Morgan and Caster 



(7) The linearized theory of the duct with suitable nonlinear correc- 

 tions appears to be generally satisfactory if separation does not 

 occur on the duct. 



! ! 



(8) The importance of separation should be emphasized, and, if predic- 

 tions are to be reasonable, the duct must be designed so that 

 boundary-layer separation does not occur. 



(9) Lifting- surface theory of the propeller should be used in predicting 

 the interaction between the propeller and duct and for the propeller 

 design. This mathematical model of the propeller would have the 

 same linearized boundary conditions as presently used for the duct. 



(10) Adequate consideration must be given to the influence of the guide 

 vanes and stator vanes. 



ACKNOWLEDGMENTS 



We wish to express our appreciation for the encouragement received from 

 the management of the Naval Ship Research and Development Center in the 

 preparation of this paper. The permission of the Admiralty Research Labora- 

 tory for the use of their ducted propeller data is gratefully acknowledged. We 

 wish to express our appreciation to Mr. Geoffrey G. Cox for review of this 

 paper and his numerous suggestions, to Mrs. Shirley Childers for preparation, 

 and to Mrs. Mary Dickerson for review of the manuscript. 



NOTATION 



a Duct -chord length 



Cjj Drag coefficient, -^ 



L 



C^ Lift coefficient, -r 



Cj^ Lift coefficient, ^j 



C„ Moment coefficient, - 



m I 



2 P" ^/y^ 

 C* Moment coefficient, ^j 



Cp Pressure coefficients on outside and inside of duct, 



[p(x^. x^) - Pq] 



1340 



