Global Analysis of Floating Global Analysis of Floating Structures – M.H. KimStructures – M.H. Kim
WINPOST ProgramWINPOST Program 3-D Coupled Analysis3-D Coupled Analysis
Hull – BEM (3-D panel)Hull – BEM (3-D panel) Moorings & Risers – FEM (EI included)Moorings & Risers – FEM (EI included)
– Taut/Catenary MooringTaut/Catenary Mooring– Top Tensioned, CR, or Flexible RisersTop Tensioned, CR, or Flexible Risers
Time & Frequency Domain ModelsTime & Frequency Domain Models Simultaneous Solution of Integrated SystemSimultaneous Solution of Integrated System Convergence Fast Convergence Fast
Single & Multi-Body ProblemsSingle & Multi-Body Problems GUI InterfaceGUI Interface
Global Analysis of Floating Global Analysis of Floating Structures – M.H. KimStructures – M.H. Kim
WINPOST ProgramWINPOST Program EnvironmentEnvironment
Non-Parallel Waves, Winds, CurrentsNon-Parallel Waves, Winds, Currents Uni-direction & Directional Irregular WavesUni-direction & Directional Irregular Waves Dynamic WindsDynamic Winds Up to 3 CurrentsUp to 3 Currents
Verification & ApplicationsVerification & Applications TLPTLP Classic & Truss SparClassic & Truss Spar FPSOFPSO
Turret – Moored FPSOTurret – Moored FPSO
Elements (half)
Body: 1843
Free Surface: 480
WINPOST vs. MARIN FPSO WINPOST vs. MARIN FPSO Model TestsModel Tests
Vessel Motions Unit Mean Stdv Max
Surge total at turret m -38 11 -61 Sway at turret m 14 3 28 Heave at turret m 0 2 8 Roll deg 0 2 5 Pitch deg 0 1 4 Yaw deg 16 2 27
Mooring Tension
Line#2 total kN 1651 170 2149 Line#8 total kN 884 180 1774
Riser Top Tensions
Liquid prod. (#13) kN 1299 181 2653 Water injection (#22) kN 2252 276 4179 Gas export (#25) kN 528 129 1395
25-50 %
<25 %
> 50 %
Percentage Differences based on data in Wichers (2001)
Multi-Body InteractionMulti-Body InteractionOTRC FPSO + Shuttle Tanker OTRC FPSO + Shuttle Tanker
(Tandem Moored @ 30m)(Tandem Moored @ 30m)
Global Analysis of Floating Global Analysis of Floating Structures – M.H. KimStructures – M.H. Kim
WINPOST ProgramWINPOST Program 3-D Coupled Analysis3-D Coupled Analysis
Hull – BEM (3-D panel)Hull – BEM (3-D panel) Moorings & Risers – FEM (EI included)Moorings & Risers – FEM (EI included)
– Taut/Catenary MooringTaut/Catenary Mooring– Top Tensioned, CR, or Flexible RisersTop Tensioned, CR, or Flexible Risers
Time & Frequency Domain ModelsTime & Frequency Domain Models Simultaneous Solution of Integrated SystemSimultaneous Solution of Integrated System Convergence Fast Convergence Fast
Single & Multi-Body ProblemsSingle & Multi-Body Problems GUI InterfaceGUI Interface
Global Analysis of Floating Global Analysis of Floating Structures – M.H. KimStructures – M.H. Kim
WINPOST ProgramWINPOST Program EnvironmentEnvironment
Non-Parallel Waves, Winds, CurrentsNon-Parallel Waves, Winds, Currents Uni-direction & Directional Irregular WavesUni-direction & Directional Irregular Waves Dynamic WindsDynamic Winds Up to 3 CurrentsUp to 3 Currents
Verification & ApplicationsVerification & Applications TLPTLP Classic & Truss SparClassic & Truss Spar FPSOFPSO
Turret – Moored FPSOTurret – Moored FPSO
Elements (half)
Body: 1843
Free Surface: 480
WINPOST vs. MARIN FPSO WINPOST vs. MARIN FPSO Model TestsModel Tests
Vessel Motions Unit Mean Stdv Max
Surge total at turret m -38 11 -61 Sway at turret m 14 3 28 Heave at turret m 0 2 8 Roll deg 0 2 5 Pitch deg 0 1 4 Yaw deg 16 2 27
Mooring Tension
Line#2 total kN 1651 170 2149 Line#8 total kN 884 180 1774
Riser Top Tensions
Liquid prod. (#13) kN 1299 181 2653 Water injection (#22) kN 2252 276 4179 Gas export (#25) kN 528 129 1395
25-50 %
<25 %
> 50 %
Percentage Differences based on data in Wichers (2001)
Multi-Body InteractionMulti-Body InteractionOTRC FPSO + Shuttle TankerOTRC FPSO + Shuttle Tanker
Side-by-Side MooredSide-by-Side Moored-
PlanPlan Develop CFD method for unsteady separated flow and Develop CFD method for unsteady separated flow and
