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Abstract

A RoRo-ship usually has a fine hull form with large flare at bow and stern. In order to achieve large cargo space, large ratio of the beam to draught are quite common for this kind ship. Such a hull configuration can be subjected to considerable variation of the metacentre height as she sailing in waves. As a consequence the parametric excitation becomes considerably great so that a large roll motion appears. This is a strongly nonlinear problem. A simplified model is formulated in this paper to take account for the parametrically excited roll motion of a RoRo-ship in irregular following waves. The nonlinear parametric excitation is approched by a Volterra system. Monte-Carlo simulations are used to analyse the two most probable roll modes of a RoRo-ship due to the parametric excitation. The numerical result of the studied ship shows that the nonlinear parametric excitation has to be taken into account for the assessment of the roll motion behaviour. The parameter study related to the significant wave height and wave period has shown that a large roll motion can take place to the ship in reality with an non-negligible probability depending upon the wave statistics of the service sea area.

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