箱式超大型浮体结构在规则波中的水弹性响应研究

利用三维线性水弹性理论研究了箱式超大型浮体结构在正弦规则波中的动力响应，用Bernoulli-Euler梁解析解计算结构在真空中的动力特性，用弹性体三维势流理论计算结构的水动力系数，浮体结构在单位波幅规则波中的刚体运动幅值与DNV／WADAM程序的计算结果进行了比较，并给出了垂向弯曲模态的位移，弯矩随波浪频率的变化规律，由于箱式浮体结构的低阶固有频率很低，相应的弹性振型的响应与刚体运动耦合，结构在波浪中没有发现明显的低阶弹性模态谐振。     

应用比例边界有限元法求解多种二维浮体水动力特性

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。     

筏式波浪能发电装置浮体水动力相互作用与能量俘获研究

基于三维势流理论,建立筏式波浪发电装置多浮体水动力模型。利用AQWA水动力软件研究多浮体水动力相互作用对发电装置浮体单元水动力系数的影响;将能量转换系统等效成刚度-阻尼模型后,对其进行不规则波时域模拟,对比分析方向谱和频率谱波浪模型对波浪发电装置能量吸收的影响。结果表明:浮体之间的水动力相互作用对浮体单元纵荡方向上的附加质量与辐射阻尼系数有明显的影响,对垂荡和纵摇方向上的水动力系数影响较小;不同的波浪模型下,能量俘获功率有着较大的差别,特别是在迎浪状态下。     

用直接法分析超大型浮体的水弹性响应

探讨了浮舟桥型超大型浮体结构的水弹性响应分析问题。将超大型浮体结构简化成弹性平板模型,用压力分布法计算流体压力,用直接法计算流体-结构系统,给出了它们的数学计算模型。计算表明本计算方法和程序是正确的,并能保证充分的精度,进而计算了更大尺度的超大型浮体,分析了波长、波向等对响应振幅的影响。     

近距离靠泊条件下钻井支持平台与生产平台相对运动研究

为了探究钻井支持平台及生产平台组成的复杂多浮体耦合系统在近距离靠泊状态下的相对运动情况,基于多浮体三维势流理论及时域耦合分析方法,计算了半潜式钻井支持平台和张力腿(TLP)生产平台耦合系统在三种不同环境方向,即迎浪、斜浪、横浪下两平台的相对运动和平台间连接栈桥的运动响应,为平台运动分析和栈桥设计提供指导。并将计算结果与水池模型试验结果进行对比,验证了数值方法的可靠性。为进一步了解多浮体间耦合水动力的影响,计算了该近距离靠泊系统在不考虑浮体间水动力相互干扰下的运动响应。研究表明除在横浪作用外,其他环境条件下的多浮体水动力干扰作用明显,对浮体运动响应的影响不可忽略,且有效波高在小范围内变化时,平台间的相对运动幅值基本与其呈线性关系。     

并联式后弯管波力发电浮体模型性能试验研究

对并联式后弯管波力发电浮体模型的波能转换性能和锚泊力进行了试验研究。结果表明并联式后弯管浮体模型的最佳响应周期基本不变，各单元浮体性能略有差异，位于中间的单元浮体性能略低于两侧的浮体，波能转换性能随浮体数量增加而下降，多点系泊使并联式后弯管装置效率提高。并联式后弯管波力发电装置采用标准化单元设计，灵活组成不同装机容量的装置，将大大降低锚泊系统、海底电缆系统的费用。     

两层流体中矩形箱浮体的附加质量和阻尼系数

研究了两层流体中矩形箱浮体的辐射问题。基于特征函数匹配理论,针对矩形箱浮体的三种振荡运动模式(横荡、垂荡和横摇),建立两层流体中矩形箱浮体辐射势的求解方法,导出矩形箱浮体附加质量和阻尼系数的计算公式。对所建立的求解模型进行了数值计算分析,结果表明在矩形箱浮体的某个振荡频率范围内,流体的分层效应对其附加质量和阻尼系数有显著影响的。     

