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TECHNICAL PAPERS

Active and Passive Control of Spar Vortex-Induced Motions

[+] Author and Article Information
R. A. Korpus

 Applied Fluid Technologies, 326 First Street, Suite 34, Annapolis, MD 21043rkorpus@appliedfluidtech.com

S. Liapis

 Shell International Exploration and Production Company, 3737 Bellaire Blvd., Houston, TX 77025Stergios.Liapis@shell.com

J. Offshore Mech. Arct. Eng 129(4), 290-299 (Feb 09, 2007) (10 pages) doi:10.1115/1.2746400 History: Received July 18, 2006; Revised February 09, 2007

Spars have become an “industry solution” for deepwater developments. Vortex-induced motion (VIM) of spar platforms in currents remains an important design concern. Although strakes are effective at suppressing riser VIM, all three straked classical spars in the Gulf of Mexico have experienced significant VIM events. These are not examples of poor design but indicate a lack of adequate tools for predicting spar VIM. This paper presents the development and validation of unsteady Reynolds-averaged Navier-Stokes (URANS) methods to predict real-world spar VIM behavior. It includes the ability to address rough surfaces and high supercritical Reynolds numbers. The resulting algorithms are used to assess the effectiveness of active and passive control strategies for suppressing spar VIM. Active control consists of injecting high-pressure water tangentially into the boundary layer and is shown to be extremely effective at reducing drag and VIM amplitudes. Passive control utilizes a sleeve to channel high-pressure stagnation flow into the boundary layer and is found less effective.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Roughness model validation—flat plate drag

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Figure 2

Roughness model validation—boundary layer profile

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Figure 4

Vorticity behind a smooth cylinder at Re=7×106

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Figure 5

Vorticity behind a rough cylinder at Re=7×106

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Figure 6

Velocity (colored by vorticity), smooth at Re=104

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Velocity (colored by vorticity), smooth at Re=7×106

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Drag of stationary rough cylinders

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Figure 10

Time history of bare cylinder transverse force

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Time history of transverse displacement

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Figure 12

Cylinder VIM versus system-reduced velocity

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Figure 13

Drag versus displacement for bare cylinders

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Velocity (colored by pressure) around injection outlet

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Vorticity for VINJ=2×freestream

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Vorticity for VINJ=4×freestream

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Figure 18

Vorticity for VINJ=6×freestream

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Figure 19

Vorticity for VINJ=7×freestream

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Figure 20

Effect of injection on transverse displacement

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Figure 21

Effect of injection on inline displacement

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Drag versus injection velocity

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Figure 26

Passive injection sleeve geometry

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Figure 27

Vorticity around sleeve

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Streamwise component of velocity around sleeve

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Figure 29

Velocity magnitude near sleeve inlet

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Figure 31

Boundary layer thickness on hull and sleeve

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Figure 32

Momentum thickness on hull and sleeve

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Figure 33

Passive sleeve transverse displacement versus exit

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Figure 34

Passive sleeve drag versus exit angle

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Figure 8

Velocity (colored by vorticity), rough at Re=7×106

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Figure 30

Velocity (colored by magnitude) near sleeve outlet

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Figure 24

Transverse amplitude versus injection velocity

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Figure 23

Effect of injection on inline force

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Figure 22

Effect of injection on transverse force

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Figure 14

Computational grid around injection outlet

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Figure 3

Vorticity behind a smooth cylinder at Re=10,000

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