27 



A HYPOTHESIS FOR THE STRIATION PHENOMENON 



It Is interesting to observe that the flow over the float while it 

 is still submerged and is being towed in a "cavity" formed in the water, ex- 

 hibits the same type of striations near the points of separation, Figure 21a, 

 as is shown by a sphere or projectile dropped through a free surface. A 

 photograph of a sphere dropped into the transparent-wall tank at the Taylor 

 Model Basin exhibits these striations clearly, as is shown in Figure 25. 

 Similar striations also appeared during the tests of the balsa-wood displace- 

 ment float; see Figure 52. 



Figure 25 - Photograph of Aluminum Sphere Dropped into the 

 Transparent-Wall Tank at the Taylor Model Basin 



The entraince velocity was approximately 29 feet per second. 



It has been suggested that the striations on a sphere dropped into 

 water are the result of the formation of cavities about minute nuclei on or 

 near the surface of the sphere. However, the very even spacing of the stria- 

 tions on the planing float, as well as on the sphere shown in Figure 25, sug- 

 gests that a phenomenon other than that due simply to a random distribution 

 of nuclei is more likely to be the cause of the configuration. Although the ~ 

 condition of the surface of the experimental specimen is undoubtedly an im- 

 portant variable in the flow configuration, as evidenced by many sphere drops 



