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Diver entry and exit was made using a long flat aluminum 

 ladder tied to the top of one of the tank walls. 



3. Tests and Results 



The facility was, at the time, in the final week of testing 

 rubble mound breakwater structures. So the DPG tests conveniently 

 "piggy-backed" with the regularly scheduled tests. Sets of eleven 

 waves of 1 meter nominal height (3.28 feet) and 5 second period were 

 run every 4 to 5 minutes. Wave height and period were monitored by 

 resistance probes and recorded on a strip chart located inside the 

 trailer. 



Initially, the three differential channels monitored appeared 

 ill-behaved (Figure V-7) . The fourth, dP2, had already been 

 confirmed inoperative due to a broken arm tubing connector. It was 

 then discovered that the end-cap on the dP3 arm had accidentally been 

 left on. The instrument was assembled for the CERC tests with the 

 arm isolation diaphragms flush with the end of the PVC arms. With 

 the arm plugged, the diaphragm could communicate with the ambient 

 water only through a thin crescent part-way around the diaphragm 

 housing. It is assumed that such a small gap dampened the dynamic 

 pressure field of the passing waves. 



