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内波的波致流为沿水深方向非均匀分布的剪切流,而深海平台立管的自然模态具有低频、密集的特性,这种流场和结构的特点使得深水立管的涡激振动表现出高阶模态、多阶模态参与振动的特点。该文研究了大长径比立管在内波流场作用下的锁频特性,建立了基于模态能量理论的多模态锁频的计算方法,并应用于改进的尾流振子模型进行立管涡激振动响应预测。结合实例,进行了深海平台立管的涡激振动响应分析,比较了内波、海流等不同流场作用下立管的涡激振动响应;分析了波致流速对响应位移和应力的影响,结果表明随着波致流速的增大,响应的RMS振幅和应力有不同程度的增大;需要注意高应力响应伴随高频率振动对结构疲劳寿命的影响。
The wave induced flow of internal waves is a shear flow distributed non-uniformly along the depth of water, while the natural modes of the deep-sea platform riser have low frequency and dense characteristics. The characteristics of the flow field and the structure make the vortex-induced vibration Showing high-order mode, multi-order mode to participate in the characteristics of vibration. In this paper, the frequency-locking characteristics of a large-diameter-ratio riser under internal wave field are studied. A multi-modal frequency-locking method based on modal energy theory is established and applied to the improved wake oscillator model Prediction of vortex induced vibration of tube. The vortex-induced vibration response of the deep-sea platform riser was analyzed with the example. The vortex-induced vibration response of the riser was compared under different flow fields, such as internal wave and ocean current. The effect of wave velocity on response displacement and stress was analyzed. The results It shows that the RMS amplitude and the stress of the response increase with the increase of the wave velocity. It is necessary to pay attention to the influence of the high stress response with the high frequency vibration on the fatigue life of the structure.