Prior Year Project Plan
Global Analysis of FPSO and Shuttle Tankers during Offloading
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.
ANTICIPATED PROJECT DURATION: 2 years
PROJECT PLAN FOR YEAR 2 (2004-2005):
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
o the interaction model
o sensitivity analyses
o 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
PROJECT PLAN FOR YEAR 1 (2003-2004):
Scope of Work and Anticipated Results:
· Full development of the FPSO-shuttle model to reasonably simulate tandem and side-by-side offloading operation
· More verifications against the planned FPSO-shuttle experiments at the OTRC wave basin (in collaboration with Dr. Rick Mercier)
· Full development of GUI and 3D animation tools: The user-friendly software will be installed on OTRC computers to assist future experiments
· The inclusion of the effects of unsteady currents in the time-domain simulations
· The inclusion of the effects of gust wind loading which changes directions in relatively short duration
· The simulation of DP-assisted FPSO/shuttle will be started.
SPONSORSHIP: OTRC Industry Consortia (MMS has also funded this and related research in previous years)
PRINCIPAL INVESTIGATOR (S) & OTHERS INVOLVED IN PROJECT:
PI(s): “Joseph” M.H. Kim
Others: Graduate students
2002-2003 OTRC PROJECT: FPSO GLOBAL RESPONSE ANALYSIS
OBJECTIVE:
During the past several years, PI has developed very powerful software called WINPOST for hull/mooring/riser nonlinear coupled dynamic analysis in time domain. The program has been extensively tested and verified against experimental results for various kinds of spars and TLPs. The WINPOST has since been extended to turret-moored FPSO analysis including large yaw motions, and successfully compared against other DeepStar FPSO results and Marin’s experiments. The WINPOST is further extended to handle FPSO-shuttle combination both in tandem and side-by-side mooring cases. The major part is now developed and some preliminary results have been obtained. It will be completed and extensively verified. (Note that the computer program can be further extended in future research to handle more complicated multi-body system with more complicated combination of mooring lines, such as spar/TLP-drilling barge-FPU combination.)
APPROACH:
For the hydrodynamics of FPSO and shuttle-tanker interactions, WAMIT MULTI-BODY version has been used. The moored multi-bodies connected by elastic cables and hawser-lines are solved simultaneously in a combined matrix. Other computer programs of similar capability typically use iteration methods, which account for multi-body hydrodynamic interactions partially. Using the combined matrix method, which is supposed to be the most accurate, the cases with full, partial, and zero hydrodynamic interactions can be straightforwardly compared. The published data for multi-body interactions are rare and more verification is needed. The preliminary comparison against KRISO experimental results for both tandem and side-by-side mooring is promising. Animation tools have been developed to better illustrate the FPSO-shuttle coupled analysis results.
OTRC will conduct a series of experiments in 2002-2004. First, both FPSO and shuttle tanker will be moored by soft spring in waves so that only the hydrodynamic interaction between the two hulls can be investigated without worrying about the effects of mooring lines and risers. Next, the same combination with risers, hawser lines, and mooring lines will be tested. Both cases will be modeled by WINPOST and the experimental results will be systematically compared with numerical prediction.
DEPLOYMENT OF RESULTS:
WINPOST-GUI has been successfully developed from other funding sources and now the WINPOST program is highly user friendly including very powerful graphic interfaces and post-processors. The program will be installed in OTRC computers and a demo-case will be developed for the OTRC FPSO experiment. The GUI will be extended to include multi-body application. Three standard versions (WINPOST, WINPOST-FPSO, WINPOST-MULTI) will be available to offshore industry for lease after commercialization. The methodology and key results will be published in conference and journal papers.
ANTICIPATED PROJECT DURATION: 1 year
PROJECT PLAN FOR YEAR 1 (2002-2003):
Scope of Work & Anticipated Results:
Topic Scope Deliverable Remarks
Analysis of FPSO Exp No.1 (3/00) § Estimate FPSO properties from available data§ Predict response statistics§ Demonstrate application of GUI WINPOST. § Predicted vs. Measured Response Statistics§ WINPOST model with GUI users manual & example application. § Mooring system problematic (missing info, untypical system)§ Can undertake as a analysis to provide a gross validation of vessel motions?
