深水中的模型试验

Possible solutions:
- Ultra small scales (1:100 - 1:200) - scale effects?* - Integrated tests & computer analysis (“hybrid techniques”)* - Outdoor testing* - Numerical analysis only - New ultra-deep basin?
Challenge:
Depths ~ 1000m - 3000m: Too deep for testing at “conventional” scales (1:50 - 1:100) in available basins How to keep the benefits from “complete” system - couplings etc.?
Modeling of deep-water currents - challenges:
- Vertical profile (magnitude & direction) - Homogenous & constant current velocity / turbulence? - Full-depth limitations in available laboratory basins - Combine with equivalent force / numerical models
Not recommended: Truncation without subseq. computer-extrapolation*
* Stwenku.baidu.comdies carried out at MARINTEK: VERIDEEP; NDP; Deepstar
Ultra-small scale model testing: Comparing 3 scales
Cross-section of Ocean Basin
Length: 80 m - Width: 50 m - Depth: 0 -10 m
S:\ ve rh a \ o sto \mta .p t o e dh u n vd p
80 m
OCEAN BASIN
TOWING TANK
20 01-0 4-17
Second-order deep-water random wave model (numerical)
Modeling of waves Items of particular interest
- Nonlinear effects (crests; wave heights; kinematics) - Extreme waves (probability; mechanism; freak waves?) - Multi-directionality - Multiple-peak spectra (in frequency & in direction) - Non-stationarity (in frequency & in direction) - Repeatability - Minimum scale of reproduction?
MARINTEK’s 50m x 80m x 10m Ocean Basin
The Ocean Basin Laboratory
Double-flap wave maker Multi-flap wave maker Double-flap wave maker Multi-flap wave maker 50 m
Measured vs. second-order wave model
Modeling of waves Items of particular interest
- Nonlinear effects (crests; wave heights; kinematics) - Extreme waves (probability; mechanism; freak waves?) - Multi-directionality - Multiple-peak spectra (in frequency & in direction) - Non-stationarity (in frequency & in direction) - Repeatability - Minimum scale of reproduction?
Contents of presentation
- Deepwater metocean conditions - physical modelling
- Deepwater floating systems - physical modelling - Particular areas of experimental investigation - Laboratory limitations - and solutions - Areas of uncertainty and further development
u
Example: 3000m depth trunc. at 1000m
Modeling combined metocean:
Wind waves + swell + current + wind
- Collinear & non-collinear - Optimal model scale - Modeling of rapid change in hurricane system?
FPSO in extreme wave event
Semisubmersible in extreme wave event
Particular areas of experimental investigation
Motions - slow-drift forces in extreme waves with current - viscous damping - motion coupling effects - Dynamic line tension in extreme wave groups - Dynamic coupling to vessel motions
Moder./High High
Gulf of Mexico
Offshore Brazil West of Africa (Newfoundland)
Steep/High
Moderate Low High
High
High High High
High
Moder. Moder. High Ice
Physical modelling of deepwater metocean conditions in a laboratory basin
Deepwater oil and gas fields (d ~ 500m - 3000m): Critical metocean design conditions
Waves
Norwegian Sea Atlantic Margin High High
Current
High
Wind
High
Others
Deepwater floating systems
Deepwater floating systems - physical modelling
Traditional hydrodynamic verification:
- Modeling of “complete” system hull+mooring+risers (+DP) - Scales ~1:50 - 1:100 - Dynamic (& static) coupling between floater & lines/risers - Individual line models - dynamic line tension - Line drag induced slow-drift damping - Complex behaviour of total system / “new” effects? - Extreme nonlinear responses in storm conditions / need for calibration of numerical models - Operations - Measurements: Vessel motions - Line forces - Relative wave Green sea - Slamming - Video observations
Numerical visualisation (from coupled analysis study)
Dynamic line tension: 1:55 model tests vs. coupled analysis
Laboratory limitations - and solutions
MODEL TESTING FOR DEEPWATER CONCEPTS
C.T. Stansberg Norwegian Marine Technology Research Institute A.S (MARINTEK), Trondheim, Norway
OGP Workshop on Technology Requirements for Floating Systems, London, UK, 23-24 April, 2001
Mooring
Risers
- Steady drag forces - VIV (model testing of separate components)
Relative wave / Green Sea - Probability of green sea / negative air gap - Impact loads & structural responses Extreme responses Numerical analysis - non-Gaussian processes - combined / integrated with experiments
Modeling of waves items of particular interest
- Nonlinear effects (crests; wave heights; kinematics) - Extreme waves (probability; mechanism; freak waves?) - Multi-directionality - Multiple-peak spectra (in frequency & in direction) - Non-stationary hurricanes (in frequency & in direction) - Repeatability - Minimum scale of reproduction - 1:150 ?
Verification tests on the P-26 project, a polyester taut mooring system
Testing in scales 1:100 - 1:150 (200) is feasible,
depending on floater, condition etc. Practical limitations today (environmental modelling) Scale effects on line tension can be accounted for; smaller effects on slow-drift Particular attention and care in preparation and execution Special limitations: Thruster modelling (> 1:100) Truss structure details Spar models with moonpool