1 



I 







0.8 





LEGEND SHIELDS NUMBER ,y~^ 







lAfl TRANSITION 

 \J/ SHIELDS NUMBER 



. / FL47 SED 



0.6 





RIPPLES 



,„- SMALL LAf 



/ SHEET FLOW ^ > 0.58 





qe y' 







FLAT BED 









y 





0.3 



- 



/ 1 





0.2 



- 



/ 1 



4k 1 



SUSPENDED * > 0. ?9 





^SSALTATIONJ 









_^^0. 10 < * < 0.36 











I 



I 



0<+ <0.23 









«0 MOTION + = 









I 1 I I 1 



1 1 1 



MID-FLOW SPEED (CM/S) 

 I I 



TRANSITION TO TURBULENCE 



80 100 120 



REYNOLDS NUMBER IX10 3 ) 

 -4— 



TURBULENT 



Figure 22. Bed configuration and sand movement as a function of 

 midflow speed, Reynolds number, and Shields number 



65. Water depth and flow speed were controlled by raising and lowering 

 a sluice gate at the end of the tank and by opening or closing the flow input 

 pipe (Figure 21). Water depth for all sand transport tests was fixed at 



20 cm. This water depth allowed two to three nozzles (depending on nozzle 

 design) to be fully immersed in the flow and produced a flat-bed (sheet-flow) 

 transport condition as normally exists in the surf zone (absence or near 

 absence of bedforms) at higher flow speeds. Water temperature over the course 

 of the 1.5 -month- long experiment was approximately 20° C. 



66. The threshold flow speed for sand movement in the 20-cm-deep water 

 was found to be 28 cm/sec in the middle of the water column and 18 cm/sec 

 approximately 0.5 cm (half probe diameter) from the bed. Significant sand 

 movement occurred at flow speeds greater than 42 cm/sec. At the 42 -cm/sec 



46 



