超大型浮体的水弹性响应分析

针对海上超大型浮体与波浪相互作用这一流固耦合问题,把超大型浮体简化为二维薄板,应用特征函数展开法求解流场速度势,采用正弦模态函数对结构运动进行模态展开分析,计算浮体的水弹性响应。     

迎浪端配置减振板的超大型浮体平板模型水弹性响应分析

在箱型超大型浮体迎浪端引入水下减振平板,依据势流理论,采用模态展开法和特征函数展开法求解流体速度势,并将其代入水弹性运动方程,求解该浮体的水弹性响应。探究减振板板宽、入水深度等参数对超大型浮体水弹性响应的影响;对比有无配置减振板情况下,入射波波长变化对浮体水弹性变形的影响,这些为今后的工程应用提供了理论依据。     

非均匀海底环境下铰接超大型浮体的水弹性响应分析

本文采用基于离散模块思想的频域水弹性分析方法,对处于非均匀海洋环境下的铰接超大型浮体的水弹性响应进行分析.该方法首先将连续浮体离散为多刚体系统;然后应用三维势流理论获得各个刚体的水动力系数,将其与弹性梁刚度阵进行耦合,得到浮体在波浪作用下的运动学方程;随后引入铰接约束矩阵,建立铰接超大型浮体在非均匀海底环境下的运动学方程,在频域中求解该方程得到浮体的位移响应;最后利用梁的弯曲理论,获得浮体的弯矩分布以及铰接点处的轴向力和剪力.通过对比不同入射角度、波长和海底条件下浮体的水弹性响应,发现非均匀海底对铰接点的位移和受力有明显的影响.     

海洋浮体二阶非线性水弹性力学分析——基本理论

将考虑到二阶的流场压力在浮体瞬时湿表面上积分，得到用于非经恶性水弹性理论分析的广义一阶流体作用力和广义二阶流体作用力，广义一阶流体作用力中的波浪激励力，辐射力和恢复力和线性水弹性理论中的广义流体力具有相同的形式，仅比线性水弹性理论多了一项，反映了由刚体的转动引起的对一阶流体恢复力的影响，广义二阶流体力由五部分组成，即：与人射势和反射势有关的广义二阶波浪激励力，与辐射势有关的广义二阶辐射力，由辐射势与入射势及反射势的耦合引起的广义二阶力，由于湿表面的移动引起的一阶流场静态压力对广义二阶流体力的贡献，以及由于瞬时湿表面积的变化引起的广义二阶力，同时推导了不规则波中的广义一阶及二阶流体动力系数的表达形式。建立了在不规则波中航行浮体的线性和非线性水弹性运动方程，给出了求解方法，后续文章中将给出海洋浮体二阶非线性水弹性力学分析的部分数值计算结果。     

三维水弹性分析中不规则频率消除及在船舶上的应用

三维水弹性力学是求解浮体和波浪流固耦合作用的重要方法,在求解时存在不规则频率的问题,这些不规则频率的存在会对高频波激振动响应的判断和二阶波浪力的精确计算产生影响。论文采用在水线面建立网格和扩展边界积分方程的方法来消除不规则频率。通过圆柱形浮体的计算,验证该方法在三维水弹性响应计算中的有效性。在此基础上,将该方法应用于一艘散货船,对比了不规则频率处理前后的水动力系数,并给出了船体的水弹性响应。计算结果表明,将不规则频率消除方法应用于三维水弹性响应的计算,可以获得更好的结果,显著改善不规则频率点处的水弹性响应。     

波浪作用下弹性板的水动力响应

为准确预报聚焦波作用下弹性板的非线性动力响应，充分掌握极端波浪条件对超大型浮体动力响应的影响，选用一种基于离散模块-梁单元的水弹性分析方法，对弹性板在规则波和聚焦波作用下的不同响应特性进行研究。同时，开展水槽模拟试验，并将试验结果与理论结果进行对比，验证该水弹性分析方法的有效性。试验结果表明：基于离散模块-梁单元的水弹性分析方法在超大型浮体动力响应分析方面具有良好的准确性和简便性；在规则波作用下，随着规则波波陡和波长的增加，弹性板响应幅值增大；在聚焦波作用下，谱峰波长和最大波幅对弹性板响应的峰值和谷值有显著影响。     

