Hydraulic Efficiency 



30 



40 50 60 



Flow Speed (cm/s) 



70 



80 



Superduck 



Cube 



Duck85 



Figure 20. Hydraulic efficiency with midflow speed 



nozzle had hydraulic efficiencies closest to unity for the uniform flow case; 

 however, the C nozzle performed best for the bottom flow condition. Both the 

 DUCK85 and SUPERDUCK nozzles had low hydraulic efficiencies for the lower flow 

 speeds in Figure 19 (bottom flow condition) . 



51. The H-S sampler consistently had hydraulic efficiencies greater 

 than unity, with significant variations in flow speed at the nozzle at higher 

 flow rates. The C nozzle had the highest average efficiency for the two- 

 streamer tests, with the SUPERDUCK and DUCK85 nozzles having similar efficien- 

 cies (Figure 20) . 



52. Table 3 presents a summary of the average hydraulic efficiency for 

 each nozzle for each testing condition (on bed, off bed, and two streamers). 

 The maximum standard deviation for a nozzle for a flow speed during a 

 particular testing condition was chosen as a conservative representative 

 value. These four nozzles, as well as selected other nozzles of special 

 interest, were further examined in the sand-trapping test (Part IV). 



40 



