Borden 



8 103 



48 Inch Tunnel 

 O Ciicular Arc 1 

 ti Triangle ) 



12 Inch Tunnel 

 • Ciicular Arc 



Ciiculai Ate 

 Triangle 



8 = 0.453 



k Triangle i 



^ Circular Arc 

 A Triangle ' 



5 = 0.U9 



Fig. 2 - Local cavitation number as a function of the local Reynolds 

 number (ORL two-dimensional data based on u, ) 



log aj^ = A + B log Fj. 



(6) 



were fitted to the data in Figs. 1 and 2 by the method of least squares. Values 

 of the parameters A and b for the different roughness geometries are listed in 

 Table 1. 



Table 1 



Values of A and B For Two- and Three- 



Dimensional Roughness Elements 



In two-dimensional flow, all the streamlines in the boundary layer are 

 deflected by a two-dimensional roughness element. Since the roughness cre- 

 ates a large disturbance in the local flow, u^ (computed from the power law) 

 does not seem to be an appropriate local velocity for computing the cavitation 

 parameters. Holl (4) tried to predict cavitation indices of his circular- arc 

 roughness elements by frozen streamline theory. This computation was labo- 

 rious and gave poor correlation with the experimental values. He later obtained 



186 



