As ribbon towcable has found important applications in fleet systems, 

 particularly in submarine towed communications buoys and various airborne mine 

 countermeasure systems, the need for accurate towing configuration prediction 

 has increased. Knowing the hydrodynamic loading on the ribbon cable is required 

 for configuration prediction. 



Typically one of two methods is used by the David Taylor Naval Ship Research 

 and Development Center (DTNSRDC) to develop the hydrodynamic loading functions. 

 The first involves direct measurement of the hydrodynamic loading on a two-dimen- 

 sional (rigid) model in the towing basin. In the second technique an at-sea 

 experiment is performed in which certain parameters describing the towing con- 

 figuration are measured and the hydrodynamic loading functions are deduced by a 

 regression analysis process until a match of computed and measured configurations 

 is attained. 



This latter technique was used to determine the hydrodynamic loading func- 

 tions for a particular ribbon cable. This report describes the at-sea experiment 

 including towcable model, instrumentation, and experimental procedures; presents 

 the results of the sea-trial and loading function analysis; and presents conclu- 

 sions. Comparison of the loading functions with an independent data base is 

 performed in Appendix A. 



BASIC CONSIDERATIONS 

 The differential equations describing the steady-state two-dimensional 



towing configuration and forces in a cable-body system are well defined based on 



2 

 certain simplifying assumptions. Solutions can be obtained by numerical inte- 



. 3 ... 

 gratxon requiring as inputs: 



1. Tension and angle at some point on the cable, usually an end condition 

 specified at the towed body termination, 



2. The form of the hydrodynamic loading functions, and 



3. The characteristic drag coefficient for the towline. 



The body forces defining the cable end conditon typically are measured 

 quite accurately in towing basins or wind tunnels. 



A complete list of references is given on page 21. 



