Cox 



I would like to note that the same approach to the problem was made in the 

 U.S.SJl. by Dr. V. M. Lavrentjev and later by V. M. Ivchenko. The outline of 

 Ivchenko's theory is given in the book titled "Problems and Methods of Hydro- 

 dynamics of Hydrofoils and Propellers," published in Kiev in 1966. 



When making numerical computations at the Kiev Institute of Hydrodynam- 

 ics, they came to the conclusion that for thin cavities, which are typical for the 

 design conditions, the effect of cavity thickness can be estimated approximately 

 by making use of two-dimensional theory. It would be most interesting to know 

 the author's opinion on this subject. 



DISCUSSION 



J. W. English 

 National Physical Laboratory 



Felthan, England ,, 



I would like to endorse the importance that is attached to obtaining numeri- 

 cal results from the work of Dr. Cox. The problem he had in attacking it is 

 truly the heart of the fully cavitating propeller problem. 



Could I ask the author if he has any ideas as to how he might allow for the 

 known nonlinear effects that occur with the growth of the cavities that arise 

 with increasing loading and reduced cavitation number. Does he consider, for 

 example, that it might be necessary to resort to some empiricism, or might it 

 be possible to allow for this growth by establishing an approximate mathemati- 

 cal technique to be used after his initial linear theory calculations. 



DISCUSSION 



C. Kruppa 

 Technische Universitdt, Berlin 



I stated in a lecture series held at Michigan University last year that, in 

 my opinion, all fully cavitating propellers, designed so far, have to be regarded 

 as designed on an empirical or at least semiempirical basis. This statement 

 does not, of course, deny that fully cavitating propellers have been designed in 

 the past which have met certain design specifications and performed more or 

 less satisfactorily in service. It simply means that, for fully cavitating pro- 

 pellers, no design method exists which can be compared with the lifting- surface 



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