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Hull/Mooring/Riser Coupled Dynamic Analysis of a Turret-Moored FPSO Compared with OTRC Experiment 원문보기

Journal of ship and ocean technology, v.8 no.3, 2004년, pp.26 - 39  

Kim Young-Bok (Shipbuilding) ,  Kim Moo-Hyun (Civil Engineering Department, Texas A&M University, USA)

Abstract ▼ AI-Helper 아이콘AI-Helper

A vessel/mooring/riser coupled dynamic analysis program in time domain is developed for the global motion simulation of a turret-moored, tanker based FPSO designed for 6000-ft water depth. The vessel global motions and mooring tension are simulated for the non-parallel wind-wave-current 100-year hur...

주제어

#vessel-mooring-riser coupled dynamics   #turret-moored FPSO   #truncated mooring   #OTRC experiment   #GoM non-parallel environmental condition  

AI 본문요약
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제안 방법

  • A scale of 1:60 was used in the OTRC model tests. Due to the limitation of basin depth, a truncated mooring system that can give reasonable surge stiffness was devised and used in the model testing. However, a separate numerical coupled dynamic analysis was conducted with the prototype mooring system extended to full water depth to indirectly observe the coupling effects and the problems and deficiency associated with the truncated mooring system.
  • Due to the limitation of basin depth, a truncated mooring system that can give reasonable surge stiffness was devised and used in the model testing. However, a separate numerical coupled dynamic analysis was conducted with the prototype mooring system extended to full water depth to indirectly observe the coupling effects and the problems and deficiency associated with the truncated mooring system.
  • In the numerical model for this study, the full-length X-shaped prototype mooring system is devised so that their surge stiffness and the total drag force are as close as possible to the original target mooring system. However, the truncated mooring system devised in the experiment to represent the same target original mooring system is not numerically modeled because it contains springs, clump weights, and buoys which make the numerical modeling more difficult.
  • In this study, a tanker-based turret-moored FPSO designed for the water depth of 6, 000 ft and tested in the OTRC wave basin is adopted for the verification of the hull/mooring/riser coupled static and dynamic analyses by a computer program WINPOST-FPSO developed at Texas A&M University. The FPSO hull is moored by 12 chain-polyester-chain taut mooring system and also supports 13 steel catenary risers.
  • 8 rad/sec and the intermediate values for other frequencies are interpolated. The hydrodynamic coefficients and wave forces are expected to vary appreciably with large yaw angles and the effects should be taken into consideration for the reliable prediction of FPSO global motions. Therefore, they are calculated in advance for various yaw angles with 5-degree interval and the data are then tabulated as inputs.
  • The methodology of WINPOST-FPSO was published, for example, in Kim and Kim (2001). The paper contains the simulation results of the static offset test, the free-decay test, and hurricane-condition simulations for a 6000-ft FPSO adopted for DEEPSTAR study. In the OTRC experiments, the same FPSO hull shape and mooring system were used compared to the DEEPSTAR study but the turret location, vessel draft, and wind/current are different.

대상 데이터

  • The mooring lines and risers are hinged to and spread from the turret. In the original design data there are 12 combined mooring lines consisting of chain, polyester, and chain, and 13 steel catenary risers. There are 4 groups of mooring lines, each group consists of 3 mooring lines 5-degrees apart.

데이터처리

  • In the present study, the global motions and mooring dynamics of a deepwater turret- moored FPSO in non-parallel 100-yr hurricane are numerically simulated and the numerical results are compared with the OTRC 1:60 model-testing results with truncated mooring system. The system's stiffness and line tension as well as natural periods obtained from the OTRC measurement are checked through numerically simulated static- oflset and free-decay tests by WINPOST.

이론/모형

  • For experiments and simulations, the following 100-year extreme hurricane condition at the Gulf of Mexico (GoM) is used as the DeepStar case. The wave condition is given by JONSWAP spectrum with significant wave height of 12 m, the peak period of 14 sec, and the overshooting parameter of 2.
  • As for global vessel motions, the analysis results are reasonable compared to the experiments in view of overall trend. It needs to be reminded one more time that in the present simulations, the Newman's approximation scheme is used for evaluating the second-order difference-frequency wave forces and wave drift damping neglected.
  • In the same paper, natural frequencies and damping measured from the free decay test in the OTRC wave basin are also given. The added mass and radiation damping, first-order wave-frequency forces, and second-order mean and difference-frequency forces are calculated from the 3D second-order diffraction/radiation panel program WAMIT. Figurre 4 shows the distribution of pan the body surface.
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참고문헌 (22)

  1. Arcandra, T. 2001. Hull/Mooring/Riser Coupled Dynamic Analysis of a Deepwater Floating Platform with Polyester Lines. Ph.D. Dissertation, Texas A&M University 

