engleski

Dynamic instabilities in following seas caused by parametric rolling of C11 class containership

Parametric roll resonance is known as one of dangerous modes of ship motions in waves. This resonance occurs as a result of roll restoring energy variations in astern or head seas. Post-Panamax container ships seem to be particularly susceptible to parametric rolling because the vessels tend to feature wide beam and large bow flares in order to carry more containers on deck while at the same time minimizing the resistance and improve propeller performance with the streamlined underwater hull. This paper focuses on the parametric resonance observed in following seas. A 6 degree-of-freedom model has been used to explain the parametric roll resonance of the ship taking into account coupling between roll and vertical motions. Parametric rolling resonance in following waves was also investigated experimentally. Several experiments using a scale model of a post-Panamax containership were carried out in regular following waves at the CEHIPAR basin in Spain. In these experiments the wavelength, the wave height, the model speed and the encounter angle were widely varied to clarify overall property of parametric rolling resonance in following waves. As a result, conditions in which the parametric rolling resonance is likely to occur were determined. Also outlined in the paper are recommendations for additional research needed to better understand the influence of vessel design and operational considerations on the propensity of post-Panamax containerships towards parametric roll-ing.

dynamic stability; parametric rolling; seakeeping

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