45 



The pressure p ( and the velocities u l and u. may be referred to the. refer^n-o^g 

 position at radius r 2 by the pressure and continuity relations (neglecting 

 friction) : 



and 



r 2 u - r/U 2 [25]. 



Furthermore, for a conical diffuser, the radius r ; , expressed in terms of the 

 throat radius r. , the cavity length I, and the diffuser half-angle o, is 



oh 



r = r, + I sin a [26] 



Thus, from [25] and [26] , 



— Ea5a =% [27] 



(r, + i sin or £ 



where 



l^+^sino [28] 



Combining [23], [24], and [27] to eliminate p ( and u h the result may 

 be written in the following form 



? 2 ~ P v + _ j_ _ 2 rv / r 2N 2 



l.Ti 2 * 4 



Defining the cavitation number a 2 as 



P , "P. 



Or. ~ 



& - en 



and letting 



r 2 



Equation [29] becomes 



? 4 (1 + <x 2 ) - 2r 2 ? 2 + (2k - 1) = [30] 



