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Technical Briefs

An Overview of Relevant Aspects on VIM of Spar and Monocolumn Platforms

[+] Author and Article Information
Rodolfo T. Gonçalves

TPN—Numerical Offshore Tank, Department of Naval Architecture and Ocean Engineering, Escola Politécnica, University of São Paulo, Avenida Professor Mello Moraes 2231, Cidade Universitária, São Paulo, São Paulo 05508-900, Brazilrodolfo_tg@tpn.usp.br

Guilherme F. Rosetti

TPN—Numerical Offshore Tank, Department of Naval Architecture and Ocean Engineering, Escola Politécnica, University of São Paulo, Avenida Professor Mello Moraes 2231, Cidade Universitária, São Paulo, São Paulo 05508-900, Brazilguilherme.feitosa@tpn.usp.br

André L. C. Fujarra

TPN—Numerical Offshore Tank, Department of Naval Architecture and Ocean Engineering, Escola Politécnica, University of São Paulo, Avenida Professor Mello Moraes 2231, Cidade Universitária, São Paulo, São Paulo 05508-900, Brazilafujarra@usp.br

Kazuo Nishimoto

TPN—Numerical Offshore Tank, Department of Naval Architecture and Ocean Engineering, Escola Politécnica, University of São Paulo, Avenida Professor Mello Moraes 2231, Cidade Universitária, São Paulo, São Paulo 05508-900, Brazilknishimo@usp.br

J. Offshore Mech. Arct. Eng 134(1), 014501 (Oct 13, 2011) (7 pages) doi:10.1115/1.4003698 History: Received April 01, 2010; Revised December 06, 2010; Published October 13, 2011; Online October 13, 2011

Vortex-induced motions (VIM) of floating structures are very relevant for the design of mooring and riser systems. In the design phase, spar and monocolumn VIM behavior, as well as semisubmersible and tension leg platform flow-induced motions, is studied and evaluated. This paper provides a checklist of topics and evidence from a number of sources to justify the selection that should be considered when designing spars or monocolumn platforms regarding the VIM phenomenon. An overview of the influential aspects of the VIM is presented such as heading, external appendages of the hull, concomitant presence of waves and currents, motion suppressor, draft condition (immersed portion of the hull), and external damping due to the presence of risers. Previous works concerning the VIM studies on spar and monocolumn platforms are also addressed. Whenever possible, the results of experiments from diverse authors on this matter are presented and compared.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Pictures of spar model in different appendage configurations with strakes (bare case, anodes only, pipes and chains no anodes, and complete case) by Roddier (12)

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Figure 2

Comparison between results of spar model with all appendages (base case) and spar model with strakes and chains and pipes (variation 1) by Roddier (12)

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Figure 3

Comparison between MonoGoM and MonoBR: heading effect: (a) 0 deg and (b) 180 deg

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Figure 4

Layout of the position of fairleads and chains for the (a) MonoGoM and (b) MonoBR platforms

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Figure 5

Comparison between (a) MonoGoM by Gonçalves (6) and (b) MonoBR by Gonçalves (7): position of fairleads and chains on the scale model

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Figure 6

Trajectories on the XY plane due to the VIM of the MonoBR platform by Gonçalves (7)

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Figure 7

VIM response of a spar platform for current direction in (a) symmetrical and (b) asymmetrical with relation to a mooring line system by Irani and Finn (13). It is important to observe that the position of appendages, mooring lines, etc., relative to the flow direction may change the vortex shedding pattern, thus influencing the amplitude of motions.

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Figure 8

Temporal series examples of VIMs of a spar with the presence of waves by Finnigan (15)

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Figure 9

Example of a time series of VIM of a MonoBR with the presence of regular waves by Gonçalves (7)

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Figure 10

Comparison between results for spar model bare hull and hull with strakes by Wang (16)

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Figure 11

Comparison between (a) MonoGoM by Gonçalves (6) and (b) MonoBR by Gonçalves (7): the effect of suppressor motions (spoiler plates)

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Figure 12

Comparison between MonoBR and SSP Piranema: immersed portion effect

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Figure 13

External damping effect on the VIM response of MonoBR platform by Gonçalves (7)

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