The following dimensionless parameters were varied during the towing experiments: 



• Reynolds number, Re„ = Ksin 9 D/v, based on the normal component of the incident flow; 



• Length-to-diameter ratio, L/D ; 



• Angle, 9 , between the cable and the incident flow; 



• Tuning parameter, 2T/p V^DL, which determines the mode of vibration, i.e. fundamental, second 

 harmonic, etc. (Tis the tension in the cable); 



2 

 Density ratio, pjp = — 



cable's mass per unit length. 



2m 



PD' 



, where p^ is the density of the cable material and m is the 



In order to specify these and other parameters the following measurements were made during the 

 experiments: 



• In-line and transverse displacements along the span of the cable to characterize the various mode 

 shapes; 



• In-line (drag), transverse (lift) and tangential forces at one end of the cable; 



• Static tension at the other end of the cable; 



• Tow speed. 



Three models (Double Armor Steel, Uniline and Small Diameter Cables) were fabricated to vary 

 the cable density and length-to-diameter ratio; the physical characteristics of the models are listed in 

 Table 3.1. The added mass and damping properties of these cables are discussed in Appendix C of this 

 report. A rotatable twin strut assembly was used in which cables up to 4.4 m (14.5 fl) in length could 

 be held at static tensions up to 2225N (500 lb) and towed at speeds up to 2.6 m/s (5 kt) at various 

 angles to the tow direction between 0=0 and 90°. A sketch of the test rig is shown in Fig. 3.6. Two 



54 



