ocean surface ocean surface 
pump pump 
20,000 ft 20,000 ft 
eee 
ocean floor ocean floor 
motor motor 
Figure 11. Closed seawater hydraulic Figure 12. Open seawater hydraulic 
system. system. 
For the linear-motion cable system, the required input horsepower 
to develop 100 hp on the ocean floor with cable velocities of 10 ft/sec and 
5 ft/sec are given in Table 1. Using 1-inch galvanized bridge rope with a 
tensile strength of 90,000 pounds, the input horsepower was calculated — 
presuming that the only resistance forces were skin friction and the retardation 
imposed by the hydraulic pump, since the cable’s weight would be counter- 
balanced. Applying the equation (Daugherty and Francini, 1965), 
2 
F = G BL 
where F = drag force 
C; 
| 
friction-drag coefficient 
V_ = cable velocity 
length of surface parallel to flow 
B 
transverse width 
the efficiency was found high at either velocity, with the better efficiency 
at the lower velocity. 
