selected at various distances of separation to be followed from frame to frame 

 over time, [n each frame the scalar distance between the floats as weQ as their 

 separation along two perpendicular vectors (x and y) was obtained. These data 

 were then analyzed using the relationship given by Batchelor (1950). 



e = 



io 



2/3 



3/; 



(5) 



where 



(2^ is the initial scalar distance between floats 



2 is the initial distance between the floats 



1 



projected on the x axis 



C^, is the distance between the floats after some 

 x-> 



- time. t. projected on the x axis 

 e is the rate o( turbulent energy flux 



The same operation was carried out for the 'y" vector which should yield a 

 similar value if the turbulent field is isotropic. Unfortunately, it is extremely 

 difficult to extend the analysis to a third dimension and it is not practical to 

 use the method to explore the horizontal turbulent field below the surface. 



Additional Relative Turbulence Measures 



As discussed earlier, the flux of turbulent energy influences the rate at 

 which materials may be exchanged across a laminar boundary layer. This 

 suggests that the dissolution rate of a solid substance placed in the water may, 

 at least to some degree, be a function of the turbulent energy of the fluid. The 

 importance of the turbulent effect should be greatest for materials that are 

 near saturation in sea water. After some exploration, we have found that the 

 mineral gypsum (CaSO^) is particularly well suited for this purpose. It is easily 

 obtained, inexpensive, and a large number of uniform pieces can be cut from a 

 single rough block. The dissolution rate is influenced somewhat by temperature 

 and salinity, but these relationships are easily established in the laboratory in 

 order to compare measurements made under different conditions. Since the 

 rate of weight loss is also a function of size, we have found it best to use 

 standard pieces of gypsum measuring ~2.5 x 1.8 x 0.7 cm with an initial 

 weight of about 6-8 gms. Blocks of this size are suitable for making 

 measurements of weight loss over periods ranging from about 6-24 hrs. 

 Replication appears to be quite good and duplicate blocks are hung off a fixed 

 or free floating Une to obtain a vertical profile of dissolution rate. 

 Unfortunately, however, the CaSOn dissolution rate may provide only a 

 relative measure of turbulent energy and it is not clear if it is possible to relate 



391 



