Comparison of Theory and Experiment on Ducted Propellers 



A stringent verification of these theories means that 



(1) the ducted propellers are designed according to the theory (experi- 

 ments carried out after the calculations); 



(2) the comparison between theory and experiment are made only at 

 the design point. . . J • . . :^. 



As far as I know, these requirements are fulfilled only by 



(1) the four ducted propellers tested at SSPA (42), 



(2) one of the ducted propellers tested at Karlsruhe (44), and possibly 



(3) some of the ducted propellers tested at NSMB (45). 



In many of the ducted propeller investigations described, however, the calcula- 

 tions have been carried out after the tests. Since, so far, no stringent theory 

 has been presented for this direct-direct approach of the problem, the theories 

 used must involve some more or less satisfactory approximations. The authors 

 have mentioned some of them in their paper, for example, the pressure jump at 

 the propeller assumed in Refs. (19, 21, 22), but it would be valuable to get some 

 information also about the more reliable method used in (20). The paper seems 

 to indicate that the authors use the measured propeller thrust rather than a the- 

 oretical value. If, instead, one starts from the pitch and camber distributions 

 of the propeller and not from the measured propeller thrust, how large will the 

 difference between the experimental and theoretical values of propeller thrust 

 be for the three ducted propellers described in (20)? 



DISCUSSION 



George Rosen : , - 



Hamilton Standard Division of United Aircraft Corp, ; : • 



Windsor Locks, Connecticut '■--■' 



The authors should be complimented on an excellent contribution toward the 

 improving technology on ducted propellers. It is from this type of continuing 

 correlation of advanced theoretical and experimental work that the necessary 

 refinements in design criteria must come. 



At the Ducted Propeller Panel meeting I described some extensive wind- 

 tunnel tests conducted by Hamilton Standard on a series of systematic ducted 

 propeller configurations. Unfortunately, the results of these tests were not 

 available in time for the authors to include them in the studies reported in this 

 paper. I hope that they will have the opportunity to do this in the near future. 



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