The two-degrees-of-freedom of vortex-induced vibration（VIV）of the long risers is numerically simulated with the software ANSYS/CFX. The VIV characteristic, in the two different conditions (A/D=0.07 and A/D=1), is analyzed. When A/D is around 0.07, the amplitude ratio of the riser’s VIV between in-line and cross-flow direction in the lock-in is lower than that beyond the lock-in. The frequency of in-line VIV is twice of that of cross-flow VIV beyond the lock-in, but in the lock-in, it is the same as that of cross-flow VIV and the same as that of lift force. When A/D is around 1, the amplitude ratio of the VIV between in-line and cross-flow direction in the lock-in is obviously larger than that beyond the lock-in. Both in the lock-in and beyond the lock-in, the frequency of in-line VIV is twice of that of cross-flow VIV. The frequency of in-line VIV is the same as that of drag force and the frequency of cross-flow VIV is the same as that of lift force.
Fan Jie-li;Huang Wei-ping.
The Numerical Research of Two-degrees-of-freedom Vortex-induced Vibrations of Long Risers[J]. Journal of Vibration and Shock, 2012, 31(24): 65-68
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