水下打桩和船舶噪声对斑海豹听觉影响的初步分析

通过测定水下打桩和船舶噪声,利用Matlab软件对两类典型海洋噪声的时-频统计特性进行分析,结合斑海豹听阈和发声频域特性,分析水下打桩和船舶噪声对斑海豹的影响.结果表明:水下打桩及船舶噪声的主要能量分布频段(0～4.0 kHz)与斑海豹听阈敏感频段(0.1～ 100.0 kHz)及发声频段(0.4 ～ 1.5 kHz)相重叠;水下打桩噪声所产生的强噪声声源级(206 dB)会高于斑海豹可忍受的最高声源级(190 dB).由此推断,两类噪声会对斑海豹的生境产生严重干扰,轻者可能导致斑海豹的习性改变及感知和交流能力减弱,重者则会造成斑海豹的听阈丧失.本研究为斑海豹的声学保护提供声学参数依据,并为进一步深入研究提供参考.     

基于COS-2S模型的ADCP海浪方向谱估计

美国RD公司声学多普勒流速剖面仪(ADCP)使用的波向估计算法是迭代的最大似然算法(IMLM),IMLM可以准确估计出主浪向,但波向估计结果在主浪向以外其他方向上存在由噪声带来的能量分布,使得估计结果变得不准确。设计了基于COS-2S模型的波向估计方法,模型中只含有主波向,算法在准确估计主波向同时有效去除其他方向上噪声带来的能量分布。将一种混合遗传算法(HGA)代替遗传算法(GA)应用到波浪模型的参数求解中,HGA相对GA收敛更快,可有效找出全局最优解。仿真分析和实测数据表明,HGA和IMLM都能准确估计出波浪的主浪向,但HGA可有效去除主浪向以外其他方向上噪声带来的能量分布,HGA比IMLM更加适用于海洋各种噪声存在条件下的测量环境。     

水下加筋圆柱壳结构声散射特性研究

采用有限元/边界元(FEM/BEM)方法对水下加筋圆柱壳结构的声散射特性进行分析。考虑入射声场激发弹性结构振动产生二次辐射声场,总声场为入射场与散射场之和。基于Mindlin理论建立结构受迫振动的有限元模型,考虑入射声场为简谐激励,采用模态叠加法求出结构振动表面速度。根据声学边界元相关理论,利用有限元方法计算得出的弹性结构表面动力相应,可求出弹性结构的散射声场。研究结果表明,在同一波数下,不加筋结构后向散射强于加筋结构;加筋结构的散射指向性图案分叉较为明显;同种结构在波数增加的时候后向散射强度逐渐增大,前向散射强度逐渐减弱。     

基于LES和FEM/AML方法对潜标结构流噪声预报研究

为了更合理地预报潜标结构在海洋环境下的流噪声情况,采用基于大涡模拟(LES)结合远场自动匹配层(FEM/AML)技术的声学混合方法,以某NACA翼型结构为研究对象对其进行水下声学分析。该方法得到了频域条件下标体结构在特征点处的声压级频率响应曲线与表面声压分布情况,并与FLUENT计算结果进行对比,脉动压力结果与表面声压分布吻合良好,证明了该方法预报水下结构流噪声的可靠性。研究结果表明,标体结构流噪声能量主要集中在低频段,集中区域位于该标体的中后段,辐射噪声沿标体结构上下表面成瓣状分布,标体中部辐射范围大,标体头部、尾部辐射范围较小。     

China Ocean Engineering Contents of Volume 20, 2006

第24卷,第1期,2006年2月浮式生产储油船振动噪声混合数值预报………………………………………………………………………杨德庆,戴浪涛(1)浅水浮式生产储油系统(FPSO)二阶定常力数值仿真研究…………………………………………王磊,李欣,杨建民(9)圆弧面防波堤波浪力初步研究……     

