EXPERIMENTAL ARRANGEMENT AND PROCEDURES 



The experiment was conducted at sea from the R/V PATRICK KILEY in the New 

 Providence Channel off the Bahamas during July 1970. The operational area was 

 selected for minimum sea state conditions to obtain, as nearly as practicable, 

 steady-state towing. 



The general towing arrangement is shown in Figure 5. A cable dominated 

 system was chosen assuring curvature over a significant portion of the towline. 

 Use of the AN/SQA-13(XN-1) winch and handling system accommodated the large size 

 towcable and simplified system deployment and retrieval. 



The system was towed in a calm sea at nominal speeds of 6, 8, 10, 12 and 

 14 knots (3.1, 4.1, 5.1, 6.2, and 7.2 m/s). At each speed, measurements were 

 taken at nominal wetted cable scopes of 200, 400, 600, 800 and 1000 ft (61, 122, 

 183, 244 and 305 m) . 



Prior to recording data for each new speed and scope, body depth was 

 monitored to assure that the system had established a new equilibrium configura- 

 tion and was no longer influenced by speed change transients. Four separate sets 

 of measurements were taken for each data run. 



RESULTS AND DISCUSSION 

 The averaged measured values of cable tension at the ship and depressor are 

 shown in Figures 6 and 7. Also shown in the figures are computer model predic- 

 tions (solid lines) based on a regression-analysis determination of the hydro- 

 dynamic loading functions f and f and the drag coefficient C . These functions 

 represent the best fit to the data and were obtained through a trial and error 

 process. The values of the functions are: 



f = 0.4986 - 0.2499 cos* + 0.2527 sind, - 0.2487 cos2<}> (4) 



n 



f = -0.2255 + 0.3417 cos* + 0.2255 sine)) - 0.0811 sin2<f> (5) 



C = 5.7467 - 0.93 log., n R (6) 



K J-U e 



These functions are shown graphically in Figures 8 and 9 and apply to the 



Reynolds number range from 5.2 x 10 to 1.28 x 10 . In assessing the goodness of 



fit of computed-to-measured data it is seen that tension predictions are generally 



within 10% of measured values with the body force zeroed out (within 5% with body 



force included). Body depth predictions are within 5% of measured values except 



14 



