近岛礁地形影响下的浮式平台运动响应

近岛礁附近的地形一般呈现高低不平的状态,水深从几十米到几米不等。远场波浪向近岸传递过来时在礁盘上会经过复杂的演化,使得浮体附近的波浪呈现一定的非均匀性,不同于常规的长峰规则波,同时礁盘的起伏变化会对波浪中的浮体的运动产生影响,最终使得浮体在复杂地形下的水动力运动响应不同于一般均一水深下的浮体响应。该文通过建立浮体和礁盘地形的耦合水动力模型,计算了礁盘对浮体入射波力、绕射力、辐射水动力系数以及运动的影响,同时与水池模型试验对比了浮体运动,两者较为一致。研究表明复杂地形对浮体的水动力运动存在较大的影响,在某些周期附近会增大浮体的运动响应,因此需要理性考虑复杂地形对浮体的影响。     

海底地形对浮体慢漂响应的影响研究

浮体在波浪中的运动经常受到海底地形的影响,文章基于势流理论,采用高阶边界元方法计算海底地形对浮体慢漂运动响应的影响,计算中充分考虑了海底地形在波浪传播中对其的绕射影响。计算结果表明,变浅的海底地形会导致波浪场的波高增加,浮体运动响应增大,分别对浮体相对海底地形不同位置时浮体受到的波浪力和运动响应进行了定性及定量的分析,分析了浮体相对海底地形不同位置时浮体的水动力特性及运动特性,说明为了更准确模拟近岸或者离岸线性约束浮体的水动力情况,海底地形的影响不能忽略。     

复杂地形条件下浮式栈桥运动响应的频域分析

为了研究复杂地形条件下浮式栈桥的运动响应,并探讨波浪圆频率及浪向角等因素对浮式栈桥运动响应的影响。论文利用势流理论及波浪绕射/辐射理论对浮式栈桥所处流场的速度势进行了分析,并对复杂海底地形条件下浮式栈桥的运动特性进行了水池试验和数值模拟研究。基于水动力计算软件AQWA,将复杂海底地形作为一个潜体置于海底,进而考虑其与上部浮体及波浪的水动力干扰,从而建立了海底地形-浮式栈桥-波浪水动力耦合计算模型,模拟计算了浮式栈桥在复杂地形条件下的运动响应,并通过水池试验对数值计算结果进行了验证。结果表明,耦合计算模型能够较为准确地预报复杂地形条件下浮式栈桥的运动响应;复杂海底地形条件下浮式栈桥各桥节的运动响应有较显著的差异,且桥节RAOs随浪向角的变化曲线与平坦海底地形条件下的RAOs曲线有一定差异;浅水环境下海底地形对浮式栈桥运动响应和波浪传播特性的影响不能忽视。     

有航速纵向连接多联浮体频域特性分析

针对水深和浪向等参数对有航速纵向连接多联浮体运动产生影响的问题,基于势流理论分析了有航速的纵向连接多联浮体的水动力特性,并利用水动力计算软件AQWA分别对不同水深、不同浪向和不同航速下多联浮体结构进行了频域计算,得到了多联浮体RAOs随波浪圆频率的变化曲线。计算结果表明,水深越浅,垂荡RAOs会减小,但纵摇与首摇RAOs会增大,对于所研究的纵向连接多联浮体而言,8 m以上水深可以看作无限水深进行分析和计算;不同浪向对纵向连接多联浮体各自由度影响不同,若多联浮体产生较大的运动响应时,应及时改变航向;在较高航速下纵向连接多联浮体各自由度RAOs会产生较大的响应,在低中频段航行时应适当降低航速航行,在高频段航行时可以适当提高航行速度。     

