水深对软刚臂式FPSO浅水效应及触底的影响
发布时间：2018-11-06 12:45
【摘要】：对于浅水软刚臂式单点系泊FPSO,浅水效应和触底问题是引起系泊载荷过大和FPSO结构损坏的重要因素,也是当前研究的两大热点问题。本文针对30万吨级、16万吨级和5万吨级软刚臂式单点系泊FPSO的共八种装载工况,分别采用Newman近似法和Pinkster近似法考虑FPSO所受二阶波浪力,计算了不同WD/T(水深吃水比)条件下单点系泊系统受力,分析系泊系统受力随WD/T变化的规律。此外,本文给出了计算FPSO须考虑浅水效应的/LWD T(临界水深吃水比)的方法,分别计算了三艘FPSO在八种装载工况下的/LWD T,分析了该临界值随FPSO吃水、吨位变化的规律,并进一步对“FPSO须考虑浅水效应的/LWD T数据库”进行概念设计。本文还从频域和时域两个方面分别对三艘FPSO满载工况下的触底问题进行了研究和分析。通过本文的研究工作,得出了如下主要结论:(1)FPSO的二阶波浪载荷传递函数矩阵值整体随水深的增加逐渐减小;对于某些差频项,在浅水条件下,Pinkster近似法计算得到的二阶波浪载荷传递函数值远大于Newman近似法的计算值。(2)采用Newman近似法考虑二阶波浪力时,FPSO所受系泊力随WD/T的增加先增大后减小,但变化范围不大;采用Pinkster近似法考虑二阶波浪力时,系泊力随WD/T的增大逐渐减小,且浅水条件下的系泊力远大于深水条件下的系泊力。(3)浅水条件下,Pinkster近似法计算得到的单点系泊力远大于Newman近似法计算得到的系泊力;在超过一定WD/T时,Pinkster近似法计算得到的单点系泊力将小于Newman近似法计算得到的结果;两种方法的所得系泊力相等时对应的WD/T,可作为工程上FPSO须考虑浅水效应的/LWD T。(4)对于同一FPSO,须考虑浅水效应的/LWD T随吃水的增加而减小;利用FPSO排水体积将FPSO吃水无量纲化后,对于同一吃水,FPSO须考虑浅水效应的/LWD T随FPSO吨位的增加而减小。(5)将FPSO的型式、设计排水量、吃水等参数作为变量,可以建立FPSO须考虑浅水效应的/LWD T数据库;在工程设计中,仅需根据FPSO的各项设计参数,即可在数据库中查找其须考虑浅水效应的/LWD T。(6)给出了频域和时域内FPSO触底问题的分析方法,并在时域内计算了满载工况下各FPSO发生触底的/LWD T,30万吨级FPSO的/LWD T为1.04,16万吨级FPSO的/LWD T为1.05,5万吨级FPSO的/LWD T为1.34。
[Abstract]:The shallow water effect and bottom contact of FPSO, with soft rigid arm mooring in shallow water are the important factors that cause the excessive mooring load and the damage of FPSO structure, and are also two hot issues in current research. In this paper, the second order wave force of FPSO is considered by Newman approximation method and Pinkster approximation method for eight loading conditions of 300, 160, and 50, 000 tonnage soft rigid arm mooring FPSO, respectively. The forces of mooring system with different WD/T (depth to draft ratio) conditions are calculated and the law of mooring system with WD/T is analyzed. In addition, this paper gives a method to calculate the / LWD T (critical depth draught ratio of FPSO considering the shallow water effect, calculates the / LWD T of three FPSO ships under eight loading conditions, and analyzes the rule of the critical value changing with the draught and tonnage of FPSO. Furthermore, the conceptual design of FPSO / LWD T database considering shallow water effect is carried out. In this paper, the bottom problem of three FPSO under full load condition is studied and analyzed in frequency domain and time domain respectively. The main conclusions are as follows: (1) the second order wave load transfer function matrix of FPSO decreases with the increase of water depth; For some differential frequency terms, in shallow water, the second order wave load transfer function calculated by Pinkster approximation is much larger than that by Newman approximation. (2) when the second order wave force is considered by Newman approximation, The mooring force of FPSO increases first and then decreases with the increase of WD/T, but the range is not changed. When the second order wave force is considered by Pinkster approximation, the mooring force decreases with the increase of WD/T, and the mooring force in shallow water is much larger than that in deep water. (3) in shallow water, the mooring force in shallow water is much larger than that in deep water. The single point mooring force calculated by Pinkster approximation method is much larger than that by Newman approximation method. The single point mooring force calculated by the Pinkster approximation method is smaller than that obtained by the Newman approximation method when it exceeds a certain WD/T. When the mooring force of the two methods is equal, the corresponding WD/T, can be regarded as / LWD T. (_ 4 where the FPSO should consider the shallow water effect for the same FPSO,) / LWD T decreases with the increase of the draught. When FPSO draught is dimensionless by using FPSO drainage volume, for the same draught, the / LWD T of the shallow water effect should be reduced with the increase of FPSO tonnage. (5) the parameters such as FPSO type, design displacement, draught and so on are taken as variables. The / LWD T database with shallow water effect in FPSO can be established. In engineering design, only according to the design parameters of FPSO, we can find / LWD T. (6, which should consider shallow water effect, in the database. The analysis method of FPSO bottom problem in frequency domain and time domain is given. In the time domain, the / LWD T of / LWD T = 1.04t FPSO / LWD T = 1.05t FPSO / LWD T is 1.340.The ratio of / LWD T of 300,000t FPSO to that of FPSO / LWD T = 1.05t FPSO is calculated in the time domain under the condition of full load.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U674.38
