Adaptation of STAR-CCM+ Numerical Wave Tank to an...
Transcript of Adaptation of STAR-CCM+ Numerical Wave Tank to an...
Adaptation of STAR-CCM+ Numerical Wave Tank to an Offshore Floater Design Tool
Jang Whan KimChief Technical Advisor, Offshore Technology Services
Agenda
Introduction
Design Spiral
Requirements on Design Tools
Technology Readiness / Gap
Euler Overlay Method
Applications
Technip Presentation3
Three Generations of Spar Platforms
CLASSIC TRUSS CELL TRUSS
Technip has delivered 14 out of the 19 spars worldwide, in a water depth range of 590 – 2,382 meters using both dry and wet tree completions.Four more spars are under design/construction by Technip
Technip Slide Library4
Offshore Floaters
WindFPSO/FLNGSparSemi-submersibleUnideck®TPG 500 TLP
Supporting subsea systemOperations in harsh environmentSurvive and protect crew / equipments in extreme environmentsSmall Motion
Design Spiral of Offshore Floater Design
Global Performance
WAMIT / MLTSIMMotion Solver
Model Test6 month after project start
Hull Sizing Calibration
Base Design
Air gap / green water / Slamming / VIM / Topsides wind load
•Wind•Wave•Tow
Design Spiral of Offshore Floater Design with CFD
Global Performance
Validation Model Test
before project
Hull Sizing
CFD
Less uncertainties
Shorter design period
More design optimization
Expectations on Design Tools (Global Performance)
Accuracy
Tolerance < 10%
Preferably conservative side
Robustness
No crash
No surprise
Predictable schedule
Speed (Screening Tool)
Less than 10 min for a short-term (3-hr) simulation
Runtime (Final Evaluation Tool)
One run < 12 hr for diagnostic runs
One run < 24 hr for production runs
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Existing Design Tools
Nonlinear Time-Domain Motion (MLTSIM)
Hydrodynamic coeff. From WAMIT
Morison drag
Nonlinear Froude-Krylov force
Large amplitude formulation
Mooring / SCR Modeling
Quasi-Static Analysis (FMOOR)
Catenary model
5-10 min for 3-hr simulation
Screening Tool
Model Test
MLTSIM Calibration
Run up / Air Gap / Green Water
Ringing
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Design Tools with Numerical Wave Tank
Nonlinear Time-Domain Motion (MLTSIM)
Hydrodynamic coeff. From WAMIT
Morison drag
Nonlinear Froude-Krylov force
Large amplitude formulation
Mooring / SCR Modeling
Quasi-Static Analysis (FMOOR)
Catenary model
5-10 min for 3-hr simulation
Screening Tool
Numerical Wave Tank
MLTSIM Calibration
Run up / Air Gap / Green Water
Ringing
Technology Readiness
STAR-CCM+ Features
Free-surface capturing
Moving mesh technique
DFBI
Embedded DFBI X
Overset X
Powerful built-in pre/post processors
Hardware
In-house cluster (144 cores)
TACC Stampede ( ~ 10,000 cores)
1-hr simulation in one day (Semi-submersible)
Stampede – TACC, Univ. of Texas at Austin
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Intel Sandy Bridge CPU
102,400 Cores in 182 Racks
2 Peta (1011) FLOPS
STAR Program
• $25,000 Annual Fee for Access
to 10,240 Cores
$0.05 / Core‐Hr
Technology Gap / Solution
Wave Input
5th-Order Stokes Wave
Good for deep water
Not good for shallow water extreme waves
Random wave input does not meet industry best practice
Random seeding
Wheeler stretching
Many users were using customized user functions
Far-Field Closure
No wave-absorbing mechanism in up-wave side
Larger domain required
Numerical damping sometimes help
Mooring / Riser Modeling
Built-in catenary model
Good for tendon and taut mooring
Not good for SCRs and non-taut mooring
No dynamics
Euler-Overlay Method
In-house Catenary / Rod models
Fully-nonlinear wave models
In-house wave codes
Euler Overlay Method
History
Bai & Yeung (1974): Matching FE/BE solution with analytic solution
Kim & Bai (1991): Nonlinear radiation problem (Matching)
Kim, Kyoung, Ertekin & Bai (2003): Nonlinear diffraction (Overlaying)
Kim, Rajeev & O’Sullivan (2011): Nonlinear diffraction (CFD, Overlaying)
Kim, Read & O’Sullivan (2012): Nonlinear diffraction (STAR-CCM+, Overlaying)
Far-Field Solution
Euler solution
Overlaying
Boundary condition
Momentum and volume fraction source / sink term in blending zone
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Long-Crested Wave and a Vertical Column (OMAE2012)
2D Euler Wave Flume
Length: 105 m
CFD Domain
Length: 2 m
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Ringing Analysis of a GBS (Short-Crested Irregular Wave)
Dynamic amplification of structural load due to resonant response of structure to higher-harmonic load
Semi-Submersible Motion Simulation
Mooring and Riser Model
Look-up table for SCR and Mooring Force
Heave RAO from White-Noise Wave Test
1-hr simulation
16 hours with 640 cores
WAMIT
Hull Optimization for Dry-Tree Semisubmersible
Footer can be customized17
Case1 & Case5: Original TTR and MooringC009201 & C0093: Revised TTR and Mooring
Computational Cost
TLP
3.0 mil cells, dt = 0.025 s
5 min simulation Stampede Star‐CCM+
Number
of CoresRun Time
Service
UnitUnit Cost Cost
Service
UnitUnit Cost Cost Total Cost
640 11 7331 0.05 367 11 15 172 $ 538.36 320 18 5760 0.05 288 18 15 270 $ 558.00
Semi
1.5 mil cells, dt = 0.1 s
1 hr simulation
Stampede Star‐CCM+
Number
of CoresRun Time
Service
UnitUnit Cost Cost
Service
UnitUnit Cost Cost Total Cost
640 16 10240 0.05 512 16 15 240$ 752.00