变化海底地形上浮驳的水弹性响应

在岛礁附近的海底地形通常是不平整的,这种复杂的海底地形也是海洋环境中非常重要的因素。文章利用考虑浅水变深的三维水弹性分析方法计算了一艘浮驳在非均匀海底地形情况下的波激响应及其载荷。通过与均匀水深的对比,复杂海底地形的影响显而易见。通过模态叠加的方法,三维水弹性可以预报规则波下诸如弯矩和应力等波激振动响应,从而得到设计波下对应的载荷。通过在岛礁附近服役的浮式结构物波浪载荷预报可以看出非均匀海底产生了很大的影响,原因是不同的水深和变化的海底地形。而一旦考虑地形,在整个流固耦合分析中,大量的水动力网格就需要借助并行计算来减少计算耗时。     

考虑近岛礁复杂海底地形的浮式平台水动力性能分析

基于可以考虑复杂海底地形对波浪传播变形影响的水波模型和可以考虑波浪与浮式结构物相互作用的RANKINE源法,建立近岛礁浮体水动力性能直接分析耦合模型,给出详细的理论推导及数值求解方法,并编制了相关的计算程序THAFTS-BR。首先以均匀水深下百米级浮式平台为研究对象,通过与THAFTS和AQWA等商业软件的计算结果进行对比分析,初步验证了THAFTS-BR程序的正确性和可靠性。随后基于模型试验和前面建立直接分析耦合模型,对比分析了考虑近岛礁海底地形后该浮式平台的运动及载荷响应特性,给出了一些重要结论,为后续布置于岛礁附近的浮式结构物动响应分析、设计与建造等提供了参考依据。     

气浮海洋平台的水动力系数分析

文中以某气浮结构平台为研究对象,基于三维势流理论通过MOSES对气浮体和实浮体在相同波浪下的响应、不同吃水下、不同水深下的下气浮结构的水动力系数进行了研究分析.分析结果表明：气浮体和实浮体在相同波浪条件下的响应是不同的,气浮体垂荡响应大于实浮体,而气浮体的摇摆响应和横荡响应要小于实浮体,气浮体内部气体具有减摇的作用;在相同的扰动波浪周期下,随着水深的增加,气浮体的水动力系数呈下降趋势;在相同的扰动波浪周期下,随着吃水的增加,垂荡的水动力系数呈下降的趋势,而横荡的水动力系数呈上升的趋势,对于纵摇的水动力系数影响不大.     

柔性连接装置约束下的相邻浮体频域响应分析

许多海上工程作业会涉及两个或多个浮体相邻作业,如海洋平台组块双船浮托安装等。在波浪作用下,相邻多浮体会发生水动力干扰现象,在特定条件下引起强烈的间隙共振,产生的巨大波浪力会对浮体造成破坏。相邻多浮体之间往往会存在柔性连接,需要考虑多浮体水动力干扰及柔性连接构件的约束力对浮体运动响应的耦合作用,以及约束力本身对刚性或柔性连接构件的影响。因此,需要建立多浮体耦合的水动力—结构动力模型研究相互连接的海上浮式结构在复杂环境载荷下的动力响应。文中以双船浮托安装作业为背景,开发了耦合的水动力—结构动力模型分析平台组块在双船拖运过程中的复杂动力响应。通过结合动态子结构法和静凝聚法,考虑连接构件的柔度,将连接构件的质量和刚度凝聚到构件与双船的连接点处。结合多浮体频域水动力分析,研究了双船在柔性构件约束下和复杂水动力干扰共同作用下的运动响应。     

柔性连接装置约束下的相邻浮体动力响应分析

许多海上工程作业中会出现两个或多个浮体相邻作业的情形,如海洋平台组块双船浮托安装等.在波浪作用下,相邻多浮体会发生水动力干扰现象,在特定条件下引起强烈的间隙共振,产生的巨大波浪力会对浮体造成破坏.相邻多浮体之间往往会存在柔性连接,需要考虑多浮体水动力干扰及机柔性连接构件的约束力对浮体运动响应的耦合作用,以及约束力本身对刚性或柔性连接构件的影响.因此,需要建立多浮体耦合的水动力-结构动力模型研究相互连接的海上浮式结构在复杂环境载荷下的动力响应.本文以双船浮托安装作业为背景,开发耦合的水动力-结构动力模型分析平台组块在双船拖运过程中的复杂动力响应.通过结合动态子结构法和静凝聚法,考虑连接构件的柔度,将连接构件的质量和刚度凝聚到构件与双船的连接点处.结合多浮体频域水动力分析,研究双船在柔性构件约束下和复杂水动力干扰共同作用下的运动响应.     

