarser material has been used to protect a buried marine pipeline from wave-induced seabed instability. However, most previous investigations of the wave–seabed–pipe interaction problem have been concerned only with such a problem either in an isotropic single layer or a rigid pipe. This paper proposes a two-dimensional finite element model by employing the principle of repeatability to investigate the wave-induced soil response around a buried pipeline. The elastic anisotropic soil bahavior and geometry of cover layer are included in the present model, while the pipe is considered to be an elastic medium. This study focuses on the effects of a cover layer (including thickness B and width W of the cover layer) on the wave-induced pore pressure in the vicinity of a buried pipeline. 相似文献
16.
HUANG Yuying 《中国海洋工程》2000,14(1):1-13
—As a further development of the authors'work(Huang and Qian,1993),in this paper a newnumerical method based on the time domain boundary element technique is proposed for solving fluid-sol-id coupling problems,in which a rigid body impacts normally on the calm surface of a half-space fluid.Afundamental solution to the half-space potential flow problem is first derived with the method of images.Then,an equivalent boundary integral equation in the Laplace transform domain is established by meansof Green's second identity.Through the inverse Laplace transform and discretization in both time andboundary of the fluid region,the numerical calculation for the problem under consideration has been car-ried out.Several examples demonstrate that the present method is more efficient than existing ones,fromwhich it is also seen that the shape of the impacting body has a considerable effect on the total impactforce. 相似文献
17.
Christopher J. Damaren 《Ocean Engineering》2010,37(2-3):252-261
In previous work, the problem of optimizing the shape of a thin floating plate to maximize radiation damping was investigated. The plate was modelled with zero draft and floated on the surface of an irrotational, incompressible ocean of infinite extent. For simplicity, only rigid heave motions were considered and the damping coefficient at one wave number was maximized. In the present work, the hydroelastic properties of the optimized plate are determined and compared with those of circular and square plates. The added mass, damping, and diffraction force coefficients in each mode are determined as a function of wave number. The amplitude responses of the plate deflection and bending moments are also presented. The finite element method is used to determine the vibration mode shapes and the flow problem is analysed using the Chen and Mei variational principle wherein the potential field inside a hemisphere surrounding the plate is represented using a spherical harmonic expansion and matched on the hemisphere to an outer field described by distributing sources on the hemisphere. 相似文献
18.
A three-dimensional coupled analysis of the interaction of a floating buoy and its mooring is studied. External loads include hydrodynamic forces, tether tensions, wind loads and system weight and buoyancy. Nonlinearities include large rotational and translational motions and non-conservative fluid loads. The mooring problem is formulated as a nonlinear two-point-boundary-value-problem. At each instant in time, the mooring problem is solved by direct integration using a successive iterative algorithm to satisfy boundary conditions. Buoy kinetic and kinematic equations are derived assuming large angles represented by Euler parameters. Coupling between the buoy and the mooring is enforced by matching the velocities of the tether and buoy at the attachment point. A predictor-corrector coupling algorithm is used with multiple sizes of time steps used to provide stability for the separate mooring and buoy models. Numerical results are compared to experimental responses of three types of buoys (sphere, spar and disc) subject to both regular and irregular waves. 相似文献
19.
In this paper, the problem of incident waves propagating over a submerged poro-elastic structure is studied theoretically. A linear wave theory is used to describe the wave motion. The submerged poro-elastic structure is modeled based on Biot's theory, in which the fluid motion is described using the potential wave theory of Sollitt and Cross (1972). In the present approach, the problem domain is divided into four subregions. Using general solutions for each region and matching dynamic and kinematic conditions for neighboring regions, analytic solutions are derived for the wave fields and poro-elastic structure. The present analytic solutions compare very well with simplified cases of impermeable, rigid structures, and with those of porous structures. Using the present analytic solution, the effects of a poro-elastic submerged structure on waves are studied. The results show that softer poro-elastic structures can induce higher reflection and lower transmission from incident waves. For low permeability conditions, the elasticity of the structure can induce resonance, while higher permeability can depress the resonant effects. 相似文献
20.
植物激素对海带配子体克隆附着的影响 总被引：3，自引：0，他引：3
实验研究 2 ,4 - D、KT、IAA、NAA四种植物激素对海带配子体克隆附着的影响。结果表明 :2 ,4 - D对附着有较明显的促附着作用 ,最有效浓度为 2 .5mg/L 和 5mg/L,其 4 h的附着率分别是对照的 2 .79倍和 2 .95倍 ;KT的作用较复杂 ,在浓度为 1mg/L 时 ,对附着有明显的促进作用 ,其 4 h的附着率是对照的 2 .3倍 ;IAA对配子体附着没有明显的促进或抑制作用 ;NAA对附着有抑制作用 ,浓度越高 ,抑制作用越强。 相似文献