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Coupled Analysis of Floating Structures with Mooring Lines

Author: YuanZhiMing
Tutor: ZuoChunYan
School: Jiangsu University of Science and Technology
Course: Design and manufacture of ships and marine structures
Keywords: floating structures mooring systems semi-submersible platform coupled analysis time domain
CLC: U674.381
Type: Master's thesis
Year: 2011
Downloads: 138
Quote: 3
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Abstract

Mooring system is an essential part of floating structures, and dynamic analysis playsan integral role in the design of floating production systems. As thus, coupled analysis offloating productions systems is of great significance in theoretical research and engineeringapplication.In this paper, full time domain coupled method is employed to analyze a typicalsemi-submersible in order to acquire the dynamic responses of vessel and lines. And then,the comparative analysis is carried out between full coupled, semi-coupled and non-coupledmethod before the validation of the superiority of the full time domain coupled method.On this basis, a new mooring system integrating catenary with taut mooring is proposed andafter that, a semi-submersible platform is simulated to illustrate the improvement of the newmooring system in hydrodynamic performance of the floating system. Meanwhile, the effectof water depth on mooring systems is discussed. The paper’s main research concludes:1. Research is carried on the dynamic performance of the vessel. Based on linear wavetheory and second order wave theory, 3D Green’s function is adopted to solve thediffraction and radiation potential in order to obtain the wave loads on vessel. Moreover,the vessel is simulated by SESAM software to obtain the added mass, radiation dampingand RAO of the vessel.2. Research is carried on the full time domain coupled analysis on the hydrodynamicperformance of the floating system. Motion performance of floating structure coupledwith mooring lines is simulated by employing full coupled analysis method,semi-coupled analysis method and non-coupled analysis method. And then thedifference can be figured out between these three methods before the validation of thesuperiority of the full time domain coupled method.3. Research is carried on the conceptual design and performance analysis of the newmooring system. The merits and demerits of catenary mooring system and taut mooringsystem, which are commonly used nowadays, are analyzed. Falling somewhere betweenthese two systems, a new mooring system integrating catenary with taut mooring is proposed. In order to expound and prove the advantages of this new system, the motionperformance of the new mooring system is simulated. Comparing the result of newmooring system with that of taut mooring system, it can be concluded that themovement of the platform using the new type mooring system is smaller than that usingthe taut mooring system, which ensures a better working conditions. Furthermore, thenew mooring system is also compatible with the characteristic of catenary mooringsystem, which eliminates the requirement of anti-uplift capacity of the anchors.4. Research is carried on the adaptive water depth range of the new mooring system.Several typical water depths ranging from 500m to 3000m are simulated in order toacquire the displacement of the vessel, the tension of the lines and the arrangement ofthe lumped masses varying with the water depth. And then the optimal water depth canbe found.

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