畸形波作用下的浮式结构水弹性响应分析

本文基于时域下CFD-FEM方法,在三维粘性数值水池中建立畸形波浪与弹性浮体相互作用的耦合数值模型。基于JONSWAP波浪谱的组合聚焦模型,采用推板造波方法,模拟数值水池中畸形波波浪的生成。流场区域采用CFD方法求解,得到流场中的速度场与压力场的变化;浮体结构采用FEM方法进行计算,获得结构内各节点的垂向位移变化情况,数值方法可以准确地模拟所期望的畸形波以及分析弹性浮板的水弹性响应。计算结果表明,聚焦波的浪向、聚焦位置和频带宽度对浮板的水弹性响应均有较大影响。     

铰接多浮体耦合解析计算

利用Lagrange方程求解波浪作用下的铰接多浮体结构运动响应.基于二维微幅波理论,将流场分成若干子区域,在每个子区域内将速度势用特征函数展开,在各区域边界上进行速度势及水平速度的匹配并结合运动方程耦合求解速度势中的系数及结构响应值.计算与实验结果的比较表明,所采用的计算方法是合理的,可以为研究波浪与铰接多浮体相互作用作为参考.     

一种基于离散模块的浮体水弹性响应预报方法

文章基于传统的多体水动力学和有限元方法,将连续的浮体离散为由有限个弹性梁元连接的刚体子模块,各个模块不仅受到相邻模块的水动力的干扰,同时还受到为保证结构连续性而引入的等效连接梁的作用,从而建立了一种新的可以用于求解浮体水弹性响应的数值方法。采用文中的数值计算方法,对一个箱形的超大型浮体的水弹性响应进行了研究。并通过与传统的水弹性方法计算结果的对比,证明了文中的方法的正确性和可靠性。该文的数值计算方法可为以后非均匀海洋环境下浮式结构物的水弹性响应计算提供依据。     

结构刚度变化对箱式超大型浮体结构水弹性响应的影响

结构刚度改变会导致结构固有频率变化和结构广义刚度的变化。必然会对结构在波浪中的水弹性响应产生影响，本文在某箱式超大型浮体结构单位幅值正弦规则波和不规则波水弹性响应计算的基础上，假定结构质量分布不变，研究了结构刚度变化对箱式超大型浮体结构水弹性响应的影响。得到了一些有价值的结论。     

On the hydroelastic behavior of two-dimensional articulated plates

The hydroelastic behavior of two-dimensional articulated plates is investigated analytically within the scope of linear theory. The connectors are modeled by singular line loading and its derivatives. The velocity potential under the free surface and plate is obtained by use of a wave-maker theory. The characteristics of large displacements at the upstream and downstream edges of the plate and the connectors are obtained from the closed-form solutions. It is also shown that the hydroelastic properties are strongly dependent on the stiffness of the connectors and incoming wave frequency. Finally, the method is used to solve for the response of a multi-module articulated plate.     

Fluid-structure-material coupling analysis for a floating laminated structure consisting of high-stiffness panels and a soft core

