On the oscillations response prediction of a small liquid petroleum gas carrier in random oblique waves

Abstract

The research from this paper is focused on the dynamic study of a small liquid petroleum gas carrier, with mono-hull shape, length of 125.6 m and maximum speed 17 knots. As loading cases, full cargo and ballast conditions are considered. The random waves are modelled on short-term by the ITTC averaged power density spectrum, with the maximum significant wave height 12 m, corresponding to unrestricted navigation cases. The oblique random waves heading angle has 0-360 degrees values. The seakeeping analysis includes the main oscillation components, heave, roll and pitch, based on eigen program DYN (OSC). The numerical analyses include the oscillation transfer functions computation and the short-term evaluation in oblique random waves, for the prediction of the most probable statistical response. For the roll oscillation component, supplementary the influence of the vertical position of the small LPG gravity centre is analysed. The seakeeping criteria are formulated in terms of admissible oscillation statistical most probable amplitudes. The short-term dynamic responses of the small LPG, assessed by the seakeeping criteria, deliver the oscillations cumulative safety polar diagrams. The predicted seakeeping response of the small LPG leads to practical results for the ship’s navigation safety limits in oblique random waves.