Savitsky 



A range of wave heights and lengths used in these tests were 

 as follows: 



Test Procedure : Several experimental procedures were 

 used in these studies. In one group of tests, the grid was held 

 stationary 70 ft forward of the wavemaker until several waves had 

 passed through the grid. The grid was then towed and wave measure- 

 ments were made with the moving wave wires. For certain runs, 

 after approximately 50 - 60 ft of grid tow, the aft moving wave 

 wire (16. 50 ft aft) was released irom the tow and remained stationary 

 in the tank. Thus , wave height measurements were taken both at a 

 fixed position relative to the moving grid and at a fixed position in 

 the tank (variable position relative to the grid). The other test pro- 

 cedure was to first tow the grid for a distance of approximately 

 50 ft which developed a turbulent wake and then start the waves which 

 ran through the wake and overtook the moving grid. This technique 

 avoided the possibility of a secondary wave formation as the incident 

 wave ran through the moving grid. It was established that the results 

 obtained with both test procedures were essentially similar. 



Two-Dimensional Grid Studies 



The two-dimensional grid studies were conducted in Tank 

 No. 2 of the Davidson Laboratory. This tank is 75 ft square and has 

 a water depth of 4. 5 ft. A plunger mechanical type wavemaker spans 

 one side of the tank and a sloping beach is installed on the opposite 

 end to absorb the generated wave energy. 



Grid Characteristics: Two turbulence grids, one 3 ft wide 

 and another 5.5 ft wide, were separately towed in a direction away 

 from the wavemaker. The grid centerline was 17 ft from one edge 

 of the tank. Figure 3 shows the test setup. As in the one-dimen- 

 sional tests , two mesh sizes - - M = 0. 36 ft and M = 0.71 ft -- were 



396 



