Numerical Investigation On The Vortex-induced Vibration Of 2d Marine Rise With Stream-wise Vibration And In-plane Rotation

It becomes quite urgent to comprehensively understand the mechanism of vortex-induced vibration which results a number of costy projects ruined. The problem of vortex-induced vibration has been a hotspot. Vortex-induced vibration appears in many engineering fields, such as bridges, motors, mansions, marine risers, seabed oil pipelines and so on.The thorough mechanism of vortex-induced vibration still remains to be fully explained after tens of years of study. Due to the character of multi-degree of freedom, strong nonlinearity, and phenomena of self-excitation and self-limitation, the mechanism behind the problem is still unclear.As a part of the project (The Study of Vortex-Induced Vibration of Marine Risers Considering the In-Line Vibration and 3D Wake Effect, No. 50809047) supported by the National Natural Science Foundation, the influence of stream-wise vibration and in-plane rotation on the VIV response of 2D cylinder is fully analysed in this paper.The vortex-induced vibration (VIV) of a 2D cylinder with low Reynolds number is investigated by applying the FEM software ADINA, under the consideration of the stream-wise vibration and the in-plane rotation. The cylinder's VIV response sequence characterized by the lock-in state in which the cylinder experience large vibration amplitudes due to the resonance between cylinder vibration and fluid dynamic force caused by vortex shedding is reproduced. The contribution of the stream-wise vibration and in-plane rotation to the cylinder's VIV response is also investigated. Numerical results show that the cross-flow response amplitude increases slightly in the case of stream-wise vibration. However, a significant increment is observed in the cross-flow response amplitude when the cylinder undergoes the stream-wise vibration and the in-plane rotation simultaneously. In this paper, three conditions including only considering the cross-flow oscillation ,considering the cross-flow and stream-wise oscillations at the same time, and considering the cross-flow oscillation,the stream-wise oscillation and the in-plane rotation at the same time are considered. When the mass ratio is 2, the cylinder's maximum dimensionless cross-flow vibration amplitude is 1.23 times of the cylinder's diameter for the case of considering cross-flow, stream-wise vibrations and in-plain rotation. Meanwhile, the lock-in range expands with lower mass ratio. These trends become even more evident with decreasing mass ratio.At the end of this paper, it is concluded the in-plane rotation is a very important factor to the VIV problem of 2D cylinder with low mass ratio.