Analysis of FPSO Exp. No. 2A (7/02) - FPSO in soft mooring § Validate wave frequency response portion WINPOST for FPSO in a soft mooring§ Predict response time series§ Further validate wave/low frequency response model § Predicted vs. measured time series§ WINPOST model with GUI users manual & example application § Analysis can begin 10/02§ Preparation for analyzing FPSO Exp. No. 2B (FPSO + shuttle tanker)
FPSO + Shuttle tanker analytical model, program development, and verification § Complete analytical model and programming§ Compare w and w/o hydrodynamic interactions§ Compare full-coupling (combined matrix) vs. partial coupling (iteration) § WINPOST Model for FPSO + shuttle tankers complete with GUI and output graphics § Wind & current data for 2 bodies§ Dynamic instability of tandem offloading§ Tandem & side-by-side offloading
Analysis of FPSO Exp. No. 2B (11/02) - FPSO + shuttle tanker in soft mooring § Validate wave frequency response portion WINPOST for FPSO + shuttle tanker in a soft mooring§ Predicted response time series§ Further validate wave/low frequency response model § Predicted vs. measured time series§ Documented WINPOST model extended to FPSO + shuttle tanker with GUI & example application § Analysis can begin 1/03PRINCIPAL INVESTIGATOR (S) & OTHERS INVOLVED IN PROJECT:
PI(s): “Joseph” Moo-Hyun Kim
Others: 2 Ph.D. students and 1 visiting scholar
Date: December 2004
Project Name: FPSO/Shuttle Offloading Global Analysis
Project Number: 488 Task Order: 73604
Principal Investigators: “Joseph” M. H. Kim
Estimated Completion Date: Oct. 2005
Project Description:
Multiple floating structures are being considered for a variety of offshore oil and gas projects. Examples include FPSO and a shuttle tanker during loading; LNG carriers and floating or fixed offshore unloading terminals; and floating drilling rigs a separate support barge in tendered drilling operations. The responses of each structure in the system can be influenced by interactions with the other structure(s), and the relative motion between the structures during operations is an important design and operational consideration. An analysis tool that can accurately and reliably predict the relative motions of multi-structure systems is needed. The analyses must consider the hulls of the floating structures, the mooring lines and any risers attached to each structure, and any interconnections between the structures (e.g., lines, umbilicals, yokes, and fenders). Few existing numerical models fully account for the complete hydrodynamic and line interactions between the coupled floating units. WINPOST is now being extended to be able to analyze the motions and interactions of FPSO and shuttle tanker during both side-by-side and tandem offloading scenarios.Progress:
The dynamics of moored multiple ship-shaped vessels connected by elastic cables and hawser-lines were solved (1) simultaneously in a combined matrix (CMM=Combined Matrix Method), and (2) iteratively using a method that solves each vessel matrix separately and iterates between matrices for each vessel (SMM=Separated Matrix Method), which ignores or partly accounts for multi-body hydrodynamic interactions. The three different cases with full, partial and no hydrodynamic interactions were compared both for tandem and side-by-side arrangement of FPSO and shuttle tanker. Hydrodynamic interactions between two vessels in tandem arrangement are much less than that of side-by-side arrangement. Therefore, existing approximation methods, such as SMM popular in current offshore industry, are generally acceptable for tandem arrangement. However, in the case of side-by-side arrangement, even the off-diagonal terms of hydrodynamic-interaction coefficients are very important, and the existing approximation methods may lead to significant error. Therefore, the performance of global motions of two vessels with all lines and hawsers should be carefully checked by the most accurate prediction method available.Transient responses of the multiple vessels due to rapid changes in winds (e.g., a squall) and currents (e.g., the build up of currents due to an approaching Loop Current Eddy) will 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.
Reports & Publications: None this period.
Date: June 2004
Project Name: FPSO/Shuttle Offloading Global Analysis
Project Number: 488 Task Order: 73604
Principal Investigators: “Joseph” M. H. Kim
Estimated Completion Date: September 2004 (1st phase), September 2005(2nd phase)
Project Description: During the past several years, a robust and reliable nonlinear coupled dynamic analysis in time domain computer program for hull/mooring/riser has been developed. The program has been extensively tested and verified against various experimental results. In particular, the predicted turret-FPSO results for two different water depths (3000ft & 6000ft) and mooring/riser designs compared reasonably against Marin’s and OTRC’s experimental data. The vessel-mooring-riser coupled analysis program is now successfully extended to handle two-body interaction problems. It is planned to be generalized to multi-bodies. It is also extended to include novel yoke-mooring system whose stiffness can continuously vary with time. This extension will be particularly useful for the feasibility study and/or down-time analysis of LNG floating-terminals and LNG carriers both in side-by-side and tandem offloading operation.
