scholarly journals Mooring System Optimisation and Effect of Different Line Design Variables on Motions of Truss Spar Platforms in Intact and Damaged Conditions

2019 ◽  
Vol 33 (4) ◽  
pp. 385-397 ◽  
Author(s):  
O. A. Montasir ◽  
A. Yenduri ◽  
V. J. Kurian
Keyword(s):  
Mooring System ◽  
Spar Platforms ◽  
Design Variables ◽  
Truss Spar ◽  
System Optimisation ◽  
Line Design

Improved Strake Design for Vortex Induced Motions of Spar Platforms

2005 ◽  
Author(s):  
Mehernosh Irani ◽  
Lyle Finn
Keyword(s):  
Model Test ◽  
Model Tests ◽  
Test Results ◽  
Test Program ◽  
Test Set ◽  
Test Methodology ◽  
Spar Platforms ◽  
Truss Spar ◽  
Set Up

An extensive model test program was conducted to explore the effectiveness of alternate strake designs to reduce Truss Spar VIV response. Different strake configurations were tested to minimize VIV response. The paper presents results of the model tests. The model test set-up is described, important parameters that are modeled (including hull and truss geometry, strake configuration, mass and mooring properties) and considerations of instrumentation and test methodology are discussed. The paper also describes the analysis of the test results and shows the effectiveness of new strake design. The present results are compared with VIV response of existing Truss Spars with conventional strake design.

Sensitivity Analysis of Different Parameters of Taut Mooring System of a Truss Spar

2019 ◽  
Author(s):  
Zhuang Kang ◽  
Rui Chang ◽  
Youwei Kang ◽  
Shanchuan Liu
Keyword(s):  
Design Parameters ◽  
Mooring Line ◽  
Main Body ◽  
Mooring System ◽  
Spar Platform ◽  
Truss Spar Platform ◽  
Hole Position ◽  
Line Force ◽  
Truss Spar ◽  
Nonlinear Solutions

Abstract The taut mooring system is widely used for some advantages, such as smaller mooring radius, lighter total weight and better anti-corrosion performance. In this paper, the taut mooring system of a Truss Spar platform which was taken as the research object was investigated under the condition of 2000 m water depth in South China Sea. Firstly, the main body of the platform was analyzed in frequency domain based on the 3-d potential theory, and then the nonlinear solutions of platform displacement and mooring line force were obtained by using coupling analysis method in time domain, which determined the preliminary design parameters of mooring system. The sensitivity of the taut system is studied by changing several design parameters such as the top angle of mooring line, cable hole position and method of mooring disposal. In summary, the variation of the motion and dynamic response of the platform and mooring system has been explored and summarized by studying the design process and influential parameter of dynamic characteristics of mooring system and optimizing ideas of relevant parameters, which can further provide technical support and engineering reference for the design and application of the taut mooring system of deepwater Truss Spar platforms.

The Effect of Mooring System and Sheared Currents on Vortex Induced Motions of Truss Spars

2003 ◽  
Author(s):  
Radboud R. T. van Dijk ◽  
Arjan Voogt ◽  
Paul Fourchy ◽  
Saadat Mirza
Keyword(s):  
Gulf Of Mexico ◽  
Mooring System ◽  
Test Results ◽  
Current Profile ◽  
Scaled Model ◽  
Production Platform ◽  
Helical Strakes ◽  
Truss Spar ◽  
Set Up ◽  
Program Show

Since 1996 Spars have been used as production platform in the Gulf of Mexico. Spar Vortex Induced Motions (VIM) in strong currents like the hurricane and loop currents are an important consideration for the design of the mooring system and risers. This is important for the extreme offsets as well as fatigue in risers and the mooring system. This paper compares the VIM behavior of a truss Spar in sheared currents, like the Hurricane current in the Gulf of Mexico, with tow test results. Experiments have been carried out on a scaled model in both a complete mooring system and in a towing set-up with a simplified horizontal mooring. The Spar model consists of a hard tank with removable helical strakes, a truss section and a square soft tank. The results of this model test program show that both the choice of the mooring system and current profile have a significant influence on the VIM response of the Spar. The paper discusses the results of this research and also addresses important issues and considerations for VIM model tests.

An Internal Turret Mooring System Design Under Squalls Off The Coast of West Africa

2015 ◽  
Author(s):  
Xiaochuan Yu ◽  
Liqing Huang
Keyword(s):  
Wind Speed ◽  
West Africa ◽  
System Design ◽  
Mooring System ◽  
Wind Condition ◽  
Low Level ◽  
Wind Speeds ◽  
Line Design ◽  
The Way ◽  
Tandem Offloading

Squalls are intense, low-level winds associated with storms, and they always begin suddenly and last for minutes. They are characterized by large variation of wind speeds. Squalls control the design wind condition for floating production, storage and offloading systems (FPSOs) off the coast of West Africa. In this paper, an internal turret mooring system is designed to study the effects of squalls on the prediction of extreme tensions and offsets, which will be compared with the results from the way of using constant wind speed. Various statistic values of extreme tensions will be calculated and applied in the design. The differences between these values will also be discussed. Finally, the tandem offloading analysis is also performed in order to calculate the extreme hawser loads for the purpose of hawser line design.

