Free Surface Effects in Hull Propeller Interaction 
(a-ap) = Bi, -Bi (C14) 
Cy (@)-Crp = 2nr(a-apn)k (C15) 
Boia me ay |Cy, (a) - Cyp|“? (C16) 
It is thus seen that in all five arbitrary constants (Jp, Cpp>k:, ay» a>) 
were usedto match the calculated propeller performance to the 
actual measured performance . By trial and error the following best 
fit values were determined for our propeller : 
Fiavesc lal ads.aGinmnaaan ee 
k = 0.67 
Ba ee alts” gb oe =" 1G (G17) 
Note that the only critical parameter here is the factor k , which may 
be interpretedasan empirical catch-all to account for viscous losses 
and miscellaneous three-dimensional effects . 
The degree of agreement finally achieved between the measu- 
red and calculated (more precisely , simulated) performance of the 
propeller is obvious from the following table and from Fig. 10. 
Further details of this method of calculating off-design perfor- 
mance and results obtained with other propellers are reported ina 
recent paper by Ostergaard , Kruppa and Lessenich (1971) 
Measured Simulated 
1909 