不同干结构模型对箱式超大型浮体结构水弹性响应的影响

三维线性水弹性力学利用结构在真空中弹性振型的正交性 ,对结构振动进行模态分析 ,用弹性体三维势流理论计算结构的水动力系数。因此 ,结构的干模态计算是十分重要的。应用三维线性水弹性理论研究箱式超大型浮体结构在波浪中的动力响应时 ,分别采用梁模型和三维空间有限元模型计算结构的干模态 ,并且采用同样的水动力模型 (弹性体三维势流理论 )研究了不同干结构模型对结构水弹性响应的影响     

多点系泊下后弯管波力发电浮体模型试验研究

在大型造波水池中，对最佳后弯管浮体模型3－3，进行了多点系泊下浮体模型试验研究。测定了该模型在不同系泊条件下，气室平均输出气流功率随波周期的变化曲线NA－T，最大锚泊力与入射波高之比随波周期的变化曲线Fmax/Ho-T和最大纵荡距离与入射波高Ho之比随波周期变化曲线Xmax/Ho-T。选定L型链三点系泊为最佳系泊方案。进行了不同喷嘴比的性能试验和不类来波方向的试验，测定了浮体波能转换性能、最大锚泊力、最大纵荡距离随来波方向的变化。     

箱式超大型浮体的水弹性模型试验

近年来，超大型浮体VLFS(Very Large Floating Structure)越来越受到人们的关注和重视。VLFS可以用作开发海洋资源的平台和海上军事基地等，具有很高的经济和军事价值。以海上机场VLFS为研究对象和试验模拟原型，进行了箱式VLFS在波浪作用下的水弹性模型试验，研究了波浪的浪向、周期和水深对VLFS水弹性性能的影响。     

Dual floating breakwaters

A numerical model is developed to investigate the behavior of a pair of flexible, floating breakwaters consisting of complaint, beam-like structures anchored to the sea bed. Each structure is kept under tension by a small buoyancy chamber at the tip, additional stiffness in each case is provided by mooring lines attached to the buoyancy chamber. The fluid motion is idealized as linearized, two-dimensional potential flow and the equation of motion of each breakwater is taken to be that of a one-dimensional beam of uniform flexural rigidity and mass per unit length subjected to a constant axial force. The boundary integral equation method is applied to the fluid domain. Modifications are made to the basic formulation to account for the zero thickness of the idealized structures, and the dynamic behavior of the breakwaters is described through an appropriate Green's function. Numerical results are presented which illustrate the effects of the various wave and structural parameters on the efficiency of the two-breakwater systems as a barrier to wave action. It is found that by adjusting the spacing between the breakwaters acceptable wave reflection characteristics may be obtained even with relatively flexible structures.     

浮式塔的动力计算

采用频域二阶摄动法研究了浮式塔在给定环境条件下的动力响应.计算了浮式塔在不规则波上的一阶运动响应函数和运动谱以及张力谱,同时进行了相应的模型试验.由结果的比较可以看出,试验结果与理论方法计算得到的结果吻合较好.计算结果表明,波浪的二阶作用对浮式塔的低频纵荡有影响.计算结果与试验结果的比较说明频域二阶摄动法可以用于浮式塔的动力分析.     

Vertical membrane floating breakwater

The basic purpose of any breakwater is to protect a harbor, moored vessels or an offshore structure from excessive incident wave attack. Breakwater can be classified as either fixed structures or floating ones. The vertical membrane floating breakwater which will be introduced in this paper belongs to the latter.     

Dual pontoon floating breakwater

The hydrodynamic properties of a dual pontoon floating breakwater consisting of a pair of floating cylinders of rectangular section, connected by a rigid deck, is investigated theoretically. The structure is partially restrained by linear symmetric moorings fore and aft. The fluid motion is idealized as linearized, two-dimensional potential flow and the equation of motion of the breakwater is taken to be that of a two-dimensional rigid body undergoing surge, heave and pitch motions. The solution for the fluid motion is obtained by the boundary integral equation method using an appropriate Green's function. Numerical results are presented which illustrate the effects of the various wave and structural parameters on the efficiency of the breakwater as a barrier to wave action. It is found that the wave reflection properties of the structure depend strongly on the width, draft and spacing of the pontoons and the mooring line stiffness, while the excess buoyancy of the system is of lesser importance.     

