波浪对非淹没水平圆柱作用的数值分析

该文选取URANS方程为控制方程结合k-?湍流模型,采用Level-Set方法追踪自由面,建立一种用于研究波浪与非淹没水平圆柱作用问题的二维数值模型。运用该数值模型对较小KC数条件下波浪与单个以及两个串联非淹没水平圆柱作用问题进行深入的探讨。结果表明,在单个非淹没水平圆柱工况中,不同波幅以及淹没深度条件下数值模型对水平圆柱竖直方向波浪力随时间的演化曲线做了准确预测,并揭示了波幅以及淹没深度对圆柱波浪力的影响规律;在两个串联非淹没水平圆柱工况中,圆柱间距对上游圆柱波浪力的影响较为明显:圆柱间距较大时,上游圆柱波浪力的大小以及演化规律与单个圆柱工况相近;而圆柱间距较小时,上游圆柱波浪力负向峰值明显增加。     

柔性连接多浮体在不规则波中运动的预报方法

本文介绍了一种频、时域杂交法，用于预报柔性连接多浮体在波浪中的运动。其中采用三维频域法适时求解浮体的水动力系数，在时域内求解浮体的运动方程，可同时求解非线性锚链力、连接器受力和护舷受力。利用本方法预报了柔性连接的“口”字形六浮体系统在波浪中的运动，结果与试验结果具有较好的吻合程度。     

波浪作用下浮体自由升沉运动对月池共振影响研究

当波浪激励频率与月池的固有频率耦合时,月池流体会产生大振幅共振行为,引起流体和浮体的剧烈运动,使工程作业存在一定的安全隐患。该文基于开源流体力学计算软件OpenFOAM~?软件包建立了黏性流数值波浪水槽,对波浪作用下,浮体自由升沉运动诱发的月池内流体共振水动力行为进行了研究分析。为验证该数值模型,将其结果与实验数据进行对比,以确保数值计算的准确性。结果表明：在波浪作用下,浮体自由升沉运动诱发的月池内流体共振存在双峰现象,而固定浮体仅存在单峰。自由升沉系统两共振频率对应的月池内波幅响应和浮体运动响应的峰值,均随入射波高的增加而减小,共振频率不随入射波高而变化。同时,考虑结构物吃水的影响,发现该系统共振频率随吃水增加而减小,表明吃水对月池内波响应和浮体运动响应均有显著的影响。     

环境荷载参数对钢悬链线立管动力响应的影响

海洋环境变化多端,钢悬链线立管(SCR)在复杂的环境荷载作用下容易发生疲劳破坏而影响安全,为研究立管在环境荷载作用下的动力响应,本文利用ABAQUS有限元软件对SCR建模,在立管上部悬挂点施加位移边界条件模拟浮体的运动,在立管的触地段采用刚度基于P-y曲线的非线性弹簧单元模拟立管与海床的相互作用,并通过调节立管环境荷载参数,研究了浮体运动、波浪振幅、周期和海流速度等参数对钢悬链线立管动力响应的影响。结果表明:钢悬链线立管随着环境荷载参数的变化呈现出不同的动力响应,立管对浮体的垂荡运动更敏感;波浪的振幅越大、周期越小,立管触地点与悬挂点的动力响应越大;海流速度增大,悬垂段长度会变大。     

应用比例边界有限元法研究波浪与带狭缝三箱作用的共振现象

比例边界有限元法（SBFEM）是一种半解析的新数值分析方法,比完全数值方法具有更高的分析精度.本文应用该方法求解波浪与有限水深中三个相同,但之间存在狭缝的二维固定方箱的作用问题,为波浪与多模块超大型浮体的相互作用提供一些规律。文中给出了各箱的波浪力及反射、透射系数的数值结果,与BEM结果进行了比较,吻合良好.发现波浪与三箱的作用存在双共振现象而且中间箱的共振形式与两边箱不同.进一步分析了箱体吃水深度、狭缝宽度和箱体宽度对三箱共振频率的影响.这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。数值结果证实该方法用较少单元便能得到精确结果,这为超大型浮体的水动力分析提供了一个可行的分析方法。     

深海安装中多浮体作业的水动力分析

海上安装是深海工程中的重要一环,也是浮式结构投入使用前的最后一项重大工程,多浮体相互作用分析对于指导安装期间的安全性和安装效率,对作业的成功完成起到很大的作用.此文假想以荔湾3-1气田Spar平台上部模块安装为背景,考虑了起重船、运输船和Spar平台之间的多浮体相互干扰以及小间隙共振现象,依据三维频域势流理论浮体受到的一阶波浪力和浮体运动进行了分析,并根据谱分析的方法筛选出了安装作业最佳的海浪环境参数和多浮体相对阵位.     

