Coexisting attractors in floating body dynamics undergoing parametric resonance

Abstract This study pertains to analysing the dynamical behaviour of a floating body undergoing parametric resonances. A simple vertical cylinder, representing classical spar-buoy, is considered, limiting its motion heave and pitch degrees freedom. Its geometry mass distribution are chosen such that 2:1 ratio pitch/roll natural frequency makes spar-buoy prone resonance. The system then studied by shooting method, combined with pseudo-arclength continuation, harmonic balance procedure. Results show an extensive bistable region exists, where stable resonance coexists regular response. analysis also unveiled existence quasiperiodic motions existing in correspondence both qualitatively validated using model based on explicit nonlinear Froude–Krylov force calculation.