Study on Moonpool Resonance Effect on Motion of Modern Compact Drillship

Yang, Seung Ho; Yang, Young Jun; Lee, Sang Beom; Do, Jitae; Kwon, Sun Hong

doi:10.5574/ksoe.2013.27.3.053

Cited by 4 publications

(2 citation statements)

References 5 publications

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“…Molin [8] derived analytic formulas to evaluate the moonpool resonance frequency based on potential theory. Yang et al [11,12] confirmed validity of Molin's analytic formula through experimental studies.…”

Section: Introductionmentioning

confidence: 63%

Experimental study on piston- and sloshing- mode moonpool resonances

et al. 2016

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An experimental study was performed on the piston-and sloshing-mode moonpool resonances of offshore structures. Two different geometries were considered to investigate the flow characteristics in a plain moonpool and a moonpool with a cofferdam. To examine the efficiency of a cofferdam for reducing the flow in a moonpool, three cofferdam geometries were tested. The plain moonpool presented violent flows as a result of the piston-and sloshing-mode resonances. However, the moonpool with the cofferdam introduced violent sloshing waves instead of the ascent and descent of the water column in the pistonmode moonpool resonance. Among three different cofferdam geometries, the model with a right triangle facing to the left on the top of the cofferdam was most effective in reducing the flow in the moonpool when compared with the other models.

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Section: Introductionmentioning

confidence: 63%

Experimental study on piston- and sloshing- mode moonpool resonances

et al. 2016

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“…However, previous studies could not address hydrodynamic characteristics of moonpool such as resonance frequency on motion free condition and the shift of moonpool resonance by cofferdam inside moonpool. According to Yang et al (2012), moonpool resonance can be predicted through motion analysis of floating offshore structure. For example, surge and heave Response Amplitude Operators (RAOs) present peaks at resonance frequency.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on moonpool resonance of offshore floating structure

Yang¹,

Kwon²

2013

International Journal of Naval Architecture and Ocean Engineeri

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Offshore floating structures have so-called moonpool in the centre area for the purpose of drilling, installation of subsea structures, recovery of Remotely-Operated Vehicle (ROV) and divers. However, this vertical opening has an effect on the operating performance of floating offshore structure in the vicinity of moonpool resonance frequency; piston mode and sloshing mode. Experimental study based on model test was carried out. Moonpool resonance of floating offshore structure on fixed condition and motion free condition were investigated. And, the effect of cofferdam which is representative inner structure inside moonpool was examined. Model test results showed that Molin's theoretical formula can predict moonpool resonance on fixed condition quite accurately. However, motion free condition has higher resonance frequency when it is compared with that of motion fixed. The installation of cofferdam moves resonance frequency to higher region and also generates secondary resonance at lower frequency. Furthermore, it was found that cofferdam was the cause of generating waves in the longitudinal direction when the vessel was in beam sea.

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

Ponnappan

Surendran

2017

Journal of Offshore Mechanics and Arctic Engineering

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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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Study on Moonpool Resonance Effect on Motion of Modern Compact Drillship

Cited by 4 publications

References 5 publications

Experimental study on piston- and sloshing- mode moonpool resonances

Experimental study on piston- and sloshing- mode moonpool resonances

Experimental study on moonpool resonance of offshore floating structure

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

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