Turning characteristics of KVLCC2 tanker in long-crested irregular head waves

Abstract

In this study, 1/100 scaled 35 degrees turning circle tests of KVLCC2 tanker are performed in irregular head waves. Propeller revolution rates are fixed as 17.5 and 8.2 RPS, which are corresponded to the full-scale speeds of 15.5 knots (design speed) and 7.0 knots in calm water. Long-crested irregular waves for sea state 5 and 6 are generated in KRISO Ocean Engineering Basin. To investigate the deviations of trajectory drifts in irregular waves, five kinds of time histories of waves are calibrated per each sea state, all the actual wave spectrums are in good agreements with desired spectrums. Based on the definitions of drifting distance and angle in the previous study, the characteristics of trajectory driftsin irregular waves are statistically analysed. As the sea state is higher and the ship speed is lower, not only mean values but also standard deviations of drifting distances become larger. In addition, 35 degrees turning tests are also carried out in regular waves. When the regular wave height is the mean height of irregular waves, and the regular wave period equals to the mean period of irregular waves, trajectory drifting distances and angles in regular waves are similar to those in irregular waves.