Roll characteristics of the Naples Systematic Series

In the present paper, the results from an experimental campaign aimed at the characterization of the roll characteristics of the warped hard chine models of the Naples Systematic Series (NSS) are presented. The Levenberg–Marquardt non-linear parameter identification technique has been employed to determine the damping and restoring coefficients from roll decay tests. Three differential models have been analysed to evaluate the one that provides the best fit of the experimental data. It is found a that quadratic damping model is sufficiently accurate to describe damping non-linearity, whereas a cubic restoring term is recommended to properly model the roll dynamics. Roll decay tests have been further analysed considering the linear decrement of the roll angle. The equivalent damping coefficient has been calculated for all the considered methods. Response Amplitude Operators (RAO) in regular beam waves at zero speed are presented as well as roll-heave phase response. RAOs have shown a relatively similar response of the vessels in terms of roll and heave motions. Finally, an analysis of the behaviour of the hard chine hull forms in irregular beam waves is presented, with particular emphasis on roll and heave amplitude and phase responses.