基于灰理论的FPSO服务模式经济分析方法研究

近年来,随着浮式生产储存卸货装置(FPSO)逐渐成为世界海洋石油开发的主流方式,FPSO租赁业也随之兴盛起来。然而,迄今为止海洋石油领域仍缺乏对FPSO各服务模式的界定以及对其服务模式进行经济分析的理论依据。论文在调研目前世界范围内FPSO租赁业状况的基础上,对海洋石油领域现有的三种FPSO服务模式(干租、湿租及类湿租)进行了定性分析,首次对其各自的定义进行了归纳,并对其特点、性质进行了总结。此外,文中提出了在贫信息状态下利用灰关联度分析和GM(1,N)模型相结合的方法对FPSO服务模式进行定量经济分析的模型。通过对此模型参数包的求解,给出目标系统中各影响因素对FPSO租赁报价的贡献量,从而为FPSO所有者租赁报价的制定提供合理的科学依据。实例分析表明,这种经济分析模型所需信息量小,建模精度高,分析结果具有较高的可靠度。     

声学调查设备系统自噪声测量方法研究

声学调查设备重要功能之一是用来获取海洋中的背景噪声信号,这些信号都是弱信号,因此系统自噪声是声学调查设备中一项重要性能指标。提出了3种声学调查设备系统自噪声测量的方法,其中短路噪声测量法是实验室应用较多的一种方法,试验结果表明采用短路噪声测量法测量系统自噪声的结果可验证声学调查设备自噪声性能是否满足设计指标。低噪声环境自噪声测量法可以作为设备整机的功能及性能测试。     

应用比例边界有限元法求解狭缝对双箱水动力的影响

比例边界有限元法(SBFEM)是一种半解析数值分析的新方法,既融合了有限元法和边界元法的优点,又有其特有的优点。用该方法可求解有限水深下狭缝对双箱水动力作用的影响,为波浪与多浮体超大型结构的相互作用探索一些规律。整个计算域划分成2个无限子域和4个有限子域,并利用加权余量法在各个子域上推导了SBFEM的积分方程;计算了4个数值算例并与边界元等其它数值方法进行了比较,验证了该方法是一种用很少单元便能得到精确结果的高效方法。应用SBFEM对不同箱体宽度、不同狭缝宽度、不同吃水深度条件的双箱作了计算,得出了狭缝对双箱水动力干涉影响的一些规律,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。     

海上重力式建筑物基底的渗压荷载

本文研究了怎样应用有限元方法求解在波浪场作用下海底三维渗流对海上重力式建筑物的作用荷载。提出了符合问题物理意义的H₀1(Kr)、exp(Kz)及H₀1(Kr)exp(Kz)等衰减类型的无限元的应用,采用有限元和无限元对整个渗流域进行数值模拟,在已知波浪场的情况下,求解建筑物底面上的渗流作用力。本文的结果表明,海上大型重力式建筑物基底上的渗压荷载是一项不容忽视的设计荷载。欲全面地考虑海洋建筑物的环境条件及完善与之相适应的设计条件,就必须考虑建筑物底部的渗流作用问题。     

新型圆筒型FPSO串靠外输作业耦合水动力响应分析

针对1 000 m水深作业的新型圆筒型浮式生产储卸油系统（FPSO）,选择多点系泊FPSO和穿梭油轮串靠外输方案,分析串靠方案在中国南海的可行性。FPSO和穿梭油轮作业时两者之间相互影响的研究较为重要,通过ANSYS-AQWA建立水动力耦合分析模型,基于多浮体水动力学方法进行时域耦合仿真模拟。在FPSO作业海况下,分析了串靠外输时系泊锚链及系泊大缆的张力特性和两浮体的运动响应,对大缆的长度和刚度参数变化进行了分析。结果表明：串靠外输方案满足新型圆筒型FPSO的作业环境。随着系泊大缆长度增加,其张力最值逐渐减小,FPSO和穿梭油轮的最小间距逐渐增大。两浮体最小距离稳定在83 m左右。随着系泊大缆刚度增加,其张力最值增大,相比于大缆长度,大缆刚度对耦合系统的影响较弱。     

非线性波浪波面追踪的一种新模式

基于Laplace方程的Green积分表达式和波面BemouUi方程所建立的非线性波动数学模型,是一个时域上具有初始值的边值问题,而精确地追踪自由表面的波动位置,给出波面运动瞬时的波面高度和波面势函数,是建立时域内非线性波浪数值模式的基础。本文采用0-1混合型边界元剖分计算域边界并离散Laplace方程的Green积分表达式,采用有限元剖分自由水面并推导满足自由表面非线性边界条件的波面有限元方程,联立计算域内以节点波势函数和波面位置高度的时间增量为未知量的线性方程组,通过时步内的循环迭代,给出每个时步上的波面位置和波面势函数,从而建立了一种新的非线性波浪波面追踪模式。数值造波水槽内的波浪试验表明,其数值模拟结果具有良好的计算精度。     

