oOO < — CF 



-500. 



. 100 II I I I I 



FREQUF.NCYjIN CPS 



a. 



b. 



Fig. 7- Tests at Lerner Marine Laboratory dock, Bimini, on 28 June 1962: 



(a) oscilloscope, single sweep, 1 ms/cm, (b) Panoramic, 20 sweeps, 

 ^-second tape loop, (c) Panoramic, 16 sweeps, continuous segment 

 and (d) Panoramic, 60 sweeps, continuous segment. 



this instrument will produce no greater error 

 than do other integrating types. 



Analysis of the frequency spectrum exhibits a 

 predominant frequency which corresponds to the 

 primary or average flow component and other side- 

 band frequencies that are proportional to the 

 product of the direction cosines and velocity of 

 turbulent flow. The major contributing component 

 is comparable to a carrier frequency and the 

 turbulence to modulation sidebands. In order to 

 exploit the instrument's sensitivity to turbu- 

 lence it could be designed to operate in three 

 planes with simultaneous velocity and direction 

 sensing sections, suitable for tape recording, 

 that would give the mean and turbulent components 

 of motion in each coordinate direction. High 



sampling rates can be used for obtaining an 

 extremely fine structure. 



Tests in the towing tank, which represented an 

 apparently homogeneous particle-free environment, 

 confirmed the requirement for the presence of 

 particulate matter for reflection of the acoustic 

 beam. Tests in the ocean off Bimini demonstrated 

 the ability of this instrument to respond to 

 water particle motion induced by swells in an 

 otherwise currentless environment. Another appli- 

 cation to be explored is a 2-plane instrument 

 mounted on a free drifting neutrally buoyant 

 float . It would read only turbulence components 

 because current flow would be cancelled by the 

 float drift. 



133 



