Analytic Solution of Interaction Between Surface Waves and Floating Elastic Plates with Elastic End-Restraints

Based on the dynamic theories of water waves and Mindlin plates,the analytic solution of interaction between surface waves and two-dimensional floating elastic plates with edge-restraint is constructed by use of the Wiener-Hopf technique.Firstly,without regard for elastic edge restraint,the wave-induced responses of elastic floating plate analyzed by the present method are in good agreement with the results from literature and experimental results.Therefore,it can be shown that the present method is valid.Secondly,three end-restraint cases(i.e.,the left-end elastic restraints,the both-end elastic restraints,and the right-end elastic restraints)are proposed to reduce the vibration of floating plates,in which the spring is used to connect the sea bottom and the floating plate's left(or right)edge.The relations between the spring stiffness and the parameters of wave-induced responses of floating plates are discussed.Moreover,the effective method to reduce the vibration of floating elastic plates can be obtained through comparison.     

Random Processes with Stationary Increments and Composite Spectra

Izvestiya, Atmospheric and Oceanic Physics - A technique for deriving and interpreting fractal geophysical processes with power-law spectra of a different nature is described. Examples include the...     

Dynamic Analysis of Submarine Pipelines on an Elastic / Viscoelastic Foundation

This paper presents a new finite element method for solving static and dynamic problems in laying operation of pipelines. The effect of the viscoelastic soil behavior is considered by using the Pasternak foundation model. Some examples are also presented.     

Dynamic Plastic Response of Circular Plates Resting on Fluid with Finite Deformation

This paper concerns the dynamic plastic response of a circular plate resting on fluid subjectedto a uniformly distributed rectangular load pulse with finite deformation.It is assumed that the fluid isincompressible and inviscous,and the plate is made of rigid-plastic material and simply supported along itsedge.By using the method of the Hankel integral transformation,the nonuniform fluid resistance is de-rived as the plate and the fluid is coupled.Finally,an analytic solution for a circular plate under a mediumload is obtained according to the equations of motion of the plate with finite deformation.     

Analysis of Dynamic Structure-Fluid Interaction Response of a Floating Laminated Composite Plate

In consideration of the effects of transverse shear deformation and structure-fluid interaction,the analytical expression of fluid force between a floating laminated composite plate and liquid surface isobtained.By expanding the displacements into Fourier series.the structure-fluid coupling dynamic re-sponse is solved.The effects of lamination angle,layer number,depth of fluid region and loading forms ondynamic response are investigated.     

不同节点布置下二维涡激振动的无单元法参数化分析

尝试建立1种基于无单元法的涡激振动数值模拟算法,并给出适用于涡激振动分析的前处理自动布点方法.基于无单元法理论,使用动最小二乘法构造形函数,利用无单元伽辽金法,采用速度和压力分离模式,及手工布点和自动布点2种方法所得出的节点布置形式,对流场控制方程进行空间离散,模拟二维涡激振动的流场形态,并对VIV相关参数进行分析,计算不同节点布置情况下的升力系数(Cl)、曳力系数(Cd)及斯特罗哈数(St),并与物理模型实验结果进行对比.计算结果表明,无单元伽辽金法应用于立管VIV分析是可行的,且文中采用2种布点方法均能较好的模拟流场中泻涡脱落的形态,计算结果与传统方法和物理模型实验结果吻合良好.证明文中2种布点方法都能用于固定圆柱的二维VIV分析,但自动布点法能够更好地适用于复杂问题的计算及圆柱体在流场中的VIV动力响应分析.     

海中输流立管涡激振动试验研究及疲劳寿命分析

为研究海洋立管涡激振动响应并预测其疲劳寿命,在中国海洋大学物理海洋实验室大型风-浪-流水槽进行海洋立管涡激振动模型试验.考虑管内流体的流动,运用相似理论将实际海洋立管缩放为试验模型,施加不同流速的外流,测得立管在涡旋脱落时顺流向及横向振动的应变时程曲线,根据实测结果,采用Miner理论对立管进行疲劳寿命分析.结果表明:立管横向振动比顺流向振动强烈,大约高一个数量级;随骀着外流流速的增加,管道横向及顺流向振动明显增加,立管的疲劳寿命降低;立管中部及端部振动比较强烈,疲劳寿命较其它位置处低,容易发生疲劳破坏.     

