Abstract: The vortex-induced vibration (VIV) of a cylinder with mass ratio 2.6 and damping ratio 0.0036 at different reduced velocities has been numerically simulated based on the overset grid method. The amplitude, frequency ratio, wake vortex shedding modes and nonlinear characteristics of the VIV response are systematically analyzed. With the increase of the reduced velocity, the VIV response of the cylinder switches four times, but only once the phase difference between the transverse flow vibration response and the vortex force coefficient changes abruptly, which causes the wake vortex shedding mode to change from “2T” mode to “2P” mode. In addition, the velocity variation range of the VIV of the cylinder is smaller than its displacement variation range under any reduced velocities. When the reduced velocity is 4.0, the VIV of the cylinder is chaotic in both the streamwise and transverse directions. When the reduced velocity is 8.0, the VIV of the cylinder is also chaotic in the transverse direction, but still is self-limited. Under the other reduced velocities, the vibrations of the cylinder are regular and stable in the streamwise and transverse directions.

Key words: marine riser, vortex-induced vibration, overset grid, nonlinear characteristic, wake vortex shedding mode

摘要： 该文基于重叠网格法对在不同约化速度下质量比和阻尼比分别为2.6和0.003 6的圆柱涡激振动进行数值模拟研究,系统地分析了其响应幅值、频率比、尾流漩涡脱落模式及其非线性特性。随着约化速度的增大,圆柱涡激振动响应共发生4次切换,但只有其中1次切换时横流向振动响应与涡流力系数的相位差时发生了突增变化,这次突增促使尾流漩涡由“2T”模式转变为“2P”模式。此外,任何约化速度下的圆柱涡激振动速度变化范围均小于其位移变化范围。当约化速度为4.0时,圆柱来流向和横流向的涡激振动均处于混沌状态;当约化速度为8.0时,圆柱横流向涡激振动同样处于混沌状态,但仍然具有自限性;在其他约化速度下,圆柱来流向和横流向的振动稳定且规律。

关键词: 海洋立管, 涡激振动, 重叠网格, 非线性特性, 尾流漩涡脱落模式