单点系泊FPSO气隙预报的时域和频域分析

Time domain and frequency domain analysis of air gap prediction of FPSO with single point mooring

以单点系泊的FPSO为研究对象,Matlab软件为计算工具,在百年一遇的极限海况下,采用频域和时域方法对FPSO的气隙进行了数值模拟。针对频域计算结果,预报FPSO在不同浪向下的上浪危险点,并基于时域和频域计算结果,比较FPSO的气隙预报的差异。分析表明:频域方法能够用来快速预测气隙危险点的位置,但是会相对低估各个上浪分析点处的气隙高度值,而且无法考虑风标效应,频域方法无法模拟FPSO在实际环境中真实的气隙变化过程,这会高估在横浪下的FPSO的危险性。

Taking the FPSO in the single point mooring as an object and using MATLAB software as a computing tool,respectively in time domain and frequency domain,the air gap prediction of FPSO is studied in a once-in-a-century extreme sea condition. In the frequency domain,from the aspect of air gap,the points of danger of the FPSO in waves from different incident angles are predicted. In the extreme condition of once in one hundred years,the air gap prediction values in time domain and frequency domain are compared.the analysis shows： the frequency domain method can be used to predict the location of the air gap risk point rapidly. But compared with the time domain method,the frequency domain method underestimates the value of the air gap height at each wave analysis point.Without considering weathercock effect,the frequency domain method can not simulate the air gap changes of FPSO in the actual environment,which will lead to an overestimation of the risk of FPSO under the waves in the definite direction.