基于Longuet-Higgins分布的深水立管疲劳分析

Fatigue analysis of deepwater risers based on Longuet-Higgins distribution

利用Longuet-Higgins分布将表征长期海况的波浪散布图分解为单个规则波的散布图,以此进行深水立管的疲劳分析,并与雨流法的计算结果进行了比较.结果表明:波浪散布图的离散应充分考虑系统响应的影响;若将波浪散布图离散得较为理想,则采用该方法计算得到的疲劳寿命将和雨流法的结果非常接近,且离散的越精细,其结果也和雨流法的越接近.该方法计算速度快、占用硬盘空间少,可用于实际工程中深水立管的疲劳分析.

The Longuet-Higgins distribution was employed to decompose the wave scatter diagram into an individual regular wave scatter diagram, based on which a global fatigue analysis was performed for a deepwater riser. The results were compared with that obtained from the stochastic time domain analyses and rainflow counting technique. Comparative analysis shows that the system response should be fully considered in the decomposition process of sea states. Provided that the regular wave bin discretisation is performed well, the predicted fatigue life from this method will generally agree well with that from the equivalent rainflow analysis. With much less calculation time and disk storage requirement, the presented method can therefore be used for the fatigue assessment of deepwater risers in industry practice.