PARAMETRIC STUDIES WITH TWO PREDICTION METHODS 



Prior to making direct comparisons between measured and predicted 

 results, computations were made to determine the effect of arbitrary 

 parametric variations on the cable configurations and tensions computed 

 by each of the two methods using the hydrodynamic characteristics of the 

 body, given by the faired curves in Figure 7. The cases considered were 

 for scopes of 100, 200, and 280 feet. For Method 1, cable drag coefficients 

 Cj^of0.8, 1.5, and 1 . 8 in combination with f values of 0. 01, 0.02, and 

 0.03 were used for the computations. For Method 2, cable drag coefficients 

 of 0.8, 1.5, and 1.8 were used. The results of these computations for 

 Methods 1 and 2 are presented in tabular form in Appendixes B and C, 

 respectively, and selected representative cases (280-foot scope) are 

 shown in graphical form in Figures 8 through 13. 



The effects of variations of Cr and f values on the depth y, net tension 

 T-T Q , and cable angle § are summarized for the two methods by Table 3. 

 The values in the table correspond to the case of a cable scope of 280 feet 

 and a speed of 1 1 knots. The net tension T-T Q is the difference between 

 the tension at the ship T and the tension at the towed body T Q , Consequently, 

 it is due only to the hydrodynamic and hydrostatic forces acting on the cable. 



TABLE 3 



Effect of Parametric Variations on 

 Predictions with Methods 1 and 2 



(Values are for a speed of 1 1 knots, a scope 

 of 280 feet, and a tension at the body of 

 637 . pounds) 



Table 3a - Effect of Variation of Cr 



Cr 



:Method 1 (f = 0.02) 



Method 2 



y 



T-T 



<!> 



y 



T-T 



+ 



0.8 

 1.5 

 1.8 



125.5 



109.3 



98.3 



70.6 

 102.5 

 117.5 



17.4 



10.4 



9.0 



153.4 



110.8 



99.9 



120.8 

 207. 1 

 245.5 



17.8 



10.9 



9.5 



Table 3b - Effect of Variation of f 



f 



Method I(Cr =1.5) 



y 



T-T 



1 L o 



* 



0.01 

 0.02 

 0.03 



108.5 

 109.3 

 110. 1 



60.4 

 102.5 

 144.7 



10.2 

 10.4 

 10.6 



10 



