Determination of the Response Amplitude Operator(s) of an FPSO

The driving necessities of cost reduction and the need to develop fields at ever increasing water depths have led to the use of floating structures. Among these structures are the Floating Production Storage and Offloading (FPSO) units whose motion analysis is considered in this paper. In actual environmental condition, it is required to accurately determine or predict large amplitude motion of the FPSO before any offshore operation. This paper seeks to present a detailed method of computing the Response Amplitude Operator(s) (RAOs) for the six (6) degrees of freedom using ANSYS AQWA. The results indicate for Heave motion a tendency for the heave peak value to move slightly higher dimensionless encounter-frequency as the wave moves from Head sea to Beam sea direction. A MATLAB source code was developed to validate the result for heave motion at head sea. Although a small difference in predicted heave motion occurred, it is pertinent to note that the comparisons between results generated in the MATLAB program and ANSYS AQWA demonstrate generally good agreement, and the roll response of the FPSO is noted to be critical.

浅水效应及其对软刚臂单点泊FPSO安全影响研究

浮式生产储油装置(FPSO)作为海上油气开发的重要设施,确保其结构强度和完整性对于在海洋环境下开展原油集输至关重要。基于势流理论,对目标FPSO进行频域分析,研究浅水效应对船体水动力特性的影响,以及不同水深下船体的固有周期和运动幅值响应算子等水动力特性的变化趋势。结果表明,目标FPSO工作水域水深较浅时,船体垂荡、横摇和纵摇固有周期均增大;在不同水深具有相同吃水比时,除了垂荡和纵摇外,其他自由度响应均随水深吃水比的增大而减小。

基于IMO分级的MASS岸基操控人员法律地位探析

随着AI技术的发展,人工智能与传统设备的结合已深刻改变了人类的生产生活。MASS(Maritime Autonomous Surface Ships)全称为海上自主水面船舶,其作为人工智能的产物,代表着未来船舶的发展趋势,也推动MASS岸基操控人员这一新兴海事主体的产生。“自动化”并不意味着在MASS的操作过程中完全消除人员因素的干扰,在IMO所定义的MASS发展四阶段中,人在循环中的角色是不断变化的,其职能、责任、法律地位均有所不同,关于岸基操控人员法律地位的认定,具有基础性和高度优先性。L1级别MASS无需岸基操控人员;L2级别MASS岸基操控人员可视作L3级别岸基操控人员的实习或见习期;L3级别岸基操控人员可视为船长或“外部船长”;L4级别MASS系统的优先程度高于人,岸基操控人员仅具有“监督”与作出“降级”决定的职责,不排除其成为新兴海事主体的可能性。

Experimental Study on Influencing Factors of Motion Responses for Air-Floating Tetrapod Bucket Foundation

Air floating transport is one of the key construction technologies of bucket foundation.The influences of draft,water depth and bucket spacing on the motion response characteristics of tetrapod bucket foundation(TBF)during air-floating transportation were studied by models tests.The results showed that with the increase of draft,the natural periods of heave motion increased,while the maximum amplitudes of oscillating motion decreased.The maximum amplitudes of heave motion decreased while pitch motion increased with the increasing of water depth;further,the period range of oscillating amplitude close to the maximum amplitude was expanded due to shallow water effect.With increasing bucket spacing,the maximum amplitudes of heave motion first increase and then decreased,whereas the maximum amplitudes of pitch motion decreased.Therefore,the favorable air-floating transportation performance can be achieved by choosing a larger bucket spacing under the condition of meeting the design requirements and reducing the draft under shallower water.

Experimental Study on the Influencing Factors of Motion Responses on an Air-Floating Caisson with Multiple Compartments

The structure of an air-floating caisson is suitable for the major structure of caisson-type artificial islands.Thus,it has been rapidly developed and widely used in the exploration and development of oil and gas fields in shallow sea and intertidal zones.Air-floating transportation technology is one of the key technologies employed in this structure.In this paper,the factors influencing the dynamic response characteristics of air-floating caisson with multi-compartments(AFCMC)were studied using model tests.The length and the height of each air-floating structure in the model were 1.0 and 0.1 m,respectively.In addition,the 1:100 models with 6,8,and 10 compartments under regular waves were tested in the wave flume,respectively.In the experiments,the respective water depths were set at 0.2,0.3,and 0.4 m,and the corresponding drafts were 0.05,0.06,and 0.07 m.Results show that with the increase of draft,the heave natural period increased and the maximum amplitude of the heave motion decreased.Meanwhile,the pitch motion decreased at 6 and 8 compartments and increased at 10 compartments.As the water depth increased,the maximum amplitude and amplitude change of heave and pitch motions first increased and then decreased.However,several amplitudes close to the maximum amplitude appeared in the measured period at shallower water depth,thereby indicating the vertical movements of the structure enhanced under shallow water.The increase in the number of compartments reduced the vertical movements under 6.0 m draft,but it increased the vertical movements under 5.0 and 7.0 m draft.Thus,increasing the number of compartments has a limited capacity to improve the motion performance of the structure.

