This paper has experimentally studied fishtailing motions of single and multiple tankers mooring to a SPM system and forces of the mooring system. Three connexions with a SPM system for the tanker(s) are considered here: single, series and parallel. Experiments are carried out concerning motion responses of the moored tanker(s) in the horizontal plan under the effects of wind and current, and influence of the motion responses to mooring forces and chain tension. It is found that the effect of the change of wind and current on the motion of tanker is not monotonous and the response and force may have different regularity in different mooring conditions. Some conclusions here is not identified with that obtained before.
Single Point Mooring system has been widely used in the world while studies of it are increasing everyday, especially for the slow fish-tailing motion of the tanker (Jun Obokata, 1982, 1983, Bernitsas, 1986, Wang, 1987, Halliwell, 1988). But effects of dynamic force of the chain are omitted in most of those theoretical or experimental studies. In the experimental study presented here, SPM model is installed on a movable bottom and effects of chain's dynamic force are included. In the experiment, motion characteristics of a tanker and a master tanker attached by a smaller one (series or parallel) are also condisdered, and about the latter condition there is no available data published yet.
The experiment parameters include the velocity of wind and current (but their directions keep opposite), and the characteristics of mooring force, chain tension, motion period, and sway and yaw of the tanker under the mooring conditions which are single master tanker (case A), master tanker strung by Q smaller one (case B), and master tanker para] leled by a smaller one (case C).