The 12th International Conference on Hydrodynamics
18 – 23 september 2016, Egmond aan Zee, The Netherlands
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EXPERIMENTAL STUDY ON ROLL MOTION OF DRILLSHIP WITH APPENDAGES


Go-down ichd2016 Tracking Number 124

Presentation:
Session: Ship hydromechanics resistance V
Room: Room 1
Session start: 14:00 Tue 20 Sep 2016

Jaehoon Lee   naoe06@snu.ac.kr
Affifliation:

Yonghwan Kim   yhwankim@snu.ac.kr
Affifliation:

Je-Eun Choi   choijeeun@dsme.co.kr
Affifliation:

Chuel-Hyun Kim   chhkim@dsme.co.kr
Affifliation:

Young-Bum Lee   yblee@dsme.co.kr
Affifliation:


Topics: - Ship hydrodynamics resistance, propulsion, powering, seakeeping, manoeuvrability, slamming, sloshing, impact, green water, - Hydrodynamics in ocean, coastal and estuary engineering

Abstract:

This paper considers the nonlinear roll characteristics of the ship shaped platform with and without appendages. Due to high nonlinearity in roll motion, experimental method, empirical formula or recently computational fluid dynamics have been adopted rather than potential based method. However, for non-typical hull shape or newly designed appendages, existing empirical formula or numerical methods are not fully validated. In this study, to effectively capture the roll characteristics with or without appendages in zero speed operational condition, experimental approach was applied. In the towing tank test, roll motion was measured by inertia-gyro fusion sensor with lightly strained soft-spring system both in calm water and regular beam waves. Appendages which can induce nonlinear effect are analysed using various test conditions. Variation of initial roll amplitudes in free decay test in calm water and different wave amplitudes and wave frequencies in regular beam waves were considered to analyze the nonlinear nature of roll damping and restoring moment. Nonlinear characteristics in free roll decay test were examined using two different methods; high-order polynomial damping model proposed by Froude and Hilbert transform method. Hilbert transform has been studied in the signal processing field (Feldman, 1994) and adopted to ship and offshore research field by several authors (Lewandowski, 2011; Kim and Park, 2014). Effect of roll damping in motion responses were also examined by seakeeping test in regular beam waves. From experimental results, linear and nonlinear characteristics and related parameters of roll motion were discussed.