Investigation of Pitch Motion Portion in Vertical Response at Sides of a Tension-Leg Platform

Tendons vertically moor Tension-Leg Platforms （TLPs）, thus, a deep understanding of physical tendon stresses requires the determination of the total axial deformation of the tendons, which is a combination of the heave, pitch, and surging responses. The vertical motion of the lateral sides of the TLP is coupled with surge and constitutes a portion of the pitch motion. Tendons are connected to the sides of the TLP; hence, the total displacement of the lateral sides is related to the total deformation of the tendons and the total axial stress. Therefore, investigating the total vertical response at the sides of the TLP is essential. The coupling between various degrees of freedom is not considered in the Response Amplitude Operator （RAO）. Therefore, in frequency domain analysis, the estimated vertical RAO is incomplete. Also, in the time domain, only the heave motion at the center of TLP is typically studied; this problem needs to be addressed. In this paper, we investigate the portion of the pitch motion in the vertical response at the sides of the TLP in both the frequency and time domains. Numerical results demonstrate a significant effect of the pitch motion in the vertical motion of the edges of the TLP in some period ranges.

基于ANSYS-AQWA的垫挡船码头靠泊特性分析

船舶逐步向标准化、大型化的方向发展,有效减少或避免大型船舶对码头碰撞是工程领域亟待解决的问题。采用ANASYS-AQWA仿真软件,基于三维势流理论与时域分析方法,结合山区河流水流湍急、流量变幅大的特点,采用数值分析的方法,研究了船舶在不同系泊方式下的系泊运动响应特性。研究结果表明:0°和180°的浪向角对纵荡幅值响应算子的影响最明显;90°的浪向角对横荡、垂荡和横摇响应较大,对纵荡、纵摇和艏摇影响较小;2-7-2系泊方式对于船舶的横向运动限制更好;4-4-4系泊对于船舶的纵向运动限制更好。

浮式平台运动加速度短期极值快速预报方法

提出一种基于浮式平台运动响应幅值算子(RAO)的频域方法,对浮式平台上任意位置加速度短期极值进行快速预报。假设浮式平台为刚体,通过运动互相关函数与运动谱密度函数的转换关系得到运动谱传递关系;从浮式平台重心运动谱快速转换得到任意点加速度谱,基于谱分析方法得到短期极值预报结果;对一艘浮式生产储油船(FPSO)船进行加速度短期极值预报,采用时域计算结果对该方法的准确性与有效性进行验证。研究结果表明,所提预报方法预报精度良好,同时具有极高的预报效率,能满足工程应用需求。

漂浮式风力机Spar平台垂荡板强迫振荡的优化探讨

为优化传统Spar平台的垂荡性能,以Umaine-Hywind Spar平台为模型,运用数值计算方法对附有不同形状垂荡板平台进行垂荡和纵摇响应RAO的频域和时域特性分析。结果表明,以直径9.4 m圆形垂荡板的性能为基准,保持各板面积、周长和当量直径不变,分别对不同形状垂荡板的优化效果进行比较,在各板周长相等的情况下,正方形垂荡板的优化效果最为突出,随着正多边形边数的增多,其优化效果逐渐减弱;当量直径相等时,正方形垂荡板的优化效果最不理想。

基于实测波频数据的海洋核动力平台多体动力特性评估

基于现有的渤海浮式生产储卸油装置(Floating Production Storage and Offloading,FPSO)实测数据,开展海洋核动力平台(Marine Nuclear Power Platform,MNPP)定位系统多体动力特性分析。建立MNPP定位系统的多刚体动力学模型,通过MNPP与渤海某FPSO的响应幅值算子(Response Amplitude Operator,RAO),计算FPSO船体实测数据与MNPP响应的比例系数;根据FPSO船体实测数据计算MNPP六自由度数据,并采用经验模态分解(Empirical Mode Decomposition,EMD)方法保留原始数据的波频成分,在此基础上计算定位系统的系泊回复能力和各铰节点的受力行为。通过与FPSO软刚臂系泊系统受力状态进行对比分析,验证MNPP定位系统在实测海况下设计的合理性。可为MNPP系泊结构设计和安全运行提供科学的分析手段。

