The fluctuating forces of the fluid exerted on the top tensioned riser (TTR) in the in-line and cross-flow directions are both modeled by van del Pol wake oscillator model and the nonlinear coupled dynamics of the in-line and cross-flow vortex-induced vibrations (VIV) of the riser are analyzed in time domain in this paper. The numerical simulation results of the riser's in-line and cross-flow displacements and curvatures are compared with experimental measurements and the comparison shows the validity of this method in modeling some main features of the riser's VIV. Finally,the effects of the riser's top tensions and internal flow velocities on the coupled vibrations of the riser are investigated.
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