Summary
Objective
A sustained research effort has resulted in a powerful and versatile computer analysis program WINPOST for hull/mooring/riser nonlinear coupled dynamic analysis in time domain. The program was initially developed for TLP’s and spars, and then extended to be able to analyze turret-moored FPSO’s. During its development, WINPOST has been validated with data from TLP, spar, and FPSO model tests.
WINPOST is now being extended to be able to analyze the motions and interactions of multiple floating structures, such as an FPSO and a shuttle tanker during offloading. This extended version of WINPOST will be completed and applied to study multi-body problems of interest (including an FPSO and shuttle tanker during offloading) and documented.
Approach
The extension to WINPOST under development is targeting the fully coupled dynamic analysis of multiple floating systems that are interconnected with elastic lines (e.g., hawsers) or mechanical yokes. A combined matrix method is used to simultaneously solve the dynamics of multiple floating systems in the time domain and account for the interactions between the systems. The analysis of each floating systems is a fully coupled analysis of the hull and its mooring and riser systems (as applicable).
Deployment of Results
The numerical analysis tool will be made available for industry use. The GUI (Graphics User Interface) including pre- and post-processors, graphics, and animations will be continuously developed. A user-friendly version will be installed in the OTRC computer system to assist future experiments. Research results will be published in a final OTRC report, journals and conference proceedings.
Project Plan
Scope of Work:
Work will focus on completing and verifying the interaction model. The interaction model will be used as a basis for assessing accuracies of various approximations and comparisons with other simpler approaches to describing interactions.
Predictions will be compared to available experimental data, but published data on interactions between multiple floating systems is scarce. Limited comparisons with FPSO/shuttle experiments conducted in Korea for both tandem and side-by-side mooring look promising, and will be finalized and documented.
The characteristics and importance of hydrodynamic interactions for various multiple vessel systems will be illustrated through a series of analyses for different multiple vessel systems. FPSO systems studies will include
- an FPSO offloading to a tandem-moored shuttle tanker
- an FPSO offloading to a side-by-side moored shuttle tanker
Realistic Gulf of Mexico operating environments will be used. Transient responses of the multiple vessels due to rapid changes in winds (e.g., a squall) or currents (e.g., the build up of currents due to an approaching Loop Current Eddy) will also be studied.
This analysis tool will also be used to conduct a preliminary study of an LNG carrier offloading to a stationary gravity-base receiving terminal. LNG carrier will be connected to the second “vessel”, i.e. a stationary gravity-base structure, by moorings and mechanical yokes. The effects of a larger vessel size and shallow water (the depth of the GBS will be ~200 ft) will be included in the analysis.
A GUI and 3D animation tools will be completed, and a user-friendly version of the software will be installed on OTRC computers to assist future experiments
Anticipated Results
Anticipated results include:
- A final report documenting the interaction model, sensitivity model, and studies of example FPSO and LNG systems in Gulf of Mexico operating environments
- A user-friendly computer program with a GUI and 3-D animations installed on OTRC’s computing system
- A numerical analysis tool available for use by operators, class societies, and regulators
Related Publications
Arcandra & Kim, M.H. “Hull/mooring/riser coupled dynamic analysis and sensitivity study of a Tanker Based FPSO”, Journal of Applied Ocean Research , 2003, vol. 25, no6, pp. 367-382 .
M.H. Kim and Y.B. Kim, “Hull/mooring/riser coupled dynamic analysis of a tanker-based turret-moored FPSO in deep water” Proc. 12th International Offshore and Polar Engineering Conference, Kita Kyushu, 2002
Arcandra, Ran, Z. and Kim, M.H., “Hull/mooring/riser coupled spar motion analysis with buoyancy-can effects” Proc. 12th International Offshore and Polar Engineering Conference, Kita Kyushu, 2002
Arcandra, P. Nurtjahyo, and M.H. Kim, “Hull/mooring/riser coupled analysis of a turret-moored FPSO 6000ft: comparison between polyester and buoy-steel mooring lines.” SNAME 2002 Symposium, Texas
Arcandra, Ran, Z. and Kim, M.H., “Hull/mooring/riser coupled dynamic analysis of a turret moored FPSO compared with OTRC experiment” Proc. Deepwater Mooring Systems Symp. ASCE, Houston, 2003
Arcandra, T., Prahoro, N. and Kim, M.H. 2004 Effect of line dynamics and hull viscous drag on the motion of turret-moored FPSO. OMAE Specialty Conference on FPSO Integrity, Houston
Kim, M.H., Koo, B.J., Mercier, R.M., and Ward, E.G. 2005. Vessel-mooring-riser coupled dynamic analysis of a turret-moored FPSO compared with OTRC experiment. J. of Ocean Engineering, Vol.32, pp1780-1802
Koo, B. J., Kim M. H., and Randall, R. E. 2004. The Effect of Nonlinear Multi-contact Coupling with Gap between Risers and Guide Frames on Global Spar Motion Analysis. J. of Ocean Engineering. 31/11-12 pp. 1469-1502
Koo, B. J. and Kim M. H. 2005 Motion Analysis of Two Floating Platform with Mooring and Hawser Lines in Tandem Moored Operation by Combined Matrix Method and Separated Matrix. J. of Ocean Engineering and Technology. Vol.19, pp. 1-15
