STUDY ON THE TOWLINE TENSION DURING TOWING - 2ND REPORT: BEHAVIOUR OF THE TOWLINE IN WAVES

A towing experiment in waves was carried out in order to investigate the effect of the towing length, towing speed, types of towed vessels, sea state and the tow motion on the towline tension. Two types of offshore structure models such as a barge and a semi- submersible were used in the experiment. Comparison between the towline tension of the hawser and the bridle was made and static analysis of the dynamic towline tension was carried out. The applicability of the Hermite moment model to the statistical distribution of the towline tension is discussed, and the effect of the towline tension on the motion of tug and tow investigated. A forced oscillation test with the towline cable model in still water was also carried out to clarify the dynamic towline tension during towing. The experimental results were compared with the theoretical calculation such as Fylling's simplified analysis, lumped mass method and Shin's method using a clipping-off model. It is concluded that Shin's method agrees well with the experimental results even in the case of a strong non-linearity like a snapping.