Optimum Design of Spread Mooring Systems

1982 ◽  
Vol 104 (1) ◽  
pp. 78-83 ◽  
Author(s):  
H. L. Jones ◽  
J. K. Nelson
Keyword(s):  
Optimal Design ◽  
Mathematical Programming ◽  
Optimum Design ◽  
Loading Condition ◽  
Optimization Problem ◽  
Mooring System ◽  
Computer Solution ◽  
Initial Tension ◽  
Design Variables ◽  
Problem Design

The design of a spread mooring system of given pattern with single segment lines on a flat seafloor is formulated as a mathematical programming (optimization) problem. Design variables are the outboard length and initial tension in each line. Constraints limit maximum tension, anchor pull and anchor uplift for each line under each loading condition. Maximum vessel excursion is limited to a circle of specified radius. The optimal design is that which minimizes total weight of outboard line and is obtained by computer solution of the optimization problem. Three examples are presented to demonstrate the method.

Vortex-Induced Motion: Model Testing of a Monocolumn Floater

2006 ◽  
Author(s):  
Marcos Cueva ◽  
Andre´ L. C. Fujarra ◽  
Kazuo Nishimoto ◽  
Lui´s Quadrante ◽  
Ana Paula Costa
Keyword(s):  
Three Dimensional ◽  
Mooring Line ◽  
Small Scale ◽  
Extensive Literature ◽  
Offshore Platforms ◽  
Spar Platforms ◽  
Vortex Induced Vibrations ◽  
Induced Motion ◽  
Electrical Cables ◽  
Line Design

The vortex-induced vibrations - VIV have been studied for several fields of engineering due to its occurrence in different structures, such as electrical cables, industries chimneys and offshore risers. Although available an extensive literature describing its fundamental issues, these vortex-induced phenomena still deserve investigation, particularly in the offshore platforms installed in regions with high current speed. Recently, the Vortex-Induced Motions - VIM, a particular case of vortex-induced vibration with high magnitude of response amplitude, have been observed in SPAR platforms installed in Gulf of Mexico - GoM, opening a new investigation field. For those motions, aspects such as asymmetric mooring restoring stiffness and the probable three-dimensionality of the flow turn the problem even more complex. Since 2003, in partnership with University of Sao Paulo and consultant companies, PETROBRAS has been studying the use of monocolumn floaters for oil production in Campos Basin and GoM. Considering the environmental conditions in these areas and assuming that monocolumn floaters can exhibit similar VIM behavior of SPAR platforms, it was started an experimental investigation focusing on VIM responses of small-scale monocolumn floaters in towing tank. Although based on the state of art procedures used for SPAR platforms, the monocolumn experiments considered the different geometry of this concept and the larger susceptibility to the three-dimensional effects, due to the smaller relation draft/beam. Special attention was given to the ratio roughness/beam in order to guarantee similarity between the experiments and its respective real cases. Additionally, different heading conditions were also tested. Thus, the present work presents a set of preliminary results and discussions concerning VIM of monocolumn floaters and its impact on the mooring line design and riser specification.

Effect of mooring line configurations on the dynamic responses of truss spar platforms

2015 ◽  
Vol 96 ◽  
pp. 161-172 ◽  
Author(s):  
O.A. Montasir ◽  
A. Yenduri ◽  
V.J. Kurian
Keyword(s):  
Dynamic Responses ◽  
Mooring Line ◽  
Spar Platforms ◽  
Truss Spar

Strake Design and VIM-Suppression Study of a Cell-Truss Spar

2010 ◽  
Author(s):  
Ying Wang ◽  
Jianmin Yang ◽  
Tao Peng ◽  
Haining Lu
Keyword(s):  
Oil And Gas ◽  
Hydrodynamic Performance ◽  
Design Stage ◽  
Concept Design ◽  
Ocean Engineering ◽  
Design And Optimization ◽  
Fluid Field ◽  
Spar Platforms ◽  
Helical Strakes ◽  
Truss Spar

Along with the development of offshore technology, Spar platforms have been widely used in deep-sea oil and gas exploitation. Due to the deep draft cylinder hull piercing into the water, Spar platforms could be subjected to Vortex-Induced Motions (VIM) in certain current conditions. To mitigate VIM, helical strakes are used on the Spar hulls, and they have been proved to be effective. Cell-Truss Spar is a new concept of Spar platform which has recently been put forward by State Key Laboratory of Ocean Engineering (SKLOE) of Shanghai Jiao Tong University. It combines some good qualities of the Cell Spar and Truss Spar designs, aiming to bring in the lighter truss section and heave plate damping feature of the Truss Spar to obtain satisfactory heave motion performances, while reduce manufacture and installation difficulties by means of cell concept. Since the Cell-Truss Spar is a new design concept that has physical characteristics which are different from the existing Spars, the global motion performance should be carefully studied and verified. Researches about the VIM performance of the Cell-Truss Spar have been carried out recently (see Wang Ying et al, 2008, etc). Since it is still at the concept design stage, the Cell-Truss Spar configuration is considered without detail strake design in these studies. For the Cell-Truss Spar, which is still on concept design stage at the present time, the design and optimization of the helical strakes is very important to control the VIM response and improve the hydrodynamic performance. In this paper, strake design and VIM-Suppression Study of the Cell-Truss Spar is carried out. As a result of the unique characters on the hull, the outer surface of the Cell-Truss Spar does not form a regular cylinder. Hence, the strakes should be designed more carefully. In this study, four different configurations of strake groups are put forward and studied, and the one with the highest efficiency is chosen to be applied on the Cell-Truss Spar. The fluid field around the hard tank of the hull, the vortex disturbance near the strakes, and the forces acting on the hard tank with different strakes are simulated by CFD method, and the strake efficiency is assessed through model test combining with CFD computation. The optimized strake configuration is finally chosen, and the VIM performance of the strake-equipped Spar is studied.

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