Integrated Station-keeping and Seakeeping Predictions

It is a consolidated procedure to investigate vessel station-keeping capability disjoint from her seakeeping qualities during operations at field in storm conditions. This is mainly due to the fact that the station keeping problem is essentially related to surge, sway and yaw motions, while seakeeping predictions deal at most with heave, roll and pitch motions. The operational limitations on ship motions and accelerations are for sure more restrictive than the DP capability in head sea, and could also be that certain criteria would be reached when the station-keeping capability is no more effective. Referenced theoretical models are fully disjoint as well as the most commonly implemented software codes, which are daily used for design and operability analysis. An integrated approach simultaneously dealing with the two problems of station-keeping and seakeeping has not yet been considered. In this paper, we present a newly developed procedure for integrated station-keeping and seakeeping investigations with the aim of obtaining more realistic predictions on the vessel effective capability of carrying out field operations and maintaining position during different storm conditions. To this aim the final result will be expressed in terms of vessel hydrodynamics statistically evaluated through meteorological data of the geographic area of interest. In this way, an effective index could be evaluated for an offshore vessel operating in a field during heavy weather conditions, taking into account both the above mentioned main topics.