An experimental study of the maneuverability of a blunt ship: the effect of water depth

In infinite depth and calm water conditions the wave resistance is important for the cost necessary to maintain the design speed. In shallow water the safety aspects become more important. First, wave generation in shallow water can lead to an increase of the trim and sinkage with high risk of ship grounding. Second, due to the strong variation of the added mass, i.e. of the linear derivatives, even small changes in trim and sinkage cause a local variation of the depth to draft ratio, h/T, altering the features of the directional stability. Finally in very shallow water conditions, three-dimensional effects ca nmatter, causing a strong flow around the ends of the ship and influencing the wave pattern around the hull. Therefore the possibility to predict the characteristics of maneuverability in shallow water is a fondumental task for blunt and large draft vessels during the operations near the coast or in the harbors. Here we discuss an experimental study of the maneuverability features of a VLCC ship versus the ration h/T. Because our study is of fundamental nature, particular care has been given in performing dedicated uncertainty analysis of the PMM experiments, following the procedure described in Simonsen (2004).