Progress: The vessel-mooring-riser coupled dynamics of two-bodies connected by yokes and hawser-lines are solved simultaneously in time domain by a combined-matrix method, which is by far known to be the most accurate method. Other existing commercial computer programs of similar capability typically use iteration methods between two vessels ignoring or partly accounting for the full 12x12 hydrodynamic interaction matrix. The iteration-based separated matrix method has also been developed independently for comparison purpose. The computer programs have been successfully applied to the modeling of FPSO-shuttle offloading operation in both tandem and side-by-side modes. The three different cases with full, partial, and no hydrodynamic interactions are systematically compared to assess the performance of the existing technology. Our preliminary results show that the inclusion of full hydrodynamic interaction is very important in the case of side-by-side offloading operation. The offloading between LNG floating terminals and LNG carriers connected by a novel yoke mooring system is also being investigated. The fender-contact effects for side-by-side offloading can also be realized in time domain simulations using a step-function like spring model. The numerical analysis will be compared and calibrated against the planned OTRC offloading experiment.
Reports & Publications:
Y.B. Kim “Dynamic analysis of multi-body floating platforms coupled with mooring lines and risers” (May, 2003), Ph.D. ThesisB.J. Koo “Evaluation of the effect of contact between risers and guide frames on spar motions” (Aug. 2003), Ph.D. Thesis
Arcandra and M.H. Kim, “Hull/mooring/riser coupled dynamic analysis of a turret-moored FPSO” (In Press) Journal of Applied Ocean Research
Koo, B.J., Kim, M.H., Randall, R, “Mathieu instability of spar platform with mooring and risers” (In Press) J. of Ocean Engineering
Koo, B.J., Kim, M.H., Randall, R.,“The effects of nonlinear multi-contact coupling with gap between risers and guide frame on global spar motion analysis” Journal of Ocean Engineering (In Press)
A. Steen, M.H. Kim and M. Irani, “Prediction of spar responses: model test vs. analysis” Proc. 2004 OTC, Offshore Technology Conference, Houston, 2004
Arcandra, P. Nurtjahyo and M.H. Kim, “Effects of line dynamics and hull viscous drag on the response of a turret-moored FPSO” Proc. OMAE-FPSO 2004, Houston
M.H. Kim, Y.B. Kim, R. Mercier, E.G. Ward, “Hull/mooring/riser coupled dynamic analysis of a turret-moored FPSO compared with OTRC experiment”, International Symposium on Deepwater Mooring Systems 2003, Houston.
S. Ryu and M. H. Kim, 2003. “Coupled Dynamic Analysis of Thruster-Assisted Turret-Moored FPSO,” OCEANS 2003 MTS/IEEE, San Diego, California.
Date: December 2003
Project Name: FPS0/Shuttle Global Response Analysis
TEES Project Number: 32558-60720 MMS Task Order: 73604 MMS Project Number: 488
Principal Investigator: “Joseph” M. H. Kim
Estimated Completion Date: September 2005
Project Description:
The importance of the coupled dynamic analysis of multi-floating units including numerous slender members is becoming more important as offshore development projects in deep water become more and more complicated. The design and operation of multiple closely connected floating units, e.g., FPSO and shuttle offloading, multiple production structures, requires reliable predictions of the relative motions of the floating structures. Few existing numerical models fully account for the complete hydrodynamic interaction between the coupled floating units.
A more complete numerical model is being developed for the coupled dynamic analysis of multiple floating units. This model is being developed as an extension to WINPOST (a hull/mooring/riser nonlinear coupled dynamic analysis in the time domain), and will include all hydrodynamic interaction effects. WINPOST has been well verified with experimental data for single floating units such as spars, TLP’s, and FPSO’s. This new model will be tested against OTRC experiments and used to examine the reliability of existing approximate methods.
Progress:
The WINPOST program is being extended to analyze multi-floating units in two different ways. One is the combined-matrix-method, which solves the whole system in a combined matrix, and the other is iteration between individual units. The former is more accurate but less computationally efficient. The latter is expected to do a good job in tandem offloading but may be erroneous in side-by-side offloading operation. It will be verified after the two independent methods are fully developed.
A state-of-the-art GUI (Graphical User Interface) and pre-/post processors for WINPOST are now fully developed for the use of OTRC and offshore industry.
Reports and Publications:
Koo, Bon-Jun, “Evaluation of the effects of contact between risers and guide frames on offshore spar platform motions” (August, 2003)
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 and M.H. Kim, “Hull/mooring/riser coupled dynamic analysis of a turret-moored FPSO” (In Press) Journal of Applied Ocean Research
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Date: June, 2003
Project Name: FPSO/Shuttle Global Response Analysis
Project Number: 32518-5887GM Task Order: 18032
Principal Investigators: “Joseph” M.H. Kim
Estimated Completion Date: 8/31/03
Project Description:
During the past several years, PI has developed very powerful software called WINPOST for hull/mooring/riser nonlinear coupled dynamic analysis in time domain. The program has been extensively tested and verified against experimental results for various kinds of spars and TLPs. The WINPOST has since been further extended to turret-moored FPSO analysis including large yaw motions. Computed FPSO results compared reasonably with Marin’s experiments. The purpose of the present project is to more extensively compare WINPOST FPSO results with experimental data to more completely calibrate and verify WINPOST, and to extend WINPOST to multiple-body problems, e.g. an FPSO and a Shuttle Tanker.
