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Comprehensive Study on the Linear Hydrodynamic Analysis of a Truss Spar in Random Waves

Authors: Roozbeh Mansouri, Hassan Hadidi

Abstract:

Truss spars are used for oil exploitation in deep and ultra-deep water if storage crude oil is not needed. The linear hydrodynamic analysis of truss spar in random sea wave load is necessary for determining the behaviour of truss spar. This understanding is not only important for design of the mooring lines, but also for optimising the truss spar design. In this paper linear hydrodynamic analysis of truss spar is carried out in frequency domain. The hydrodynamic forces are calculated using the modified Morison equation and diffraction theory. Added mass and drag coefficients of truss section computed by transmission matrix and normal acceleration and velocity component acting on each element and for hull section computed by strip theory. The stiffness properties of the truss spar can be separated into two components; hydrostatic stiffness and mooring line stiffness. Then, platform response amplitudes obtained by solved the equation of motion. This equation is non-linear due to viscous damping term therefore linearised by iteration method [1]. Finally computed RAOs and significant response amplitude and results are compared with experimental data.

Keywords: Truss Spar, Hydrodynamic analysis, Wave spectrum, Frequency Domain

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1073257

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References:


[1] M. Patel, J. Witz, "Compliant Offshore structures," Butterworth- Heinemann Ltd.: Oxford, UK, 1991.
[2] S. Chakrabarti, "Hydrodynamics of Offshore Structures," Computational Mechanics Publications, Southampton.ISBN 0 905451 66 X, 1987.
[3] CT. Stansberg, I. Nygaard, H. Ormberg, et al, "Deep-water truss spar in waves and current-experiments vs. time-domain coupled analysis," Deep Offshore Technology Conference, Rio de Janeiro, 2001.
[4] MJ. Downie, JMR Graham, C. Hall, et al, "An experimental investigation of motion control devices for truss spars," Marine Structures 13:75-90, 2000.
[5] I. Nygaard, W. Lian, CT. Stansberg, "Motion behaviour of a truss spar in deep water," Deep Offshore Technology Conference, New Orleans, 2000.
[6] K. Sadeghi, A. Incecik, "An Approximation Model for the First- and Second-Order Dynamic Response Analysis of Truss Spar platforms," 25th conf. on Offshore Mechanics and Arctic Engineering, Hamburg, Germany, 2006.
[7] A. Incecik, "Design Aspects of Hydrodynamic and structural Loading on Floating Offshore Platforms under Wave Excitation," PhD thesis University of Glasgow, UK, 1982.
[8] M. Patel, "Dynamics of Offshore Structures," Butterworth- Heinemann, ISBN 10:0 408 01074 6, 1989.
[9] O. Faltinsen, "Sea Loads on Ships and Offshore Structure," Cambridge, Ocean Technology Series, Cambridge University Press, Cambridge, UK. ISBN 0 521 45870 (paperback), 1990.
[10] J.N. Newman, "Marine Hydrodynamics," The MIT press, Massachusetts, USA. ISBN 0 262 14026 8, 1977.
[11] B. Mekha, D. Weggel, C. Johnson, J. Rosset, "Effects of Second order Diffraction Forces in the Global Response of Spars," in- Proceeding of the sixth International Offshore and Polar Engineering Conference-, Vol. 1, The International Society of Offshore and Polar Engineers, ISOPE, Los Angeles, USA, pp. 273-280, ISBN 1 880653 23 0 (vol. 1), 1996.
[12] R.C. McCamy, RA. Fuchs, "Wave Forces on Pile: A Diffraction Theory," US Army Corps of Engineering, Beach Erosion Board, Technical Memo No. 69 pp 1-13, Washington, DC, 1954.
[13] JM. Niedzwecki, AS. Duggal, "Wave run-up and forces on cylinder in regular and random waves," J Waterway Port Coast Ocean Eng 118:615-634, 1992.
[14] D. Weggel, J. Rosset, "Vertical hydrodynamic forces on truncated cylinders," in-Proceedings of the fourth International Offshore and Polar Engineering Conference-, Vol. 3, The International Society of Offshore and Polar Engineers, ISOPE, Osaka, Japan, pp. 210-217. ISBN 1 880653 13 3 (vol. 1), 1994.
[15] T. Sarpkaya, M. Isaacson, "Mechanics of Wave Forces on Offshore Structures," van Nostrand Reinhold Company, New York, USA. ISBN 0 442 25402 4, 1981.
[16]A. Incecik, "Lecture notes in mar855 advanced offshore design," Department of Marine Technology, University of Newcastle, UK, 1999.