Tjjfaye Generator : 



A plunger type wave generator was used. The generator was supported by a 

 movable frame and could be placed at any position along the ripple tank. The 

 amplitude of the movement was controlled by an eccentric and could be varied 

 from to about 3/4 of an inch. The frequency of the plunger could be varied 

 from about 1 to 20 per second. By trial a wave steepness was selected so as 

 to produce a series of clear images on the screen. 



Test Conditions : 



A pictorial summary of this study of wave motion in various idealized condi- 

 tions is presented in Figures 3a through 3g. The various phenomena presented 

 in these figures and the test conditions are summarized in Table I. 



DISCUSSION 



In water of uniform depth periodic waves are propagated with uniform velocity 

 and without change of form. The wave orests remain parallel to each other. 

 This is demonstrated in Run 1 (Figure 3a). The relationship between period, length 

 and velocity characteristics of periodic wave phenomena is 



L = C T . (1) 



Where L is the length, C the velocity and T the period of the waves. 



If water of constant depth is disturbed by small periodic impulses, the wave 

 length and velocity are related to the depth by the equation 



&. tanh 12*" (2) 



17T L 



where d is the water depth. As long as the surface tension has negligible in- 

 fluence and the wave height is small as compared with d and L, this equation 

 applies to both deep-water and shallow-water waves. 



For waves where surface tension is not negligible (where the radius of curvature 

 is very small) the velocity is given by the equation 



C s 



JL. +J&2L 



tanh £SJL (3) 



|2 7T f L J L 



where * is the surface tension in lbs/ft and T is the density of water in 

 slugs/ft 3 . 



Experiments by A. J. Chinn (Reference 4), indicated that for wave lengths of 

 0.075 ft. or less, the effect of surface tension had to be considered, but that 

 the second term {Z-f 'ft '/ ' J* L) in the velocity equation had to be modified. Chinn 

 found that the average experimental results for waves in this region were 11. 5> 

 lower than indicated by the theory and in order to correct this discrepancy the 

 term (ztfjr/ fL) was reduced by 40#*. For the present ripple tank studies the 



*The author of the present report is of the opinion that this statement should 

 be viewed with caution and that additional laboratory experiments should be per- 

 formed. This statement is based upon the results of a few measurements. 



