An enhanced semi-coupled methodology for the analysis and design of floating production systems

2020 ◽  
pp. 1-33
Author(s):  
Aldo Roberto Cruces Giron ◽  
William Steven Mendez Rodriguez ◽  
Fabrício Nogueira Correa ◽  
Breno P Jacob
Keyword(s):  
Equilibrium Position ◽  
Production Systems ◽  
Equations Of Motion ◽  
Coupled Analysis ◽  
Mooring Lines ◽  
Analysis And Design ◽  
Stiffness Matrices ◽  
Linear Effects ◽  
The Mean ◽  
Nonlinear Static

Abstract This work presents an enhanced hybrid methodology for the analysis and design of floating production systems (FPS). The semi-coupled (S-C) procedure exploits advantages of coupled and uncoupled models, incorporated into a three-stage sequence of analyses that can be fully automated within a single analysis program, presenting striking reductions of computational costs. The procedure begins by determining, through a full nonlinear static coupled analysis, the mean equilibrium position of the FPS with its mooring lines and risers. Then, it automatically evaluates equivalent 6-DOF stiffness matrices and force vectors representing the whole array of lines. Finally, these matrices/vectors are transferred to the dynamic analysis, solving the global 6-DOF equations of motion restarted from the static equilibrium position. This way, the S-C methodology represents all non-linear effects associated to the lines and consider their influence on the dynamic behavior of the hull. However, in some situations it could still overestimate dynamic amplitudes of LF motions, and/or underestimate amplitudes of line tensions. Thus, to improve the overall accuracy, enhanced procedures are incorporated to better represent damping and inertial contribution of the lines. Results of case studies confirm that this methodology provides results adequate for preliminary or intermediary design stages.

Influence of Nonlinear Mooring Stiffness on Hydrodynamic Performance of Floating Bodies

2009 ◽  
Author(s):  
Huilong Ren ◽  
Jian Zhang ◽  
Guoqing Feng ◽  
Hui Li ◽  
Chenfeng Li
Keyword(s):  
Equilibrium Position ◽  
Equations Of Motion ◽  
Offshore Structures ◽  
Hydrodynamic Performance ◽  
Coupled Analysis ◽  
Mooring System ◽  
Main Function ◽  
Ocean Engineering ◽  
Mooring Lines ◽  
Floating Structures

Coupled dynamic analysis between floating marine structures and flexible members such as mooring lines and risers, is a challenging work in the ocean engineering field. Coupled analysis on mooring-buoy interactions has been paid more and more concern for recent years. For floating offshore structures at sea, the motions driven by environmental loads are inevitable. The movement of mooring lines occurs due to the excitation on the top by floating structures. Meanwhile the lines restrict the buoy’s motion by forces acting on the fareleads. Positioning is the main function of mooring system, its orientation effects can’t be ignored for floating structures such as semi-submersible, FPS, and TLP, especially when the buoy’s equilibrium position shifting to another place. Similar as hydrostatic restoring forces, mooring force related with the buoy’s displacement can be transformed into mooring stiffness and can be added in the differential equations of motion, which is calculated at its equilibrium point. For linear hydrodynamic analysis in frequency domain, any physical quantity should be linear or be linearized, however mooring stiffness is nonlinear in essence, so the tangent or differential stiffness is used. Steel chains are widely used in catenary mooring system. An explicit formulation of catenary mooring stiffness is derived in this article, which consists of coupled relations between horizontal and vertical mooring forces. The effects of changing stiffness due to the shift of equilibrium position on the buoy’s hydrodynamic performance are investigated.