基于AQWA的新型10 MW浮式平台运动响应分析

随着海上风机由近海进入深海,低功率的风机不再满足海上发电需求,需要设计出新的海上浮式平台来支撑更大功率的风机。基于频域与时域的分析方法,运用AQWA软件,对一种新型10 MW浮式平台在风、浪、流联合作用下的水动力性能进行研究。通过对不同浪向角下幅值响应算子(RAO)、附加质量、运动响应以及系泊张力的计算,结果表明,平台垂荡、横摇和纵摇的固有周期可以有效避开海上波浪能量集中的周期范围;在极限工况下纵荡、纵摇以及垂荡的最值分别为16.83 m、11.81°以及-6.213 m,说明有着良好的运动性能;系泊缆的安全系数为1.92,于允许安全系数1.67,能够保证平台安全运行。

椭圆形悬浮隧道管节沉放过程的波激运动特性分析

为了理清悬浮隧道施工过程中波浪参数与沉放体系中管节运动规律、系泊锚索张力的关系,以沉放过程中的大尺度椭圆形悬浮隧道管节为研究对象,基于ANSYS-AQWA软件采用数值模拟方法分析管节在规则波作用下的波激特性。在通过已有悬浮隧道管节的缩尺模型试验验证本文所用数值方法正确性的基础上,研究波浪环境中大尺度椭圆形悬浮隧道管节运动的时程历程曲线、RAO曲线以及锚索支撑的索力分布规律,得到沉放系统时域、频域运动特性与波浪参数(周期、波高、入射角)及管节的沉没深度、浮重比(BWR)之间的变化关系。结果表明:1)波高、周期增大时,管节位移与缆绳缆力均显著增加,增至一定程度时管节位移出现非线性特征,锚索出现松弛现象。2)在入射角增大的过程中,垂荡RAO曲线图分布规律基本一致,横摇值增大,纵摇值减小。3)不同沉没深度时横荡RAO曲线规律一致;垂荡RAO曲线对沉没深度非常敏感,其增加时垂荡值减小;沉没深度越大,横摇RAO值越小。4)管节浮重比减小时,管节横荡位移幅值减小,变为周期运动或准周期运动,缆索索力均大于零,松弛现象消失,索力时间历程呈现准周期规律。

叠船运输方式下的半潜船耐波性分析

以叠船运输方式下的半潜船为研究对象,采用CATIA软件进行三维建模。基于AQWA软件计算在规则波中不同浪向、不同航速和不同吃水下的响应幅值算子(Response Amplitude Operator,RAO),分析在不规则波中不同海况条件下货物绑扎设计关键点的加速度变化,发现浪向、航速和吃水等因素对RAO的影响规律。研究结果可为叠船运输方式下的半潜船安全运输提供运动预报,为货物绑扎设计提供依据。

深水八角形FDPSO垂荡性能数值分析

FDPSO是深水油气生产的重要装备之一,合理设置其垂荡板参数可较好地提高FDPSO垂荡运动性能。该文利用数值分析技术,以深水八角形FDPSO为研究对象,研究环绕型垂荡板主要参数对垂荡运动性能的影响。研究中利用SESAM软件计算得到不同垂荡板参数下平台运动响应曲线,进而得出不同垂荡板参数对垂荡性能的影响规律,确定最佳垂荡板参数。计算结果表明,合理设置垂荡板设计参数可明显改善垂荡及纵摇运动性能。

Numerical and Experimental Study on Hydrodynamic Performance of A Novel Semi-Submersible Concept

The Multiple Column Platform(MCP) semi-submersible is a newly proposed concept, which differs from the conventional semi-submersibles, featuring centre column and middle pontoon. It is paramount to ensure its structural reliability and safe operation at sea, and a rigorous investigation is conducted to examine the hydrodynamic and structural performance for the novel structure concept. In this paper, the numerical and experimental studies on the hydrodynamic performance of MCP are performed. Numerical simulations are conducted in both the frequency and time domains based on 3D potential theory. The numerical models are validated by experimental measurements obtained from extensive sets of model tests under both regular wave and irregular wave conditions. Moreover, a comparative study on MCP and two conventional semi-submersibles are carried out using numerical simulation.Specifically, the hydrodynamic characteristics, including hydrodynamic coefficients, natural periods and motion response amplitude operators(RAOs), mooring line tension are fully examined. The present study proves the feasibility of the novel MCP and demonstrates the potential possibility of optimization in the future study.

