Savitsky 



Parametric variations in this study will Include: 



1. length and width dimensions of turbulence area; 



2. depth of turbulence area below water surface; 



3. spacing of verticsd oscillating rods alone to investigate 

 the interaction between vertically oriented vortices and 

 gravity waves; 



4. spacing of horizontal oscillating rods to investigate the 

 interaction between horizontally oriented vortices and 

 gravity waves; 



5. combination of (3) and (4) to construct a grid having a 

 rectangular mesh of varying dimensions to provide for 

 various scales of two-dimensional turbulence; 



6. vary speed of grid oscillation to obtain various levels of 

 turbulence intensity; 



7. vary length and height of gravity waves. 



Measurements should be made of the wave-height tincie 

 history at various locations both inside and outside of the turbulence 

 patch. A spectral analysis of these wave height time histories 

 should be carried out to determine the extent of wave scattering due 

 to the presence of turbulence. Further, a hot film probe should be 

 slowly towed through the turbulence area to characterize its statisti- 

 cal properties with and without the presence of passing waves. 



It is believed that the suggested experimental procedure is 

 practical and can provide data necessary for basic studies of gravity 

 waves interacting with local turbulence areas. 



V. CONCLUSIONS 



An experimental study was undertaken to investigate the 

 interaction between deep water gravity waves progressing Into a 

 turbulent flow field generated by a finite width grid moving In the 

 wave direction In a large towing tank. It was found that the lateral 

 gradient of the mean longitudinal flow in the wake had predominsint 

 Influence on wave deformation and precluded an evaluation of the 

 direct effect of turbulence. 



The presence of the velocity gradients resulted in combined 

 refraction, diffraction and Interference between finite and adjacent 

 segments of the Incident crest line. Their combined effects were to 

 reduce the wave heights In the wake area to approximately 10% of 

 their original value. The wave heights outside of the wake were 

 Increased to values 75% larger than their original value. 



444 