双浮体自由垂向振荡响应特性

双圆柱体系统在波能装置和防波构件中得到应用，该系统是一个多自由度受迫阻尼振荡系统，阻力和激励力都来自于波浪力。本文采用线性波理论和特征函数展开皮配法，在平面入射波条件下，求解了双圆柱体垂荡运动辐射速度势和圆柱体固定不动时的绕射速度势，推导了附加质量、阻尼系数、波浪激励力表达式，列出了浮体垂荡运动微分方程。最后讨论了下浮体尺度及位置对系统响应特性的影响。数值计算表明无论下浮体尺度及位置如何变化，它只影响到浮体垂荡响应在低频端的值，下浮体的振幅值总是小于入射波的振幅值，而且它在一个较窄的频率范围内从较大的值很快变化接近于零。下浮体半径与上浮体半径之比的变化不仅影响到两个浮体的响应幅值，而且也影响到曲线的变化趋势；两浮体距离的变化对曲线的变化趋势影响不大，但对曲线的幅值有影响；下浮体厚度的变化只少许改变了响应曲线的幅值。     

DTC在斜浪作用下船舶漂移力的计算

船舶在波浪中行驶时,船体会在波浪力的作用下改变原有的航向。为了估计波浪对船舶操纵性能的影响,该文对波浪作用下的DTC(Duisburg Test Case)船模进行了计算,对船舶受到的平均波浪力进行了分析并与试验进行了对比。计算基于自主开发的naoe-FOAM-SJTU求解器,利用VOF(Volume of Fluid)方法对自由液面求解,利用重叠网格技术和六自由度运动模块对船舶的波浪运动响应进行了计算,利用waves2Foam开源程序对数值波浪进行模拟。计算结果显示,波浪平均漂移力的计算结果与试验结果吻合良好,波浪频率对船体受力及运动起主导作用。同时计算也捕捉到了波浪对船体的强烈砰击作用。该文实现了对波浪漂移力的精确模拟,为进行船舶在波浪中的运动计算模拟及分析提供了支持。     

有限流动水域浮体受力及侧倾研究

为研究浮体结构在淹没状态下运行过程中的受力以及力矩,采用物理模型试验,对不同体型和 流速下的浮体结构在水流作用下产生的作用力以及侧倾力矩进行了比较分析。结果表明,不同浮体结 构的长高比对浮体结构在垂直方向所受动水压力、浮体结构侧倾力矩都存在显著影响,随着长高比的增 加,两者明显增大;但对浮体结构水平受力影响不大;而不同水流流速对浮体结构所受水平作用力影响 巨大,随着来流流速的增加,水平作用力明显增大,对浮体结构在垂直方向的受力影响微小,且在一定程 度上,随着来流流速的增大侧倾力矩同样增大。     

地震、波浪联合作用下深水大跨桥梁响应分析

深水大跨桥梁在地震作用时同样受到波浪力作用,研究地震、波浪联合作用下桥梁动力响应具有重要意义。通过ＡＮＳＹＳ建立一个连续大跨刚构桥的整桥模型,地震波采用天津波与ＥｌＣｅｎｔｒｏ波,利用辐射波浪理论计算地震作用下内域水动水压力、利用基于频率降低率的附加质量比法计算外域水地震动水压力,利用绕射波浪理论计算波浪力,对比仅地震作用、仅波浪作用、两者联合作用三种工况下桥梁动力响应结果。结果表明,水体存在会增大结构地震动力响应,且增幅与地震波特性、水深、有无内域水等有关;波浪以不同波长所得波浪力施加时结构动力响应不同,影响程度较仅地震作用时小;波浪的存在会影响结构地震动力响应,应合理考虑地震与波浪的关系。     

