STATE-OF-THE-ART PROCEDURE 



Application of the foregoing mooring dynamic model (as 

 formulated in the time domain) to the analysis of inertia- 

 dominated systems as exemplified by a tanker is approached by 

 the following stepwise procedure: 



1. For each frequency corresponding to the partitioned 

 components of the input wave spectrum, the following 

 quantities are computed: 



a. First order forces corresponding to the 

 sum of the incident and scattered wave 

 potentials (that is, the first order 

 forces corresponding to the diffraction 

 potential). These forces are those that 

 would exist if the vessel were fully 

 restrained and the theory employed is that 

 outlined by V/ehausen and Laitone (1960). 

 There are no simplifying assumptions in 

 this procedure except that for an ideal 

 irrotational fluid. 



b. First order unit amplitude radiation 

 potentials and corresponding unit ampli- 

 tude transfer functions. The real and 

 imaginary components of the latter are 

 directly related to the added mass and 

 damping coefficients which are frequency 

 dependent. Implicit in this process is 

 the assumption that the vessel responds 

 at the same frequency as the input excit- 

 ing wave frequency. 



c. Using a frequency domain description of 

 the dynamical equations of motion, the 

 first order motions (i.e., amplitudes) 

 are computed. 



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