Instrument 2. The second system was a single-beam, 600-kHz transducer 

 looking straight down. The system was built as a purely experimental tool 

 and was employed to detect rapid changes in the concentration of suspended 

 particles. The system consists of a large-bandwidth acoustic transducer, 

 transmit and timing circuitry, a pre-amplifier, and an analog-to-digital (A/D) 

 converter. This setup allows considerable flexibility in data collection 

 strategy, and it was used to investigate both the scatter from the water column 

 and to test velocity-measuring algorithms. 



Location 



RD Flow operated in the offshore region of the wave channel, near instru- 

 ments operated by the University of Florida (UF), Ohio State University 

 (OSU), and Quest Integrated, Inc. The 2.4-MHz and 600-kHz systems were 

 attached in the middle of a mobile carriage mounted on top of the channel 

 walls (Figure 8-2). OSU mounted their instrument array on the onshore side 

 of the carriage. UF and Quest mounted their instruments to the channel 

 walls. Between each run, and sometimes within a run, the carriage was 

 moved to different locations within the offshore region and aligned with either 

 of the two instrument groups fixed to the wall. 



Figure 8-2. Position of the offshore instrument carriage 



The two acoustic instruments were mounted in a frame attached to a verti- 

 cal pole mounted through the center of the carriage. The two instruments 

 were located approximately 1.0 m below the water level. Depending on the 

 exact lateral position, the distance to the bottom was 1.0 to 1.2 m. The pole 

 was secured with guide wires to prevent movement during wave action. 



Figure 8-3 shows the relative position of the offshore instrument arrays. 

 The Benthic Acoustic Stress Sensor and Profilometer systems operated by 



140 



Chapter 8 ADCP Measurements at SUPERTANK 



