independently to produce simultaneously up to ten wave trains of 

 different heights, directions, and phase, though of only two different 

 wave periods. A gravel wave absorber along three sides of the tank 

 minimizes reflections from the side and rear walls. A planned 

 supplementary tidal system will produce a complete tidal cycle in 40 

 minutes with a maximum 3-inch fluctuation of water level. The tidal 

 flow from a 40 X 40-foot sump 10 feet deep (Figures 9 and 11) will be 

 introduced through a perforated pipe which runs the length of three 

 full sides of the tank under the gravel absorbing slope. An additional 

 pumping system of 2,200 gpm capacity is available for superimposing a 

 forced littoral current. 



The basin is equipped with two motor driven instrument and 

 personnel carriers, one for each of the two existing sections (although 

 Figures 8 and 9 show one only over the larger section, a carriage has 

 now been installed in the smaller section also). The carriers (Figure 

 10) operate on tracks along the entire length of each section, cover- 

 ing a 100-foot width in the larger section and a 5-foot width in the 

 smaller. A Bilby tower 100 feet high, is located next to the beach 

 side of the tank for photographic use. A number of eductors, an 

 end loader, and a garden scraper -tract or are available for moving 

 sand. Figure 8 is a general view of the tank, with nine of the wave 

 machines installed. Figure 9, a view of the basin taken from the 

 Bilby tower, shows the generating faces of five of the movable wave 

 generators. Figure 10 shows the instrument and personnel carrier for 

 the larger section and the Bilby tower. Shown in Figure 11 is the 

 tide sump and part of the pumping system. 



Tank for Generation of Large Waves . - This concrete wave 

 tank is 635 feet long, 15 feet wide, and 20 feet deep. An instrument 

 carriage operates on rails mounted the entire length of the tank on 

 top of both side walls. The instrument carriage is designed to carry 

 personnel as well as instruments required in the performance of tests. 

 Electrical outlets are spaced along the tank wall to provide 110-volt 

 single-phase, and 208-volt three-phase electric power for use with 

 instruments and auxiliary equipment. Another feature of the wave 

 tank is a removable bulkhead and three sets of slots, by means of 

 which the tank may be partitioned into sections of various lengths. 

 A 100-foot Bilby tower is located beside the tank about the midpoint 

 of its length for photographic purposes. Operating at the usual 

 water depth of 15 feet, the tank requires approximately one million 

 gallons of water. The tank is filled through either of two 6-inch 

 lines leading from an 8-inch water supply pipe. Filling normally 

 takes about 8 to 10 hours, but valves may be set to automatically 

 cut off at any predetermined level so that filling may take place 

 during the night without loss of normal work time. Figure 12 is a 

 view of the 6-foot wave in the tank and Figure 13 is a view of the 

 tank looking toward the beach end showing an endloader being lowered 

 into the tank to be used for moving sand. 



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