predictions. Although both experimental measurements showed Reynolds number 

 effects, the correlation between PSP predictions and the new experimental values 

 improved substantially. 



The larger discrepancy at r/R = 0.9 on the suction side may be due to real 

 flow effects. However, experimental inaccuracy demonstrated at r/R = 0.5, or the 

 coarse modeling for the global solution in the analytic treatment of the flow in 

 that region can also be a possible source of the discrepancy. 



NSMB MODEL PROPELLER 



The steady pressure distribution was computed on the NSMB model propeller at 

 J = 0.4 and 0.5 to correlate with experimental data. This propeller has simple 

 geometric characteristics; no rake, no skew, and a single section shape over the 

 radius. It was originally designed for bubble cavitation investigation. 



The open-water performance was calculated and compared with experimental re- 

 sults in Figure 16. The predicted K„ and K^ are in excellent agreement with the 

 experimental values for the range of J values except for very reduced ones. 



In Figures 17 and 18, the predicted pressure coefficients are compared with 

 experimental measurements obtained at NSMB at J = 0.4 and 0.6, respectively, at 

 five different radii; r/R = 0.4, 0.5, 0.6, 0.7, and 0.8. At r/R =0.9, only pre- 

 dicted values are plotted since the pressure was not measured at that radius. The 

 pressure was measured by transducers mounted within both sides of the blade surface. 



The experimental measurements were made twice within a six-month period in 

 order to assess the repeatability. The two series of experimental results are 

 shown in Figures 17 and 18. The repeatability is generally good. The predicted 

 values on both sides are in good agreement with experimental measurements at both 

 J values. 



COMPARISON WITH OTHER PROCEDURES 



In 1978, the ITTC Propeller Committee surveyed existing prediction methods for 



22 

 pressure distribution on the propeller blade surface. They compared the pre- 

 dictions made by various methods from sixteen participating institutions throughout 

 the world. The propeller selected for the comparative calculations was DTNSRDC 

 Propeller 4118, a three-bladed research propeller tested thoroughly at DTNSRDC for 

 open-water performance, cavitation, and unsteady forces. 



11 