Numerical simulations of 2-D floating body driven by regular waves

An improved meshing method based on Fluent is used to update the computational meshes in solving the Navier-Stokes(N-S) equations for viscous and incompressible free surface flows with the volume of fluid(VOF) method. To maintain the meshquality when updating meshes for a moving structure, the computational domain is separated into several parts and each part corresponds to a specific type of body motion. The numerical results of the interaction between the floating body and the regular wavesagree well with the experimental data. A total of eight typical motion types are simulated separately to understand the correlationbetween the motion types and the wave transmission as well as the forces acting on the floating body. Numerical experiments showthat the wave transmission increases in the case of sway and heave motions and decreases in the case of pitch motion as comparedwith the stationary case. It is also found that the sway motion reduces the horizontal wave force acting on the floating body, while theheave motion enhances the vertical wave force.     

Time-domain hydrodynamic analysis of pontoon-plate floating breakwater

The hydrodynamic behaviors of a floating breakwater consisting of a rectangular pontoon and horizontal plates are studied theoretically. The fluid motion is idealized as two-dimensional linear potential flow. The motions of the floating breakwater are assumed to be two-dimensional in sway, heave, and roll. The solution to the fluid motion is derived by transforming the governing differential equation into the integral equation on the boundary in time domain with the Green’s function method. The motion equations of the floating breakwater are established and solved with the fourth-order Runge-Kutta method to obtain the displacement and velocity of the breakwater. The mooring forces are computed with the static method. The computational results of the wave transmission coefficient, the motion responses, and the mooring forces of the pontoon-plate floating breakwater are given. It is indicated that the relative width of the pontoon is an important factor influencing the wave transmission coefficient of the floating breakwater. The transmission coefficient decreases obviously as the relative width of the pontoon increases. The horizontal plates help to reduce the wave transmission over the floating breakwater. The motion responses and the mooring forces of the pontoon-plate floating breakwater are less than those of the pontoon floating breakwater. The mooring force at the offshore side is larger than that at the onshore side.     

漂浮式风力机的结构动力学响应

湍流风和波浪是影响漂浮式风力机安全最主要的客观因素。为分析漂浮式风力机在湍流风和波浪联合作用下的结构动力学响应,以NREL实测数据为湍流风场数据源,结合波浪作用,研究了风力机平台及各柔性部件的动力学响应。结果表明:漂浮式平台在纵荡方向响应较剧烈,垂荡和横荡方向响应可忽略不计,平台转动首摇方向较为剧烈;叶片根部挥舞方向力矩波动剧烈程度远大于摆振方向和俯仰方向,纵向剪力波动程度远大于横向剪力;塔尖在俯仰、横摇、偏航方向所受力矩量级较为接近,但初始时刻横摇方向力矩波动较为剧烈;塔基俯仰方向力矩波动剧烈程度远大于横摇方向。     

Detection of wave groups from the motion behaviour of a discus buoy

A scale modeled discus data buoy was tested for its motion characteristics under the action of wave groups of different frequencies in a wave tank. The wave groups were theoretically simulated based on the methodology of Xu et al., (1993, Statistical simulation of wave groups, Applied Ocean Research, 15, 217–226) and then converted to paddle displacement signals to drive the wave maker. The motion responses of the buoy model were measured using potentiometers as well as with a non-contact motion tracking camera system. The details of the model, instrumentation, testing conditions and the analysis are presented. The displacement and wave elevation time histories were analysed through statistical, envelope, wavelet transform and phase-time approaches to detect the wave groupiness. The effect of groupiness parameters on the surge, heave and pitch motions of the buoy are detailed in this paper.     

Detection of wave groups from the motion behaviour of a discus buoy

A scale modeled discus data buoy was tested for its motion characteristics under the action of wave groups of different frequencies in a wave tank. The wave groups were theoretically simulated based on the methodology of Xu et al., (1993, Statistical simulation of wave groups, Applied Ocean Research, 15, 217–226) and then converted to paddle displacement signals to drive the wave maker. The motion responses of the buoy model were measured using potentiometers as well as with a non-contact motion tracking camera system. The details of the model, instrumentation, testing conditions and the analysis are presented. The displacement and wave elevation time histories were analysed through statistical, envelope, wavelet transform and phase-time approaches to detect the wave groupiness. The effect of groupiness parameters on the surge, heave and pitch motions of the buoy are detailed in this paper.     

