The viv-FOAM-SJTU solver is used to carry out the numerical simulation of the vortex induced vibrations of a riser under different top oscillation excitation amplitudes.

The flow field is computed by the strip theory and Reynolds-averaged Navier-Stokes (RANS) method, while the Bernoulli-Euler bending beam theory and finite element method are employed to model the structure of the riser.

The simulation results show that the cross-flow vibrations transform from multi-mode to single mode with the decrease in oscillation amplitude. At the same time, the inline vibrations maintain single mode, but the amplitude of the mode vibration decreases.

With the variation in top oscillation excitation amplitudes, the washing out of the riser by shed vortices affects the characteristics of vortex induced vibrations.