Numerical simulation research of vortex-induced vibrations of the long circular cylinders with high mass-ratio

The two-degrees-of-freedom vortex-induced vibrations (VIV) of the long circular cylinders with high mass-ratio are numerically simulated with the software ANSYS/CFX. The VIV characteristic of the cylinder is analyzed in the different conditions (Ur = 3, 5, 6, 8, 10). When Ur is 5, 6, 8 and 10, the conclusion is different from the vortex-induced vibrations of the cylinder with low mass-ratio. When Ur is 3, the frequency of the drag force on the cylinder is twice of that of the lift force and the in-line VIV frequency of the cylinder is twice of that of the cross-flow VIV. The in-line VIV amplitude of the cylinder is much smaller than the cross-flow VIV amplitude. The motion trace is the crescent. When Ur is 5 and 6, the frequency ratio between the drag force and lift force is still 2, but the main in-line VIV frequency of the cylinder is mainly the same as that of the cross-flow VIV and the secondary in-line VIV frequency is equal to the frequency of the drag force. The in-line VIV amplitude is still very small compared with the cross-flow VIV amplitude. When Ur is up to 8 and 10, the in-line VIV frequency of the cylinder is the same as the main frequency of the cross-flow VIV which is close to the inherent frequency of the cylinder and is different from the frequency of the drag force or lift force. But the secondary cross-flow VIV frequency of the cylinder is equal to the frequency of the lift force. The amplitude ratio between in-line VIV and cross-flow VIV is about 0.5. When Ur is 5, 6, 8 and 10, the motion trace is mainly the oval.