This paper presents a fluid-structure-material coupling analysis for the interaction between water waves and a very large floating laminated structure (VLFLS), which is consisted of two enhanced ultrahigh-performance concrete (UHPC) panels and a middle lightweight foamed rubber core. The representative volume element (RVE) method is used to design the mechanical properties of enhanced UHPC and foamed rubber, and the parameterized formulas are presented to reveal the dependency between macroscale mechanical properties and mesoscale hierarchical characteristics. By idealizing the rubber core as a uniformly distributed spring layer, an eighth-order differential equation of motion of the laminated structure is derived. In the context of linear potential flow theory, a hydroelastic analytical model is developed for the floating laminated structure with finite length under wave action. In the process of solving velocity potentials, a complicated dispersion equation for the wave motion below the laminated structure is derived, and this equation contains two pairs of conjugate complex roots with positive real parts. The various hydrodynamic quantities, including reflection coefficient, transmission coefficient, deflection, shear force, and bending moment, are calculated. The hydroelastic model is confirmed by considering the convergence of calculation results and the energy conservation of wave propagation. The coupled effects of wave action, material characteristics, structural parameters, and edge conditions on the hydroelastic and mechanical response of the floating laminated structure are clarified to provide important information regarding the optimal design of such structures.     

Hydroelastic Analysis of a Flexible Floating Body for the Variation of Incident Wave

As for the hydroelastic response of a flexible floating body, various kinds of simplified analytical and numerical methods based on the different assumption have been developed, however, the most versatile and applicable approach is the three-dimensional hydroelasticity theory. Currently, most studies mainly focused on the wave condition of head seas without taking the differences for the variation of the incident wave angle into account. In this paper, based on the three-dimensional hydroelasticity theory, an investigation into the variation of the hydroelastic response for different incident wave angles is presented; also some comparisons are demonstrated and discussed.     

On the dispersion relation of hydroelastic waves in a plate

This paper deals with the dispersion relation of hydroelastic waves in pontoon-type very large floating structures (VLFS) using a simple beam modeling, where the term hydroelastic waves means propagation of deflection vibrations in VLFS. The purpose of this paper is to show the properties of the hydroelastic waves. The dispersion relation of hydroelastic waves propagating in an infinite plate floating on the water is derived based on the linear water wave theory. The effects of the water depth and of the bending rigidity of the floating plate on the wavelength, phase velocity, and group velocity of the hydroelastic waves are shown theoretically or numerically. Then, the dispersion relation of hydroelastic waves in a finite plate floating on shallow water is investigated. It is shown that the wavelength or the phase velocity of the hydroelastic waves varies with the location in the plate. Received for publication on April 7, 1999; accepted on Aug. 20, 1999     

基于一个二维修正水弹性方法的集装箱船体梁动态前极限强度评估研究

海上极端波因其巨大的波高常常导致船体的极限破坏。该文提出了一个二维的修正水弹性方法来研究一个集装箱船船体梁在极端波中的动态前极限强度。传统的极限强度评估基于准静态方法,没有动态效应被考虑。而船体在波浪下的动态结构响应是基于水弹性方法,传统的水弹性方法并不能计算船体梁的动态非线性强度。该二维修正的水弹性方法考虑时域波浪和非线性船体梁之间的耦合,将水弹性方法和Smith方法结合,用Smith方法计算船体梁的刚度,而其刚度与船体梁的强度和变形曲率有关。所以该时域的非线性刚度被用于修改水弹性方法里的常数项的结构梁刚度。几组极端波模型被用以产生船体梁的大变形和非线性动态垂向弯矩。文中分别采用修正水弹性方法和普通水弹性方法,通过改变四个重要的极端波参数如极端波最大波高、规则波的波高、波速和波长等来研究其对船体梁船中处的大变形转角和非线性垂向弯矩的影响,通过采用修正的水弹性方法计算得来的结果与水弹性方法计算得来的结果相比较,得到了一些差异和结论。     

Hydroelastic analysis of oblique irregular waves with a pontoon-type VLFS edged with dual inclined perforated plates

