On the seakeeping response analysis of a large off-shore drillship

Abstract

For an off-shore structure the operation safety must be assessed by several criteria as those specific for the seakeeping, ship oscillations in irregular waves. In this study the seakeeping analyses of an off-shore drillship, with 210 m length and two displacement conditions, are carried out. The short-term irregular waves are modelled by the ITTC power density spectrum, for a full set of 360 deg oblique waves condition and maximum significant wave height of 12 m. The numerical seakeeping analyses are done by our own program DYN_OSC, based on a linear strip theory formulation, including heave, pitch and roll ship’s oscillation components. The first drillship seakeeping analyses are done for the zero speed case, specific to the drill operation into a research location. The second drillship seakeeping analyses simulate the navigation for several speeds between operation locations. Based on the numerical results of this study, the operation safety assessment of the off-shore drillship by seakeeping criteria is accomplished.