Experimental Study on Coupled Cross-Flow and in-Line Vortex-Induced Vibration of Flexible Risers

In this work, we study the coupled cross-flow and in-line vortex-induced vibration （VIV） of a fixedly mounted flexible pipe, which is free to move in cross-flow （ Y- ） and in-line （ X- ） direction in a fluid flow where the mass and natural frequencies are precisely the same in both X- and Y-direction. The fluid speed varies from low to high with the corresponding vortex shedding frequency varying from below the first natural frequency to above the second natural frequency of the flexible pipe. Particular emphasis was placed on the investigation of the relationship between in-line and cross-flow vibration. The experimental results analyzed by using these measurements exhibits several valuable features.     

Stability Analysis of Aquatic-Sand Pile Composite Foundation Reinforcing for New Shore-Connecting Structure

The Yangshan deepwater port is the only container port built in the islands off the mainland of China. Batter piles with a sheet-pile-supported platform bulkhead structure were first used as a new shore-connecting structure to connect the front main wharf structure and the back land. Large-diameter sand columns were also used to reinforce the soft foundation of the shore-connecting structure in the deep water of the open sea. A 3D nonlinear FEM model based on real geological conditions was built to optimize the large-diameter sand columns’ reinforcing scheme and investigate shore-connecting structures’ mechanical properties under different construction conditions. The replacement ratio of 30%, the bottom elevation of the fourth soil layer, and the soft soil just below and directly adjacent to the shore-connecting structure were determined as optimal replacement ratio, reinforcing depths, and reinforcing area of the large-diameter sand columns reinforcement by assessing the force and deformation of the shore-connecting structure. By numerical computing, the maximum displacement of the supported platform was 11.03 cm, which was close to the measured value; and the piles’ maximum stress, displacement and moments were all smaller than the design strength. These indicated that the shore-connecting structure could remain stable by an optimal sand columns reinforcing scheme.     

海洋桩基平台钢管桩自由站立深度分析与问题探讨

钢管桩基础是海洋导管架平台比较常用的一种基础形式,对钢管桩自由站立深度的准确预测是导管架平台安装项目中的一项重要工作。如果自由入泥深度评估不准确,现场施工时可能会导致钢管桩发生变形损坏,进而可能影响到整个油气田的生产运营。基于实际生产项目,讨论了钢管桩自由站立深度实际结果与预测值之间的关系,分析了造成实际结果的原因,论证了除自身结构性质外,钢管桩自由站立深度的影响因素主要包括海底地层性质和沉桩速度。海底浅部地层性质直接决定土对桩的承载力;沉桩速度决定土对桩的应力类型。实践表明,应用多种方法对钢管桩自由站立深度进行综合分析评价,能够考虑到多种影响因素,从而使评估工作更加全面,大大提高预测的准确度。     

Effect of Internal Flow on Vortex-Induced Vibration of Submarine Free Spanning Pipelines

At present, most researches on the vortex-induced vibration of submarine free spanning pipelines ignore the effect of internal flowing fluid; furthermore, there are no research reports considering the coupling effect of internal and external fluid with the free span. In this paper, combining Iwan‘s wake oscillator model with the differential equation derived for the dynamic response of submarine free spanning pipelines with inclusion of internal flow, the pipe-fluid coupling equations are developed to investigate the effect of internal flow on the vortex-induced vibration of the free spans. The finite dement approximation is implemented to derive the matrix equations of equilibrium. The Newmark method combined with simple iteration is used to solve the system of equations. The results indicate that the internal fluid flow may cause the shift of resonance band to the lower frequency and a slight decrease in the peak value; the effect will be mare pronounced with the increase of the span length and can be weakened in the presence of the axial tension.     

Study on Seepage Characteristics of Composite Bucket Foundation Under Eccentric Load

Under the effect of eccentric loads,when the suction pressure of the composite bucket foundation is leveled,the seepage failure is very easy to occur.The seepage failure occurrence causes the foundation to settle unevenly and impairs the bearing performance.This study uses ABAQUS finite element software to establish a composite bucket foundation model for finite element analysis.The model simulates the seepage of the foundation penetrating process under eccentric load to reveal the induced seepage characteristics of the bucket foundation.The most vulnerable position of seepage failure under the eccentric loading is elucidated.Critical suction formulas for different offset eccentric moment strategies are derived and compared with existing literature formulas.Then the derived formula is supplemented and corrected according to the pressure difference between adjacent cabins.Conclusions can be drawn:(1)Under eccentric loads,the critical suction decreases about 7%?10%.(2)The pressure difference between adjacent cabins impacts significantly on the seepage field,and the critical suction,at most,can be reduced by 17.56%.(3)the offset strategies have little effect on the seepage field.Efficient and appropriate strategies can be selected to meet the requirement of leveling in engineering project.     

