The optimal mooring line system of a weather vane ship can be chosen using the software introduced in the paper. 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 motions. The damping 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, the total offset of the ocean unit (steady and quasi-steady) can be determined, together with the maximum tension in all lines, as a function of this control parameter. 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 to choose the "best" pre-tension to fit some design criteria.

  • Supplemental Notes:
    • OMAE 1995, 14th Intl Conf on Offshore Mechanics & Arctic Engng; 18-22 June 1995; Copenhagen, Denmark. Sponsored by ASME et al. Procs. Publ by ASME, ISBN 0-7918-1307-X. Vol I, Pt B, p 231 [6 p, 9 ref, 2 fig]
  • Authors:
    • Martins, C A
    • Leite, A
    • Aranha, J A
  • Publication Date: 1995


  • English

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Filing Info

  • Accession Number: 00718501
  • Record Type: Publication
  • Source Agency: British Maritime Technology
  • Files: TRIS
  • Created Date: Mar 27 1996 12:00AM