时域分析波浪中浮体运动的时延函数计算

Calculation of Retard Function for Time-Domain Analyzing Floating Body in Waves

针对时域分析波浪中浮体运动的时延函数,分别采用直接时域法和频时域转换法进行了数值计算和比较研究.直接时域法理论统一、完善,但计算耗时;频时域转换法计算快捷,但受到频率范围的限制,数值处理存在误差.对无航速和有航速情况下的wigley型船以及圆柱形平台各模态的时延函数和阻尼系数分别进行了相互转换计算和对比,两种方法得出结果吻合良好,数值上证明了克拉梅尔斯-克罗尼格关系,表明计算时延函数的直接时域法和频时域转换法皆有效,频时域转换法在计算时间上具有较大的优势,更加高效和实用.在此基础上考察了船舶在有航速情况下频率共振引起的奇异现象,并就不同航速对时延函数结果的影响进行了讨论.

The numerical calculation and comparisons of retard function for time-domain analyzing floating body in waves were conducted by the direct time-domain method（DTM） and the transformation method from frequency to time-domain（FTTM）.DTM is a unified and self-contained theory.It needs heavy CPU time-consuming to obtain retard function by DTM while it is easy and quick by FTTM.For the limitation of frequency band,numerical error is uncertain and may occur when FTTM is used.A wigley-hull-form ship and a cylindrical platform floating in waves were analyzed and verified,and the corresponding retard functions are in good agreement by the two methods.It also indicates FTTM is efficient and practical in dealing with engineering problems.Based on the discussions of the advantage and disadvantages of the two methods,the odd phenomenon due to frequency resonance of ship moving with forward speed was investigated.The influences of various speeds to retard function were also discussed.