旁靠系泊油船水动力相互作用分析

为了研究多浮体水动力相互作用下的波浪载荷和船体响应,针对旁靠系泊的穿梭油船与FPSO进行模拟计算。其中二阶波浪力采用近场方法求解。计算分析发现,由于屏蔽效应的影响,穿梭油船上的波浪绕射力受水动力相互作用的影响较大,平均二阶波浪漂移力在波频的高频段受水动力相互作用影响显著,在低频段几乎不受影响,而附加质量和辐射阻尼以及船体响应的RAO受影响则较小。另外,随着穿梭油船与FPSO相对距离的小范围变化,水动力相互作用的影响并没有太大的差别。     

A study on the estimation of the seaquake response of a floating structure considering the characteristics of seismic wave propagation in the ground and the water

 Seaquakes, which are characterized by the propagation of vertical earthquake motion at the sea bottom as a compression (longitudinal) wave, are reported to cause damage to ships, and their effect on floating structures is a matter of great concern. To comprehend the basic properties of seaquakes, we first discuss a method to calculate the displacement of the seabed when it is subjected to hydrodynamic pressure. To investigate the interrelationship between the vibration of a floating structure and the deformation of the seabed, a new boundary integral equation is derived which assumes that the seabed is a semiinfinite homogeneous elastic solid in order to analyze the seaquake-induced hydrodynamic pressure acting on the floating structure. By considering the propagation of the seismic wave in the ground and in the water, the incident wave potential in seaquake problems is also deduced and its characteristics are discussed. Finally, the response of a very large floating structure in a seaquake is investigated using a fluid force analysis method, and considering the interrelationship between the vibration of the floating structure and the deformation of the seabed. Received: August 19, 2002 / Accepted: November 11, 2002 Address correspondence to: H. Takamura (hiroaki_takamura@nishimatsu.co.jp) Updated from the Japanese original, which won the 2002 SNAJ prize (J Soc Nav Archit Jpn 2001;189:87–92,93–100 and 190:381–386)     

半无限开敞水域船舶水动力系数问题研究

在解决三维浮体靠泊的水动力问题时,正确处理浮体和壁面之间的相互作用是分析计算的关键所在。文章运用边界元法和叠加格林函数法对箱型浮体的靠泊问题进行求解,通过与SESAM软件对比分析浮体水动力系数的结果,验证这种方法编写的程序计算结果的精确度。并通过改变浮体与壁面之间的距离,计算壁面对三维浮体的影响,并对计算结果进行分析。     

深海系泊浮体物面非线性时域耦合动力分析

文章基于三维时域势流理论和弹性细长杆理论,研究并提出了深海系泊浮体物面非线性时域耦合动力分析方法。该方法采用时域物面非线性理论方法在瞬态位置直接时域模拟系泊浮体所需水动力,结合有限元方法计算系泊缆索的动力响应,利用异步耦合方法实现浮体和系泊缆索的时域耦合动力求解。既满足系泊浮体时域水动力耦合,又满足系泊浮体和系泊缆索动力耦合。通过对二阶非线性不规则波作用下深海系泊半潜式平台的时域耦合响应特性进行研究,将不同海况下物面非线性时域耦合静力响应和动力响应与间接时域耦合动力响应的三种方法计算结果进行比较。研究结果表明,系泊缆索动力响应明显,平台瞬态空间位置对垂荡低频运动影响较大,有必要在平台瞬时湿表面采用动力响应方法进行深海系泊浮体时域耦合响应分析。     

Time-domain,shallow-water hydroelastic analysis of VLFS elastically connected to the seabed

