AN EXPERIMENTAL INVESTIGATION OP THE HYDRODYNAMIC FORCES 

 ON STRANDED CABLES 



by 



Leonard Pode 



ABSTRACT 



Experimental evidence verifies the sine- square law for the normal component 

 of the hydrodynamic force acting on stranded cables. The side component appears to 

 be proportional to the sine of the angle of inclination of the cable to the stream for 

 very snriall angles, attaining a maximum value at an angle that depends upon the size 

 and construction of the cable. 



INTRODUCTION 



During the summer and fall of 1945 a series of experiments was con- 

 ducted at the David Taylor Model Basin by Alice E. MacDonald and Dr. M.A, 

 Garstens, to determine the angle of tow and to measure the forces acting upon 

 freely trailed stranded cables. The purpose of these experiments was to study 

 the relationship between the hydrodynamic forces acting on cables and the an- 

 gle of tow; the main interest being the investigation of this relationship 

 vfhen the angle of the cable to the stream is small, i.e., less than ten de- 

 grees. Although the results of the original analysis of the data were obscure, 

 these results indicated a marked deviation from the sine-squared law for the 

 component of the hydrodynamic force acting normal to the cable and lying in 

 the plane including the directions of the cable and the stream. However, a 

 subsequent analysis, made in the summer of 19^7, by the writer, together with 

 William E. Cummins, led to significant results which accounted for the appar- 

 ent discrepancy. 



Eight samples of cable were tested, four of 1 /I 6-inch diameter, 

 three of 1 /8-inch diameter and one of lA-inch diameter (see Table 1 ). 



THEORY OF THE EXPERIMENTAL METHOD 



The basis of the experimental method rests on the theory that a free- 

 ly towed flexible cable vjill assume the configuration of a straight line and 

 that this line will be inclined at such an angle that the component of the re- 

 sultant force that is normal to the cable vanishes. If end effects are 