Progress:
Recently, a new study is being conducted to compare WINPOST simulations with the OTRC experiments conducted for a single turret-moored 6000ft-FPSO in various environmental conditions. There will be more FPSO experiments in the coming months including FPSO/shuttle interaction problems. In addition to motions, various hydrodynamics for the FPSO hull including second-order effects and wave drift damping will be revisited, extensively assessed, and compared with experimental results. The leading edge GUI including pre- and post-processors, graphics, and animations will be continuously developed and the user-friendly version will be installed in the OTRC computer system to assist future experiments.
The extension of WINPOST to handle multi-body interactions is almost completed. The moored multi-bodies connected by elastic cables and hawser-lines are solved simultaneously in a combined matrix, which is by far the most accurate method. Other computer programs of similar capability typically use iteration methods, which ignores or partly account for multi-body hydrodynamic interactions. The three different cases with full/partial and without hydrodynamic interactions can be compared in the future. The published data for multi-body interactions are rare and more verification is needed. The preliminary comparison against KRISO FPSO/shuttle experiments for both tandem and side-by-side mooring looks very promising. The present computer program is developed targeting the coupled dynamic analysis of multi-unit floating production system connected by complicated lines. The fully coupled analysis of tandem or side-by-side FPSO/shuttle assisted by a DP (dynamic positioning) is also being developed.
Reports & Publications: (2002-2003)
Ph.D. Thesis: Y.B. Kim “Dynamic analysis of multi-body floating platforms coupled with mooring lines and risers” (May, 2003)
Refereed Journal Papers: Arcandra and M.H. Kim, “Hull/mooring/riser coupled dynamic analysis of a turret-moored FPSO” (In Press) Journal of Applied Ocean Research
Refereed Conference Papers:
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
Date: November 10, 2002
Project Name: FPSO/Shuttle Global Response Analysis
Project Number: 32518-5887GM Task Order: 18032
Principal Investigators: “Joseph” M.H. Kim
Estimated Completion Date: 8/31/2003
Project Description:
During the past several years, PI has developed powerful software called WINPOST for hull/mooring/riser nonlinear coupled dynamic analysis in time domain. The program has been extensively tested and verified against experimental results for various kinds of spars and TLPs. The WINPOST has since been extended to turret-moored FPSO analysis including large yaw motions, and successfully compared against other DeepStar FPSO results and Marin’s experiments. The WINPOST is further extended to handle FPSO-shuttle combination both in tandem and side-by-side mooring cases. The major part is now developed and some preliminary results have been obtained. It will be completed and extensively verified against future OTRC experiments. The computer program will further be extended to handle more complicated multi-body system with more complicated combination of mooring lines, such as spar/TLP-drilling barge-FPU combination.Progress:
For the hydrodynamics of FPSO and shuttle-tanker interactions, WAMIT MULTI-BODY version has been used. The moored multi-bodies connected by elastic cables and hawser-lines are solved simultaneously in a combined matrix. Other computer programs of similar capability typically use iteration methods, which account for multi-body hydrodynamic interactions partially. Using the combined matrix method, which is supposed to be the most accurate, the cases with full, partial, and zero hydrodynamic interactions can be straightforwardly compared. The published data for multi-body interactions are rare and more verification is needed. The preliminary comparison against KRISO experimental results for both tandem and side-by-side mooring is promising. Animation tools have been developed to better illustrate the FPSO-shuttle coupled analysis results.OTRC will conduct a series of experiments in 2002-2004. First, both FPSO and shuttle tanker will be moored by soft spring in waves so that only the hydrodynamic interaction between the two hulls (without mooring lines and risers) can be investigated. Next, the same combination with risers, hawser lines, and mooring lines will be tested. Both cases will be modeled by WINPOST and the experimental results will be systematically compared with numerical prediction. WINPOST-GUI has been successfully developed from other funding sources and now the WINPOST program is highly user friendly including very powerful graphic interfaces and post-processors. The program will be installed in OTRC computers and a demo-case will be developed for the OTRC FPSO experiment. The GUI will be extended to include more complicated multi-body application.
Reports & Publications: Arcandra & Kim, M.H. “Hull/mooring/riser coupled dynamic analysis and sensitivity study of a FPSO” Journal of Applied Ocean Research (In Press)