Pien and Strom-Tejsen 



-^d-} 



Fig. 4 - Division of the pro- 

 peller blade into three regions 

 for numerical integration in 

 the radial direction 



As discussed previously, without the pitch distribution the dipole distribution 

 is not known prior to the design calculation, and an iterative procedure is neces- 

 sary. Both the /3 angle and the p. angle obtained from the lifting line results of 

 Cheng (6) were used in our design example as starting values in two independent 

 calculations. To obtain accurate camber and pitch distributions with the /3- angle 

 required three iterative steps, whereas only two were necessary for the design 

 calculation starting with the /3. angle. Camber values were calculated for ten 

 positions on the chord and for nine radial sections. 



Some results of this design example are shown in Figs. 5 and 6. Figure 5 

 gives the pitch distribution and Figure 6 the maximum camber as function of 

 radius. In both figures the results are comparedwiththoseobtainedby Cheng (6). 



Example of Inverse Calculation 



In predicting propeller performance in the steady condition, we are sup- 

 posed to determine the steady blade loading. The blade loading is presently rep- 

 resented by an expression similar to Eq. (64): 



with 



n=0 m=0 



COS my 



^Pi = Z] E ^nm ^ —) C°^ "^y (84) 



1 - r^. 



118 