  2. Arcandra, T., P. Nurtjahyo and M.H. Kim. 2002. Hull/mooring/riser coupled analysis of a turret-moored FPSO 6000 ft: comparison between polyester and buoys-steel mooring lines. Proc. 11th Offshore Symposium, The Texas Section of the Society of Naval Architects and Marine Engineers, SNAME, 1-8 

  3. Baar, J.J.M, C.N. Heyl and G. Rodenbusch. 2000. Extreme responses of turret moored tankers. Proc. Offshore Technology Conference, OTC 12147 (CD-ROM), Houston, Texas 

  4. Dean, R.G. and R.A. Dalrymple. 1992. Water Wave Mechanics for Engineers and Scientists. Advanced Series on Ocean Engineering, 2. World Scientific Press, Dover, D.E 

  5. Faltinsen, O.M. 1998. Sea Loads on Ships and Offshore Structures. The Cambridge University Press, Cambridge 

  6. Garrett, D.L. 1982. Dynamic analysis of slender rods. J. Energy Resources Technology, Trans. of ASME, 104, 302-307 

  7. Kim, M.H. 1992. WINPOST V3.0 Users Manual. Dept. of Ocean Engineering, Texas A&M University 

  8. Kim, M.H, R.S. Mercier, G. Gu, C. Wu and D. Botelho. 1993. PC-based wave load computation for large volume multi-column structures. Proc. of the 4th Int. Offshore and Polar Eng. Conference, ISOPE 

  9. Kim, M.H., T. Arcandra and Y.B. Kim. 2001a. Validability of spar motion analysis against various design methodologies/parameters. Proc. 20th Offshore Mechanics and Arctic Eng. Conference, OMAE01-OFT1063 (CD-ROM), L.A., Califonia 

  10. Kim, M.H., T. Arcandra and Y.B. Kim. 2001b. Validability of TLP motion analysis against various design methodologies/parameters. Proc. 12th Int. Offshore and Polar Eng. Conference, ISOPE, 3, 465-473 

  11. Kim, M.H. and Y.B. Kim. 2002. Hull/mooring/riser coupled dynamic analysis of a tankerbased turret-moored FPSO in deep water. Proc. 13th Int. Offshore and Polar Eng. Conference, ISOPE 

  12. Lee, C.H. 1999. WAMIT User Manual. Dept. of Ocean Engineering, Massachusetts Institute of Technology, Cambridge, M.A 

  13. Ma, W., M.Y. Lee, J. Zou and E. Huang. 2000. Deep water nonlinear coupled analysis tool. Proc. Offshore Technology Conference, OTC 12085 (CD-ROM), Houston, Texas 

  14. Nordgen, R.P. 1974. On computation of the motions of elastic rods. ASME J. Applied Mechanics, 777-780 

  15. OCIMF 1994 Prediction of Wind and Current Loads on VLCCs. 2nd Edition, Witherby & Co. Ltd, London, England 

  16. Ran, Z. and M.H. Kim. 1997. Nonlinear coupled responses of a tethered spar platform in waves. Proc. of the 8th Int. Offshore and Polar Eng. Conference, ISOPE 

  17. Ward, E.G., M.B. Irani and R.P. Johnson. 2001. The behavior of a tanker-based FPSO in hurricane waves, Winds, and Currents. Proc. 11th Int. Offshore and Polar Eng. Conference, ISOPE, 4, 650-653 

  18. Wichers, J.E.W. 1988. A Simulation Model for a Single Point Moored Tanker. Ph.D. Dissertation, Delft University of Technology, Delft, The Netherlands 

  19. Wichers, J.E.W. and C. Ji. 2000a. On the coupling term in the low-frquency viscous reaction forces of moored tankers in deep water. Proc. Offshore Technology Conference, OTC 12086 (CD-ROM), Houston, Texas 

  20. Wichers, J.E.W and C. Ji. 2000b. Deepstar-CTR 4401- theme structure benchmark analysis for tanker based FPSO-GoM. Technical Rep. 15629-1-0E, MARIN, Wageningen, The Netherlands 

  21. Wichers, J.E.W. and P.V. Develin. 2001. Effect of coupling of mooring lines and risers on the design values for a turret moored FPSO in deep water of the gulf of mexico. Proc. l lth Int. Offshore and Polar Eng. Conference, ISOPE, 3, 480-487 

  22. Wichers, J.E.W, H.J. Voogt, H.W. Roelofs and P.C.M. Driessen. 2001. Deepstar-CTR 4401- benchmark model test. Technical Rep. 16417-1-0B, MARIN, Wageningen, The Netherlands 

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