Summarizing, correlation of mean pressure distributions with data from existing 

 analytical methods produces poor results compared to similar measurements on planar 

 wings. It is thought that improved correlation could be obtained with theories 

 accounting more completely for observed three-dimensional flow effects. 



INFLUENCE OF REYNOLDS NUMBER ON MEASURED PRESSURE DISTRIBUTIONS 



It was thought that over the range of Reynolds numbers covered by the tests 



ft ft 



(6x10 >R >2xl0 ) the pressure distributions would be essentially independent of 

 Reynolds number at a given design point. With an absence of cavitation and boundary- 

 layer separation, it was expected that the measured pressure coefficients at constant 

 J would match a potential flow model, being independent of Reynolds number or, in 

 this case, carriage speed V , resultant inflow speed V , or rotational speed n. 



To investigate this, runs were conducted at design advance coefficients over 



ft 6 



ranges of carriage speeds in a Reynolds number range of 2.50 x 10 to 4.63 x 10 for 



ft ft 



Propeller 4718, and 3.08 x 10 to 6.20 x 10 for Propeller 4679. A limited number 



of speed runs were also made at off -design conditions. Results shown in Figures 12 



and 13 indicate a relatively large speed dependence of the pressure coefficients in 



various chordwise regions of the blade. 



At the 0.5R radial position, a dramatic increase in pressure coefficient oc- 

 curred on the suction side with increasing speed in the mid-to-af t chord region on 

 Propeller 4718, representing the greatest speed effect observed. A variation, 

 similar in effect, occurred in a similar region on Propeller 4679, but to a lesser 

 degree. On the pressure side of Propeller 4718, a pressure increase with increasing 

 speed occurred near the leading edge; however, for the gage nearest the leading edge 

 the C was essentially constant. The pressure side of Propeller 4679 showed less of 

 a speed effect than Propeller 4718 with the exception of increased values of C on 

 the lowest speed run, contradicting the usual trend of increasing C with increasing 

 speed. 



At the 0.7 radial position on Propeller 4718, values of C increased on the 

 suction side with increasing speed in the fore- to mid-chord regions. On the 

 pressure side, a similar variation occurred. In both cases, little or no variation 

 occurred at the leading and trailing edges. Propeller 4679 produced a similar trend 



19 



