Guidelines for Navy Mooring Research 



The conclusions listed in the previous section are universal and 

 are somewhat independent of specific needs. The conclusions in this 

 section are applicable to the development of a Navy mooring analysis 

 capability. An overview of this development within the CEL Mooring 

 Systems Prediction Project can be found in CEL Technical Memorandum 

 M-44-80-9." 



Some of the specific recommendations made during and after the 

 seminar are listed below: 



• A few minor additions could be made to DSSM to improve its 

 generality. Examples are: 



(1) Build in additional wind wave spectral models and allow 

 for shoaling. 



(2) Allow for wave orbital velocities in the dynamic analysis. 



In shallow water, these velocities would approach the magnitude 

 of the dynamic motions and should be accounted for. 



(3) Allow for unsteadiness in the wind loading by introducing 

 a wind spectrum. 



(4) Allow for cylindrical surface buoys to complement the spherical 

 buoy dynamic characteristics already in DSSM. Results from an 

 extensive investigation into the dynamic characteristics of 

 floating cylinders will be reported soon from the U.S. Naval 

 Academy. 



• The relative effect of many of the idealizations used in the 

 DSSM model can be determined through parametric studies. 

 Examples of this include: 



(5) Errors caused by the use of spheres to represent all surface 

 buoys. The dynamics of buoys were considered of secondary 

 importance compared to the ship when this section of the model 

 was formulated. 



(6) Errors associated with the linearization of the mooring cable 

 response for the frequency-domain analysis. The moored ship 

 response is first calculated in the frequency domain. A 

 second time-domain analysis with fully nonlinear cable response 

 is then performed separately, using the linear ship response 



as excitation to the top of the cables. Relative comparisons 

 of the cable responses would help determine the significance 

 of this linearization. 



(7) Importance of the inclusion or exclusion of the dynamics of 

 surface buoys in the dynamic analysis. The wave-induced 

 motions of the buoys certainly contribute to the loads in 



*Civil Engineering Laboratory. Technical Memorandum M-44-80-9: A 

 review of the CEL mooring systems prediction product area, FY 79 and 

 FY 80, by P. A. Palo. Port Hueneme, Calif., Sep 1980. 



