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Research Papers: Offshore Technology

Experimental and Numerical Study on the Flow Reduction in the Moonpool of Floating Offshore Structure

[+] Author and Article Information
Seon Oh Yoo

Samsung Heavy Industries,
217 Munji-ro,
Yuseong-gu 34051, Daejeon, South Korea
e-mail: seonoh.yoo@samsung.com

Hyun Joe Kim

Samsung Heavy Industries,
217 Munji-ro,
Yuseong-gu 34051, Daejeon, South Korea
e-mail: hyunjoe.kim@samsung.com

Dong Yeon Lee

Samsung Heavy Industries,
217 Munji-ro,
Yuseong-gu 34051, Daejeon, South Korea
e-mail: dy7.lee@samsung.com

Booki Kim

Samsung Heavy Industries,
217 Munji-ro,
Yuseong-gu 34051, Daejeon, South Korea
e-mail: booki.kim@samsung.com

Seung Ho Yang

Department of Naval Architecture and
Ocean Engineering,
Ulsan College,
57 Daehak-ro,
Nam-gu 44610, Ulsan, South Korea
e-mail: shyang@uc.ac.kr

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received July 22, 2017; final manuscript received July 1, 2018; published online August 13, 2018. Assoc. Editor: Carlos Guedes Soares.

J. Offshore Mech. Arct. Eng 141(1), 011301 (Aug 13, 2018) (13 pages) Paper No: OMAE-17-1122; doi: 10.1115/1.4040799 History: Received July 22, 2017; Revised July 01, 2018

Recently, drillship moonpools are getting longer and wider for the higher operability. With this trend, violent internal flows are getting more concerned in terms of the safety and operability, which have been reported during the operations even in mild seas. Also, it is well known that the internal flow gives higher resistance during the transit of drillship. In this study, to see the effect of larger damping devices, a series of experimental and numerical study was carried out for the four moonpool designs; the ordinary plain moonpool, the moonpool with a recess deck, the moonpool with an isolated recess deck (island deck), and moonpool with a combination of island deck, splash plates, and wave absorber. From the model tests, it was found that the internal flow of the moonpool was significantly reduced by the application of the wave absorber. In case of the moonpool with the island deck, the sloshing mode oscillations was not observed due to the gap flow between the inner wall of the moonpool and the recess. For the in-depth understanding of the flow behaviors and characteristics, the internal flow of the moonpool has been investigated using Reynolds-averaged Navier–Stokes based computational fluid dynamics (CFD) code. The various moonpool designs were simulated to identify the effect of each device for the internal flow reduction of the moonpool. The CFD analysis results with regular waves, the water surface responses inside moonpool such as the flow pattern and resonance frequency, were compared with model test results and showed reasonably good agreements.

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References

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Figures

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Fig. 1

Two-dimensional wave flume at KRISO

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Fig. 2

Moonpool model (left: ISO view, middle: top view, and right: front view)

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Fig. 3

Installation of moonpool model and wave probes (left: measurement of incident wave, middle: installation of moonpool model, and right: wave gauge inside moonpool)

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Fig. 4

Moonpool models with different shapes and appendages

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Fig. 5

RWEs with different moonpool models (model test result, Case 0 [△], Case 1 [], Case 2 [□], and Case 3 [x])

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Fig. 6

A sketch of moonpool problem (left: side view, right: front view)

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Fig. 7

Moonpool configurations for CFD simulation

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Fig. 8

Water elevation at numerical probe (RW2) under three different incident waves (T = 0.77, 1.0, and 1.64 s)

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Fig. 9

Grid test regions inside the moonpool (△g = grid size, Lm: moonpool length)

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Fig. 10

Grid test regions outside the moonpool (△g = grid size, Lm: moonpool length)

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Fig. 11

Comparison of the RWE for different grid sizes (RW2)

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Fig. 12

Comparison of RWE between model test and CFD simulation (Empirical formula [vertical dotted line], Model test: Case 0 [□], and CFD: ID-0 [x])

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Fig. 13

Instantaneous snapshots of velocity vector inside moonpool under incident wave T = 0.93 s (Plain moonpool)

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Fig. 14

Comparison of RWE between model test and CFD simulation (Model test: Case 1 [□] and CFD: ID-1 [x])

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Fig. 15

Comparison of RWE with different incident wave periods (Model test: Case 1 [solid line] and CFD: ID-1 [x], 1.08 s [], 1.12 s [], 1.13 s [])

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Fig. 16

Comparison of RWE between model test and CFD simulations (Model test: Case 2 []; CFD: ID-0 [], ID-2 [x])

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Fig. 17

Comparison of RWE with different moonpool models (CFD: ID-0 [solid line], ID-1 [], ID-3 [], and ID-4[x])

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Fig. 18

Comparison of RWE with different moonpool models (CFD: ID-0 [], ID-1 [], and ID-5 [x])

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Fig. 19

Comparison of RWE with different moonpool models (CFD: ID-0 [], ID-1 [], and ID-6 [x])

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Fig. 20

RWE along the x-direction location inside moonpool (ID-1 [] and ID-6 [] under the incident wave T = 1.1 s)

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Fig. 21

Comparison of RWE with different moonpool models (Model test: Case 3 []; CFD: ID-7 [], ID-8 [+], and ID-9 [x])

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Fig. 22

Comparison of plain moonpool, moonpool with a recess, and moonpool with the combination of devices for internal flow reduction (Model test: Case 0 [], Case 1 [], and Case 3 []; CFD: ID-0 [], ID-1 [], and ID-9 [])

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Fig. 23

Comparison of velocity vector between ID-0, ID-1, and ID-3 [Incident wave T = 0.91 s]

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Fig. 24

Comparison of velocity vector between ID-1, ID-5, and ID-6 [Incident wave T = 1.11 s]

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Fig. 25

Comparison of velocity vector between ID-7, ID-8, and ID-9 [Incident wave T = 1.11 s]

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