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Research Papers: Ocean Engineering

Motion Responses of a Catenary-Taut-Hybrid Moored Single Module of a Semisubmersible Very Large Floating Structure in Multisloped Seabed

[+] Author and Article Information
Yiting Wang

State Key Laboratory of Ocean Engineering,
School of Naval Architecture,
Civil and Ocean Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: zjgwangyiting@sjtu.edu.cn

Xuefeng Wang

Professor
State Key Laboratory of Ocean Engineering,
School of Naval Architecture,
Civil and Ocean Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: wangxuef@sjtu.edu.cn

Shengwen Xu

State Key Laboratory of Ocean Engineering,
School of Naval Architecture,
Civil and Ocean Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: shwen.xu@sjtu.edu.cn

Lei Wang

Professor
State Key Laboratory of Ocean Engineering,
School of Naval Architecture,
Civil and Ocean Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: wanglei@sjtu.edu.cn

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 June 23, 2017; final manuscript received October 26, 2017; published online December 6, 2017. Assoc. Editor: Ron Riggs.

J. Offshore Mech. Arct. Eng 140(3), 031102 (Dec 06, 2017) (11 pages) Paper No: OMAE-17-1094; doi: 10.1115/1.4038501 History: Received June 23, 2017; Revised October 26, 2017

Motion responses of moored very large floating structures (VLFSs) in coastal regions are remarkably influenced by shallow water, seabed topography, and mooring system, which were given particular focus in this paper. A three-dimensional (3D) numerical model of a moored semisubmersible single module (SMOD) was described, and time domain simulated and experimentally validated. A catenary-taut-hybrid mooring system was adopted considering coastal space limitations. Large-scale catenary mooring lines were deployed on the deep water side, while taut chains were used on the shore side to decrease the anchor radius. Although the mooring system may induce a stiffness difference between the two sides, the effectiveness of the mooring system was demonstrated by time-domain simulation and model tests. The moored semisubmersible SMOD in shallow water exhibits significant low frequency characteristics. Water depth, asymmetric stiffness, and bottom topography effects were investigated by a series of sensitivity studies. The results show that these factors play an important role in motion responses of the moored SMOD, which can further conduce to better understandings on the hydrodynamic of the semisubmersible-type VLFSs.

