Sand Flux (g/cm2/min) 



10 



DUCK85 



30 



(V-V*) (cm/s) 



50 



Figure 35. Modified basin flux for 5-min test and power 

 threshold fit nozzle fluxes 



e. Sand transport during all trap testing was greater than during 

 basin tests due to an unknown systematic experimental error. 



Each of the above-listed possibilities is discussed below. 



a. The C nozzle increased flow speed in its vicinity. Because 

 the hydraulic tests indicated an average hydraulic efficiency 

 for the C nozzle of 0.95, this theory does not appear 

 tenable. In addition, characteristics observed for the H-S 

 pressure-difference nozzle (i.e., material moving from sides of the 

 nozzle into the mouth; nozzle burying itself in test section) were 

 not observed during testing of the C nozzle. 



b. Loss of sand through basin cloths was significant. Loss of sand 

 through adjacent basin cloths could have occurred, although a 45 

 percent loss of sand (approximately 1,100 g for 2. 5-min and 4,300 g 

 for 7. 5-min basin tests) would have resulted in an obvious residue 

 at the bottom of the basins after the cloths were removed (which 

 was not found) . Loss of sand through adjacent basin cloths could 

 have occurred to some degree; however, this factor cannot account 

 for the entire discrepancy. 



71 