added mass and damping coefficients about 2-D hull in roll added mass and damping coefficients about 2-D hull in roll motions motions
Use 2-D coefficients (evaluated at different hull stations) to Use 2-D coefficients (evaluated at different hull stations) to adjust the FPSO roll coefficients predicted by WAMITadjust the FPSO roll coefficients predicted by WAMIT
Extend 2-D method to predict the fully 3-D unsteady Extend 2-D method to predict the fully 3-D unsteady separated flow and coefficients about the FPSO hull with separated flow and coefficients about the FPSO hull with the bilge keelsthe bilge keels
Validate with other methods and experimentsValidate with other methods and experiments
FPSO Roll PredictionFPSO Roll Predictionand Mitigation (S.A. Kinnas)and Mitigation (S.A. Kinnas)
ObjectiveObjective Develop accurate computationally efficient model to Develop accurate computationally efficient model to
predict the hydrodynamic coefficients in roll for a FPSO predict the hydrodynamic coefficients in roll for a FPSO hullhull
Investigate effectiveness of bilge keels (size, shape, Investigate effectiveness of bilge keels (size, shape, location across and extent along the hull) on roll mitigationlocation across and extent along the hull) on roll mitigation
FPSO Hull Motions: FPSO Hull Motions: Heave & Roll Coordinate SystemHeave & Roll Coordinate System
Description of boundary conditions on a hull moving at the free surface
Grid used for the heave motionresponse for a rectangular hull form
Computational Domain
Kinematic BC
Far Boundary
u=v=0
v body • n = q fluid•n
Dynamic BC =0
Hull
Bilge Keel Details
Oscillating Flow Past a Flat PlateOscillating Flow Past a Flat Plate
Grid for Oscillating Flat Plate
u = - Um ← u = 0 →
Axial velocity and streamlines predicted by Euler solver at instant t=0 & T/4 for oscillating flow (-UmCos(ωt)) past a flat plate
Oscillating Flow Past a Flat PlateOscillating Flow Past a Flat Plate
Comparison between Euler solver, Navier-Stokes solver and experimental data from Sarpkaya, 1995
Oscillating Flow Past a Flat PlateOscillating Flow Past a Flat Plate
Euler Navier Stokes Sarpkaya
Euler Navier Stokes Sarpkaya
Cd Cm
Numerical Results: Heave MotionNumerical Results: Heave Motion
Comparison of the added mass and damping coefficients with Newman(1977) for B/D=2 & No bilge keel
Convergence of force histories with increasing grid density
B/D = 2 Fr x D = 1.5
130 30 cells
220 60 cells
310 70 cells
Predicted Roll Added Mass & Damping Coefficients for Different Bilge Keels
Flow Field Around HullFlow Field Around Hull
StatusStatus Developed CFD model to solve the Euler Developed CFD model to solve the Euler
equations around a 2-D hull subject to heave equations around a 2-D hull subject to heave and roll motionsand roll motions
Validated for a flat plate subject to an Validated for a flat plate subject to an oscillating flow. Euler results comparable to oscillating flow. Euler results comparable to those from Navier-Stokes and in reasonable those from Navier-Stokes and in reasonable agreement to experimental dataagreement to experimental data
Demonstrated that modelDemonstrated that model Can describe free surface effects by comparisons Can describe free surface effects by comparisons
with potential flow results for a 2-D hull in heavewith potential flow results for a 2-D hull in heave Results are practically grid independentResults are practically grid independent Can describe unsteady separated flow around a Can describe unsteady separated flow around a
plate in oscillating flow and around the bilge keel of plate in oscillating flow and around the bilge keel of a 2-D hull subject to roll motionsa 2-D hull subject to roll motions
Can predict expected increase in added mass and Can predict expected increase in added mass and damping coefficients with increasing bilge keel sizedamping coefficients with increasing bilge keel size
