正弦激励下零浮力海洋拖缆动力特性与实验研究

海洋地震拖缆是海洋油气资源勘探中的关键设备,为研究海洋地震拖缆的动力特性及其在不同频率正弦激励干扰下的动力响应,建立了零浮力拖缆的数学模型,设计了一套完整的实验方案,通过弹性测力机构放大张力信号以排除环境干扰,测量了不同拖曳速度与激振频率条件下拖缆首部的张力变化及缆上位移响应情况,初步分析了正弦激励作用下零浮力拖缆的动力学响应。弹性测力机构具有良好的线性度与可重复性,拖缆受到的水阻力与拖曳速度的平方成正比,数值计算与实验结果对比验证了数学模型的正确性,初步分析了正弦激励作用下零浮力拖缆的动力学响应。     

基于嵌入式水鸟的海洋地震拖缆运动状态仿真研究

研究分析了嵌入式水鸟作用下的海洋地震拖缆运动状态.在现有的理论基础上,简化地震拖缆运动数学模型,并进行仿真求解,结果表明定深水鸟在使地震拖缆保持水平状态起了重要作用.利用前处理软件建立了定深水鸟几何模型,并用数值计算软件进行了分析计算,得到了定深水鸟的水动力特性及在不同攻角下的升力分布情况,为水鸟运动控制策略提供理论依据.     

水下拖曳升沉补偿系统水动力数学模型研究

建立变缆长的水下拖曳升沉补偿系统水动力学偏微分方程组和边界条件.拖缆动力学模型基于Ablow and Schechter模型,拖体采用水下运载体六自由度方程模拟,运用有限差分法离散偏微分方程组和牛顿迭代法计算变缆长情况下拖体深度与拖缆各点张力的动态取值.数值计算结果表明采用收放拖缆的升沉补偿方法能够有效削弱母船升沉运动对拖体深度和拖缆张力的影响.     

水下非均匀拖缆稳态动力学分析

水下拖缆物理参数不均匀会影响拖缆的动力特性,研究非均匀拖缆的参数变化对拖缆动力特性的影响有一定的工程实际意义。建立了拖曳系统运动的三维数学模型,推导出了水下非均匀拖缆的稳态运动控制方程,在首尾两端加上相应的定解条件,直接求得或使用嵌套二分法求得非均匀拖缆在端点的初始值,进而求解稳态动力学方程。借助文献中的拖缆—海底拖车系统算例,通过计算结果的对比,验证了数学模型及计算方法的正确性。通过四阶龙格库塔法进行数值仿真计算,得到了稳态解,分析了非均匀拖缆自身物理参数变化对缆绳系统稳态运动的影响。结果表明,非均匀拖缆的切向阻力系数、法向阻力系数、直径和密度变化会影响稳态缆形和张力分布,影响的程度各不相同。最后给出了两个尾拖船系统非均匀拖缆的稳态运动算例。     

地震拖缆的复模态振动主动控制

地震拖缆系统的振动是影响海上油气勘探数据采集效率的主要因素,为提高勘探作业效率,研究了地震拖缆系统的主动振动控制问题。地震拖缆系统的重阻尼特性使得实模态控制技术难以实施。在地震拖缆系统有限元模型的基础上,基于模态观测器,在独立复模态空间,通过选择合适的权重矩阵,对地震拖缆的低阶模态设计了稳定的最优控制规律。通过对带有四个水鸟的拖缆系统的主动控制仿真,证明基于复模态的地震拖缆最优控制策略,在最大程度上利用水鸟自带电池能量的基础上,有效地抑制拖缆系统的振动,既能减少悬挂式水鸟更换频率,又能提高数据采集的质量,进而提高勘探作业效率。     

Optimal Towline Calculation of Distressed Vessel

运用非线性规划的方法对满足破损船舶安全性要求的可行航速下的拖缆参数进行优化计算,并通过目标决策方法选择最优航速及拖缆参数方案,对于方案的可用程度给出了定量的评价,提供了破损船舶拖带计算的一种方法.     