Towards the Integration of Analysis and Design of Mooring Systems and Risers: Part I — Studies on a Semisubmersible Platform

2002 ◽  
Author(s):  
Stael Ferreira Senra ◽  
Fabricio Nogueira Correa ◽  
Breno Pinheiro Jacob ◽  
Ma´rcio Martins Mourelle ◽  
Isai´as Quaresma Masetti
Keyword(s):  
Motion Analysis ◽  
Production Systems ◽  
Companion Paper ◽  
Coupled Analysis ◽  
Mooring Line ◽  
Mooring System ◽  
Analysis And Design ◽  
Design Methodologies ◽  
Campos Basin ◽  
Fully Coupled

The objective of this paper is to study different analysis methodologies for the design of floating production systems. The main issues are the use of uncoupled and coupled analysis methods, and the integration in the analysis and design of the mooring system and the risers. This paper is a companion to another paper also presented in the OMAE2002 Conference [1] The present paper begins describing a “basic” classic, uncoupled methodology, and proceeds with comments on some refinements in the representation of the behavior of the lines in the motion analysis of the vessel. Comments regarding the introduction of some level of integration between mooring line and riser behavior are also presented. These issues are illustrated with studies applying some of the considered design methodologies to the P-18 semi-submersible platform in Campos basin. The companion paper [1] proceeds describing a fully coupled methodology, and some hybrid methodologies that combine coupled and uncoupled analysis tools, and illustrates their application to a DICAS system for deepwater applications in Campos basin.

An Integrated Methodology for the Design of Mooring Systems and Risers of Floating Production Platforms

2012 ◽  
Author(s):  
Aldo Roberto Cruces Girón ◽  
Fabricio Nogueira Corrêa ◽  
Breno Pinheiro Jacob ◽  
Stael Ferreira Senra
Keyword(s):  
Production Systems ◽  
Coupled Analysis ◽  
Mooring Line ◽  
Design Practice ◽  
Structural Behaviour ◽  
Coupled Models ◽  
Mooring Lines ◽  
Hydrodynamic Behaviour ◽  
Integrated Methodology ◽  
Analysis Tools

Nowadays, coupled analysis tools that allow the simultaneous modelling of the hydrodynamic behaviour of the hull and the structural behaviour of the lines of floating production platforms have been increasingly used. The use of such tools is gradually allowing the introduction of some feedback between the design of risers and mooring systems. In the current practice, that comprises the so-called “hybrid” methodologies, mooring designers have been using these tools to consider the influence of the risers on the platform motions. On the other hand, riser designers can use motions that result from coupled simulations for the analysis of each riser. Such integration is already being implemented in the design practice of Petrobras; however, elsewhere the design of risers and mooring systems may still be performed separately, by different teams, therefore not fully exploiting the benefits that the coupled analysis tools can provide. In this context, this work describes an innovative, fully integrated methodology for the design of mooring systems and risers of floating production systems (FPS). This methodology considers different design stages (from preliminary to advanced), integrating the design activities of mooring lines and risers in a single spiral, allowing gains in efficiency and cost reduction. The initial design stages already include a feedback between riser and mooring analyses. The integrity of the risers can be considered in the mooring design by determining their safe operational zones, and therefore, mooring line pretensions can be modified to improve its structural performance. Then, in advanced stages critical design cases for both mooring and risers systems can be identified and rigorously verified by using fully coupled models. The application of the proposed methodology is illustrated with a case study of a typical FPS, representative of the platforms that have been recently considered for deepwater applications. It should be stressed that the methodology described here does not reflect the current design practice of Petrobras. Presently it is merely a proposal that is being studied and assessed; this work comprises the first draft of the methodology, which will be enhanced and consolidated as the result of current and future studies.

Semi-Coupled Scheme for the Analysis of Floating Production Systems

2013 ◽  
Author(s):  
Fabrício Nogueira Corrêa ◽  
Breno Pinheiro Jacob
Keyword(s):  
Dynamic Analysis ◽  
Production Systems ◽  
Equations Of Motion ◽  
Coupled Analysis ◽  
Design Practice ◽  
Load Case ◽  
Current Profile ◽  
Hydrodynamic Analysis ◽  
Computational Costs ◽  
Numerical Tools

