INFLUENCE OF HEAVE MOTION ON VORTEX-INDUCED VIBRATIONS OF FDPSO RISERS

Based on the conceptional design of FDPSO, the mechanical model and partial differential governing equation of risers are presented. Riser’s top tension is variable with time because of FDPSO heave motion and it aslo changes with axial considered gravity. The fluid force expression includes both the votex-shedding effect and fluid damping force. The nonlinearly equation is solved through numerical method. The dynamic analysis is done to research the influence of parametric excitation to vortex-induced vibrations rooted from FDPSO heave motion. The comparison of the results of three special working cases reflects that risers have large response under the combined action of “lock in” and parametric resonance; the higher modes response have quite a little proportion in total displacement especially in the bending moment and shearing force; the amplitude of heave motion has little effect on the vibrations.