velocities because the former quantities were directly measured, whereas the 

 shear velocity must be inferred from a flow speed profile. 



86. Figures 25 and 26 present the 2.5- and 7.5-min basin-determined 

 fluxes with the power threshold fit equations. A relationship for basin flux 

 F with a 5.0-min testing period was obtained by subtracting values obtained 

 with the 2.5-min equation from values obtained using the 7.5-min threshold 

 power equation: 



F - 2.06 (1(T 5 ) (V mid - 28) 3 - 37 (15) 



87. Figures 27 through 29 present threshold power equations and data 

 for the DUCK85, SUPERDUCK, and C nozzles, respectively. An equation was not 

 fit to the H-S data; evaluation of this nozzle was terminated after two tests 

 because of its unrealistic sand- trapping characteristics. 



88. Sand flux data and power threshold predictive equations for the 

 bottom nozzles and basin are summarized in Figure 30. The DUCK85 nozzle 

 collected the least amount of sand over the flow conditions tested. Fluxes 

 obtained with the SUPERDUCK nozzle fall quite close to the basin transport 

 fluxes for most flow conditions. The SUPERDUCK fluxes with midflow minus 

 threshold flow speeds (V mid - V*) from approximately 28 to 32 cm/sec show 

 considerable scatter. Occasionally developed bedforms in this flow range were 

 observed to occur as migrating ripples, and the SUPERDUCK nozzle occasionally 

 scoured at the bottom lip in this flow range. Results for the H-S sampler lie 

 far above values in the plot for the two flow conditions tested; indeed, the 

 greater-than-unity hydraulic efficiency of the H-S sampler caused it to become 

 buried in the test section almost to the top of the sampler. 



Comparison of transport formulae 



89. A comparison of the form of various transport formulae compiled 

 from Sleath (1984) and Horikawa (1988) for both unidirectional and oscillatory 

 flow was conducted to evaluate how well the laboratory tests agreed with 

 theoretical and empirical relationships. Table 6 indicates that all of the 

 threshold power formulae, with the exception of the DUCK85 equation, relate 

 sand flux to a form of flow speed raised to a power ranging from 3.5 to 4.6. 



59 



