• Improved calculations of steady drift forces 



• More reliable static solution method 



• Calculation of unsteady drift forces 



• New capability in DYN solution to deal with rigid-body dynamics 

 including slave/master constraints 



• Improved statistical evaluations 



• General logic development to tie the steps together 



APPROACH B - TIME DOMAIN SOLUTION 



1. Calculate the initial static reference state with steady 

 components of wind, current, workloads, etc. 



2. Generate the retardation function for the moored body in the 

 reference state. 



3. Generate the time sequence of wave loads representing the wave 

 spectra. 



4. Solve the large displacement time domain equations until 

 significant motion occurs. 



5. Repeat steps 2 through 4 until the time span is completed. 



6. Make statistical evaluations of the output. 



Changes required in SEADYN: 



• Completely new coding representing steps 2, 3, and 6 



• New capability in DYN to deal with the convolution equation form 

 and the slave/master constraints 



• A reasonable algorithm for estimating when significant movement 

 occurs (step 4) 



• General logic development to tie the steps together 



APPROACH C - STOCHASTIC METHODS 



This is a very loosely defined approach that would rely on the 

 generation of second order transfer functions for the coupled mooring 

 system. The fact that second order terms are contained in the transfer 

 functions makes it possible to include the second order drift forces 

 directly. It is obvious that a static reference state must be obtained 

 first as in the other approaches, but the procedure beyond that point is 

 not clear. The second order transfer function depends on the static 

 reference state since it is based on a Taylor Series expansion relative 

 to that state. The procedure for dealing with large shifts in the 

 reference state is undefined. Work is also needed to define the second 

 order terms for the mooring line stiffness, damping, and mass. The 



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