Nonlinear Coupled Analysis of a Single Point Mooring System

Coupled effects on a single point mooring(SPM) system subjected to the combined action of wind,waves and current are studied in this paper. Due to the complicatedness of the sea state and the huge size of the vessel,physical experimental study is both time consuming and uneconomical,whereas the numerical study is cost-effective and DNV software provides powerful SESAM software in solving the issues. This paper focuses on the modeling process of the SPM system,catenary equilibrium calculation,static analysis of the vessel in three different scenarios,and dynamic response simulation of the SPM system under environmental excitations. The three scenarios in study are as follows:the SPM is under the combined function of(a) wind,waves and current,(b) wind and waves,(c) current and waves. They are so set that one can compare the contributions of different types of loads in both static and dynamic studies. Numerical study shows that wind and current are the two major factors contributing to the mooring line tension,and surge and sway are the two dominant motions of the moored vessel subjected to environmental excitations.

The motion performance and mooring system of deepwater semi-submersible drilling unit

This paper analyzes the motion performance and mooring system of deepwater semi-submersible drilling unit in the district of the South China Sea using the MOSES procedure system. After the 3-D panel model of the unit was built, the 3-D diffraction-radiation theory was used to obtain the hydrodynamic loads on the wet surfaces and the response amplitude operators （RAO） of the unit. According to the environmental data, the short-term motion response to motion performance of the unit is predicted by the spectral method. Then a time-domain calculation was done to analyze the motion of the unit with its mooring system. The research results can be a reference for the model test of unit.

Resistance and Seakeeping Numerical Performance Analyses of a Semi-Small Waterplane Area Twin Hull at Medium to High Speeds

The hydrodynamic analysis of a new semi-small waterplane area twin hull （SWATH） suitable for various applications such as small and medium size passenger ferries is presented. This may be an attractive crossover configuration resulting from the merging of two classical shapes： a conventional SWATH and a fast catamaran. The final hull design exhibits a wedge-like waterline shape with the maximum beam at the stem; the hull ends with a very narrow entrance angle, has a prominent bulbous bow typical of SWATH vessels, and features full stern to arrange waterjet propellers. Our analysis aims to perform a preliminary assessment of the hydrodynamic performance of a hull with such a complex shape both in terms of resistance of the hull in calm water and seakeeping capability in regular head waves and compare the performance with that of a conventional SWATH. The analysis is performed using a boundary element method that was preliminarily validated on a conventional SWATH vessel.

State of the art for dry tree semi technologies

Dry tree semi is a fast developing technology and becomes more and more appealing to the operators as a solution for producing deepwater reserves. Utilizing a dry tree semi means spending less cost on well mainte-nance and interventions,while the production platform can be integrated and commissioned at quayside. This paper presents a comprehensive overview of various technologies for dry tree semi,such as E-semi,T-semi,paired-column semi and long stroke tensioners. Each dry tree semi concept is briefed in terms of global performance,top tension riser (TTR) tensioner system,quayside integration and feasibility to environment.

Rigid‑Body Analysis of a Beveled Shape Structure in Regular Waves Using the Weakly Compressible Smoothed Particle Hydrodynamics(WCSPH)Method

In many cases of wave structure interactions,three-dimensional models are used to demonstrate real-life complex environ-ments in large domain scales.In the seakeeping context,predicting the motion responses in the interaction of a long body resembling a ship structure with regular waves is crucial and can be challenging.In this work,regular waves interacting with a rigid foating structure were simulated using the open-source code based on the weakly compressible smoothed par-ticle hydrodynamics(WCSPH)method,and optimal parameters were suggested for diferent wave environments.Vertical displacements were computed,and their response amplitude operators(RAOs)were found to be in good agreement with experimental,numerical,and analytical results.Discrepancies of numerical and experimental RAOs tended to increase at low wave frequencies,particularly at amidships and near the bow.In addition,the instantaneous wave contours of the sur-rounding model were examined to reveal the efects of localized waves along the structure and wave dissipation.The results indicated that the motion response from the WCSPH responds well at the highest frequency range(ω>5.235 rad/s).