基于全耦合时域计算的半潜平台气隙预报

Airgap prediction of semi-submersible platform based on coupled time-domain analysis

半潜式平台具有甲板面积大和平台支柱相对细长的结构特点,当波浪直接砰击甲板时会对平台结构造成严重的破坏,需要对平台各处上浪危险点进行局部加强,因此准确对平台的气隙进行预报,对平台设计工作有着十分重要的意义。以半潜型生产平台为研究对象,分析平台系泊耦合系统在风浪联合作用下的气隙预报。该文通过建立半潜平台模型,计算频域下平台的运动响应特性,再建立系泊系统模型,计算不同浪向下平台的运动响应,以及不同浪向下气隙响应时域结果,并与频域结果进行比较分析,得出了两种方法对于气隙预报的差异,分析了影响气隙预报结果的因素。研究表明,时域预报相对波面升高和气隙值的计算结果和频域预报结果走势基本保持一致。频域分析方法相比时域方法的优点在于计算时间短且计算过程简便,可用于平台初步气隙预报。然而,时域结果能更真实准确地反映在实际海况中平台的气隙响应变化,时域分析方法所得到的相对波面升高数值总体较频域结果更大,并且后立柱附近的气隙值总是小于前立柱附近气隙值。

The semi-submersible platform has the characteristics of large deck area and relatively slender platform pillars.When the wave hits the deck directly,it will cause serious damage to the platform structure,which needs to be locally strengthened at various points on the platform.Therefore,it is significant to forecast the airgap on the platform deck.By establishing a semi-submersible platform model,the motion response characteristics of the platform in the frequency domain are computed.Then,the mooring system model is established to compute the motion and airgap responses of different wave headings to the platform in time domain.The results are compared with the frequency domain results.The differences between the two methods for predicting airgap are obtained,and the factors affecting the results are analyzed.The research shows that the computation results of time domain prediction of relative wave elevation and airgap are basically consistent with the trend of frequency domain prediction.The advantage of frequency domain analysis method is that the computation time is short,and the computation process is simple.Therefore,it can be used for preliminary predicting airgap of the platform.However,the time domain results can be more accurately reflected in the airgap response changes of the platform in the actual sea state.In general,compared with the frequency domain results,the relative wave elevation obtained by the time-domain analysis method is larger,and the air gap value near the back column is always smaller than that near the front column.