Figure 6. Streamer traps used at DUCK85 



types of racks (Kraus 1987), and optimization of the trap nozzle geometry 

 (Rosati and Kraus 1988, Rosati and Kraus in preparation). Streamer nozzles 

 were mounted vertically on stainless steel racks and pointed into the direc- 

 tion of flow so that they were located forward of the racks and any scour 

 clouds produced by the rack and trap operator. Visual observation during 

 operation indicated that scoured sand at the rack did not move upstream and 

 into the streamers. Data collection was always performed in a unidirectional 

 current so that the streamer never reversed direction, a situation which might 

 cause collected sand to be lost. 



22. The nozzles on the traps used at DUCK85 were made of 1/4-ln. stain- 

 less steel bar and had a width of 15 cm and height of 9 cm (Figure 7). 

 Nozzles were attached to the trap racks by mounting bars and secured in place 

 by plates with wing nuts. Figure 8 gives a schematic of the complete trap, 

 with only one streamer shown for clarity. Typically, five streamers were 

 mounted on the racks . 



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