Failure Statistics Analysis Based on Bayesian Theory: A Study of FPSO Internal Turret Leakage

The load and corrosion caused by the harsh marine environment lead to the severe degradation of offshore equipment and to their compromised security and reliability. In the quantitative risk analysis, the failure models are difficult to establish through traditional statistical methods. Hence, the calculation of the occurrence probability of small sample events is often met with great uncertainty. In this study, the Bayesian statistical method is implemented to analyze the oil and gas leakages of FPSO internal turret, which is a typical small sample risk but could lead to severe losses.According to the corresponding failure mechanism, two Bayesian statistical models using the Weibull distribution and logarithmic normal distribution as the population distribution are established, and the posterior distribution of the corresponding parameters is calculated. The optimal Bayesian statistical model is determined according to the Bayesian information criterion and Akaike criterion. On the basis of the determined optimal model, the corresponding reliability index is solved to provide basic data for the subsequent risk assessments of FPSO systems.     

Improving the prediction of extreme FPSO hawser tension,using another highly correlated hawser tension with a longer time record

The floating production storage and offloading unit (FPSO) is an offshore vessel that produces and stores crude oil prior to tanker transport. Robust prediction of extreme hawser tensions during the FPSO offloading operation is an important safety concern. Excessive hawser tension may occur during certain sea conditions, posing an operational risk. In this paper, the finite element method (FEM) software ANSYS AQWA has been employed to analyze vessel response due to hydrodynamic wave loads, acting on a specific FPSO vessel under actual sea conditions.In some practical situations, it would be useful to improve the accuracy of some statistical predictions based on a certain stochastic random process, given another synchronous highly correlated stochastic process that has been measured for a longer time, than the process of interest. In this paper, the issue of improving extreme value prediction has been addressed. In other words, an efficient transfer of information is necessary between two synchronous, highly correlated stochastic processes. Two such highly correlated FPSO hawser tension processes were simulated in order to test the efficiency of the proposed technique.     

完全非线性波浪与二维固定结构物作用的IGN-BEM耦合分析模型

为高效准确地对完全非线性波浪与二维固定结构物的相互作用进行模拟分析,建立了二维完全非线性时域耦合模型。耦合模型将计算域划分为靠近结构物的内域和远离结构物的外域,每个区域均采用满足完全非线性自由水面边界条件的波浪模型进行求解。在内域使用Laplace方程描述流体运动并采用高阶边界元法（BEM）对其进行求解;而在没有结构物的外域,波浪运动的控制方程为Irrotational Green-Naghdi（IGN）方程并采用有限元法（FEM）对其进行求解。内域和外域通过一段重叠区域进行耦合,从而实现模型间变量的传递。首先利用耦合模型分别对规则波的传播、直墙前立波的生成以及相关物理模型试验进行模拟,数值结果与精确解和试验结果的良好吻合验证了耦合模型耦合方式的合理性以及处理非线性问题的准确性;然后使用耦合模型模拟分析了波浪与固定结构物间的相互作用,并将结果与线性解析解以及完全非线性BEM模型的结果进行了对比分析,进一步证明了耦合模型的正确性与高效性。     

The coupled finite element and boundary element analysis of nonlinear interactions between waves and bodies

A coupled finite element (FEM) and boundary element (BEM) method is developed to analyse the nonlinear interaction between bodies and water waves. The former is used away from the body while the latter is used in a region near body. The combination is based on consideration of the efficiency of FEM and BEM in computation and mesh generation, respectively. Results for wave/body interactions are obtained by using auxiliary functions to decouple the mutual dependence of the body acceleration and the wave force.     

Time-Domain Analysis for 3-D Moored Systems

In the paper, a comprehensive numerical study on the moored system is performed in time domain. The moored system, which is composed of the floating body sub-system and the mooring line sub-system, is calculated as a whole system by coupling. A time-domain method is applied to the analysis of the mooring line sub-system, and at the same time, an indirect time-domain method translated from frequency-domain to time-domain is developed to calculate the floating body sub-system. In the end, an FPSO vessel is calculated as a numerical example by the present method. A comparison of the result of the model test and that of the numerical method indicates that the present method is exact and effective.     