Reduction of hydroelastic responses of a very-long floating structure by a floating oscillating-water-column breakwater system

The hydroelastic responses of a very-long floating structure (VLFS) placed behind a reverse T-shape freely floating breakwater with a built-in oscillating water column (OWC) chamber are analyzed in two dimensions. The Bernoulli–Euler beam equation is coupled with the equations of rigid and elastic motions of the breakwater and the VLFS. The interaction of waves between the floating rigid breakwater and the elastic VLFS is formulated in a consistent manner. It has been shown numerically that the structural deflections of the VLFS can be reduced significantly by a suitably designed reverse T-shape floating breakwater.     

气浮结构相似性分析

提出了有关气浮结构的环境压力相似判据问题,指出了在模型试验时要达到完全相似的困难。计算结果表明,对尺度比为0．1的模型,若不考虑环境压力的相似,恢复力矩的误差可接近50％。根据4筒和25筒气浮结构的计算结果,给出了将实验结果转换到原型的修正方法。     

The hydrodynamics of thin floating plates

The radiation and diffraction problems are considered in the frequency domain for a thin elastic plate of rectangular planform floating in an irrotational, incompressible ocean of infinite depth. The inner potential field inside a hemisphere surrounding the plate is represented using a spherical harmonic expansion which suits the geometry and zero-draft nature of the plate. Problems associated with distributing sources in the free surface are avoided. The Chen and Mei variational principle is used to weakly match this inner solution and its normal derivative to an outer field described by distributing sources on the exterior of the hemisphere. The validity of the procedure is first illustrated by considering a heaving circular disk. Numerous hydrodynamic coefficients are presented as benchmark data for floating flexible structures. The transient motion of the plate is simulated using rational approximations (in the frequency domain) to the radiation impedance and diffraction mapping which are implemented as ODE's in the time domain.     

Coupled analysis of floating production systems

Fully coupled global analysis of Floating Production Systems, including the vessel, the mooring system and the riser system is described. Design of the system can be a daunting task, involving more than 1000 load cases for global analysis. The primary driver for the mooring system and for the riser system is motion of the vessel. Vessel motions are driven by environmental forces, but are restrained by forces from the mooring and riser systems. Numerical models and procedures that provide accurate and efficient global modeling of the Floating Production System are presented. Both Time Domain and Frequency Domain procedures are included. The accuracy and efficiency of the procedures are illustrated in an example: a large semi with 16 mooring lines and 20 risers. The procedures provide the accuracy and efficiency for use of fully coupled analysis in design of Floating Production Systems from concept selection to final design, installation and operation.     

Performance of pile-restrained flexible floating breakwaters

The overall performance of pile-restrained flexible floating breakwaters is investigated under the action of linear monochromatic incident waves in the frequency domain. The aforementioned floating breakwaters undergo only vertical structural deflections along their length and are held in place by means of vertical piles. The total number of degrees of freedom equals the six conventional body modes, when the breakwater moves as a rigid body, plus the extra bending modes. These bending modes are introduced to represent the structural deflections of the floating breakwater and are described by the Bernoulli–Euler flexible beam equation. The number of bending modes introduced is determined through an appropriate iterative procedure. The hydrostatic coefficients corresponding to the bending modes are also derived. The numerical analysis of the flexible floating breakwaters is based on a three-dimensional hydrodynamic formulation of the floating body. A parametric study is carried out for a wide range of structural stiffness parameters and wave headings, to investigate their effect on the performance of flexible floating breakwaters. Moreover, this performance is compared with that of the corresponding pile-restrained rigid floating breakwater. Results indicated that the degree of structural stiffness and the wave heading strongly affect the performance of flexible floating breakwaters. The existence of an “optimum” value of structural stiffness is demonstrated for the entire wave frequency range.     

Controlled decoherence of floating flux qubits

In Born--Markov approximation, this paper calculates the energy relaxation time T₁ and the decoherence time T₂ of a floating flux qubit by solving the set of Bloch--Redfield equations. It shows that there are two main factors influencing the floating flux qubits: coupling capacitor in the circuit and the environment resistor. It also discusses how to improve the quantum coherence time of a qubit. Through shunt connecting/ series connecting inductive elements, an inductive environment resistor is obtained and further the reactance component of the environment resistor is improved，which is beneficial to the enhancement of decoherence time of floating flux qubits.