RECOMMENDATIONS FROM CEL MOORING DYNAMICS SEMINAR 

 J. S. Bendat 



A two-day seminar on mooring system dynamics was held at CEL on 

 10-11 January 1980 where various aspects of this field were discussed. 

 The first day was devoted to separate presentations by nine invited parti- 

 cipants on topics dealing with mooring systems analysis and cable models, 

 mean and second-order drift forces, vessel equations of motion, random wave 

 characteristics, and spectral analysis techniques for system identification, 

 The CEL cable dynamics/moored vessel model was outlined that employs finite- 

 element techniques to account for various linear and nonlinear system 

 properties. 



Group discussions on the second day concerned desired results from 

 any mooring system model and the particular results obtained by the CEL 

 model. A major open problem was pointed out on the need to obtain actual 

 experimental input/output data to provide detailed evaluations and compari- 

 sons between model predicted results and measured results. It was also 

 clear from this discussion that a strong requirement exists to be able to 

 determine the overall linear and nonlinear features of the total mooring 

 system that has been included in the CEL model from input points to output 

 points, as well as the specific linear and nonlinear system properties be- 

 tween certain measurement points. 



Recommendations 



The first recommendation is that computer simulation studies be performed 

 to determine the overall linear and nonlinear features in the present ' 

 CEL model and in later revisions of this model. Presently available 

 coherence analysis techniques can be used for this work. In particular, 

 a coherent output spectrum calculation can decompose the total measured 

 output spectrum at any frequency into two parts representing (a) the 

 overall optimum linear features and (b) the remaining uncorrelated noise 

 due to nonlinear effects as well as other causes. 



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