Morgan and Caster 



0.1 



Fig. 5 - Pressure distribution on NSRDC duct II, 

 a^ = 8 degrees and = degrees 



theoretical predictions from linearized theory are unsatisfactory but do give the 

 right general shape. The difference in the results from the two forms of the 

 Bernoulli equation is small. Apparently at an angle of incidence of 8°, this duct 

 has started to separate at the position (/> = 180°. Separation was apparent at 

 this position when the angle of incidence was 10° (33). 



Another duct (BTZ duct) for which extensive data is available is one de- 

 signed and tested by the Bureau Technique Zborowski (12). This duct has a 

 NACA 66-006 thickness distribution, zero camber, zero section angle of attack 

 and a chord-diameter ratio of 0.96. The measured pressure distribution c , 

 along with the theoretical predicted values from linearized theory with a non- 

 linear approximation (33), are plotted in Fig. 7 for the duct at a zero angle of 

 incidence. The predicted pressure distribution for this duct is very satisfac- 

 tory indeed. Experiments were conducted on this duct at angles of incidence but 

 the data are not presented here, as they show the same trends as for Duct 1 and 

 Duct II. The BTZ duct did show separation on the inside at the position = 180° 

 at an angle of incidence of 12°. The prediction is given by both forms of the 

 Bernoulli equation. 



Pressure distribution tests on annular airfoils were also made at the Admi- 

 rality Research Laboratory (35). These ducts all had NACA 0006 thickness dis- 

 tributions, slightly thickened at the trailing edge for structural reasons, and a 

 chord-diameter ratio of 0.75. Ducts Bl, B2, and B3 have maximum camber 



1320 