Future WorkFuture Work Continue validation of 2-D Hull method with other methods Continue validation of 2-D Hull method with other methods
and existing experimentsand existing experiments
Develop method to integrate the 2-D Hull results into Develop method to integrate the 2-D Hull results into WAMIT (“2-1/2 D” model)WAMIT (“2-1/2 D” model)
Use 2-1/2 D to assess effects of various bilge keel designs Use 2-1/2 D to assess effects of various bilge keel designs on motionson motions
Plan & analyze further experiments to validate modelsPlan & analyze further experiments to validate models
Develop fully 3-D methodDevelop fully 3-D method assess accuracy of the 2-1/2 D modelassess accuracy of the 2-1/2 D model Basis for refined analysis of keel designsBasis for refined analysis of keel designs Include the effects of the bilge keel “lift”Include the effects of the bilge keel “lift” Basis for more complete models in the future (e.g., non-Basis for more complete models in the future (e.g., non-
linear free-surface effects, turbulence)linear free-surface effects, turbulence)
MMS JIP Polyester RopeMMS JIP Polyester Rope GoalsGoals
Development of a rationale mitigation Development of a rationale mitigation strategy and guideline for dealing with strategy and guideline for dealing with damaged polyester ropedamaged polyester rope
Installation & In-service damageInstallation & In-service damage Mitigation strategies could includeMitigation strategies could include
InstallationInstallation– Immediate replacementImmediate replacement– Periodically monitor for possible replacement later Periodically monitor for possible replacement later
In-ServiceIn-Service– Replace ASAP (continue operations, curtail, or shut-Replace ASAP (continue operations, curtail, or shut-
in?)in?)– Periodically monitor for possible replacement laterPeriodically monitor for possible replacement later
Support API RP process to develop RPSupport API RP process to develop RP
MMS JIP Polyester RopeMMS JIP Polyester Rope
Length Effect TestsLength Effect Tests - - potential influence of potential influence of length effects on tests of damaged ropes length effects on tests of damaged ropes (small-scale rope) (small-scale rope)
Damaged Full-Scale Rope TestsDamaged Full-Scale Rope Tests – quantify – quantify the influence of damage on full-scale ropes the influence of damage on full-scale ropes (main focus)(main focus)
Verification TestsVerification Tests - verify results of - verify results of Damaged Full-Scale Rope Tests with Damaged Full-Scale Rope Tests with limited tests on longer full-scale ropeslimited tests on longer full-scale ropes
Four RopesFour Ropes
Bexco CSL Whitehill MarlowBexco CSL Whitehill Marlow
Damaged Rope Test ProgramDamaged Rope Test Program
Test
Break Strength
(T)
Nominal Diameter
Length (m)
L/D Test Site # Tests
35 36 mm (1.5 in)
2 60
35 36 mm (1.5 in)
23 560 Length Effect
35 36 mm (1.5 in)
35 1000
Lloyds Beal 24
Damaged Full-Scale
Ropes 700
178 mm (7 in) 10 60
SES CSL
26
Verification 700
178 mm (7 in)
100 560 Holloway/Lowrey 4
2 m sample with midspan damage
23 m sample with damage near splice
23 m sample with midspan damage
35 m sample with midspan damage
Length Effect Tests
Simulated Rope DamageSimulated Rope Damage
Figure 6
Damage Level 2
Figure 5
Damage Level 1
~7 in. Diameter
ResultsResults
Residual strength of damaged ropeResidual strength of damaged rope Rope behaviorRope behavior
Damage level vs. residual rope strengthDamage level vs. residual rope strength Residual strength vs. rope/splice Residual strength vs. rope/splice
constructionconstruction Scale effects on residual strengthScale effects on residual strength Effect of length on residual strength Effect of length on residual strength Effect of damage location on residual Effect of damage location on residual
strengthstrength Data to validate numerical model of Data to validate numerical model of
damaged ropedamaged rope