Table 3.2 

 Results of The DTNSRDC Towing Tank Cable Strumming Experiments 







Cable 



Vibration 





Natural 



Reduced 



Phase 



Double 



Cable type 



Experiment 



tension, 7" 



frequency, / 



Mode 



frequency 



velocity. 



angle, 



amplitude 





number 



(lb, N) 



(Hz) 





in water, /„ 



Vsm9lf„D 



^xv 



displacepient 











(Hz) 





(deg) 



lY'/D 



2R/m 





Double Armor 



10 (Tow angle. 



(65,290) 



2.46 



Fund 



4.2 



3.31 



118.5 



0.25 





steel; 



7 8= 90°) 





3.46 



(n= 1) 



(slack cable) 



5.04 



121.2 



0.91 





D = 0.6 in. 



23 





3.52 







5.60 



131.0 



0.65 





15.2 



36 



(370,1640) 



3.94 



Fund 



4.56 



4.65 







0.09 





37 





4.62 



(n= 1) 



(taut cable) 



5.37 







1.07 





30 (61 = 90°) 





4.77 







6.17 







1.28 





38 





5.05 







6.83 







1.12 





41 



(365,1620) 



5.30 







7.70 







0.97 





42 



(365,1620) 



9.00 



« = 2 



9.18 



7.25 







0.89 





45 



(375,1665) 



9.28 







7.58 







1.08 





33 (e = 90°) 



(370,1640) 



9.51 







8.19 







1.12 





48 



(375,1665) 



9.83 







8.33 







1.05 





51 





9.99 







8.73 







1.09 





109 



(265,1180) 



3.88 



Fund 



3.86 



4.82 



-1.4 



0.62 



0.64 





104 





3.96 



(«= 1) 





5.50 



-1.8 



1.22 



1.35 





105 ie = 60°) 





4.09 







6.24 



6.9 



1.40 



1.55 





108 





4.43 







7.06 



- 



0.99 



1.12 





112 





4.55 







7.80 



11.4 



1.05 



1.18 





115 



(265,1180) 



7.62 



n = 2 



7.72 



7.35 



-1.8 



0.70 



1.04 





121 (e = 60°) 





1.13 







7.87 



-0.7 



0.77 



1.19 





124 





8.31 







8.24 



-1.2 



0.81 



1.32 





127 





8.48 







8.52 



-0.9 



0.87 



1.36 



Uniline: 



72 



(216,960) 



4.25 



Fund 



4.68 



4.61 







0.33 



D = 0.6 in. 



73 





4.68 



(«= 1) 





5.34 







1.23 



15.2 mm 



59 (9 = 90°) 

 74 





4.75 

 4.80 







5.70 

 6.06 







1.09 

 1.18 





76 





5.14 







6.86 



-10.3 





1.29 





64 





11.08 



n = 2 



9.36 



6.89 





0.44 







66 





9.89 







7.25 







1.08 





68 (9 = 90°) 





11.66 







7.58 







0.41 





70 





11.89 







7.94 







0.36 





62 





12.01 







8.37 







0.38 



Small diameter; 



86 



(20.89) 



9.5 



Fund 



9.82 



4.45 







0.22 



D = 0.07 in. 



87 





9.0 



(n = 1) 





5.04 







0.62 



1.8 mm 



88 (e = 90°) 



89 



90 





9.9 

 10.8 

 11.0 







5.93 

 6.52 

 7.12 







1.07 

 1.15 

 0.99 





92 



(20.89) 



21.7 



n = 2 



19.64 



6.07 



-49.8 



0.34 







93 













6,38 



-70.4 



0.43 





94 (e = 90°) 





21.9 







6.60 



-43.8 



0.48 







95 





22.3 







6.82 



-45.8 



0.45 







96 





22.3 







7.27 



-44.9 



0.46 





tSee equation (3.4); displacement measured at the cable antinode. 



The taut cable natural frequencies in Table 3.2 were calculated from the string equation 



•^"= TF-v/^' «= 1. 2, 3... (3.2) 



where n is the mode number, T\s the static tension, L is the cable length (span) and m' is the cable's 

 virtual mass. The added mass coefficients employed in computing the cable's natural frequencies were 



57 



