Morgan and Caster 



Fig. 14 - Radial variation of the axial in- 

 duced velocity distribution in midplane of 

 ARL ducts Bl, B2, and B3 (35) 



different ducted-propeller systems. Pressure measurements were made on a 

 duct for various propeller loadings (Model 3650) in the David Taylor Model 

 Basin (20, 39). This duct has a maximum camber ratio of 0.067, at approxi- 

 mately 67% of the duct chord from the leading edge, and a maximum thickness 

 ratio of 0.045, at approximately 63% of the duct-chord length. Each duct section 

 has an angle of attack of 3.9° and the chord-diameter ratio of the duct is 1.57. A 

 five-bladed propeller with a hub radius of 0.4 was located at 28% of the duct- 

 chord length from the leading edge and six stator vanes were located aft of the 

 propeller at approximately 54% of the duct-chord length. 



The experimental and theoretical pressure distributions on the duct of 

 Model 3650 are shown in Fig. 15 at the design speed of advance, ] , of 1.27. It 

 is apparent from Fig. 15 that the predicted pressure distribution using linear- 

 ized theory with a nonlinear approximation (20) gives a slightly better predic- 

 tion on the outside of the duct than on the inside. This is also true for the 

 Meyerhoff nonlinear theory (22) of the duct. The nonlinear theory gives a 

 slightly better prediction than the linearized theory on the outside of the duct 

 and on the inside of the duct forward of the propeller. In general, both predic- 

 tions are satisfactory. The assumed pressure jump due to the propeller 



1328 



