DRAG-INDUCED INSTABILITIES AND CHAOS IN MOORING SYSTEMS

The influence of a quadratic viscous drag nonlinearity in multi-point mooring systems is examined in this paper. These systems are character ized by a nonlinear restoring force and a coupled wave-structure excit ing force. Stability analysis of system response and its corresponding Poincare map define domains of primary and subharmonic resonances and reveal the existence of coexisting nonlinear solutions. Local and glo bal tangent and period doubling bifurcations identify possible routes to chaotic motion and their controlling parameters. Thus, complex dyna mics are obtained semi-analytically resulting in identification and co ntrol of the drag-induced instabilities which are not attainable by eq uivalently linearizing the hydrodynamic drag force.