Motions of Moored Ships in Six Degrees of Freedom 



DISCUSSION 



Grant Lewison 



National Physical Laboratory 

 Feltham 3 Middlesex^ U.K. 



I should like to make one small point about the paper. The 

 author has assumed that the response of the system is entirely funda- 

 mental mode -in other words, that there is only one harmonic present. 

 This completely ignores the possibility of higher and lower mode har- 

 monics which for many moored ships are well known to provide much 

 bigger responses than the fundamental. 



REPLY TO DISCUSSION 



I-Min Yang 



Tetra Tech 3 Inc. 

 Pasadena 3 Califomia 3 U.S.A. 



Thank you for the comments. Usually for a non-linear system 

 there are some higher harmonical terms. But I compared the harmo- 

 nic solution with the exact solution for some symmetric cases. The 

 higher harmonical terms are not important. 



DISCUSSION 



Grant Lewison 



National Physical Laboratory 

 Feltham 3 Middlesex 3 U.K. 



What about the lower one - i. e. sub harmonic ? 



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