||International Ship Stability Workshop
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Recent developments towards the clarification of the dynamics of the broaching-to mode of ship instability are reported. A multi-degree nonlinear mathematical model of the automatically steered ship in astern seas, is taken as the basis of the investigation. A basic novelty of the approach lies in the fact that it unifies contemporary methodologies ofship controllability andtransverse stability studies, within thvframeworkofmodem dynamical systems' theory. Specific nonlinear phenomena are identified as responsible for the onset of broaching behaviour. Steady-state and transient responses are investigated and it is shown how capsize is incurred during the forced turn of broaching. A classification of broaching mechanisms has been developed, concerning frequencies of encounter near zero, where surf-riding plays the dominant role, as well as frequencies of encounter away from zero, where, the instability is inherent of the over/aking-wave periodic mode.