Promotie M. Bonci: schepen

15 november 2019 12:30 - Locatie: Aula, TU Delft - Door: webredactie

Manifast: The maneuvering of fast ships in waves. Promotor 1: Prof.dr.ir. R.H.M. Huijsmans (3mE).

Broaching-to is a dynamic instability event that several small vessels might face when sailing in the same direction of the waves, in following seas, for example when returning to port during a storm. A broach occurs when the ship is captured by the incoming stern waves (surf-riding), and is turned beam-to-sea by the large wave yawing moment. This research aims to investigate this instability, with the final desirable result of providing guidelines for safer vessels to designers and shipbuilders.

A large part of this research focuses on the determination of the forces acting on a fast craft when manoeuvring in following waves. This has been achieved by means of experimental tests on ship models. The results of this investigation were therefore employed in a mathematical tool meant to predict the motions of the free sailing vessel in following seas. In the last part of this thesis, the steering effectiveness and the directional stability of the fast craft were modified in order to estimate the sensitivity of the vessel to broaching with respect to these manoeuvrability properties. The number of broaching events of the rescue vessel with enhanced steering dropped compared to the original ship configuration. However, when a greater steering force is coupled with a better course-keeping, the dynamic stability of the vessel is enhanced even further, significantly decreasing the likelihood of a broach.

The findings of this thesis must still find a wider validation in realistic sea states, not only in the regular wave case object of this work. The deterministic characterisation of the manoeuvrability loads and the broaching-to dynamics in an irregular sea state will be the most challenging task.

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