The fluid-structure interaction of oblique irregular waves with a pontoon-type very large floating structure (VLFS) edged with dual horizontal/inclined perforated plates has been investigated in the context of the direct time domain modal expansion theory. For the hydroelastic analysis, the boundary element method (BEM) based on time domain Kelvin sources is implemented to establish water wave model including the viscous effect of the perforated plates through the Darcy’s law, and the finite element method (FEM) is adopted for solving the deflections of the VLFS modeled as an equivalent Mindlin thick plate. In order to enhance the computing efficiency, the interpolation-tabulation scheme is applied to assess rapidly and accurately the free-surface Green function and its partial derivatives in finite water depth, and the boundary integral equation of a half or quarter VLFS model is further established taking advantage of symmetry of flow field and structure. Also, the numerical solutions are validated against a series of experimental tests. In the comparison, the empirical relationship between the actual porosity and porous parameter is successfully applied. Numerical solutions and model tests are executed to determine the hydroelastic response characteristics of VLFS with an attached anti-motion device. This study examines the effects of porosity, submerged depth, inclined angle and gap distance of such dual perforated anti-motion plates on the hydroelastic response to provide information regarding the optimal design. The effects of oblique wave angle on the performance of anti-motion and hydroelastic behavior of VLFS are also emphatically examined.     

Hydroelastic analysis of a rectangular plate subjected to slamming loads

A hydroelastic analysis of a rectangular plate subjected to slamming loads is presented. An analytical model based on Wagner theory is used for calculations of transient slamming load on the ship plate. A thin isotropic plate theory is considered for determining the vibration of a rectangular plate excited by an external slamming force. The forced vibration of the plate is calculated by the modal expansion method. Analytical results of the transient response of a rectangular plate induced by slamming loads are compared with numerical calculations from finite element method. The theoretical slamming pressure based on Wagner model is applied on the finite element model of a plate. Good agreement is obtained between the analytical and numerical results for the structural deflection of a rectangular plate due to slamming pressure. The effects of plate dimension and wave profile on the structural vibration are discussed as well. The results show that a low impact velocity and a small wetted radial length of wave yield negligible effects of hydroelasticity.     

不规则波和流下的重力式网箱水弹性响应研究

文章对重力式网箱在不规则波和流作用下的水弹性响应分析进行了研究,通过有限元方法建立实尺度网箱模型并对网箱的运动和变形进行了分析。在数值模型中,通过非线性弹簧单元和Truss单元来模拟锚链和渔网结构,通过若干耦合的梁按照"浮力分配法"来计算浮圈的瞬时浮力。基于这个计算模型,文中充分研究了当网箱处于波流载荷下,浮圈的各阶弹性体模态所占权重。结果显示,当有义波高增大时,在垂直方向上会激发出更多的浮圈弹性体模态,而流则主要影响水平方向上的刚体模态。     

Simplified estimation for the dynamic behavior and reliability analysis of very large floating structures under wave-induced loads

This paper deals with the dynamic response and strength of very large floating structures (VLFS) in regular and irregular waves, considering the propagation of the hydroelastic deflection wave of the structure. First, a simplified estimation method is presented for the dynamic response and strength of the structure in regular waves. Then, the validity of the method is demonstrated by comparing its results with analytical results and experimental results for a mat-type floating structure model. Next, a simplified estimation method for dynamic responses under long crested irregular wave conditions is presented by using the above results and by combining them with irregular sea wave spectra. Finally, the applicability of the method is investigated through numerical examples carried out for a 4,800-m class VLFS under trial design. Characteristics of the hydroelastic waves, short-term responses, and reliability levels are numerically identified. Received for publication on April 14, 1999; accepted on Sept. 10, 1999     

航行船舶的三维非线性水弹性分析

基于Wu提出的浮体二阶水弹性理论[1],研究大浪中航行船舶的非线性水弹性响应,给出了数值方法和计算结果.在二阶水弹性分析中,主要考虑了大角度刚体转动和瞬时湿表面变化引起的非线性水动力.根据三维线性水弹性理论[2],采用移动脉动源格林函数和Kelvin定常兴波假定,求解了对二阶水动力做主要贡献的一阶速度势及响应.最后以航行于不规则波中的小水线面双体船为例,讨论了航速和定常兴波流场对水弹性响应的影响,并对线性和非线性响应的预报结果进行了比较.