Linear and Non-linear Numerical Sea-keeping Evaluation of a Fast Monohull Ferry Compared to Full Scale Measurements

The past years have seen a growing interest in fast ships for both cargo and passenger transportation. Different designs have been considered, but recently attention has been focused on fast monohull displacement ships. To gain more knowledge and experience on the behaviour of this kind of ships, full-scale measurements have been performed on board a 128 m monohull fast ferry. This paper deals with the results from these full-scale measurements. The primary results considered are pitch motion, midship vertical bending moment and vertical acceleration at the bow. Previous comparisons between model experiments and numerical sea-keeping calculations indicate that conventional low speed strip theories yield reasonable results even at very high Froude members. To confirm this, the present paper presents the results from the performed full scale members. To confirm this, the present paper presents the results from the performed full scale measurements, and compares these to results from calculations performed with 3 different software systems: I-SHIP, SGN80 and SHIPSTAR.SGN80 is a linear strip theory software system in frequency domain, I-SHIP is a more advanced system, which allows the user to compare several linear and nonlinear strip theories, and SHIPSTAR is an advanced non-linear time-domain strip theory sea-keeping code.The calculations agree well with the measurements at Fn=0.32, whereas the agreement is less satisfying at Fn=0.55. Various reasons for this disagreement are discussed and mainly attributed to the uncertainty of the headings in the journeys analysed and the assumption of the long crested waves.