Abstract

Since the pioneering work of Huse (1986, “Influence of Mooring Line Damping Upon Rig Motions,” Proc., 18th OTC Conference), it is well known that mooring lines may account for a large fraction of the overall damping present in a moored floating structure. This paper is concerned with the mooring line damping induced by the low-frequency, quasi-static, horizontal motion of the mooring line fairlead. The main advantage of the quasi-static approach is that it is much faster than the more accurate finite element methods, and, secondly, that it does not require any finite element modeling skills. A new formulation is proposed and is compared to the results of Liu et al. (1998, “Improvement on Huse’s Model for Estimating Mooring Cable-Induced Damping,” Proc., 17th OMAE Conference), as well as to time domain results obtained with FLEXRISER. The improvement with respect to the previous quasi-static methods is quite notable and our results are closer to FLEXRISER predictions. Finally, quasi-static results are compared to mooring line damping values measured during model tests for full mooring systems. The agreement between the two is very encouraging and suggests that the simpler quasi-static approach may, in some circumstances, be a valuable substitute for the more complex and time-consuming numerical tools. [S0892-7219(00)00102-3]

1.
Huse, E., 1986, “Influence of Mooring Line Damping Upon Rig Motions,” Proc., 18th OTC Conference.
2.
Huse, E., and Matsumoto, K., 1988, “Practical Estimation of Mooring Line Damping,” Proc., 20th OTC Conference, Paper No. 5676.
3.
Wichers, J. E. W., and Huijsmans, R. H. M., 1990, “The Contribution of Hydrodynamic Damping Induced by Mooring Chains on Low Frequency Vessel Motions,” Proc., 22nd OTC Conference, Paper No. 6218.
4.
Matsumoto, K., 1991, “The Influence of Mooring Line Damping on the Prediction of Low-Frequency Vessel Motions at Sea,” Proc., 23rd OTC Conference, Paper No. 6660.
5.
Le Boulluec, M., Le Buhan, P., Chen, X-B., Deleuil, G., Foulhoux, L., Molin, B., and Villeger, F., 1994, “Recent Advances on the Slow-Drift Damping of Offshore Structures,” Proc., 8th BOSS Conference, Vol. I.
6.
Raaijmakers, R. M., and Battjes, J. A., 1997, “An Experimental Verification of Huse’s Model on the Calculation of Mooring Line Damping,” Proceedings, 11th BOSS Conference.
7.
Nakamura
,
N.
,
Koterayama
,
W.
, and
Kyozuka
,
Y.
,
1991
, “
Slow Drift Damping due to Drag Forces Acting on Mooring Lines
,”
Ocean Engineering
,
18
, No.
4
, pp.
283
296
.
8.
Dercksen, A., and Wichers, J. E. W., 1992, “A Discrete Element Method on a Chain Turret Tanker Exposed to Survival Conditions,” Proc., 6th BOSS Conference.
9.
Webster
,
W. C.
,
1995
, “
Mooring-Induced Damping
,”
Ocean Engineering
,
22
, No.
6
, pp.
571
591
.
10.
Hwang, Y.-L., 1998, “Numerical Model Tests for Mooring Damping,” Proc., 17th OMAE Conference.
11.
Brown, D., and Mavrakos, S., 1999, “Comparative Study on Mooring Line Dynamic Loading,” to be published in Journal of Marine Structure.
12.
Bompais, X., Le Boulluec, M., Dekindt, F., Marin, S., and Molin, B., 1994, “Slow-Drift Motion: Practical Estimation of Mooring Line Damping,” Proc., 13th OMAE Conference.
13.
Liu, Y., and Bergdahl, L., 1998, “Improvement on Huse's Model for Estimating Mooring Cable Induced Damping,” Proc., 17th OMAE Conference.
14.
Brown, D. T., Lyons, G. J., and Lin, H. M., 1997, “Large-Scale Testing for Mooring Line Hydrodynamic Contributions at Combined Wave and Drift Frequencies,” Proc., 11th BOSS Conference.
15.
Huse, E., and Matsumoto, K., 1989, “Mooring Line Damping Due to First and Second-Order Vessel Motions,” Proc., 21st OTC Conference, Paper No. 6137.
16.
Huse, E., 1991, “New Developments in Prediction of Mooring System Damping,” Proc., 23rd OTC Conference, Paper No. 6593.
You do not currently have access to this content.