In order to ensure the safe operation of a VLFS, a combination of mooring, breakwater and other motion reducing systems is employed. In the present work, the transient hydroelastic response of a floating, thin elastic plate, elastically connected to the seabed, is examined. The plate is modelled as an Euler-Bernoulli strip, while the linearized shallow water equations are used for the hydrodynamic modelling. Elastic connectors are approximated by a series of simple spring-dashpot systems positioned along the strip. A higher order finite element scheme is employed for the calculation of the hydroelastic response of the strip-connector configuration over the shallow bathymetry. After the definition of the initial-boundary value problem, its variational form is derived and discussed. Next, on the basis of the aforementioned formulation, an energy balance expression is obtained. The effect of variable bathymetry on the response of a two connector-strip system is examined by means of three seabed profiles featuring a flat bottom, an upslope and a downslope environment. For the flat bottom case, the strip response mitigating effect exerted by the employment of two and three elastic connectors is considered. Finally, by means of the derived energy balance equation, the energy exchange is monitored, providing a valuable insight into the transient phenomena that take place in the studied configurations.     

基于有限元法的海底管道埋深计算

基于有限元分析程序ANSYS/LS-DYNA分析应急抛锚贯入海床的动态响应过程,并分析不同锚重、水深、抛锚高度、海底底质等因素对锚在海床中贯入量的影响,最终确定锚机影响作用下管道的最佳安全埋深。     

近岛礁超大型浮体连接器载荷研究

对于布置在岛礁附近的浮体,复杂海底地形的作用不可忽略.文章基于RMFC模型,同时将地形作为固定物体,研究了复杂海底地形对布置于岛礁附近的超大型浮体的运功响应和连接器载荷的影响.数值计算结果表明,地形的存在对浮体绕射力存在显著的影响,同时增加了低频区域的连接器载荷.     

Hydrodynamics of a body floating in a two-layer fluid of finite depth. Part 1. Radiation problem

A linearized 2-D radiation problem was considered for a general floating body in a two-layer fluid of finite depth. A boundary integral-equation method was developed for directly computing the velocity potential on the wetted surface of a body which is immersed in both the upper and lower layers as a general case. To do this, appropriate time-harmonic Greens functions were derived, and an efficient numerical method of evaluating those functions is proposed. Based on Greens theorem, hydrodynamic relations such as the energy-conservation principle were derived theoretically for a case of finite depth, and we confirm that those relations are satisfied numerically with very good accuracy. Experiments were also carried out using water and isoparaffin oil as the two fluids and a Lewis-form body. Measured results for the added mass, the damping coefficient, and the amplitude of the generated waves are compared with the computed results, and a favorable agreement is found.     

支撑条件对浮动式厚弹性板水弹性行为的影响分析（英文）

The hydroelastic response of very large floating structures(VLFS) under the action of ocean waves is analysed considering the small amplitude wave theory. The very large floating structure is modelled as a floating thick elastic plate based on TimoshenkoMindlin plate theory, and the analysis for the hydroelastic response is performed considering different edge boundary conditions.The numerical study is performed to analyse the wave reflection and transmission characteristics of the floating plate under the influence of different support conditions using eigenfunction expansion method along with the orthogonal mode-coupling relation in the case of finite water depth. Further, the analysis is extended for shallow water depth, and the continuity of energy and mass flux is applied along the edges of the plate to obtain the solution for the problem. The hydroelastic behaviour in terms of reflection and transmission coefficients, plate deflection, strain, bending moment and shear force of the floating thick elastic plate with support conditions is analysed and compared for finite and shallow water depth. The study reveals an interesting aspect in the analysis of thick floating elastic plate with support condition due to the presence of the rotary inertia and transverse shear deformation. The present study will be helpful for the design and analysis of the VLFS in the case of finite and shallow water depth.     

某核电工程海区水沙条件分析

为了从宏观上论证某拟建核电取水工程平面布局的合理性,依据大量实测资料,研究了该工程海区的水动力条件、泥沙环境以及岸滩冲淤演变特征。通过研究表明,该工程水域水动力不强、含沙量低、岸滩基本处于稳定状态,外界泥沙来源较少,在合理布置取水工程后不会产生较强的泥沙淤积问题。此外还结合该区的波浪及底质特点讨论了取水口位置,并进一步给出了局部防淤的相关措施。