EFFECTS OF VARYING TENSION AND STIFFNESS ON DYNAMIC CHARACTERISTICS AND VIV OF SLENDER RISER

摘要

A time-domain approach for predicting dynamic characteristics and vortex-induced vibration (VIV) response of deepwater risers is proposed by coupling finite element simulation and a hydrodynamic model. Numerical results indicate that axially varying structural parameters can efficiently change the modal wave length as well as the modal displacement. Further, VIV response indicates that vibration amplitude depends on a complex synthetical effect of tension, stiffness and wave length. Generally speaking, for lower modes the response amplitude is larger at the axial position where tension is smaller, whereas for higher modes the response amplitude is larger at the axial position where bending stiffness is lower. Moreover, vibration wave velocity increases with increasing modal wave length.