Traditionally, the design practice of floating production systems (FPS) employed uncoupled numerical tools where firstly the hydrodynamic analysis of the hull is performed with the lines represented by scalar models (leading to the hull motions); subsequently, these motions are prescribed at Finite Element (FE) models of the lines. Nowadays, it is widely acknowledged that coupled analysis tools should be employed for deep-water applications, considering that the overall behavior is dictated by the interaction between the hydrodynamic behavior of the hull and the structural behavior of the lines. In this context, considering that in some situations the use of coupled formulations can lead to excessive computing times, this work presents a formulation for the analysis of FPS, referred here as the semi-coupled (S-C) strategy. Its goal is to attain faster simulations than a coupled formulation, with better accuracy than usually provided by the classical uncoupled scheme. In this strategy, for each load case a coupled static simulation is performed. From this simulation a global 6-DOF stiffness matrix that represents the array of lines is automatically calculated and added to the global matrix for the subsequent dynamic analysis to solve the equations of motion of the hull. Therefore, this dynamic analysis will adequately consider the nonlinear stiffness contribution of the lines, as well as the effect of the current profile acting on them, all evaluated at the static mean position for each load case. Case studies are presented to compare the computational costs and accuracy of this S-C strategy with coupled formulations.

Towards the Integration of Analysis and Design of Mooring Systems and Risers: Part II — Studies on a DICAS System

2002 ◽  
Author(s):  
Fabri´cio Nogueira Correa ◽  
Stael Ferreira Senra ◽  
Breno Pinheiro Jacob ◽  
Isai´as Quaresma Masetti ◽  
Ma´rcio Martins Mourelle
Keyword(s):  
Motion Analysis ◽  
Production Systems ◽  
Companion Paper ◽  
Coupled Analysis ◽  
Mooring Line ◽  
Mooring System ◽  
Analysis And Design ◽  
Design Methodologies ◽  
Analysis Methods ◽  
Campos Basin

The objective of this paper is to study different analysis methodologies for the design of floating production systems. The main issues are the use of uncoupled and coupled analysis methods, and the integration in the analysis and design of the mooring system and the risers. This paper is a companion to another paper also presented in the OMAE2002 Conference [1]. That paper describes a “basic” classic, uncoupled methodology, and comments on some refinements in the representation of the behavior of the lines in the motion analysis of the vessel. Comments regarding the introduction of some level of integration between mooring line and riser behavior are also presented in the companion paper [1], and these issues are illustrated with studies applying some of the considered design methodologies to the P-18 semi-submersible platform in Campos basin. The present paper proceeds describing some hybrid methodologies that combine coupled and uncoupled analysis tools, and illustrates their application to a DICAS system for deepwater applications in Campos basin.

Hull-Mooring Coupled Dynamic Analysis of Two Side-by-Side Operating Vessels

2010 ◽  
Author(s):  
Mahdi Mirzaei ◽  
Mehdi Shafieefar ◽  
Mohammad Reza Moharrami
Keyword(s):  
The Other ◽  
Coupled Analysis ◽  
Mooring Line ◽  
Mooring Lines ◽  
Gas Field ◽  
Finite Element Program ◽  
Coupled Dynamic Analysis ◽  
Element Program ◽  
The Mean ◽  
The Persian Gulf

This paper contains the results of mooring analyses of two side-by-side operating crane barges in the installation procedure of a jacket type platform in an oil-gas field in the Persian Gulf. Since the vessels are proposed to operate next to a fixed structure, making sure about their displacements and a convenient clearance between them and the jacket is a highly important aspect of the design process. In essence, the analyses consist of setting an appropriate configuration and positioning of the vessels relative to each other, considering a reasonable gap between vessels and the jacket, connecting the vessels together, and studding the behavior of the moored system when it is subjected to a set of environments. In particular, an equilibrium configuration is found when the system is subjected to the mean force of the environment which consists of waves, wind gusts and currents. Then the dynamics of the system about the mean position is investigated. In order to study the influence of a dynamic mooring analysis, two cases are compared; one considering weight and buoyancy as the only forces acting on the lines and carrying out a quasi-static mooring analysis, and the other taking into account the hydrodynamic forces from the mooring lines. An accurate and efficient finite element program for the coupled analysis of the hull-mooring system is used and two types of modeling the connected vessels are compared; one using joints with restraints for all relative motions but in relative roll, and the other using slings and fenders. In all cases, the results of time domain analyses consisting of mooring line loads and motion responses of the vessels are presented in time histories and the statistics are studied.

