A Study on Hull Configurations of a Stationary Ship for Less Vertical Motion in Head Seas

This paper describes hull configurations of a stationary ship which reduces vertical motion in head seas. The conceptual background for motion reduction is the cancellation effects of vertical forces acting on the hull, one of which is a wave excitationless phenomenon and the other the cancellation caused by the coupling between heave and pitch. Theoretical and experimental investigations are carried out to find the geometric characteristics of the hull for less vertical motion in waves. The relationship between beam-draft (B/d) and length-beam (L/B) ratios in which the wave excitationless frequency coincides with the frequency of heave resonance is given for a box-shaped ship hull. In addition, for an asymmetric ship hull, it is shown that the cancellation effect by the coupling is pronounced as the vertical prismatic coefficient of the fore body of the hull is smaller than that of the aft body.