Study of applicability in minimising pitch radius gyration for different hull types to improve seakeeping performance

This paper presents an optimisation study to determine the best centre of gravity (CoG) position to improve seakeeping performance. Two varied parameters used in this study were the longitudinal and vertical centre of gravity (LCG and VCG). The Radius Gyration in the y-axis (Ry) is introduced as a novel single-objective function to be minimised, avoiding the complexity of the conventional seakeeping optimisation process. The quality of the seakeeping performance was evaluated by response amplitude operators (RAOs) of the heave, pitch, and vertical motion. Two different hull forms are compared to investigate the applicability of the Ry as the objective function in seakeeping optimisation. The patrol boat and S-60 hull form are selected as representatives of a planing hull type and a displacement hull type. The optimisation was carried out by using the Central Composite Design (CCD) and response surface methodology (RSM) to model the relationship between the CoG and Ry from large and small vessels, with the objective function minimising the Ry. The finding shows that minimising the Ry is more sensitive to the planing hull type compared to the displacement hull type in reducing the vertical motion in different Froude numbers and wave headings.