拖缆动力学离散化计算的后处理方法研究

拖缆的计算一般都是将拖缆离散化,建立非线性的动力学平衡方程组,通过龙格库塔法、Newton-Raphson迭代法等方法对非线性方程组进行求解.本方法是先将拖缆离散成若干段,列出离散段节点处的水动力学方程,并进一步建立节点处关于角加速度的线性平衡方程组,通过对角加速度的求解计算来解决拖揽的动力学问题.在计算过程中,将拖揽节点处关于角度的非线性问题转化为角加速度的线性问题,简化了求解非线性方程组的计算过程,避免了非线性方程组迭代求解中的初始点问题.     

规则波作用下水下拖缆数值分析研究

研究了水面波浪对水下拖缆的干扰。首先基于集中质量法给出了三维非均匀拖缆在规则波作用下的数学模型,然后通过四阶龙格库塔方法进行数值求解,并根据仿真计算讨论了拖缆在不同波浪作用下的稳态响应特性。仿真结果表明,水下拖缆在规则波的作用下,不仅作近似的简谐振动,还会在横向、垂向产生一个偏移量,且随浪向角的变化呈现不同的响应特征。     

海洋资源四维勘探拖缆阵列动力学特性仿真研究

面对日益增长的海洋资源勘探需求,海洋资源四维勘探拖缆阵列的研究越来越被人们所重视。作为拖缆动态控制策略研究的前提与依据,拖缆阵列的动力学特性始终是该领域在技术突破进程中的重要课题。以Ablow的经典模型为基础,采用微元法对拖缆阵列建立三维模型,并在时域上采用广义α算法对非线性方程进行离散求解,通过程序编译,对拖缆在四种工况(即拖船匀速直线航行、回转航行、变速直线航行以及拖点处存在升沉运动等)下的响应进行计算分析,着重考量其深度及张力的变化。仿真计算结果表明,广义α算法对拖缆阵列姿态在空间和时间上离散求解,算法稳定性良好,弥补了传统有限差分法对于时域不稳定的缺陷。     

高密度固体拖缆在海洋工程勘察中的应用

浅层工程勘察在海洋工程建设、工程环境地质调查等领域应用广泛,特别是对海洋工程安全具有重要的意义。介绍了中海油田服务股份有限公司自主研制的高密度固体拖缆及其在渤海某工区浅层海洋工程勘察中的应用情况,高密度固体拖缆较常规进口拖缆具有更高的分辨率,能够对浅层的小断层、小构造以及薄互层进行更精细的识别。     

Comparative steady state deep towing performance of bare and faired cable systems

The measured drag characteristics of a variety of cable fairings are reviewed and compared with those of bare cables. The effect of cable inclination angle has been studied and an empirical rule developed for dealing with faired cables, the hydrodynamic properties of which are shown to depend significantly on the section shape of the fairing.Non-dimensional cable functions are tabulated for both bare and faired cable profiles and applied to show how the addition of fairings can improve the towing performance of a given system.Simple formulae are developed for calculating faired cable system properties and for assessing the effect of fish drag on the depression angle.     

Some towing problems with faired cables

Measurements have been obtained from both wind tunnel and towing tank tests which explain the poor streaming behaviour of certain proprietary cable fairings, which had caused severe towing difficulties at sea.A simple modification applied to the fairings showed marked improvement in behaviour in laboratory tests and in sea trials.The results show the importance of good fairing cross sectional shape in order to develop adequate hydrodynamic restoring moments, and demonstrate the mechanical factors causing friction between cable and fairing.     

Optimization Design of Fairings for VIV Suppression Based on Data-Driven Models and Genetic Algorithm

Vortex induced vibration(VIV)is a challenge in ocean engineering.Several devices including fairings have been designed to suppress VIV.However,how to optimize the design of suppression devices is still a problem to be solved.In this paper,an optimization design methodology is presented based on data-driven models and genetic algorithm(GA).Data-driven models are introduced to substitute complex physics-based equations.GA is used to rapidly search for the optimal suppression device from all possible solutions.Taking fairings as example,VIV response database for different fairings is established based on parameterized models in which model sections of fairings are controlled by several control points and Bezier curves.Then a data-driven model,which can predict the VIV response of fairings with different sections accurately and efficiently,is trained through BP neural network.Finally,a comprehensive optimization method and process is proposed based on GA and the data-driven model.The proposed method is demonstrated by its application to a case.It turns out that the proposed method can perform the optimization design of fairings effectively.VIV can be reduced obviously through the optimization design.     