圆筒型FPSO优化设计与水动力性能分析

针对圆筒型海上储油装置FPSO垂荡运动性能较差、无法安装干式井口的问题,设计了带延伸筒体与矩形阻尼结构的圆筒型FPSO,根据延伸筒体与矩形阻尼结构是否通海分为两种型式。建立水动力计算模型,比较分析不同延伸筒体和阻尼结构型式对FPSO水动力性能的影响。针对南海作业海域,设计了悬链式系泊系统,基于JONSWAP波浪谱对FPSO的运动进行时域预报,并对系泊系统进行校核。分析结果表明:通海型FPSO垂荡固有周期显著提升,可以错开南海百年一遇谱峰周期,通海型FPSO满足钻井、安装干式井口的运动响应要求,系泊系统系缆张力满足规范要求。     

Hull/mooring/riser coupled dynamic analysis and sensitivity study of a tanker-based FPSO

A computer program is developed for hull/mooring/riser coupled dynamic analysis of a tanker-based turret-moored FPSO (Floating Production Storage and Offloading) in waves, winds, and currents. In this computer program, the floating body is modeled as a rigid body with six degrees of freedom. The first- and second-order wave forces, added mass, and radiation damping at various yaw angles are calculated from the second-order diffraction/radiation panel program WAMIT. The wind and current forces for various yaw angles of FPSO are modeled following the empirical method suggested by OCIMF (Oil Company International Marine Forum).

The mooring/riser dynamics are modeled using a rod theory and finite element method (FEM), with the governing equations described in a generalized coordinate system. The dynamics of hull, mooring lines, and risers are solved simultaneously at each time step in a combined matrix for the specified connection condition. For illustration, semi-taut chain-steel wire-chain mooring lines and steel catenary risers are employed and their effects on global FPSO hull motions are investigated. To better understand the physics related to the motion characteristics of a turret-moored FPSO, the role of various hydrodynamic contributions is analyzed and assessed including the effects of hull and mooring/riser viscous damping, second-order difference-frequency wave-force quadratic transfer functions, and yaw-angle dependent wave forces and hydrodynamic coefficients. To see the effects of hull and mooring/riser coupling and mooring/riser damping more clearly, the case with no drag forces on those slender members is also investigated. The numerical results are compared with MARIN's wave basin experiments.     

潮汐影响下海滩前滨波浪传播耗能过程分析

文章基于长乐海滩前滨剖面的实测波浪数据, 通过统计分析以及谱分析的方法, 探讨了潮汐过程中长乐海滩波浪参数及耗能过程的变化规律。结果表明, 观测期间内波浪以混合浪为主, 各测点谱型较宽, 存在多峰振荡现象。向岸传播过程中, 波能耗散的形式为窄频域向宽频域转变, 能量分布趋于分散, 高频波能减小, 低频波能反而有所上升, 波浪破碎后生成长重力波。破波带内的能量衰减与波浪传播距离具有良好的相关性, 破碎波能在破波带内大约衰减了98.3%。潮汐水位对波浪具有明显的调制作用。入射波能随潮汐水位的增加而有所增加, 且水位越高, 入射波能分布越分散。破波带内的有效波高和潮汐水位具有显著的正相关关系。潮汐过程中固定测点的波谱变化与波浪沿剖面的波谱变化具有明显的相似性。     

Improved time-delay estimates of underwater acoustic signals usingbeamforming and prefiltering techniques

Passive sonar systems that localize broadband sources of acoustic energy estimate the difference in arrival times (or time delays) of an acoustic wavefront at spatially separated hydrophones, The output amplitudes from a given pair of hydrophones are cross-correlated, and an estimate of the time delay is given by the time lag that maximizes the cross correlation function. Often the time-delay estimates are corrupted by the presence of noise. By replacing each of the omnidirectional hydrophones with an array of hydrophones, and then cross-correlating the beamformed outputs of the arrays, the author shows that the effect of noise on the time-delay estimation process is reduced greatly. Both conventional and adaptive beamforming methods are implemented in the frequency domain and the advantages of array beamforming (prior to cross-correlation) are highlighted using both simulated and real noise-field data. Further improvement in the performance of the broadband cross-correlation processor occurs when various prefiltering algorithms are invoked