oscillations due to wind and waves, (b) visual error in taking ga.ge read- 

 ings, and (c) variations in readings due to different observers. Wave- 

 generated oscillations were problems only with the long wave (3.75-second 

 period). Basin oscillations due to wind caused a problem perhaps once in 

 10 days. The wind effect was compensated by adjusting the water level until 

 the average of the maximum and minimum gage readings equaled the desired 

 reading. 



5. Water Depth . 



Although the water level at the gage was maintained to very strict 

 tolerances, the water depth is not considered that accurate because the 

 bottom elevation varied as much as 0.1 foot (3 centimeters) within the 

 6-foot tank and 0.05 foot (1.5 centimeters) within the 10-foot tank. A 

 contour map of a part of the 10-foot tank bottom derived from data col- 

 lected in December 1972 is shown in Figure 8. A similar drawing of the 

 6-foot tank bottom is shown in Figure 9. 



IV. WAVE GENERATOR OPERATION 



1. Experimental Setup . 



Each test area was equipped with 1 of the 10 SPTB portable wave gener- 

 ators (Fig. 10). The generator was placed perpendicular to the three 

 walls and a sufficient distance from the ends of the walls to allow maxi- 

 mum bulkhead travel without striking the walls. A plate was attached 

 perpendicular to the generator bulkhead in a position to slide against the 

 center wall, thus completely separating the two tanks regardless of bulk- 

 head position. In the 6-foot tanks, plates were also attached perpendic- 

 ular to the bulkhead just inside the outside walls (Fig. 10), thus making 

 a closed tank wall regardless of the bulkhead position. The outside walls 

 of the 10-foot tank extended to the frame of the wave generator. There 

 was no gap between the end of the tank wall and the generator frame, but 

 a 0.15-foot (4.6 centimeters) gap was between the end of the generator 

 bulkhead and the generator frame (Fig. 11). This is important in the 

 analysis of results from experiment 72B-10. 



2. System Components . 



The generators were operated from a control room on the second floor 

 of a service building overlooking the SPTB. Remote control was achieved 

 by a system of electromechanical connections. The basic components of 

 this system, for each generator, consisted of: 



(a) A 20- by 3.5-foot (6.10 by 1.07 meters) vertical bulk- 

 head. 



(b) A shaft and crank mechanism which imparted approximate 

 sinusoidal motion to the bulkhead. 



(c) A four-speed transmission connected to the crankshaft 

 by chain and sprockets. Change of gear ratios has rarely been 



