more efficient, fast algorithm such as the one used in NATFREQ could be adapted to perform cost 

 effective strumming calculations. SEADYN has a default, Reynolds number-dependent drag coefficient 

 builtin, but this can be over-ridden if the user specifies a drag coefficient or function based on other 

 independent knowledge or calculations. 



5.5 The SLAK Code. A finite element code for predicting the natural frequencies and mode 

 shapes of slack cables has been developed from a previously existing code as part of this cable dynam- 

 ics research program. A finite element formulation is employed and the range of validity is not limited 

 to small sag-to-span ratios, {si I < 0.12) as are most existing linear theories. The code is also valid for 

 arbitrary locations of the end points (i.e. an inclined cable), it is three-dimensional, and it permits con- 

 centrated applied loads (attached discrete masses) at various locations along the cable. The principal 

 results that are obtained from the code in its present form are the (in-air) natural frequencies, the sup- 

 port reaction forces, the equilibrium shape of the cable, and the natural mode shapes with respect to 

 the equilibrium shape. The code is called SLAK and it is discussed in further detail in Appendix B of 

 this report. 



These numerical models represent the first generation of cable strumming analyses. As more 

 experience is gained using these models, other ideas and techniques for improving the state of the art 

 of calculating the eff"ects of strumming on marine structures undoubtedly will evolve. At the present 

 time, these models represent the current understanding of strumming effects. 



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