本文编号：2314314
[Abstract]:The shallow water effect and bottom contact of FPSO, with soft rigid arm mooring in shallow water are the important factors that cause the excessive mooring load and the damage of FPSO structure, and are also two hot issues in current research. In this paper, the second order wave force of FPSO is considered by Newman approximation method and Pinkster approximation method for eight loading conditions of 300, 160, and 50, 000 tonnage soft rigid arm mooring FPSO, respectively. The forces of mooring system with different WD/T (depth to draft ratio) conditions are calculated and the law of mooring system with WD/T is analyzed. In addition, this paper gives a method to calculate the / LWD T (critical depth draught ratio of FPSO considering the shallow water effect, calculates the / LWD T of three FPSO ships under eight loading conditions, and analyzes the rule of the critical value changing with the draught and tonnage of FPSO. Furthermore, the conceptual design of FPSO / LWD T database considering shallow water effect is carried out. In this paper, the bottom problem of three FPSO under full load condition is studied and analyzed in frequency domain and time domain respectively. The main conclusions are as follows: (1) the second order wave load transfer function matrix of FPSO decreases with the increase of water depth; For some differential frequency terms, in shallow water, the second order wave load transfer function calculated by Pinkster approximation is much larger than that by Newman approximation. (2) when the second order wave force is considered by Newman approximation, The mooring force of FPSO increases first and then decreases with the increase of WD/T, but the range is not changed. When the second order wave force is considered by Pinkster approximation, the mooring force decreases with the increase of WD/T, and the mooring force in shallow water is much larger than that in deep water. (3) in shallow water, the mooring force in shallow water is much larger than that in deep water. The single point mooring force calculated by Pinkster approximation method is much larger than that by Newman approximation method. The single point mooring force calculated by the Pinkster approximation method is smaller than that obtained by the Newman approximation method when it exceeds a certain WD/T. When the mooring force of the two methods is equal, the corresponding WD/T, can be regarded as / LWD T. (_ 4 where the FPSO should consider the shallow water effect for the same FPSO,) / LWD T decreases with the increase of the draught. When FPSO draught is dimensionless by using FPSO drainage volume, for the same draught, the / LWD T of the shallow water effect should be reduced with the increase of FPSO tonnage. (5) the parameters such as FPSO type, design displacement, draught and so on are taken as variables. The / LWD T database with shallow water effect in FPSO can be established. In engineering design, only according to the design parameters of FPSO, we can find / LWD T. (6, which should consider shallow water effect, in the database. The analysis method of FPSO bottom problem in frequency domain and time domain is given. In the time domain, the / LWD T of / LWD T = 1.04t FPSO / LWD T = 1.05t FPSO / LWD T is 1.340.The ratio of / LWD T of 300,000t FPSO to that of FPSO / LWD T = 1.05t FPSO is calculated in the time domain under the condition of full load.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U674.38
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