深水悬链锚泊线阻尼计算

Damping calculation of a deepwater catenary mooring line

深水悬链锚泊线的阻尼主要包括流体动力阻尼、内阻尼和海床摩擦阻尼。除内阻尼由材料特性决定以外,流体动力阻尼和海床摩擦阻尼受上部浮体运动的影响比较显著。利用单根锚泊线由于上部浮体运动而吸收的能量来计算锚泊阻尼。锚泊线和海床之间的接触作用基于刚性海床假定,利用Morrison公式计算锚泊线的惯性力和拖曳力荷载。用有限元方法进行非线性时域动力分析,计算在不同流速分布条件下,上部浮体分别发生慢漂运动和波频运动时的锚泊线动力响应,比较不同工况下锚泊线的最大张力和流体动力阻尼。考虑锚泊线与海床之间的接触摩擦,比较不同摩擦系数时锚泊线的最大张力,并对摩擦阻尼进行计算。

A deepwater catenary mooring line damping mainly includes hydrodynamic drag damping,internal damping and friction damping caused by seabed interaction.Hydrodynamic drag and friction damping are significantly affected by a floating platform while internal damping is dependent on material properties.The energy dissipated by a mooring line due to floating platform oscillation was used to calculate mooring-induced damping.The interaction between mooring line and seabed was based on the hypothesis of rigid seabed.The fluid drag force and inertia force on the mooring line were calculated according to Morrison formula.Under various current velocity distribution conditions,the non-linear dynamic analysis of the mooring line was performed in time-domain with the finite element method.Moreover,the dynamic responses of the mooring line were computed under the wave drift oscillation and the wave frequency oscillation of the floating platform.The maximum tension and the hydrodynamic dampings of the mooring line were compared under the different working conditions.Considering the contact friction between the mooring line and seabed,the maximum tensions of the mooring line were compared under different friction coefficients and the friction damping was calculated.