The Effect of the Excitation Modelling in the Parameter Estimation of Nonlinear Rolling

In this paper the effect of the excitation modelling on the fitting capability of the nonlinear roll motion equation to experimental data is studied. Several frequency dependent and constant effective wave slope coefficients are derived for five different scale models corresponding to different ship typologies by a Parameter Identification Technique. The frequency domain behaviour of the obtained coefficients is discussed and compared with linear diffraction (strip theory) results and I.M.O. suggested values. It appears that a mathematical modelling with constant damping parameters and frequency dependent excitation could give very good results. As regards the excitation parameters, a common trend for slender bodies is evidenced