317 



Unfortunately, the existence of the f~'^/3 rule cannot be verified 

 generally in these results because the highest frequencies which can be 

 resolved with some accuracy in the computation scheme used, lie around 

 15 cps . Therefore, these data cannot provide conclusive evidence for the 

 existence of an equilibrium range in capillary waves. 



VI. SOME COMPARISONS BETWEEN WAVES IN THE CHANNEL AND OCEAN WAVES 



This study was not intended specifically to model waves at sea. Never- 

 theless, it is worthwhile to see where the data taken for the channel waves 

 fit into the overall picture of wind generated waves. 



The properties of the wind waves generated in the channel easily can be 

 placed in perspective with much larger scale conditions by using well known 

 pictures of wave behavior. As an illustration, the channel data have been 

 plotted schematically in two "scaling" drawings of Hicks (1963), as shown 

 in Figures I7A and B. In Figure I7A, the logarithm of the standard deviation 

 is plotted against the logarithm of fetch. The numbers near curves or points 

 refer to wind speeds taken in the field at somewhat different anemometer 

 heights. The values of wind speed for our data correspond to Uqq. Our 

 data for waves in the channel fit nicely intq the extreme region of short 

 fetch of this figure. Similarly, Figure 173 shows the variation in fjjj with 

 fetch. Again our results for small waves correspond to field data taken at 

 very small fetch. 



Another way of illustrating where the wave data for the channel fit into 

 the geophysical picture comes from the correlation curves of Wiegel (1963). 

 On dimensional grounds, the mean properties of wind generated waves (on 

 deep water) should be related to a Froude parameter with the characteristic 

 length being the fetch. This correlation shows essentially the variation 

 in standard deviation, length of significant waves, and frequently with 

 fetch. 



Wiegel 's results include data taken over an extremely wide range of 

 conditions, which include results of some laboratory experiments and field 

 studies on laJtes and on the ocean. 



A plot of a number of values of a , A , and f for the waves in the 

 CSU channel is shown in Figure I8 along with average curves estimated from 

 Wiegel' s Figure 6-5-7' The averaged curve for the correlation of standard 

 deviation (or O.33 times the significant wave height HWo) falls approxi- 

 mately along the mean of the data from this study. Furthermore, the lines 

 of maxima and minima in a , as estimated from Wiegel 's correlation, encom- 

 pass all of our values. It is interesting to note, however, that there is 

 a systematic deviation with Uqq for the parameter gp/U„^ in Figure 18. 



This indicates that the Froude criterion gF/Uoo cannot be the only parameter 

 for modeling the mean displacement of the water surface. Furthermore, it is 

 clear from the data in Figure 8 and the points for high wind velocity in 

 Figure I8 that the water depth should be included in correlating heights for 

 waves moving at finite depth in channels. 



