Castagneto and Maioli 



^ 0,4 



0,12 



tm/c 



Fig. 4 - Lift coefficient at shock-free entry- 

 conditions versus / /c and t /c. 



sections of naval propellers. In the case of an ideal foil of zero thickness, op- 

 erating at shock-free entry conditions, relation (6) becomes 



'L/ 



. K, — 



(7) 



and as such is commonly used in drawing the so-called "incipient cavitation dia- 

 grams" (5), (6), (7). 



It must be noted, however, that the approximation involved in formula (7) is 

 too wide (errors made in evaluating c, , may reach 15% or more), and the au- 

 thors who use it themselves suggest a consequent pitch correction. On the other 

 hand, the reading of such cavitation charts does not appear easier than the nu- 

 merical calculation involved in the relation suggested above, (6). 



The last term in Eq. (2) clearly leads to the conclusion 



r 1 (l + A'K,) A'V^^ dc = 1 



(8) 



In the NASA Report 824 a definite dependence of the velocity increments upon 

 the angle of attack has not been shown; this means that the relation 



1026 



