Theory of the Ducted Propeller — A Review 



0.12 



>- 0.10 



0.08 



0.6 



5 



0.4 



Fig. 13 - (See (130)) Approximation of slipstream boundary- 

 conditions at various stages of a twenty-iterative-cycle calcu- 

 lation. Cylindrical shroud: l/r^ = 0.2, U = 



1.0 

 0.9 



0.8 



0.C5 0.10 0.20 



Chord/Radius, l/r^j 



0.50 



1.00 



Fig. 14 - (See (130)) Slipstream con- 

 traction ratio for cylindrical shrouds 



duct are placed not on a cylinder but on a cone; otherwise linear theory is ap- 

 plied. He found that the results do not depend very much on the choice of the 

 approximating cone and agree sufficiently well with the usual linear theory. 



Wiedemer (113) improved the results of Dickmann and Weissinger (102) by 

 an interative procedure. In (102), duct profiles (with zero thickness) have been 

 obtained by determining the streamlines through the trailing edge that are in- 

 duced by certain vortex distributions placed on a reference cylinder. In each 

 iteration cycle, Wiedemer places the (unchanged) vortex distribution of the duct 

 on the profile obtained in the previous cycle and calculates the next profile ap- 

 proximation. One example is shown in Fig. 16, where a remarkable difference 

 between the Dickmann-Weissinger profile and the Wiedemer profile can be seen. 

 For lower values of ct the difference is smaller. A method similar to that of 



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