Ultradeepwater Monobuoys

2003 ◽  
Author(s):  
Mauro C. Oliveira
Keyword(s):  
Numerical Simulation ◽  
Time Domain ◽  
Calibration Procedure ◽  
Coupled Analysis ◽  
Global Behavior ◽  
Test Results ◽  
Mooring Lines ◽  
Analysis And Design ◽  
Deep Waters ◽  
Hull Forms

This work deals with the analysis and design of monobuoys for deep waters. The monobuoy performance evaluation is carried out using a time domain computer program due to the non linearities present in this problem. This program is used to simulate the behavior of the monobuoy under the action of waves, wind and current. A coupled analysis between the floater and the mooring lines, considering its inertia, is also employed. Initially a validation study is conducted comparing the numerical simulations with model test results for a 400 meters water depth CALM buoy. The test comprises an operational condition with a tanker connected to the buoy under the action of wave, current and wind loads. From these results a calibration procedure of the numerical simulation is proposed and different hull forms are assessed in order to verify its global behavior. The main objective is to check if there are improvements in comparison with more conventional shapes relatively to the riser forces in the connection point.

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

scholarly journals Finite Physical Dimensions Thermodynamics Analysis and Design of Closed Irreversible Cycles

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3416
Author(s):  
Gheorghe Dumitrașcu ◽  
Michel Feidt ◽  
Ştefan Grigorean
Keyword(s):  
Thermal Conductance ◽  
Heat Output ◽  
Operational Parameters ◽  
Analysis And Design ◽  
The Mean ◽  
Internal Irreversibility ◽  
Heat Transfers ◽  
Operational Constraints ◽  
Log Temperatures ◽  
Physical Dimensions

This paper develops simplifying entropic models of irreversible closed cycles. The entropic models involve the irreversible connections between external and internal main operational parameters with finite physical dimensions. The external parameters are the mean temperatures of external heat reservoirs, the heat transfers thermal conductance, and the heat transfer mean log temperatures differences. The internal involved parameters are the reference entropy of the cycle and the internal irreversibility number. The cycle’s design might use four possible operational constraints in order to find out the reference entropy. The internal irreversibility number allows the evaluation of the reversible heat output function of the reversible heat input. Thus the cycle entropy balance equation to design the trigeneration cycles only through external operational parameters might be involved. In designing trigeneration systems, they must know the requirements of all consumers of the useful energies delivered by the trigeneration system. The conclusions emphasize the complexity in designing and/or optimizing the irreversible trigeneration systems.

The Anchor-Last Deployment Problem for Inextensible Mooring Lines

1975 ◽  
Vol 97 (3) ◽  
pp. 1046-1052 ◽  
Author(s):  
Robert C. Rupe ◽  
Robert W. Thresher
Keyword(s):  
Numerical Model ◽  
Equations Of Motion ◽  
Simultaneous Equations ◽  
Mooring Line ◽  
Integration Scheme ◽  
Lumped Mass ◽  
Mooring Lines ◽  
Concentrated Masses ◽  
Predictor Corrector ◽  
Lagrange’S Method

A lumped mass numerical model was developed which predicts the dynamic response of an inextensible mooring line during anchor-last deployment. The mooring line was modeled as a series of concentrated masses connected by massless inextensible links. A set of angles was used for displacement coordinates, and Lagrange’s Method was used to derive the equations of motion. The resulting formulation exhibited inertia coupling, which, for the predictor-corrector integration scheme used, required the solution of a set of linear simultaneous equations to determine the acceleration of each lumped mass. For the selected cases studied the results show that the maximum tension in the cable during deployment will not exceed twice the weight of the cable and anchor in water.

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