The Effect of Internal Fluid on the Response of Vortex-Induced Vibration of Marine Risers

Based on Iwan‘s wake oseillator model developed with the classical van der Pol equalion, the differential equation for the response of the vortex-induced vihration (VIV) of the riser considering the effect of the internal flowing fluid and the external marine environmental condition is derived. The effect of the intermal flowing fluid on the response of VIV of the riser is studied by means of the Finite Element Method. The results show that the effect of the internal fluid velocity on the VIV of the riser is strong when the natural frequency of the riser is close to the vortex shedding frequency. In addition, the increase of the top tension can decrease the sensitivity of the riser to the internal fluid velocity.     

深水浮式系统耦合分析方法研究

深水浮式系统由系泊系统、立管系统和浮式结构(船体)构成,船体与柔性结构的耦合效应是非常显著的,文章介绍了深水平台耦合效应产生的原因和定义.耦合分析方法的步骤及其原理,并分析了传统非耦舍分析方法的不足.实例表明,耦合分析方法更接近于实际.     

筒型基础有限元分析的土体边界选取研究

利用通用的有限元程序ANSYS软件,以歧口17—2筒型基础平台为对象,采用三维八结点的块体等参元,在相同荷载和约束条件下,选取不同的土体边界,就筒型基础筒边土体的附加应力扩散行为进行了三维有限元分析。分析结果表明,筒边土体的附加应力扩散规律具有方向性;在确定土体边界尺寸时,应在水平方向取土体边界尺寸为5．0倍简体直径,在竖直方向取土体边界尺寸为2．0倍筒高,此时就可以忽略土体的边界效应,进而在有限元计算精度和求解时间之间找到一个合理的平衡点。     

一种适应性强的大型油田钻井液——SQ高温高压油气井无固机无机钻井液的研制

ＳＱ高温高压无固相无相钻井液是一种由加重剂、粘度调节剂、缓蚀剂和除氧剂组成的无机钻井液,它对储层渗透率的恢复值高（ 比现有的钻井液高出１０％ ～１３ ％ ） ,具有腐蚀性弱（０．０４９ｍｍ／ａ） 、与地下水和ＣＯ２ 等混合后不产生沉淀、耐高温（ ＞ ８０ ℃） 、密度高（１ ．５１ ～１ ．７０ｇ／ｃｍ３）等特性,故对油气层和机械设备具有良好的保护作用,是一种应性强的大型油田钻井液。     

海底沉积物弹性参数计算方法及误差分析

由海底沉积物的纵波速、横波速及湿密度,根据岩土力学原理,整理出一组计算海底沉积物弹性参数的公式;以该公式计算了南海南部海域浅层沉积物的弹性参数,计算结果与已有文献资料数据做了比较,分析了两者误差的原因.     

具有非线性能量阱的双层隔振系统抗冲击分析

近年来,非线性能量阱(NES)以其宽频减振、鲁棒性好等优点被广泛应用于隔振抗冲领域。 针对船舶隔振装置受到冲击载荷作用,建立了具有非线性能量阱的双层隔振系统动力学模型。利用三折线冲击谱来模拟基座受到的冲击波,并通过 Runge-Kutta 法计算系统的瞬态响应。通过能量分析法讨论了非线性刚度、阻尼系数、附加质量对设备的抗冲击效果的影响。计算结果表明：非线性能量阱性能良好,在最优参数范围内,可显著降低设备的冲击能量,控制残余振动。     

桶形基础平台三维有限元稳定性分析

以我国第一座桶形基础采油平台工程实例为原型，采用三维有限元计算方法对桶形基础稳定性分析。平台在波浪、风等荷载作用下，其稳定性不仅与平台的整体结构有关，而且与桶形基础及其周围土体相互作用相关。在计算中，利用薄层摩擦单元模拟土与结构间的相互作用，取得了很好的效果。分析结果表明桶形基础采油平台在设计条件下运行是较为稳定的。