Grid Turbulence in Dilute High-Polymer Solutions 

 -30| 1 1 1 — I — I — I I I I 1 1 1 



-40 



-50- 



-60 



> -70 



< -80 



-90 



-100 



-llO 



SOLUTION 



P30l-3,43hr 



C74 V 



C79 



"v^.N.L. 

 C84N \ 



J I I I I I I 



10 100 500 



FREQUENCY, cps 



Fig. 16 - Relative spectral levels in 

 Solution P301-3 at x/M = 20.2 and »; 

 age 43 hours 



because of raggedness. As raggedness decreases with solution age, the fixed 

 noise levels become more important, and at 43 hours, the noise correction is 

 about 4 db at 200 cps. Raggedness can be said to have disappeared at x/m = 20.2 

 by 43 hours because the noise-corrected spectral level curve shows no depar- 

 ture from the behavior in water of a monotonic decrease of logarithmic slope. 



All the solutions prepared in this work showed some degree of increased 

 noise level relative to water. The lowest increases were obtained with the 

 Polyox solutions. Only a limited amount of spectral analysis was done with 

 other additives than Polyox. With guar gum, there was a high level of noise, due 

 to visible particles in the suspensions, which greatly restricted the range of x M 

 in which accurate spectral data could be obtained for the standard sample lengths. 

 With Separan AP-30 and JlOO, no spectral analysis was done because the signal 

 raggedness near the grid did not decrease in time and because the higher noise 

 levels with these additives would have interfered with tests far from the grid. 



The decay of raggedness with distance from the grid is seen in the higher 

 frequency portions of the curves of Fig. 17. In these tests, Solution PC -4, 



59 