Some causes and effects of tow-off

The phenomenon of tow-off, or kiting, associated with faired cable systems has been studied in order to identify probable causes and demonstrate their effects. Three-dimensional cable profiles have been computed embodying experimentally determined values of all hydrodynamic quantities. The work encompasses fish induced and fairing induced tow-off, with light and heavy fairings, and provides generalised data for estimation purposes plus examples of the variation with towing speed and scope of the tow-off angles and fish displacements to be expected of a typical towed system.     

沙波区海底电缆的埋设

通过对沙波地形特征的分析,结合现有电缆埋设技术,从埋设器具及施工方式两方面介绍了在海鹿沙波区的电蜕埋设施工技术．同时,总结了过去电境埋设的成功经验,说明了在沙波区成功埋设电缆的原因．     

海底光缆故障判定及测试方法

在海底光缆不可避免的发生故障后，准确、迅速地判断海底光缆故障情况，以及根据所获得的测试数据来确定故障点的位置，成为海底光缆修复流程中极其关键的步骤。介绍了海底光缆故障的几种类型，并针对不同的故障类型，根据其特性给出了相应的测试方法来判定故障点，从而为海底光缆发生故障后，迅速修复奠定了技术基础。     

Dynamic Analysis of Towed and Variable Length Cable Systems

Towed cable systems are frequently used in marine measurements where the length of the towed cable varies during launch and recovery. In this paper a novel method for modeling variable length cable systems is introduced based on the finite segment formulation. The variable length of the towed cable is described by changing the length of the segment near the towing point and by increasing or decreasing the number of the discrete segments of the cable. In this way, the elastic effects of the cable can be easily handled since geometry and material properties of each segment are kept constant. Experimental results show that the dynamic behavior of the towed cable is consistent between the model and the physical cable. Results show that the model provides numerical efficiency and simulation accuracy for the variable length towed system.     

海底电缆在埕岛油田的应用及发展趋势

随着埕岛油田原油产量逐年递增,电力需求不断增加,海底电缆不断发展。文中主要介绍了埕岛油田采用的海底电缆的结构类型及特点,并对在海底电缆的维修、铺设中应注意的问题进行了分析,较为系统地对整个海上油田海底电缆进行了描述,并对今后埕岛油田海底电缆的发展方向进行了分析。     

海洋路由勘测对海底光缆工程的影响分析

介绍了水深、海底坡度、土壤剪切强度以及潮流、雷暴等海洋路由各勘测要素及其在海底光缆通信施工中的作用,并对它们在施工中的作用及其必要性进行了评价,从而使海洋路由勘测与施工的需要结合得更紧密,更具有针对性。     

钢管脐带缆扭转平衡设计

钢管脐带缆包含多种螺旋缠绕的功能单元,其在外力载荷下会发生相对运动,而且钢管的刚度较大对扭转平衡有重要影响,因此,相对于普通电缆,钢管脐带缆在扭转平衡设计时更加困难。根据扭转平衡理论公式,采用控制变量法,以第二层铠装钢丝的绞合角度为变量进行扭转平衡设计。首先建立脐带缆缆芯有限元模型,对其施加拉伸载荷,结果显示缆芯出现了扭转,这证明不能将脐带缆缆芯视为一实心圆柱。其次建立不同绞合角度的脐带缆有限元模型,设置各功能单元的材料属性和摩擦系数,分析模型在拉伸载荷下的扭转角度,并将相同拉伸载荷下的扭转角度拟合为直线,从而得到钢管脐带缆在扭转平衡状态时的最优绞合角度。最后,采用试验方法对实物钢管脐带缆进行扭转平衡测试,测试结果显示在拉伸载荷下脐带缆单位长度扭转角度十分微小,这表明缆是扭转平衡的。因此验证了使用的有限元方法在钢管脐带缆扭转平衡设计中的有效性。