Modeling Wind Shielding for FPSO Tandem Offloading using CFD Bob - - PowerPoint PPT Presentation

Modeling Wind Shielding for FPSO Tandem Offloading using CFD

Bob Gordon, Granherne Satpreet Nanda, CD-adapco

Presentation Outline

• FPSO Tandem Offloading
• Examples of Shielding in Offshore Applications
• Wind Tunnel Tests for Tandem Offloading
• Preliminary CFD Results
• Summary

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FPSO Tandem Offloading

• FPSO can be spread or turret

moored

– If turret moored, FPS orients into wind, wave and current

• Tanker approaches under its own

power and moors (with work boat assistance) to FPSO using hawsers

• FPSO & Tanker are in close

proximity during offloading and both change draft

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Turret Moored FPSO

Effects of Shielding

• FPSO shields tanker from

environment

– Impacts tanker’s maneuverability during approach – Impacts separation distance while connected

• Relative headings of the vessels

can vary significantly during

• ffloading due to shielding,

effects of current, or fish-tailing

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Spread Moored FPSO

Collisions and Near Misses During Tandem Offloading in North Sea 1996-2000

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Source: UK HSE Offshore Technology Report 2000/086

Examples of Shielding in Offshore Applications

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Truss Spar Platform Multiple Riser Towers Grouped Single Line Risers

Velocity Reduction due to Shielding

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From van Walree and Willemsen, 1988

Wind Tunnel Tests

• Part of MARIN’s Offloading

Operability JIP

• Tests performed at DNW in 2003
• Model scale was 1:250
• Barge-shaped FPSO model and

shuttle tanker

• Measurement of unshielded wind

and current forces

• Measurement of wind velocities

behind the FPSO

• Measurement of shielded forces

for validation of shielding model

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Use of CFD to Model Wind Tunnel Tests

• Collaborative effort between MARIN,

Granherne/KBR and CD-adapco

• Surface geometry models prepared by MARIN
• MARIN using in-house code and Granherne

using STAR-CCM+

• Granherne calculations performed in the blind
• Comparisons will be made against model test

data and between CFD codes

• Goal is to present joint paper at OMAE 2010

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Vessel Characteristics

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450 m

Position of Vessels Relative to Incident Wind & Velocity Profile

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Wind

Velocity Profile V/V10 Z/Z10

Surface Mesh

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Volume Mesh

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1.44 Million Cells SST k-omega turbulence model y+ wall treatment

Speed Contours in Horizontal Plane

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Z=5m Z=30m A A A A B B

Speed Contours in Vertical Plane

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A A B B

Streamlines

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Pressure Contour

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Drag and Lift on Tanker

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Tandem Arrangement (450 m separation) Shuttle Tanker Only Wind Tunnel Measurement OCIMF

DRAG LIFT

Summary

• Tandem offloading operations are sensitive to weather

conditions

• Accurate simulation of tandem offloading is difficult due to

wind shielding

• Wind loads on the shuttle tanker vary with relative wind

direction, distance from FPSO and orientation relative to FPSO

• Wind tunnel testing is limited due to relatively small

number of configurations that can be tested

• Preliminary CFD results indicate good agreement with

wind tunnel data (but little shielding for case investigated)

• CFD can provide a suitable means to augment wind

tunnel test data

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Acknowledgement

• Thanks to Dr. Arjen Koop of MARIN for

collaborating in this endeavor and for providing the vessel geometry models

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