基于AQWA的漂浮式风力机驳船式平台的动态响应

为研究漂浮式风力机驳船式平台的动态响应,建立基于ITI Energy Barge平台的NREL 5MW漂浮式风力机模型。通过辐射/衍射理论并结合有限元方法,调用水动力学软件AQWA,考虑风、浪、流环境的联合作用,对平台的动态响应进行数值模拟分析,得到了各波浪力随波浪频率的变化及平台在纵荡、垂荡和纵摇方向上的动态响应。结果表明:平台在低频波浪时容易出现较大响应;随着海洋环境恶劣程度的增加,平台的动态响应增大;平台在垂荡方向RAOs要大于纵荡方向。     

Investigation of the effects of platform motion on the aerodynamics of a floating offshore wind turbine

Along with the flourishing of the wind energy industry, floating offshore wind turbines have aroused much interest among the academia as well as enterprises. In this paper, the effects of the supporting platform motion on the aerodynamics of a floating wind turbine are studied using the open source CFD framework Open FOAM. The platform motion responses, including surge, heave and pitch, are superimposed onto the rotation of the wind turbine. Thrust and torque on the wind turbine are compared and analysed for the cases of different platform motion patterns together with the flow field. It is shown that the movement of the supporting platform can have large influences on a floating offshore wind turbine and thus needs to be considered carefully during the design process.     

有限深水中沉井的水动力计算

本文提出用特征函数展开和匹配方法计算圆筒形沉井在有限深水中的流体动力系数,其中包括垂荡、纵荡(横荡)、纵摇(横摇)及纵荡与纵摇(横荡与横摇)偶合的附加质量和阻尼系数。用文中推导的公式编制的计算程序,对已发表的有三维源汇分布法计算和实验结果的例子的计算表明本方法有效。本方法的优点是计算速度大大快于其它数值方法,而且计算结果准确。文中对一些形状的沉井进行了计算,得到了其水动力系数的若干变化规律。本文对海洋工程中沉井这一结构物在波浪中的运动估算和结构设计提供了有效手段。     

PARAMETRIC IDENTIFICATION AND SENSITIVITY ANALYSIS FOR AUTONOMOUS UNDERWATER VEHICLES IN DIVING PLANE

The inherent strongly nonlinear and coupling performance of the Autonomous Underwater Vehicles (AUV), maneuvering motion in the diving plane determines its difficulty in parametric identification. The motion parameters in diving plane are obtained by executing the Zigzag-like motion based on a mathematical model of maneuvering motion. A separate identification method is put forward for parametric identification by investigating the motion equations. Support vector machine is proposed to estimate the hydrodynamic derivatives by analyzing the data of surge, heave and pitch motions. Compared with the standard coefficients, the identified parameters show the validation of the proposed identification method. Sensitivity analysis based on numerical simulation demonstrates that poor sensitive derivative gives bad estimation results. Finally the motion simulation is implemented based on the dominant sensitive derivatives to verify the reconstructed model.     

风浪流荷载下基于AQWA的海上Spar型浮式基础稳定性分析

为了解决现阶段可再生能源利用的问题,实现深海风能的有效利用,针对设计出的OC3-Hywind 5MW Spar型浮式平台基础部分在风浪流荷载下的稳定性问题进行研究。利用ANSYS中的水动力模块(AQWA)分别对结构进行频域以及时域耦合运动响应仿真模拟,比较分析了不同工况下浮式结构各个自由度下的运动响应值,以及配重块在系泊不同位置处对结构运动响应值及系泊力的影响情况。结果表明:在不同工况作用下的浮式结构在纵摇自由度方向上的运动响应极值主要受风荷载影响,随着风速增大,响应极值也随之增大,在其他自由度上的响应极值受风、浪荷载影响较小;改变配重块在系泊缆上的悬挂位置对浮式基础在纵摇和首摇自由度方向的运动有着显著影响,并且随着配重块距离锚固点越近,响应值越大,越不利于浮式基础的稳定;未悬挂配重块的系泊力高于悬挂了配重块的系泊力,随着配重块悬挂位置离锚固点越远,系泊力越小,越能保证浮式基础在恶劣海况条件下的稳定性。