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References

Ohmatsu, S. , 2000, “ Numerical Calculation Method for the Hydroelastic Response of Poontoon-Type Very Large Floating Structure Close to a Breakwater,” J. Mar. Sci. Technol., 5(4), pp. 147–160. [CrossRef]
Ohmatsu, S. , 2005, “ Overview: Research on Wave Loading and Responses of VLFS,” Mar. Struct., 18(2), pp. 149–168. [CrossRef]
Wang, C. , and Tay, C. , 2011, “ Very Large Floating Structures: Applications, Research and Development,” Proc. Eng., 14, pp. 62–72. [CrossRef]
Wang, C. , and Wang, B. , 2015, Large Floating Structures, Springer, Singapore. [CrossRef]
Lamas-pardo, M. , Iglesias, G. , and Carral, L. , 2015, “ A Review of Very Large Floating Structures (VLFS) for Coastal and Offshore Uses,” Ocean Eng., 109, pp. 677–690. [CrossRef]
Rognass, G. , Xu, J. , Lindseth, S. , and Rosendahl, F. , 2001, “ Mobile Offshore Base Concepts Concrete Hull and Steel Topsides,” Mar. Struct., 14(1), pp. 5–23.
Kashiwagi, M. , 1998, “ B-Spline Galerkin Scheme for Calculating the Hydroelastic Response of a Very Large Floating Structure in Waves,” J. Mar. Sci. Technol., 3(1), pp. 37–49. [CrossRef]
Yago, K. , and Endo, H. , 1996, “ On the Hydroelastic Response of Box-Shaped Floating Structure With Shallow Draft,” J. Soc. Nav. Archit. Jpn., 1996(180), pp. 341–352.
Kashiwagi, M. , 1998, “ A Direct Method Versus a Mode-Expansion Method for Calculating Hydroelastic Response of a VLFS in Waves,” Eighth International Offshore and Polar Engineering Conference, Montreal, QC, Canada, May 24–29, pp. 215–222. https://www.onepetro.org/conference-paper/ISOPE-I-98-034
Kashiwagi, M. , 1998, “ A Hierarchical Interaction Theory for Wave Forces on a Large Number of Elementary Bodies of a Semisub-Type VLFS,” 14th Ocean Engineering Symposium, Tokyo, Japan, pp. 425–431.
Kashiwagi, M. , 2000, “ Hydrodynamic Interactions Among a Great Number of Columns Supporting a Very Large Flexible Structure,” J. Fluids Struct., 14(7), pp. 1013–1034. [CrossRef]
Murai, M. , Kagemoto, H. , and Fujino, M. , 1999, “ On the Hydroelastic Responses of a Very Large Floating Structure in Waves,” J. Mar. Sci. Technol., 4(3), pp. 123–153. [CrossRef]
Iijima, K. , Yoshika, K. , and Suzuki, H. , 1997, “ Structural Analysis of Very Large Semi-Submersibles in Waves,” J. Soc. Nav. Archit. Jpn., 1997(181), pp. 281–288. [CrossRef]
Newman, J. N. , 1974, “ Second-Order Slowly Varying Forces on Vessels on Irregular Waves,” Symposium on the Dynamics of Marine Vehicles and Structures in Waves, London, pp. 182–186. https://trid.trb.org/view.aspx?id=42007
Newman, J. N. , 2004, “ Progress in Wave Load Computations on Offshore Structures,” 23rd International Conference on Offshore Mechanics and Arctic Engineering, Vancouver, BC, Canada, June 20–25, pp. 20–25. http://wamit.com/Publications/newman_omae04.pdf
Pessoa, J. , and Fonseca, N. , 2013, “ Investigation of Depth Effects on the Wave Exciting Low Frequency Drift Forces by Different Approximation Methods,” Appl. Ocean Res., 42, pp. 182–199. [CrossRef]
Berkhoff, J. , 1972, “ Computation of Combined Refraction-Diffraction,” 13th International Conference on Coastal Engineering, Vancouver, BC, Canada, July 10–14, pp. 471–490. https://icce-ojs-tamu.tdl.org/icce/index.php/icce/article/view/2767
Zhang, J. , 2006, “ A Linear Hybrid Model of MSE and BEM for Floating Structures in Coastal Zones,” J. Hydrodyn., 18(6), pp. 649–658. [CrossRef]
Tegigen, P. , 2005, “ Motion Response of a Spread Moored Barge Over a Sloping Bottom,” 15th International Offshore and Polar Engineering Conference, Seoul, South Korea, June 19–24, pp. 396–405. https://www.onepetro.org/conference-paper/ISOPE-I-05-297
Buchner, B. , 2006, “ The Motions of a Ship on a Sloped Seabed,” 25th International Conference on Offshore Mechanics and Arctic Engineering, Hamburg, Germany, June 4–9, pp. 339–347. http://www.marin.nl/upload_mm/b/4/a/1807455234_1999999096_2006-OMAE-92321_Buchner.pdf
Ferreira, M. D. , and Newman, J. N. , 2009, “ Diffraction Effects and Ship Motions on an Artificial Seabed,” 24th International Workshop on Water Waves and Floating Bodies (IWWWFB), Zelenogorsk, Russia, Apr. 19–22, pp. 1–4. http://www.iwwwfb.org/Abstracts/iwwwfb24/iwwwfb24_25.pdf
Kyoung, J. H. , Hong, S. Y. , Kim, B. Y. , and Cho, S. K. , 2005, “ Hydroelastic Response of a Very Large Floating Structure Over a Variable Bottom Topography,” Ocean Eng., 32(17–18), pp. 2040–2052. [CrossRef]
Gerostathis, T. P. , Belibassakis, K. A. , and Athanassoulis, G. A. , 2016, “ 3D Hydroelastic Analysis of Very Large Floating Bodies Over Variable Bathymetry Regions,” J. Ocean Eng. Mar. Energy, 2(2), pp. 159–175. [CrossRef]
Belibassakis, K. , and Athanassoulis, G. , 2005, “ A Coupled-Mode Model for the Hydroelastic Analysis of Large Floating Bodies Over Variable Bathymetry Regions,” J. Fluid Mech., 531, pp. 221–249. [CrossRef]
Kim, T. , and Kim, Y. , 2013, “ Numerical Analysis on Floating-Body Motion Responses in Arbitrary Bathymetry,” Ocean Eng., 62, pp. 123–139. [CrossRef]
Lee, C.-H. , 1995, WAMIT Theory Manual, MIT Press, Cambridge, MA.
Orcina, L. , 2013, “ OrcaFlex Manual Version 9.6c,” Orcina Ltd., Ulverston, UK.
Yoshida, K. , Suziki, H. , Kato, S. , Sumiyoshi, H. , and Kado, M. , 2001, “ A Basic Study for Practical Use of Semisub-Megafloat,” 20th International Conference on Offshore Mechanics and Arctic Engineering, Rio de Janeiro, Brazil, June 3–8, pp. 59–66.
OCIMF, 1994, Prediction of Wind and Current Loads on VLCCs, Thomas Witherby, London.
Pinkerster, J. , 1975, “ Low Frequency Phenomena Associated With Vessels Moored at Sea,” Soc. Pet. Eng. J., 15(6), pp. 487–494. [CrossRef]
Chen, X.-B. , 2007, “ Middle-Field Formulation for the Computation of Wave-Drift Loads,” J. Eng. Math., 59(1), pp. 61–82. [CrossRef]
Maruo, H. , 1960, “ The Drift of a Body Floating in the Waves,” J. Ship Res., 4, pp. 1–10.

Figures

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Fig. 1

Sketch of the semisubmersible SMOD

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Fig. 2

Asymmetric mooring system configuration

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Fig. 3

Detailed representation of the line model

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Fig. 4

Definition of global and body fixed reference frame

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Fig. 5

Seabed topography in the SMOD operating position

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Fig. 6

Detailed sketch for experimental setup

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Fig. 7

Asymmetric moored SMOD in irregular waves

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Fig. 8

Irregular wave calibration (a) Hs = 1 m, Tp = 6.39 s and (b) Hs = 3 m, Tp = 7.48 s

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Fig. 9

Asymmetric mooring system static stiffness curves (a) 0 deg and (b) 270 deg

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Fig. 10

Time series of model tests and numerical simulations for SMOD sway, heave, and roll motions: (a) case 1, (b) case 2, (c) case 3, and (d) case 4

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Fig. 11

Statistics comparison for SMOD motions between model tests and numerical simulations (a) sway, (b) heave, and (c) roll. Here, min stands for minimum offset.

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Fig. 12

Semisubmersible SMOD RAOs in beam sea (a) sway, (b) heave, and (c) roll

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Fig. 13

Sway QTF (270 deg–270 deg) for different water depths (a) λ = 1.67, (b) λ = 4.17, and (c) λ = inf

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Fig. 14

Static stiffness curves for different taut mooring lines stiffness (a) positive y-axis and (b) negative y-axis

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Fig. 15

Effects of asymmetric stiffness (a) sway and (b) roll

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Fig. 16

Underwater topography for sensitivity analysis

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Fig. 17

Effects of different sloped bottoms (a) maximum sway and (b) maximum roll

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