在平台振荡条件下TLP张力腿的涡激非线性响应
Vortex-induced nonlinear vibrations of TLP tethers under circumstances of platform oscillation
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摘要: 给出了预测张力腿涡激横向振动的时域分析,考虑了波浪、海流、张力腿平台的横漂与垂荡诸因素.张力腿平台的垂荡引起张力周期性变化,对张力腿的涡激横向振动起参数激励的作用,使其动力响应更为复杂.讨论了参数激励下涡激响应的共振条件;以尾流振子模型为基础,发展了分析张力腿在动张力作用下的涡激振动的工程方法,并分析了一座TLP实例,给出了在横漂周期内张力腿上质点的相对位移、弯矩、剪力幅值的时间历程.结果表明,平台垂荡使张力腿的涡激响应幅值升高、高频成分增加,因此它对张力腿的疲劳设计是重要的.Abstract: A time domain analysis is presented for predicting vorex-shedding induced transverse vibration of tension leg platform (TLP) tethers which are subject to wave,current and oscillatory displacements at their upper end both in horizontal and vertical directions.Periodical variations of tether's tension caused by heaving oscillation of TLP play the role of a parametric exciter to vortex-induced vibration,and make it more complicared.In this paper,the conditions of structure-flow resonant caused by vortex,accounting for the effects of tension's parametric excitation are discussed;a method for analysis of TLP tether's dynamic responses to vortex and heaving oscillation is put forth.The time history of displacements,bending moments and shear forces of the tether are computed by the presented.It is shown clearly that the parametric excitation can raise the amplitudes of vortex-induced transverse vibration,increase the components of high frequent responses.The importance of tension variation for fatigue design of TLP tethers is illustrated.
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