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Research Papers: Offshore Technology

Hydrodynamic Study on Water Column Oscillation of Varying Cross-Sectional Moonpool and Its Effect on Resistance of a Drill Ship

[+] Author and Article Information
Sivabalan Ponnappan

Department of Ocean Engineering,
Indian Institute of Technology Madras,
Chennai 600036, Tamil Nadu, India
e-mail: siva_iitkgp@yahoo.co.in

Surendran Sankunny

Professor
Department of Ocean Engineering,
Indian Institute of Technology Madras,
Chennai 600036, Tamil Nadu, India
e-mail: sur@iitm.ac.in

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 August 25, 2016; final manuscript received October 13, 2017; published online December 6, 2017. Assoc. Editor: Ye Li.

J. Offshore Mech. Arct. Eng 140(3), 031301 (Dec 06, 2017) (8 pages) Paper No: OMAE-16-1100; doi: 10.1115/1.4038396 History: Received August 25, 2016; Revised October 13, 2017

A moonpool is meant for access to the underwater part of the ship from onboard. It is a vertical opening along the depth having an effect on the performance of the floating platform. Inside the moonpool, water motions in horizontal plane is called sloshing and in vertical planes it is called piston mode. Moonpool causes deck wetness and sometimes results in the downtime of the platform. It is the necessity of the operator to be at the safe conditions of platform facing varied environmental conditions. In the present study, vessel response in the region of moonpool resonance was investigated with different shapes of moonpool and comparison is made with Molin's (2001, “On the Piston and Sloshing Modes in Moonpools,” J. Fluid Mech., 430, pp. 27–50.) theoretical and Fukuda's (1977, “Behavior of Water in Vertical Well With Bottom Opening of Ship and Its Effects on Ship-Motion,” J. Soc. Nav. Archit. Jpn., 1977(141), pp. 107–122.) empirical formulas. It is seen that there is a shift in the frequency of resonance based on moonpool shapes. The effect of moonpool on the ship motion with forward speed is also attempted in this paper. Proven packages are used to calculate the calm water resistance of the ship with moonpool of various cross section. Wave making coefficient of the ship is modified due to opening to accommodate the moonpool. The openings to accommodate moonpool causes further entry of water both zero and nonzero Froude number especially in the presence of waves.

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References

Fukuda, K. , 1977, “ Behavior of Water in Vertical Well With Bottom Opening of Ship and Its Effects on Ship-Motion,” J. Soc. Nav. Archit. Jpn., 1977(141), pp. 107–122. [CrossRef]
Aalbers, A. B. , 1984, “ The Water Motions in a Moonpool,” J. Ocean Eng., 11(6), pp. 557–579. [CrossRef]
Faltinsen, O. M. , Rognebakke, O. F. , Lukovsky, I. A. , and Timokha, A. N. , 2000, “ Multidimensional Model Analysis of Nonlinear Sloshing in a Rectangular Tank With Finite Water Depth,” J. Fluid Mech., 407, pp. 201–234. [CrossRef]
Molin, B. , 2001, “ On the Piston and Sloshing Modes in Moonpools,” J. Fluid Mech., 430, pp. 27–50. [CrossRef]
Maisondieu, C. , and Ferrant, P. , 2003, “ Evaluation of the 3D Flow Dynamics in a Moonpool,” 13th International Offshore and Polar Engineering Conference (ISOPE), Honolulu, HI, May 25–30, pp. 493–500. https://www.onepetro.org/conference-paper/ISOPE-I-03-272
Gaillarde, G. , and Cotteleer, A. , 2005, Water Motion in Moonpools Empirical and Theoretical Approach, Maritime Research Institute, Wageningen, The Netherlands.
Faltinsen, O. M. , Rognebakke, O. F. , and Timokha, A. N. , 2007, “ Two-Dimensional Resonant Piston-Like Sloshing in a Moonpool,” J. Fluid Mech., 575, pp. 359–397. [CrossRef]
van't Veer, R. , and Tholen, H. J. , 2008, “ Added Resistance of Moonpools in Calm Water,” ASME Paper No. OMAE2008-57246.
Park, S. J. , 2009, “Hydrodynamic Characteristics of Moonpool Shapes,” M.Sc. thesis, Pusan National University, Busan, South Korea.
Kawabe, H. , Kwak, H. , Park, J. , and Ha, M. , 2010, “ The Numerical and Experimental Study on Moonpool Water Surface Response of a Ship in Wave Condition,” 20th International Offshore and Polar Engineering Conference (ISOPE), Beijing, China, June 20–25, pp. 469–474. https://www.onepetro.org/conference-paper/ISOPE-I-10-471
Choi, S. Y. , Lee, Y. G. , and Jung, K. Y. , 2010, “ A Fundamental Study for Internal Flow in Moonpool Using Marker-Density Method by Two-Dimensional Numerical Simulation,” Spring Conference of the Society of Naval Architects of Korea, Je-Ju, Korea, Oct. 21–22, pp. 107–122.
Kwon, S. H. , Yang, Y. J. , Lee, S. B. , Do, J. , and Kwon, S. H. , 2013, “ Study on the Moonpool Resonance Effect on Motion of Modern Compact Drillship,” J. Ocean Eng. Technol., 27(3), pp. 53–60. [CrossRef]
Newman, J. N. , 1977, Marine Hydrodynamics, MIT Press, Cambridge, MA, Chap. 6.
FLOWTECH International AB, 2010, “SHIPFLOW User Manual 6.0,” Flowtech International AB, Gothenburg, Sweden.
Mierlo, K. , 2006, “Trend Validation of SHIPFLOW Based on the Bare Hull Upright Resistance of the Delft Series,” Master's thesis, Delft University of Technology, Delft, The Netherlands. https://s3.slidedoc.us/uploads/DZU2017/07/09/7zz13eoO0A/98814d990623b5c7bf9204230db42c81.pdf

Figures

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Fig. 1

(a) Geometry of moonpool-A, (b) geometry of moonpool-B, and (c) geometry of moonpool-C

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Fig. 2

Surge RAO of ship without moonpool

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Fig. 3

Surge RAO of ship with moonpool-A

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Fig. 4

Surge RAO of ship with moonpool-B

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Fig. 5

Surge RAO of ship with moonpool-C

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Fig. 6

Heave RAO of ship without moonpool

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Fig. 7

Heave RAO of ship with moonpool-A

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Fig. 8

Heave RAO of ship with moonpool-B

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Fig. 9

Heave RAO of ship with moonpool-C

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Fig. 19

Variation of trim angle with Froude number

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Fig. 18

Structured grid and free surface

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Fig. 17

(a) XPAN free surface wave elevation of without and moonpool-A at Fn = 0.118. (b) Free surface elevation of without and moonpool-A at Fn = 0.157.

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Fig. 16

(a) XCHAP pressure distribution side bow, (b) XPAN pressure distribution, (c) XCHAP pressure distribution, (d) XPAN free surface without moonpool, and (e) XPAN free surface with moonpool-A

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Fig. 15

Total resistance of drillship

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Fig. 14

Calculation zones

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Fig. 13

Surge RAO of ship with different moonpool configuration at 12 knots speed

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Fig. 12

Surge RAO of ship with moonpool-B

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Fig. 11

Surge RAO of ship with moonpool-A

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Fig. 10

Surge RAO of ship without moonpool

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