Mooring system optimization with application to a weather vane ship
Conference
·
OSTI ID:194705
- Escola Politecnica-USP, Sao Paulo (Brazil)
- Petrobras, Rio de Janeiro (Brazil). Production Dept.
This paper introduces a software that allows one to choose the optimal mooring line system of a weather vane ship. It uses a frequency domain analysis of the ship motion in the horizontal plane employing recently developed analytic expressions for the low frequency sea spectrum, the related wave damping factor and an algebraic approximation for the dynamic tension in the line due to the first order ship motion. The dampings due to the ship hull and mooring lines are incorporated in the model and the only hydrodynamic information needed are the standard ones, namely: the force coefficients for unitary wind and ocean current velocities, the surge added mass at zero frequency, the RAO of the floating system in a certain range of frequencies together with the drift force coefficients for regular waves. Selecting the pre-tension in a specified line as a control parameter, one can determine the total offset of the ocean unit (steady and quasi-steady) together with the maximum tension in all lines, as a function of this control parameters. It has been observed then that the offset of the unit decreases monotonically, as expected, with the pre-tension but the maximum tension in the most loaded line does not increase steadily; this result has been explained with the help of a simplified model and it opens the possibility for one to choose the best pre-tension to fit some design criteria.
- OSTI ID:
- 194705
- Report Number(s):
- CONF-950695--; ISBN 0-7918-1307-X
- Country of Publication:
- United States
- Language:
- English
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