Wave Drift Forces on Three Barges Arranged Side by Side in Floatover Installation

Floatover is a new method for installing integrated topside of a spar platform. It has several obvious advantages such as less time and cost compared with derrick lifting. In general, the floatover installation consists of three procedures: firstly a single barge is used for long-distance transportation of the topside in order to get good stability; secondly two barges take place of the single barge for floatover installation near the operating site; finally the topside is transferred from the two barges to the spar hull and the installation is completed. Between the first and second procedures, the case occurs that the single transportation barge is sided left and right by two floatover barges in the second procedure with close proximity. This case is concerned by many designers and operators for the security problem brought by possible large relative motions and forces of the three barges in side by side configuration.The hydrodynamics of side-by-side barges are much more complex than that of a single barge in waves. In numerical simulation, it is a challenge to consider all effects including the hydrodynamic interactions, the shielding effects, the viscous effects and the wave resonance effect which has been observed in the gaps between the barges and has a significant impact on wave drift forces. In this paper, motion responses and wave drift forces were calculated in frequency domain for both the multi-body system and the single body. Far-field, middle-field and near-field method were all carried out to calculate wave drift forces. Numerical analysis was executed using potential flow code WAMIT. Corresponding model tests were also performed in the Deepwater Offshore Basin in Shanghai Jiao Tong University. Comparison between numerical and experimental results shows that numerical results agree well with the experiment and that middle-field method has better convergence than near-field method. The comparison between the multi-body system and single body shows that the hydrodynamic interactions (including wave shielding effect and Helmholtz resonance of water in the gaps) are remarkable and motion responses in the multi-body system are larger than single barge at some frequencies.Copyright © 2013 by ASME

[1]  Mun-Sung Kim,et al.  Prediction of Motion Responses between Two Offshore Floating Structures in Waves , 2002 .

[2]  R. H. M. Huijsmans,et al.  Diffraction and Radiation of Waves Around Side-by-Side Moored Vessels , 2001 .

[3]  N. Kodan,et al.  The motions of adjacent floating structures in oblique waves , 1984 .

[4]  J. N. Newman.  The Drift Force and Moment on Ships in Waves , 1967 .

[5]  J. N. Newman,et al.  Computation Of Wave Effects Using ThePanel Method , 2005 .

[6]  Jong J. Park,et al.  First- And Second-order Hydrodynamic Forces And Moments On Two Offshore Floating Structures In Waves , 2004 .

[7]  Hajime Maruo,et al.  The Drift of a Body Floating on Waves , 1960 .

[8]  Yoon-Rak Choi,et al.  An Analysis of Hydrodynamic Interaction of Floating Multi-Body Using Higher-Order Boundary Element Method , 2002 .

[9]  Yoshiyuki Inoue,et al.  A Study of Slowly Varying Drift Forces on Multi-Body Floating System , 2002 .

[10]  J. Pinkster.  Low frequency second order wave exciting forces on floating structures , 1980 .

[11]  Ming-Chung Fang,et al.  Hydrodynamically Coupled Motions of Two Ships Advancing in Oblique Waves , 1986 .

[12]  Jianmin Yang,et al.  An Experimental And Numerical Study On Motions of Three Adjacent Barges In Floatover Installation , 2012 .

[13]  A. Loken.  Hydrodynamic Interaction between Several Floating Bodies of Arbitrary Form in Waves , 1981 .

[14]  Ming-Chung Fang,et al.  On three-dimensional solutions of drift forces and moments between two ships in waves , 2002 .